WEBVTT 8ca14bac-4f56-40c1-9c1a-c4d258076e65/39-0 00:00:06.083 --> 00:00:06.843 Hey, everyone. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/51-0 00:00:07.263 --> 00:00:12.233 Welcome to the seminar of May 17, 2023. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/57-0 00:00:12.243 --> 00:00:12.903 Welcome back. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/66-0 00:00:12.913 --> 00:00:14.893 We haven't had a seminar in two weeks now. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/79-0 00:00:16.583 --> 00:00:20.393 Everyone at home please turn off your cameras and microphones. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/92-0 00:00:21.313 --> 00:00:25.473 We have, I think, absolutely no announcements today. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/97-0 00:00:26.743 --> 00:00:28.593 So everyone relax. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/111-0 00:00:28.603 --> 00:00:31.853 I will say this is my last day of the seminar 8ca14bac-4f56-40c1-9c1a-c4d258076e65/126-0 00:00:31.863 --> 00:00:36.338 person. We're about to switch in June, but I'm gonna go on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/126-1 00:00:36.338 --> 00:00:37.033 vacation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/135-0 00:00:37.043 --> 00:00:38.453 So this is my farewell. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/139-0 00:00:38.663 --> 00:00:40.683 Thanks everyone. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/162-0 00:00:44.863 --> 00:00:47.944 And with that, I'm going to hand it to Rob Skoumal to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/162-1 00:00:47.944 --> 00:00:49.133 introduce the speaker. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/168-0 00:00:49.963 --> 00:00:51.153 So Rob, go ahead. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/177-0 00:00:51.223 --> 00:00:53.753 It's my pleasure to introduce Daniel today. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/206-0 00:00:53.943 --> 00:00:57.239 Daniel received his bachelors from Stanford before going on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/206-1 00:00:57.239 --> 00:01:00.430 and getting his Masters and PhD at UC San Diego working with 8ca14bac-4f56-40c1-9c1a-c4d258076e65/206-2 00:01:00.430 --> 00:01:01.163 Peter Scharer. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/233-0 00:01:02.093 --> 00:01:04.910 He then want to Los Alamos and University Texas at Austin 8ca14bac-4f56-40c1-9c1a-c4d258076e65/233-1 00:01:04.910 --> 00:01:07.280 before starting his current position as an assistant 8ca14bac-4f56-40c1-9c1a-c4d258076e65/233-2 00:01:07.280 --> 00:01:09.293 professor at the University of Nevada, Reno. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/272-0 00:01:10.503 --> 00:01:13.358 So Daniel worked on a wide variety of different types of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/272-1 00:01:13.358 --> 00:01:16.367 research topics, including a multitude of source property, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/272-2 00:01:16.367 --> 00:01:19.528 work, earthquake early warning, and as we'll hear about more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/272-3 00:01:19.528 --> 00:01:20.293 ground motions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/304-0 00:01:21.073 --> 00:01:25.027 So I continue to be amazed at how productive Daniel 8ca14bac-4f56-40c1-9c1a-c4d258076e65/304-1 00:01:25.027 --> 00:01:28.373 has been as a scientist, and somehow he still has 8ca14bac-4f56-40c1-9c1a-c4d258076e65/325-0 00:01:28.553 --> 00:01:32.670 has time to deal with my incessant questions and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/325-1 00:01:32.670 --> 00:01:33.953 nagging email. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/334-0 00:01:34.423 --> 00:01:36.053 So thank you, Daniel for all of that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/346-0 00:01:36.183 --> 00:01:37.183 And please take it away. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/341-0 00:01:38.343 --> 00:01:38.653 Great. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/347-0 00:01:38.663 --> 00:01:39.193 Thanks, Rob. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/351-0 00:01:39.203 --> 00:01:39.473 Thanks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/358-0 00:01:39.483 --> 00:01:41.073 That was a very kind introduction. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/374-0 00:01:41.423 --> 00:01:44.324 I mean, Rob's done amazing work over the past few 8ca14bac-4f56-40c1-9c1a-c4d258076e65/374-1 00:01:44.324 --> 00:01:44.833 years too. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/398-0 00:01:44.843 --> 00:01:48.072 So it's been really nice to watch all the interesting stuff 8ca14bac-4f56-40c1-9c1a-c4d258076e65/398-1 00:01:48.072 --> 00:01:51.033 that's been going on at the Earthquake Science Center. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/402-0 00:01:51.883 --> 00:01:52.493 So yeah, I'm 8ca14bac-4f56-40c1-9c1a-c4d258076e65/415-0 00:01:52.503 --> 00:01:55.052 really honored to be able to present some of my research 8ca14bac-4f56-40c1-9c1a-c4d258076e65/415-1 00:01:55.052 --> 00:01:55.303 today. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/417-0 00:01:56.423 --> 00:01:56.823 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/419-0 00:01:57.203 --> 00:01:57.503 Let's see. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-0 00:02:00.013 --> 00:02:03.421 Uh, so as Rob mentioned, I just moved umm from Texas to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-1 00:02:03.421 --> 00:02:07.134 University of Nevada, Reno, where I'm an assistant professor 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-2 00:02:07.134 --> 00:02:10.786 here and a big part of the research that I'm working on and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-3 00:02:10.786 --> 00:02:14.195 that my group is working on is trying to understand the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-4 00:02:14.195 --> 00:02:17.786 relationship between the details of the earthquake rupture 8ca14bac-4f56-40c1-9c1a-c4d258076e65/486-5 00:02:17.786 --> 00:02:20.403 process and the relation to ground motion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-0 00:02:21.053 --> 00:02:24.326 So it's been known for a very long time that earthquakes of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-1 00:02:24.326 --> 00:02:27.762 equivalent size or magnitude can produce very different ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-2 00:02:27.762 --> 00:02:30.871 motions at the same distance from the source, and so the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-3 00:02:30.871 --> 00:02:34.144 seminar that I'm gonna present today is really gonna try to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-4 00:02:34.144 --> 00:02:37.471 export a few different pieces of work in both California and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/550-5 00:02:37.471 --> 00:02:37.853 Nevada. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/613-0 00:02:38.043 --> 00:02:42.032 I'm trying to understand various pieces of that puzzle, and so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/613-1 00:02:42.032 --> 00:02:46.084 it's gonna be kind of a two-parter today. Both of the studies that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/613-2 00:02:46.084 --> 00:02:49.567 I'm gonna refer to are published and I'll provide full 8ca14bac-4f56-40c1-9c1a-c4d258076e65/613-3 00:02:49.567 --> 00:02:53.303 publication details at the end in case you are interested. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/620-0 00:02:53.313 --> 00:02:55.203 But the first part I'm gonna focus on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-0 00:02:56.183 --> 00:02:59.560 looking at earthquake source spectra, so the frequency 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-1 00:02:59.560 --> 00:03:03.182 content of earthquakes and trying to figure out how we can 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-2 00:03:03.182 --> 00:03:06.927 measure Spectra characterized Spectra more robustly and also 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-3 00:03:06.927 --> 00:03:10.734 understand how we can extract more advanced source properties 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-4 00:03:10.734 --> 00:03:14.356 like rupture directivity from the spectral content and the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/681-5 00:03:14.356 --> 00:03:15.093 second part 8ca14bac-4f56-40c1-9c1a-c4d258076e65/715-0 00:03:15.173 --> 00:03:18.416 I'm gonna focus in on one earthquake in particular, and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/715-1 00:03:18.416 --> 00:03:22.006 the idea of trying to understand what ground motions are very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/715-2 00:03:22.006 --> 00:03:25.713 close to normal fault and what the implications are for hazard. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/727-0 00:03:26.703 --> 00:03:28.113 So that's the basic game plan for today. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/743-0 00:03:29.793 --> 00:03:33.628 But to start, we're gonna focus on a very classic problem in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/743-1 00:03:33.628 --> 00:03:34.823 earthquake physics. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/771-0 00:03:34.833 --> 00:03:38.049 So people have been using the frequency content of earthquake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/771-1 00:03:38.049 --> 00:03:40.953 or earthquake Spectra to try to infer earthquake source 8ca14bac-4f56-40c1-9c1a-c4d258076e65/771-2 00:03:40.953 --> 00:03:42.613 properties for a very long time. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/795-0 00:03:43.313 --> 00:03:47.532 The mathematical framework that most people use today dates back 8ca14bac-4f56-40c1-9c1a-c4d258076e65/795-1 00:03:47.532 --> 00:03:51.103 more than 50 years to some of the work from Jim Brune. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/798-0 00:03:51.303 --> 00:03:52.573 Umm, uh. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/833-0 00:03:52.583 --> 00:03:55.547 Trying to make kind of simple models of earthquake Spectra and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/833-1 00:03:55.547 --> 00:03:58.605 so you probably learned in your introductory seismology class on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/833-2 00:03:58.605 --> 00:04:00.393 model that looks something like this. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-0 00:04:00.403 --> 00:04:03.821 So just so we're all on the same page, the classic brune model, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-1 00:04:03.821 --> 00:04:07.240 the earthquake Spectra, if you plot log of frequency versus log 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-2 00:04:07.240 --> 00:04:10.498 of amplitude, and we're talking about a displacement Spectra 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-3 00:04:10.498 --> 00:04:13.756 here, you get a picture that should look something like this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-4 00:04:13.756 --> 00:04:16.747 where you have a flat section at low frequencies that's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-5 00:04:16.747 --> 00:04:19.845 proportional to the seismic moment and then a fall off at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/910-6 00:04:19.845 --> 00:04:20.753 high frequencies. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/922-0 00:04:21.213 --> 00:04:24.083 The power law of something about frequency to the minus two. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/959-0 00:04:24.173 --> 00:04:27.173 And then, of course, there's this transition frequency that's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/959-1 00:04:27.173 --> 00:04:29.737 called the corner frequency, that kind of marks this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/959-2 00:04:29.737 --> 00:04:32.931 transition between the flat part at the top and the steep part at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/959-3 00:04:32.931 --> 00:04:33.463 the bottom. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/987-0 00:04:33.993 --> 00:04:37.044 And so if you make enough assumptions about what this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/987-1 00:04:37.044 --> 00:04:40.321 corner frequency means, you can actually start to extract 8ca14bac-4f56-40c1-9c1a-c4d258076e65/987-2 00:04:40.321 --> 00:04:41.903 different source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1015-0 00:04:41.913 --> 00:04:45.262 And so one assumption that people will assume with this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1015-1 00:04:45.262 --> 00:04:48.910 corner frequency is that it's somehow inversely proportional 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1015-2 00:04:48.910 --> 00:04:51.063 to the rupture duration and radius. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1035-0 00:04:51.073 --> 00:04:53.377 And so this is appropriate if you have a circular source that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1035-1 00:04:53.377 --> 00:04:54.343 looks something like this. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1065-0 00:04:54.353 --> 00:04:57.832 If you have a constant rupture velocity, then very likely you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1065-1 00:04:57.832 --> 00:05:00.975 could get a Spectra that looks like this and so you can 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1065-2 00:05:00.975 --> 00:05:02.883 actually put the pieces together. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1075-0 00:05:02.893 --> 00:05:04.813 You can get a moment measurement from the Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1118-0 00:05:04.823 --> 00:05:07.761 You can get a corner frequency measurement from the Spectra, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1118-1 00:05:07.761 --> 00:05:10.700 and if you put those together you can actually get a measure 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1118-2 00:05:10.700 --> 00:05:13.879 of the static stress drop and so people do these measurements all 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1118-3 00:05:13.879 --> 00:05:14.313 the time. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1129-0 00:05:14.643 --> 00:05:17.185 They make stress drop measurements from earthquake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1129-1 00:05:17.185 --> 00:05:17.933 source Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1157-0 00:05:17.943 --> 00:05:20.975 It's almost certainly the most common type common way that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1157-1 00:05:20.975 --> 00:05:24.162 people measure stress drop, but of course it really hinges on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1157-2 00:05:24.162 --> 00:05:25.293 all these assumptions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1200-0 00:05:25.303 --> 00:05:28.848 We know that not all earthquakes look like this or circular crack 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1200-1 00:05:28.848 --> 00:05:31.857 model, and so any sort of measurement of stress drop is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1200-2 00:05:31.857 --> 00:05:34.597 kind of some indirect measurement that is really a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1200-3 00:05:34.597 --> 00:05:37.283 characterization of the frequency content itself. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1227-0 00:05:38.093 --> 00:05:41.125 And so people have challenged this idea of like whether or not 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1227-1 00:05:41.125 --> 00:05:44.206 we can actually use these stress drop measurements for anything 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1227-2 00:05:44.206 --> 00:05:44.543 useful. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1268-0 00:05:45.093 --> 00:05:47.858 But even if you don't buy this kind of assumption that we're 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1268-1 00:05:47.858 --> 00:05:50.487 actually getting a proper measurement of stress drop from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1268-2 00:05:50.487 --> 00:05:53.252 this framework, it actually ends up being a pretty important 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1268-3 00:05:53.252 --> 00:05:54.023 source parameter. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1293-0 00:05:54.293 --> 00:05:57.515 Because basically what you're doing is you're measuring some 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1293-1 00:05:57.515 --> 00:06:01.002 sort of normalized comparison of frequency content of earthquakes 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1293-2 00:06:01.002 --> 00:06:01.953 of different size. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1325-0 00:06:01.963 --> 00:06:05.477 And so earthquakes with higher spectral stress drops or broom 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1325-1 00:06:05.477 --> 00:06:08.652 type stress drops, even if you're not quite getting the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1325-2 00:06:08.652 --> 00:06:11.033 accurate static stress drop of the event. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1339-0 00:06:11.203 --> 00:06:13.593 What you're doing is essentially you're comparing energy. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1357-0 00:06:13.603 --> 00:06:17.718 The energy, the higher stress drop events as measured in this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1357-1 00:06:17.718 --> 00:06:19.643 framework are more energetic. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1384-0 00:06:19.653 --> 00:06:22.439 And so you're gonna end up with stronger high frequency ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1384-1 00:06:22.439 --> 00:06:24.783 motion pulses for the earthquakes with higher stress 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1384-2 00:06:24.783 --> 00:06:25.933 drop measured in this way. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1386-0 00:06:27.123 --> 00:06:27.493 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1405-0 00:06:27.783 --> 00:06:30.802 And so another challenge when you're actually trying to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1405-1 00:06:30.802 --> 00:06:32.473 measure earthquake stress drop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1428-0 00:06:32.623 --> 00:06:36.359 Is that what you really want is the spectrum the frequency 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1428-1 00:06:36.359 --> 00:06:40.033 content of the earthquake as it leaves the source itself? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1456-0 00:06:40.043 --> 00:06:43.269 But of course what you have is a collection of seismometers at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1456-1 00:06:43.269 --> 00:06:46.393 the surface, or, if you're very lucky, you're in a borehole. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1497-0 00:06:46.483 --> 00:06:49.601 But in any case, what you need to do is you need to take the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1497-1 00:06:49.601 --> 00:06:52.771 observed spectrum which you can measure from a seismogram and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1497-2 00:06:52.771 --> 00:06:55.634 try to correct it in some way for path effects and side 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1497-3 00:06:55.634 --> 00:06:56.043 effects. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1519-0 00:06:56.743 --> 00:07:00.274 And so there's a bunch of different frameworks that have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1519-1 00:07:00.274 --> 00:07:03.123 been used to to to try to solve this problem. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1561-0 00:07:03.433 --> 00:07:06.514 If you happen to have a setup where you have many, many 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1561-1 00:07:06.514 --> 00:07:09.760 earthquakes, you're analyzing many, many stations that are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1561-2 00:07:09.760 --> 00:07:13.282 recording this earthquake, then you can actually set this up as 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1561-3 00:07:13.282 --> 00:07:15.923 an inverse problem in the log frequency domain. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1614-0 00:07:16.433 --> 00:07:19.729 The advantage of working in the log frequency domain is that it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1614-1 00:07:19.729 --> 00:07:22.975 actually ends up being a linear problem where you can say that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1614-2 00:07:22.975 --> 00:07:26.065 at any frequency point, the observed spectrum is a sum of a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1614-3 00:07:26.065 --> 00:07:29.053 source term and the site term and some sort of path term. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1625-0 00:07:29.163 --> 00:07:31.852 And if you parameterize these appropriately, you can actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1625-1 00:07:31.852 --> 00:07:32.373 try to, umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1635-0 00:07:32.383 --> 00:07:35.993 Solve for each of these terms in isolation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-0 00:07:36.523 --> 00:07:39.900 That would make up the observed Spectra, and so there's a few 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-1 00:07:39.900 --> 00:07:42.896 different methods that have been developed under these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-2 00:07:42.896 --> 00:07:46.382 assumptions this this method is very powerful because it allows 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-3 00:07:46.382 --> 00:07:49.705 you to kind of separate the relative contributions of paths, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-4 00:07:49.705 --> 00:07:53.137 site and source, but it also has limitations in the sense that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-5 00:07:53.137 --> 00:07:56.242 because you can really only effectively isolate relative 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-6 00:07:56.242 --> 00:07:59.619 contributions, you have to make some additional assumption to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-7 00:07:59.619 --> 00:08:02.997 try to break it and get some sort of absolute source spectrum 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-8 00:08:02.997 --> 00:08:06.156 out of it that you could compare, for example, to a broom 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1735-9 00:08:06.156 --> 00:08:06.483 model. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1749-0 00:08:06.813 --> 00:08:10.736 And so different formulations of this framework make different 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1749-1 00:08:10.736 --> 00:08:11.483 assumptions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1793-0 00:08:11.973 --> 00:08:15.438 The approach that I've used is called spectral decomposition, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1793-1 00:08:15.438 --> 00:08:19.014 which is rooms that on average there's some sort of brune light 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1793-2 00:08:19.014 --> 00:08:22.647 spectrum that you can try to tie an absolute value to to extract 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1793-3 00:08:22.647 --> 00:08:23.653 the source itself. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1825-0 00:08:24.613 --> 00:08:28.241 Umm, but in any case, regardless of that method's limitations, it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1825-1 00:08:28.241 --> 00:08:30.989 can be useful for studying relative variations in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1825-2 00:08:30.989 --> 00:08:32.583 earthquake source parameters. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1844-0 00:08:32.953 --> 00:08:35.224 And so there's been a few different studies looking at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1844-1 00:08:35.224 --> 00:08:37.123 essentially spatial patterns and earthquakes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1884-0 00:08:37.133 --> 00:08:41.021 Stress drop and so these are just a couple of examples from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1884-1 00:08:41.021 --> 00:08:45.168 my work looking at earthquakes in Ridgecrest and earthquakes in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1884-2 00:08:45.168 --> 00:08:48.732 West TX and these maps, earthquakes are color coded by 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1884-3 00:08:48.732 --> 00:08:49.963 their stress drops. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-0 00:08:49.973 --> 00:08:54.000 So the bluer colors are the high frequency, higher stress drop 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-1 00:08:54.000 --> 00:08:57.963 events, and the red colors are the lower frequency low stress 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-2 00:08:57.963 --> 00:09:02.054 drop events and you can see by either of these kind of coherent 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-3 00:09:02.054 --> 00:09:05.953 spatial patterns in earthquake source properties, both along 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-4 00:09:05.953 --> 00:09:09.916 the Ridgecrest rupture zone and also within the Permian Basin 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1958-5 00:09:09.916 --> 00:09:10.683 and West TX. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1988-0 00:09:11.103 --> 00:09:14.390 And so you can kind of see by eye these spatial patterns, but 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1988-1 00:09:14.390 --> 00:09:17.571 we really are struggling with trying to understand what the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/1988-2 00:09:17.571 --> 00:09:18.313 patterns mean. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2023-0 00:09:18.323 --> 00:09:21.597 And a big part of that is that there's just a whole lot of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2023-1 00:09:21.597 --> 00:09:25.148 scatter in the earthquake source that's coming from uncertainty 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2023-2 00:09:25.148 --> 00:09:27.423 and all the assumptions that we've made. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2047-0 00:09:27.593 --> 00:09:31.204 So if you think about all the assumptions that go into making 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2047-1 00:09:31.204 --> 00:09:34.583 this type of measurement, you're taking some raw Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2063-0 00:09:34.893 --> 00:09:37.711 You're associating with some Brune model for a circular 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2063-1 00:09:37.711 --> 00:09:39.573 crack, which may not be appropriate. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2075-0 00:09:39.643 --> 00:09:41.843 You're assuming some sort of rupture velocity. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2109-0 00:09:41.953 --> 00:09:44.992 You're neglecting trade offs between, you know, high 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2109-1 00:09:44.992 --> 00:09:48.261 frequency fall off rate and corner frequency and so it's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2109-2 00:09:48.261 --> 00:09:51.243 really hard to put an error bar on a map like this. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2148-0 00:09:52.233 --> 00:09:56.003 And so that's the motivation for some of the work that I'm trying 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2148-1 00:09:56.003 --> 00:09:59.316 to present today is to try to try to develop new and more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2148-2 00:09:59.316 --> 00:10:02.286 robust methods for characterizing earthquake source 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2148-3 00:10:02.286 --> 00:10:02.743 Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2178-0 00:10:03.093 --> 00:10:06.060 And so the the classical spectral inversion methods are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2178-1 00:10:06.060 --> 00:10:09.239 really nice for looking at spatial variations in earthquake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2178-2 00:10:09.239 --> 00:10:10.193 source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2198-0 00:10:10.203 --> 00:10:12.700 But to really understand what they mean, you really have to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2198-1 00:10:12.700 --> 00:10:14.573 have a handle on what the uncertainties are. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2226-0 00:10:14.933 --> 00:10:18.440 And so the method I'm gonna describe a little bit today is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2226-1 00:10:18.440 --> 00:10:21.887 applying Bayesian inference to try to better characterize 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2226-2 00:10:21.887 --> 00:10:23.433 earthquake source Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-0 00:10:23.803 --> 00:10:26.744 And so the advantage of a Bayesian inversion is that it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-1 00:10:26.744 --> 00:10:29.842 allows you to more rigorously quantify uncertainty, and it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-2 00:10:29.842 --> 00:10:33.098 also allows you to encode some of the physical knowledge that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-3 00:10:33.098 --> 00:10:35.934 we have about earthquake properties directly into the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-4 00:10:35.934 --> 00:10:38.665 spectral inversion, which has some nice stabilizing 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-5 00:10:38.665 --> 00:10:41.763 properties, and so one of the limitations of this Bayesian 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-6 00:10:41.763 --> 00:10:44.809 paradigm is that it's more computationally intensive, but 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-7 00:10:44.809 --> 00:10:48.012 it actually happens to be, at least for this problem, pretty 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2309-8 00:10:48.012 --> 00:10:49.693 tractable with modern computers. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2338-0 00:10:49.823 --> 00:10:52.617 And there's a lot of new open source software packages that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2338-1 00:10:52.617 --> 00:10:55.505 have been developed that you can kind of adapt to solve these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2338-2 00:10:55.505 --> 00:10:56.343 types of problems. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2361-0 00:10:57.813 --> 00:11:01.365 And so the Bayesian inference paradigm, as applied to the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2361-1 00:11:01.365 --> 00:11:04.672 earthquake source spectral problem is actually pretty 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2361-2 00:11:04.672 --> 00:11:06.203 similar to other methods. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-0 00:11:06.613 --> 00:11:10.153 The only real difference is that instead of trying to solve for a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-1 00:11:10.153 --> 00:11:13.157 single best model like the optimal corner frequency for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-2 00:11:13.157 --> 00:11:16.376 event, you're essentially trying to solve for a probability 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-3 00:11:16.376 --> 00:11:19.488 distribution of all possible earthquake source parameters 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-4 00:11:19.488 --> 00:11:22.814 that are consistent both with the data itself and your priors 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-5 00:11:22.814 --> 00:11:26.354 for physical knowledge of what a reasonable corner frequency, for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-6 00:11:26.354 --> 00:11:29.680 example, or moment for example would be for the earthquake in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2441-7 00:11:29.680 --> 00:11:30.163 question. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2492-0 00:11:32.253 --> 00:11:36.039 And so, as this was a UM, the project that I'm going to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2492-1 00:11:36.039 --> 00:11:40.162 describe was supported by Skype, it was something of a pilot 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2492-2 00:11:40.162 --> 00:11:44.557 study to really try to test and demonstrate this methodology for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2492-3 00:11:44.557 --> 00:11:48.613 a suite of 14 magnitude 5 target earthquakes in California. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2509-0 00:11:48.903 --> 00:11:53.113 So these are basically all of the prominent events of similar 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2509-1 00:11:53.113 --> 00:11:53.453 size. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2532-0 00:11:53.463 --> 00:11:57.071 So magnitude 5 in this case over the past 15 years or so in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2532-1 00:11:57.071 --> 00:11:57.733 California. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2559-0 00:11:57.743 --> 00:12:01.056 So we've got a nice range of events all the way from the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2559-1 00:12:01.056 --> 00:12:04.253 Salton through in the Sanya Scinto around Los Angeles. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2574-0 00:12:04.263 --> 00:12:07.416 And then we had some several magnitude fives here in the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2574-1 00:12:07.416 --> 00:12:08.523 Ridgecrest sequence. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2618-0 00:12:08.533 --> 00:12:12.559 And then the furthest N event was the Lone Pine event, and the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2618-1 00:12:12.559 --> 00:12:16.521 idea is to try to develop this methodology for doing Bayesian 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2618-2 00:12:16.521 --> 00:12:20.420 source spectral inference and look at regional variations in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2618-3 00:12:20.420 --> 00:12:22.273 earthquake source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2669-0 00:12:22.283 --> 00:12:25.234 Obviously you know with 14 events you should be careful 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2669-1 00:12:25.234 --> 00:12:28.502 with any sort of claims about the statistical significance of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2669-2 00:12:28.502 --> 00:12:31.875 the regional variations, but it is an interesting testing suite 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2669-3 00:12:31.875 --> 00:12:35.195 to try to understand what are the strengths and limitations of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2669-4 00:12:35.195 --> 00:12:35.933 this approach. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2687-0 00:12:37.873 --> 00:12:42.055 And so the workflow here is actually not so different from a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2687-1 00:12:42.055 --> 00:12:44.523 classical spectral analysis really. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2702-0 00:12:44.533 --> 00:12:47.331 Still, the hardest part is trying to assemble and quality 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2702-1 00:12:47.331 --> 00:12:48.103 quality control. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2729-0 00:12:48.113 --> 00:12:51.708 The data sets that you're gonna use, and so you have to get the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2729-1 00:12:51.708 --> 00:12:54.741 waveform data you have to measure the Spectra in this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2729-2 00:12:54.741 --> 00:12:55.303 framework. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2751-0 00:12:55.313 --> 00:12:58.471 I'm actually using an empirical greens function approach to try 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2751-1 00:12:58.471 --> 00:12:59.803 to correct for attenuation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2777-0 00:12:59.813 --> 00:13:03.269 So the idea with that approach is that I'm finding nearby 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2777-1 00:13:03.269 --> 00:13:06.845 earthquakes that are smaller than the target event that are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2777-2 00:13:06.845 --> 00:13:07.203 share. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2818-0 00:13:07.453 --> 00:13:10.867 So the same kind of source mechanism and share essentially 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2818-1 00:13:10.867 --> 00:13:14.629 the same location, and the idea is that they they can be used to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2818-2 00:13:14.629 --> 00:13:18.217 try to correct for path and side effects instead of trying to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2818-3 00:13:18.217 --> 00:13:19.433 directly model those. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2847-0 00:13:20.463 --> 00:13:24.135 But in any case, this step one is common to all sorts, all 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2847-1 00:13:24.135 --> 00:13:27.932 sorts of spectral inference studies, and it's the one that's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2847-2 00:13:27.932 --> 00:13:29.613 still the most challenging. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2858-0 00:13:29.983 --> 00:13:32.543 But the nice thing is that this is still the hardest one. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2874-0 00:13:32.553 --> 00:13:34.531 So you don't have to change anything from your Rook 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2874-1 00:13:34.531 --> 00:13:34.873 workflow. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2908-0 00:13:35.203 --> 00:13:38.079 The new stuff that you are gonna have to do is try to think about 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2908-1 00:13:38.079 --> 00:13:40.388 what our realistic prior distributions for the model 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2908-2 00:13:40.388 --> 00:13:41.783 parameters you're interested in. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2933-0 00:13:42.373 --> 00:13:46.637 In this case, umm, I'm trying to actually solve jointly for uh 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2933-1 00:13:46.637 --> 00:13:50.563 corner frequency, moment and high frequency falloff rate. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2967-0 00:13:50.913 --> 00:13:53.837 Trying to do that kind of joint inversion is really only gonna 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2967-1 00:13:53.837 --> 00:13:56.530 work in areas that you have a whole lot of data to try to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2967-2 00:13:56.530 --> 00:13:57.783 constrain those parameters. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2998-0 00:13:58.193 --> 00:14:01.260 But in Southern California, we do have good station coverage 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2998-1 00:14:01.260 --> 00:14:04.177 and we also have additional information about the size of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/2998-2 00:14:04.177 --> 00:14:06.943 earthquakes from things like moment tensor inversions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3025-0 00:14:07.193 --> 00:14:10.280 We have information about fault geometry from things like focal 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3025-1 00:14:10.280 --> 00:14:13.222 mechanisms, so we can actually try to apply that directly to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3025-2 00:14:13.222 --> 00:14:14.283 our inference problem. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3056-0 00:14:15.853 --> 00:14:19.779 And so, once you've decided on prior distributions, the package 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3056-1 00:14:19.779 --> 00:14:23.644 that I use is an open source one that's implemented in Python, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3056-2 00:14:23.644 --> 00:14:24.503 called Pyodbc. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3081-0 00:14:25.313 --> 00:14:28.536 The details of it are not too important, but basically this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3081-1 00:14:28.536 --> 00:14:31.168 pimc package is developed completely agnostic of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3081-2 00:14:31.168 --> 00:14:32.243 earthquake sciences. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3148-0 00:14:32.253 --> 00:14:35.142 Definitely not developed for earthquake science, but it's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3148-1 00:14:35.142 --> 00:14:38.229 actually pretty easy to convert your data into a format where 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3148-2 00:14:38.229 --> 00:14:41.367 you can actually run these codes and they take care of all the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3148-3 00:14:41.367 --> 00:14:44.555 tricky parts for you in terms of doing actually a sampling of a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3148-4 00:14:44.555 --> 00:14:47.593 high dimensional space in a umm and a reasonable time frame. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3163-0 00:14:47.603 --> 00:14:51.033 So actually you can run these types of models on your laptop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3216-0 00:14:51.103 --> 00:14:54.233 It's not gonna give you the answer in one second, but you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3216-1 00:14:54.233 --> 00:14:57.364 could run it and I think a lot of the problems that I was 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3216-2 00:14:57.364 --> 00:15:00.494 working on were giving me answers within anywhere between 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3216-3 00:15:00.494 --> 00:15:04.003 10 minutes or a couple of hours, depending on the data set size. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3240-0 00:15:04.613 --> 00:15:07.827 And so the idea with this project was that for all the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3240-1 00:15:07.827 --> 00:15:10.633 events, so both the egfs and the target events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3262-0 00:15:10.643 --> 00:15:13.818 I'm trying to understand their source properties so things like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3262-1 00:15:13.818 --> 00:15:17.093 corner frequency, high frequency falloff rate and seismic moment. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3283-0 00:15:17.663 --> 00:15:20.639 And then for the target events only, because those are the ones 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3283-1 00:15:20.639 --> 00:15:22.453 that have the best azimuthal coverage. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3295-0 00:15:22.613 --> 00:15:25.443 I'm gonna try to learn something about directivity from the data. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3307-0 00:15:25.453 --> 00:15:28.343 And so we'll talk more about that framework in a few slides. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3309-0 00:15:29.483 --> 00:15:29.803 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3342-0 00:15:30.023 --> 00:15:34.122 And so this is just an example of what the algorithm did does 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3342-1 00:15:34.122 --> 00:15:38.154 here I'm showing I'm spectral ratios of a single magnitude 5 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3342-2 00:15:38.154 --> 00:15:40.733 target events with twelve of the eggs. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3363-0 00:15:40.743 --> 00:15:43.799 So these are basically 12 nearby earthquakes that are much 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3363-1 00:15:43.799 --> 00:15:45.353 smaller than the target event. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3380-0 00:15:45.783 --> 00:15:49.028 In this case, the because the target events are relatively 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3380-1 00:15:49.028 --> 00:15:50.733 large, they're all magnitude 5. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3403-0 00:15:50.823 --> 00:15:53.815 You can actually get eggs that are also relatively large, which 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3403-1 00:15:53.815 --> 00:15:56.433 has the advantage that they have really good bandwidth. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3451-0 00:15:57.023 --> 00:16:01.650 Good signal to noise across a wide range of bandwidth, and so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3451-1 00:16:01.650 --> 00:16:06.351 basically the black lines are data from different stations for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3451-2 00:16:06.351 --> 00:16:11.202 each EGF, and the red lines are the model predictions and corner 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3451-3 00:16:11.202 --> 00:16:13.963 frequencies are marked in blue here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3465-0 00:16:14.193 --> 00:16:16.433 So you can see that the algorithm is basically working. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3484-0 00:16:16.443 --> 00:16:19.691 The predictions are lining up pretty well with the data, so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3484-1 00:16:19.691 --> 00:16:21.423 it's always a good sanity check. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3494-0 00:16:21.473 --> 00:16:23.623 You don't wanna just look at the results. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3552-0 00:16:23.633 --> 00:16:26.717 You wanna make sure it actually seems to match the data, but of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3552-1 00:16:26.717 --> 00:16:29.802 course what's still missing from this plot is uncertainties and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3552-2 00:16:29.802 --> 00:16:32.549 so and really trying to understand the uncertainties and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3552-3 00:16:32.549 --> 00:16:35.345 the trade offs between all these parameters is really the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3552-4 00:16:35.345 --> 00:16:37.803 important part of running the Bayesian inversions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3571-0 00:16:39.223 --> 00:16:42.114 And so to do that, it helps to just kind of zoom in and look at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3571-1 00:16:42.114 --> 00:16:42.973 a few case studies. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3581-0 00:16:43.363 --> 00:16:47.074 This is an example where I'm plotting essentially parameter 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3581-1 00:16:47.074 --> 00:16:47.693 tradeoffs. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3605-0 00:16:47.703 --> 00:16:51.201 These are basically what are called samples from the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3605-1 00:16:51.201 --> 00:16:55.293 posterior distribution of a main shock and three of its egfs. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3618-0 00:16:55.643 --> 00:16:58.633 So what I'm plotting here is the high frequency falloff rate. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3640-0 00:16:58.643 --> 00:17:02.514 So basically, how steep the Spectra is at high frequencies 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3640-1 00:17:02.514 --> 00:17:05.073 versus corner frequency on the X axis? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3664-0 00:17:05.083 --> 00:17:08.591 And so these are basically parameter tradeoffs for the main 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3664-1 00:17:08.591 --> 00:17:11.223 shock at the top left and three of its egfs. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3675-0 00:17:11.723 --> 00:17:13.663 And So what you'll notice a few things. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3688-0 00:17:13.953 --> 00:17:17.674 The colored dots here are the actual samples from the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3688-1 00:17:17.674 --> 00:17:18.363 posterior. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3718-0 00:17:18.813 --> 00:17:22.737 The contours here are basically quantiles that are sampled from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3718-1 00:17:22.737 --> 00:17:26.477 the priors, and So what you'll notice is that the main shock 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3718-2 00:17:26.477 --> 00:17:29.543 the parameters are actually pretty well resolved. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3738-0 00:17:29.773 --> 00:17:33.093 The reason for that is that I have a whole lot of data to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3738-1 00:17:33.093 --> 00:17:34.353 study this earthquake. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3782-0 00:17:34.363 --> 00:17:37.866 I'm actually using 262 spectral ratios, which is rather a lot to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3782-1 00:17:37.866 --> 00:17:41.314 try to measure corner frequency and high frequency falloff rate 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3782-2 00:17:41.314 --> 00:17:44.656 for some of the empirical greens functions you actually don't 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3782-3 00:17:44.656 --> 00:17:46.003 have a whole lot of data. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3806-0 00:17:46.013 --> 00:17:49.282 You may be only have a few stations that meet your signal 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3806-1 00:17:49.282 --> 00:17:52.888 to noise criteria, and so that's why the uncertainties are much 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3806-2 00:17:52.888 --> 00:17:53.283 larger. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3819-0 00:17:53.293 --> 00:17:56.009 So there's this correspondence between uncertainty and data 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3819-1 00:17:56.009 --> 00:17:57.593 volume, which is rather intuitive. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3868-0 00:17:58.713 --> 00:18:02.833 The other thing that's useful to understand from these plots is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3868-1 00:18:02.833 --> 00:18:06.761 that all of these trade off curves are essentially tilted up 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3868-2 00:18:06.761 --> 00:18:10.688 and right, and So what that means is that there's a tradeoff 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3868-3 00:18:10.688 --> 00:18:14.229 between the high frequency falloff rate and the corner 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3868-4 00:18:14.229 --> 00:18:14.873 frequency. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3894-0 00:18:14.963 --> 00:18:17.847 And so if there were no trade off, what you'd see is basically 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3894-1 00:18:17.847 --> 00:18:20.273 a circle like the prior distribution that I'm using. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3912-0 00:18:20.283 --> 00:18:23.423 Is that there is no tradeoff between corner frequency and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3912-1 00:18:23.423 --> 00:18:24.993 high frequency fall off rate. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3928-0 00:18:25.203 --> 00:18:29.023 You can see that especially for these well resolved events, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3928-1 00:18:29.023 --> 00:18:30.933 there's a positive slope here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3959-0 00:18:30.943 --> 00:18:34.314 And so that means that if you fix the high frequency falloff 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3959-1 00:18:34.314 --> 00:18:37.795 rate to a given value, you'll get a different corner frequency 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3959-2 00:18:37.795 --> 00:18:39.453 than if you let it float free. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3999-0 00:18:39.463 --> 00:18:42.637 So that's an important intuition to build up, because that will 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3999-1 00:18:42.637 --> 00:18:45.860 mean that different people that make different assumptions about 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3999-2 00:18:45.860 --> 00:18:49.133 high frequency falloff rate will inevitably get different answers 8ca14bac-4f56-40c1-9c1a-c4d258076e65/3999-3 00:18:49.133 --> 00:18:50.423 in their corner frequency. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4006-0 00:18:50.433 --> 00:18:52.473 And they also get different measures of uncertainty. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4042-0 00:18:53.843 --> 00:18:57.177 Umm, so that's kind of a dive into the statistics, but what 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4042-1 00:18:57.177 --> 00:19:00.288 we're interested in most is, umm, if there are regional 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4042-2 00:19:00.288 --> 00:19:02.733 variations in earthquake source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4054-0 00:19:03.063 --> 00:19:05.453 And so that's what I'm trying to plot in this map. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4079-0 00:19:05.463 --> 00:19:08.474 Again, we have to acknowledge that the sample size is very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4079-1 00:19:08.474 --> 00:19:11.587 small, but here I'm color coding earthquakes by their stress 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4079-2 00:19:11.587 --> 00:19:11.893 drops. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4092-0 00:19:11.903 --> 00:19:14.613 So the darker red colors are low stress drop events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4142-0 00:19:14.623 --> 00:19:17.972 The blue colors are high stress drop events and you can see that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4142-1 00:19:17.972 --> 00:19:21.166 at least in this small sample size, there are pretty coherent 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4142-2 00:19:21.166 --> 00:19:24.411 spatial patterns and the salt and through we've got these very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4142-3 00:19:24.411 --> 00:19:26.833 low stress drop events, San Jacinto and below. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4159-0 00:19:26.843 --> 00:19:30.630 Los Angeles high stress drop events and Ridgecrest is kind of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4159-1 00:19:30.630 --> 00:19:31.913 somewhere in between. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4205-0 00:19:32.763 --> 00:19:36.531 The other thing again, it's a small sample size, but we can 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4205-1 00:19:36.531 --> 00:19:40.111 plot earthquake stress drop versus depth and you can see 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4205-2 00:19:40.111 --> 00:19:44.005 there's a trend for the higher stress drop events to occur at 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4205-3 00:19:44.005 --> 00:19:45.073 at larger depths. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-0 00:19:45.083 --> 00:19:48.395 So further on this plot, and that's true independent of study 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-1 00:19:48.395 --> 00:19:51.707 region, it's not just because these guys happen to be shallow 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-2 00:19:51.707 --> 00:19:55.019 events, but even if you look within a given study region, the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-3 00:19:55.019 --> 00:19:58.224 earthquake that's added a deeper depth like the Chino Hills 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-4 00:19:58.224 --> 00:20:01.215 earthquake is tends to have a higher stress drop than a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4272-5 00:20:01.215 --> 00:20:03.833 shallower earthquake like the Hopper earthquake. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4295-0 00:20:05.933 --> 00:20:08.809 Umm interestingly, we can actually compare this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4295-1 00:20:08.809 --> 00:20:12.344 methodology which I developed to other studies in Southern 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4295-2 00:20:12.344 --> 00:20:13.003 California. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4341-0 00:20:13.013 --> 00:20:16.710 You can see the spatial patterns are actually pretty similar, so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4341-1 00:20:16.710 --> 00:20:20.010 this is my study on the left and this is a study that was 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4341-2 00:20:20.010 --> 00:20:23.536 actually being done at the same time by Peter Shearer using a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4341-3 00:20:23.536 --> 00:20:25.243 completely different data set. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4348-0 00:20:25.253 --> 00:20:27.223 So I was focusing on swaves. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4355-0 00:20:27.333 --> 00:20:28.783 He was looking at P waves. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4362-0 00:20:29.213 --> 00:20:30.403 I was looking at big events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4369-0 00:20:30.413 --> 00:20:31.763 He was looking at small events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4377-0 00:20:32.293 --> 00:20:33.743 I was looking at very few events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4399-0 00:20:33.753 --> 00:20:35.820 He was looking at very many events and you can actually see 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4399-1 00:20:35.820 --> 00:20:37.233 the spatial patterns are pretty similar. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4415-0 00:20:37.663 --> 00:20:40.793 You have the low stress drop events in the Imperial Valley. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4441-0 00:20:40.803 --> 00:20:44.787 High stress drop events along the San Jacinto and Ridgecrest 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4441-1 00:20:44.787 --> 00:20:48.770 is kind of halfway in between, so that's encouraging, but it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4441-2 00:20:48.770 --> 00:20:49.293 doesn't. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4446-0 00:20:49.653 --> 00:20:50.633 You know it's. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4467-0 00:20:50.673 --> 00:20:53.192 I think there's still more work to be done to try to understand 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4467-1 00:20:53.192 --> 00:20:55.121 the relationship and the differences between the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4467-2 00:20:55.121 --> 00:20:55.593 methodology. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4492-0 00:20:56.683 --> 00:21:00.161 Umm, so one advantage of working with these really large events 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4492-1 00:21:00.161 --> 00:21:03.313 is that we can try to understand umm directivity effects. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4508-0 00:21:03.323 --> 00:21:06.779 And so we know it's been known for a very long time that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4508-1 00:21:06.779 --> 00:21:08.053 ruptured directivity. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4537-0 00:21:08.063 --> 00:21:11.547 So essentially, the direction the rupture propagates from the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4537-1 00:21:11.547 --> 00:21:15.199 upper center to wherever it ends up gives rise to a Doppler like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4537-2 00:21:15.199 --> 00:21:16.773 effect on the ground motion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4569-0 00:21:16.783 --> 00:21:19.532 So in essence, the sites and the forward rupture direction, the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4569-1 00:21:19.532 --> 00:21:22.280 ground motion piles up and you end up with larger ground motion 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4569-2 00:21:22.280 --> 00:21:22.753 amplitudes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4579-0 00:21:23.263 --> 00:21:25.494 The sites in the backward direction have the opposite 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4579-1 00:21:25.494 --> 00:21:25.783 effect. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4621-0 00:21:25.793 --> 00:21:28.910 You end up with lower ground motion amplitudes and so this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4621-1 00:21:28.910 --> 00:21:32.397 has been studying a whole lot in the time domain, but the effects 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4621-2 00:21:32.397 --> 00:21:35.515 of rupture directivity on Spectra is actually a little bit 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4621-3 00:21:35.515 --> 00:21:36.413 more complicated. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-0 00:21:36.683 --> 00:21:40.545 And so here I'm gonna try to use the same Bayesian framework to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-1 00:21:40.545 --> 00:21:44.046 try to measure directivity parameters and uncertainty and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-2 00:21:44.046 --> 00:21:47.606 focus mostly on the target events because we have a lot of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-3 00:21:47.606 --> 00:21:51.348 egfs and a lot of good azimuthal coverage to try to solve for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-4 00:21:51.348 --> 00:21:54.849 this problem, I'm so the mathematical formulation of this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-5 00:21:54.849 --> 00:21:58.651 is actually pretty complicated, and I'm gonna skip the details 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4692-6 00:21:58.651 --> 00:21:59.013 today. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4757-0 00:21:59.023 --> 00:22:02.903 It's kind of provided in the papers if you're interested in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4757-1 00:22:02.903 --> 00:22:06.849 and it, but the basic idea is that if you in the presence of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4757-2 00:22:06.849 --> 00:22:11.117 rupture, directivity, it's gonna basically impose a modulation on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4757-3 00:22:11.117 --> 00:22:15.062 the corner frequency that's gonna depend on the direction of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4757-4 00:22:15.062 --> 00:22:18.943 the rupture and the azimuth from the source to the station. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4805-0 00:22:19.873 --> 00:22:23.008 And So what I'm trying to do with this, I'm Bayesian 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4805-1 00:22:23.008 --> 00:22:26.795 inference, is try to solve for this parameter that's called the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4805-2 00:22:26.795 --> 00:22:30.226 directivity ratio and it's basically a normalized measure 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4805-3 00:22:30.226 --> 00:22:33.953 that quantifies the strength and style of rupture directivity. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4840-0 00:22:33.963 --> 00:22:37.968 So it's a value between minus one and one where 0 corresponds 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4840-1 00:22:37.968 --> 00:22:42.038 to a bilateral event and then plus and minus one correspond to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4840-2 00:22:42.038 --> 00:22:45.333 unilateral ruptures in One Direction or the other. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4871-0 00:22:45.803 --> 00:22:48.640 And so we can actually use if we have prior knowledge of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4871-1 00:22:48.640 --> 00:22:51.430 actual fault geometry from a moment tensor, we can actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4871-2 00:22:51.430 --> 00:22:53.383 use that to help stabilize the inversion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4875-0 00:22:53.873 --> 00:22:54.103 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-0 00:22:54.113 --> 00:22:57.843 If not, you can kind of let the algorithm run free and hope it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-1 00:22:57.843 --> 00:23:01.573 finds a a directive direction, but it it tends to be, at least 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-2 00:23:01.573 --> 00:23:05.185 in my experience, much more stable if you have the the fault 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-3 00:23:05.185 --> 00:23:08.619 geometry specified a priority, but the basic idea is that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-4 00:23:08.619 --> 00:23:12.112 there's kind of the mathematical relationship between this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-5 00:23:12.112 --> 00:23:15.665 directivity of parameter and the perturbation to the corner 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4946-6 00:23:15.665 --> 00:23:17.323 frequency that you'd expect. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4981-0 00:23:17.333 --> 00:23:20.785 And so if you have this chart that I've made here is basically 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4981-1 00:23:20.785 --> 00:23:24.182 showing that if you've got a strong unilateral rupture that's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4981-2 00:23:24.182 --> 00:23:27.195 gonna make an elevated corner frequency in the forward 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4981-3 00:23:27.195 --> 00:23:27.743 direction. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4984-0 00:23:29.693 --> 00:23:30.023 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4993-0 00:23:30.033 --> 00:23:31.643 And so this is what it looks like. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/4997-0 00:23:31.653 --> 00:23:31.903 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5003-0 00:23:31.913 --> 00:23:32.943 In the data space. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5015-0 00:23:32.953 --> 00:23:36.233 So this is an example taken from the southern San Jacinto Fault. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5026-0 00:23:37.623 --> 00:23:41.073 I actually just this any scinto fault in Southern California. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5049-0 00:23:41.403 --> 00:23:45.416 This is a 2016 Borrego Springs earthquake and in this case this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5049-1 00:23:45.416 --> 00:23:46.733 is what I'm plotting. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5059-0 00:23:46.743 --> 00:23:49.093 Here is basically what the models decided. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-0 00:23:49.323 --> 00:23:52.770 Directivity is in this case I'm plotting essentially the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-1 00:23:52.770 --> 00:23:56.037 perturbation to the corner frequency as a function of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-2 00:23:56.037 --> 00:23:59.363 azimuth and take off angle and so you can see that the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-3 00:23:59.363 --> 00:24:03.295 inference is that the earthquake is propagating in the northwest 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-4 00:24:03.295 --> 00:24:06.259 direction, and so we can actually map this model 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-5 00:24:06.259 --> 00:24:09.827 prediction back into the data space and what you'll see is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5131-6 00:24:09.827 --> 00:24:11.763 this strong gradient in Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5182-0 00:24:11.773 --> 00:24:15.784 So essentially the way to read this is that the earthquake, the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5182-1 00:24:15.784 --> 00:24:19.230 stations that are in the Northwest are colored in red, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5182-2 00:24:19.230 --> 00:24:23.241 and the stations that are in the Southeast are colored in blue, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5182-3 00:24:23.241 --> 00:24:26.563 and you can see this gradient from from high to low. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5198-0 00:24:26.573 --> 00:24:30.154 And that's basically what a classic unilateral rupture will 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5198-1 00:24:30.154 --> 00:24:32.243 look like in the frequency domain. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5226-0 00:24:32.253 --> 00:24:34.967 So basically our algorithm is kind of hunting for for this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5226-1 00:24:34.967 --> 00:24:37.911 type of signal and it's trying to decide whether it's seeing it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5226-2 00:24:37.911 --> 00:24:38.233 or not. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5256-0 00:24:39.183 --> 00:24:42.898 So we can repeat this exercise for all the earthquakes in our 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5256-1 00:24:42.898 --> 00:24:46.374 study region, and here I've plotted them up where the red 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5256-2 00:24:46.374 --> 00:24:47.333 earthquakes are. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5303-0 00:24:47.403 --> 00:24:50.266 Essentially, the algorithm has decided they're unilateral and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5303-1 00:24:50.266 --> 00:24:53.222 I'm trying to plot the direction where it thinks they're going, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5303-2 00:24:53.222 --> 00:24:56.085 and the blue earthquakes are bilateral, and so again, this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5303-3 00:24:56.085 --> 00:24:58.717 a very small sample size, but there are some interesting 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5303-4 00:24:58.717 --> 00:24:59.133 patterns. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5338-0 00:24:59.503 --> 00:25:02.733 Most of the bilateral events that we're seeing are in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5338-1 00:25:02.733 --> 00:25:05.903 Northern California, all the ones in the in Southern 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5338-2 00:25:05.903 --> 00:25:09.073 California that I measured were unilateral ruptures. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5368-0 00:25:09.643 --> 00:25:12.313 Interestingly, we've got three along this, so the San Jacinto 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5368-1 00:25:12.313 --> 00:25:14.940 Fault and two of them are going in One Direction, and one of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5368-2 00:25:14.940 --> 00:25:16.533 them's going in the other direction. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5378-0 00:25:16.543 --> 00:25:18.573 So it's not a very consistent pattern. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5416-0 00:25:18.583 --> 00:25:21.709 I think you really need a much larger sample size to make any 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5416-1 00:25:21.709 --> 00:25:24.634 claim, but it does seem, at least in this data set, about 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5416-2 00:25:24.634 --> 00:25:27.559 80% of the earthquake showed clear unilateral directivity 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5416-3 00:25:27.559 --> 00:25:27.963 signals. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-0 00:25:29.653 --> 00:25:32.506 Umm you can also look at the relationship between the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-1 00:25:32.506 --> 00:25:35.253 aftershock patterns and directivity, and so this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-2 00:25:35.253 --> 00:25:37.895 basically 4 examples of unilateral earthquakes in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-3 00:25:37.895 --> 00:25:41.170 Southern California where I'm plotting the ruptured direction 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-4 00:25:41.170 --> 00:25:44.657 and then the small dots that you see are basically the aftershock 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-5 00:25:44.657 --> 00:25:47.933 patterns, and you can see that in these cases, the aftershock 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5492-6 00:25:47.933 --> 00:25:51.103 seemed to be concentrated in the forward rupture direction. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5513-0 00:25:51.253 --> 00:25:54.219 There's a few different reasons why this might be the kind of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5513-1 00:25:54.219 --> 00:25:55.703 the more exciting one would be. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5524-0 00:25:55.713 --> 00:25:58.263 This is some sort of evidence for dynamic triggering. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5558-0 00:25:58.273 --> 00:26:01.512 We'd expect that for a a directive rupture, we'd have an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5558-1 00:26:01.512 --> 00:26:04.979 enhanced dynamic stresses in a forward direction which could 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5558-2 00:26:04.979 --> 00:26:07.253 cause more aftershocks to be triggered. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5612-0 00:26:07.983 --> 00:26:10.751 But this could also be just simply a finite fault effect if 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5612-1 00:26:10.751 --> 00:26:13.334 you have a long earthquake rupture and it starts in one 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5612-2 00:26:13.334 --> 00:26:16.240 place and ends up in the other and you trigger aftershocks all 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5612-3 00:26:16.240 --> 00:26:18.824 along the rupture plane, then you'd expect this type of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5612-4 00:26:18.824 --> 00:26:19.193 pattern. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5657-0 00:26:19.643 --> 00:26:22.572 So I think there's more work to be done to try to understand if 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5657-1 00:26:22.572 --> 00:26:25.363 this is meaningful or not, but it is interesting to consider 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5657-2 00:26:25.363 --> 00:26:28.384 whether directivity effects like this are important to understand 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5657-3 00:26:28.384 --> 00:26:30.443 and model in resolving triggering processes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5659-0 00:26:31.703 --> 00:26:32.163 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5673-0 00:26:32.423 --> 00:26:35.433 And so it's, you know, I think it's worth thinking about. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5706-0 00:26:35.443 --> 00:26:38.326 What are the implications for hazard with a pilot study like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5706-1 00:26:38.326 --> 00:26:41.115 this, we can't really make any strong claims about whether 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5706-2 00:26:41.115 --> 00:26:43.573 there are regional variations in source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5763-0 00:26:43.583 --> 00:26:46.594 We can only say that they're looked like they're hints of it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5763-1 00:26:46.594 --> 00:26:49.754 in the larger earthquakes, but if the patterns persist in space 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5763-2 00:26:49.754 --> 00:26:52.716 and in time, and apply to the largest earthquakes, the ones 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5763-3 00:26:52.716 --> 00:26:55.728 that are most important for hazard analysis, it really is an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5763-4 00:26:55.728 --> 00:26:56.913 important consideration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-0 00:26:56.923 --> 00:26:59.673 We know that this is just an example of a terror shake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-1 00:26:59.673 --> 00:27:02.473 simulation, but basically, whether or not you've got an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-2 00:27:02.473 --> 00:27:05.123 earthquake rupture on the southern San Andreas Fault 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-3 00:27:05.123 --> 00:27:08.223 that's rupturing to the north or rupturing to the South has a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-4 00:27:08.223 --> 00:27:11.173 tremendous impact on Hazard and similarly high stress drop 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5827-5 00:27:11.173 --> 00:27:13.173 events will have higher ground motions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5851-0 00:27:13.183 --> 00:27:15.855 So really trying to understand these spatial patterns and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5851-1 00:27:15.855 --> 00:27:18.803 whether they're robust or not is an important line of research. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5894-0 00:27:19.623 --> 00:27:23.155 And so that's what I'm hoping to do over the next few years is to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5894-1 00:27:23.155 --> 00:27:26.366 try to apply these methods at a greater scale with a larger 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5894-2 00:27:26.366 --> 00:27:29.523 sample size of earthquakes to see if the patterns hold up. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5920-0 00:27:29.843 --> 00:27:33.162 And that's focusing both on the characterizing things like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5920-1 00:27:33.162 --> 00:27:36.818 earthquake stress drop but also rupture directivity and tried to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5920-2 00:27:36.818 --> 00:27:37.493 explore the. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5929-0 00:27:38.723 --> 00:27:41.713 Using some of the methods in combination. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5958-0 00:27:41.783 --> 00:27:44.481 What I've presented so far is mostly in the frequency domain, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5958-1 00:27:44.481 --> 00:27:46.918 but we can get additional constraints using time domain 8ca14bac-4f56-40c1-9c1a-c4d258076e65/5958-2 00:27:46.918 --> 00:27:47.963 and other methodologies. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6000-0 00:27:47.973 --> 00:27:51.775 So I'm trying to figure out ways of merging those two and using 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6000-1 00:27:51.775 --> 00:27:55.280 that to kind of reduce the uncertainty ohm and so I've got 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6000-2 00:27:55.280 --> 00:27:58.488 funding for some follow up projects from the Southern 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6000-3 00:27:58.488 --> 00:28:00.983 California Earthquake Center and the NSF. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6032-0 00:28:00.993 --> 00:28:04.728 And so I'm hoping to apply that at scale in areas like the Sanyo 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6032-1 00:28:04.728 --> 00:28:08.003 Sinto, but also in other areas in California and Nevada. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6051-0 00:28:09.843 --> 00:28:13.514 Umm, so that's the the first part of my talk today was 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6051-1 00:28:13.514 --> 00:28:15.583 focusing on earthquake Spectra. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6089-0 00:28:16.223 --> 00:28:20.341 The second part is again trying to understand the relationship 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6089-1 00:28:20.341 --> 00:28:24.001 between earthquake source properties and ground motion, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6089-2 00:28:24.001 --> 00:28:27.923 but focusing on the problem of understanding ground motions 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6089-3 00:28:27.923 --> 00:28:29.623 very close to earthquakes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6118-0 00:28:30.153 --> 00:28:33.680 We're at a really interesting time in earthquake seismology, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6118-1 00:28:33.680 --> 00:28:37.034 where we're at the same time very data rich and very data 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6118-2 00:28:37.034 --> 00:28:37.323 poor. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6132-0 00:28:37.653 --> 00:28:41.375 We've seen over the past five or ten years a tremendous explosion 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6132-1 00:28:41.375 --> 00:28:41.883 in these. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6155-0 00:28:43.743 --> 00:28:46.427 Extremely detailed earthquake catalogs that are obtained 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6155-1 00:28:46.427 --> 00:28:49.253 through things like template matching and machine learning. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6173-0 00:28:49.463 --> 00:28:52.620 Whereas before we might have a sample size of 1000 events, now 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6173-1 00:28:52.620 --> 00:28:54.173 we're getting 10s of thousands. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6210-0 00:28:54.183 --> 00:28:58.278 Hundreds of thousands and even millions, but at the same time, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6210-1 00:28:58.278 --> 00:29:02.438 if you plot up a density plot of earthquake ground motions, you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6210-2 00:29:02.438 --> 00:29:06.013 plot something like rupture distance versus magnitude. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6260-0 00:29:06.083 --> 00:29:10.624 What you'll see is that a lot of our ground motion recordings are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6260-1 00:29:10.624 --> 00:29:14.545 still focused on the smallest earthquakes, and at larger 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6260-2 00:29:14.545 --> 00:29:18.467 distances basically have very little data constraints of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6260-3 00:29:18.467 --> 00:29:21.563 ground motions at close distances from large 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6260-4 00:29:21.563 --> 00:29:22.733 earthquakes, umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6273-0 00:29:22.933 --> 00:29:25.579 And so that's kind of a challenge for a number of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6273-1 00:29:25.579 --> 00:29:26.003 reasons. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6304-0 00:29:26.013 --> 00:29:29.347 We've got a bunch of different population centers all across 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6304-1 00:29:29.347 --> 00:29:32.681 California and Western Nevada that are positioned very close 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6304-2 00:29:32.681 --> 00:29:33.993 to active fault systems. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6325-0 00:29:34.003 --> 00:29:36.840 And so trying to quantify the hazard and risk in these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6325-1 00:29:36.840 --> 00:29:40.193 locations is very important, but we don't really have good data. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6367-0 00:29:40.203 --> 00:29:43.626 We don't have a lot of on scale seismic recordings at close 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6367-1 00:29:43.626 --> 00:29:46.764 distances to large earthquakes to try to constrain the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6367-2 00:29:46.764 --> 00:29:50.359 important aspects of ruptured dynamics to really get at hazard 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6367-3 00:29:50.359 --> 00:29:51.443 at those locations. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6372-0 00:29:51.733 --> 00:29:52.713 And so people can make. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6380-0 00:29:52.983 --> 00:29:54.773 Some very nice numerical models. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6419-0 00:29:54.783 --> 00:29:58.124 This is an example of recent paper from Bipolar Adal looking 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6419-1 00:29:58.124 --> 00:30:01.356 at rupture simulations of normal faults, and there's these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6419-2 00:30:01.356 --> 00:30:04.260 tremendously detailed models that involve a bunch of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6419-3 00:30:04.260 --> 00:30:06.013 different parameter assumptions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6440-0 00:30:06.423 --> 00:30:10.047 But to really rigorously test them we need a lot more data to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6440-1 00:30:10.047 --> 00:30:12.443 constrain near field rupture properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6442-0 00:30:13.483 --> 00:30:13.763 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-0 00:30:14.053 --> 00:30:17.087 And so that's the uh, the project that I'm going to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-1 00:30:17.087 --> 00:30:20.647 describe here is a is a kind of a new angle at that problem, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-2 00:30:20.647 --> 00:30:24.382 focusing in particular on normal faults and so on the east side 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-3 00:30:24.382 --> 00:30:27.942 of the Sierra, you have these all these classic faults where 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-4 00:30:27.942 --> 00:30:31.269 you basically have range bounding normal faults that can 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6507-5 00:30:31.269 --> 00:30:33.253 produce pretty large earthquakes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6541-0 00:30:33.263 --> 00:30:36.777 And so the the the fault systems that are of most interest to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6541-1 00:30:36.777 --> 00:30:40.292 people living in a place like Reno where I live, are actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6541-2 00:30:40.292 --> 00:30:42.333 these range bounding normal faults. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6580-0 00:30:42.343 --> 00:30:45.193 We know that they've historically created very large 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6580-1 00:30:45.193 --> 00:30:48.474 earthquakes and could in the future, but we have very little 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6580-2 00:30:48.474 --> 00:30:51.916 data constraints on what ground motions are gonna be very close 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6580-3 00:30:51.916 --> 00:30:53.153 to those normal faults. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6621-0 00:30:53.163 --> 00:30:57.148 And so the data that I'm gonna describe today is actually a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6621-1 00:30:57.148 --> 00:31:01.067 case study of a magnitude 6 earthquake that occurred right 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6621-2 00:31:01.067 --> 00:31:04.920 on the California, Nevada border, near the town of Walker 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6621-3 00:31:04.920 --> 00:31:05.983 in July of 2021. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6661-0 00:31:06.363 --> 00:31:10.144 And this is essentially A1 of the latest of the sequence of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6661-1 00:31:10.144 --> 00:31:13.926 large events in this kind of Eastern California Shear Zone, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6661-2 00:31:13.926 --> 00:31:17.770 Walker Lane region, including earthquakes like 9 Mile Ranch, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6661-3 00:31:17.770 --> 00:31:19.283 Ridgecrest Monte Cristo. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6706-0 00:31:19.453 --> 00:31:22.581 But it's actually the only normal fault thing event of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6706-1 00:31:22.581 --> 00:31:26.027 recent ones, and so it's a nice case study to try and understand 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6706-2 00:31:26.027 --> 00:31:29.207 what the ground motions and rupture properties are of these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6706-3 00:31:29.207 --> 00:31:31.063 large normal faulting earthquakes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6759-0 00:31:32.823 --> 00:31:36.726 And so the the reason why I got interested in this study was 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6759-1 00:31:36.726 --> 00:31:40.822 actually a series of papers that are more than 20 years old now 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6759-2 00:31:40.822 --> 00:31:44.725 looking at our fragile geologic features called precariously 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6759-3 00:31:44.725 --> 00:31:48.885 balanced rocks, all along fault systems on the California Nevada 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6759-4 00:31:48.885 --> 00:31:49.333 border. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-0 00:31:49.573 --> 00:31:53.503 And so this was a series of field surveys LED in the 1990s 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-1 00:31:53.503 --> 00:31:57.300 by Jim Bruene, where he basically walked along all these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-2 00:31:57.300 --> 00:32:01.097 fault systems and documented these rocks that are rather 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-3 00:32:01.097 --> 00:32:05.294 fragile, both in, you know, how they look, but also in, if you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-4 00:32:05.294 --> 00:32:09.091 test them with, you know, measurements in the lab or out 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-5 00:32:09.091 --> 00:32:13.221 in the field, they should be rocks that could be knocked down 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6841-6 00:32:13.221 --> 00:32:15.753 by strong earthquake, ground motions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6854-0 00:32:15.763 --> 00:32:18.410 And so they actually provide some useful constraints for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6854-1 00:32:18.410 --> 00:32:19.153 hazard analysis. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6870-0 00:32:19.363 --> 00:32:22.493 And so that was the idea of this study in the 1990s. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6930-0 00:32:22.503 --> 00:32:26.168 Basically just documenting these rocks as a data set that people 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6930-1 00:32:26.168 --> 00:32:29.776 could use to try to test hazard maps and the reason why this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6930-2 00:32:29.776 --> 00:32:33.329 interesting is that one of the field sites, the ones that I've 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6930-3 00:32:33.329 --> 00:32:36.599 circled in this table from the 20 and year 2000 paper, is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6930-4 00:32:36.599 --> 00:32:39.813 actually very, very close to the magnitude 6 earthquake. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6990-0 00:32:39.823 --> 00:32:43.581 So we have a whole bunch of photos of rocks that were 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6990-1 00:32:43.581 --> 00:32:48.175 labeled precarious in the 1990s, and we have a magnitude 6 ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6990-2 00:32:48.175 --> 00:32:52.769 magnitude 6 earthquake rupturing almost directly below it that we 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6990-3 00:32:52.769 --> 00:32:57.015 can go back and try to estimate what happened to these rocks 8ca14bac-4f56-40c1-9c1a-c4d258076e65/6990-4 00:32:57.015 --> 00:33:00.843 that experience these very near source ground motions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7004-0 00:33:00.923 --> 00:33:04.763 And so that's the premise of the study that I'm gonna describe. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7031-0 00:33:04.773 --> 00:33:08.294 I think it helps the to do a quick 101 on what these 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7031-1 00:33:08.294 --> 00:33:12.213 precariously balanced rocks are and what they're used for. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7066-0 00:33:12.463 --> 00:33:16.989 And so this is a kind of a line of research that dates back more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7066-1 00:33:16.989 --> 00:33:21.307 than 30 years and it's kind of a mixture of engineering sized 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7066-2 00:33:21.307 --> 00:33:24.023 nology and and ground motion analysis. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7098-0 00:33:24.573 --> 00:33:27.832 So you can derive I'm not gonna do it here, but you can show 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7098-1 00:33:27.832 --> 00:33:30.663 that if you wanna knock a rock that looks like this. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7121-0 00:33:31.373 --> 00:33:35.042 If you kind of push on it quasi statically, so just push on it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7121-1 00:33:35.042 --> 00:33:37.023 and harder and harder and harder. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7173-0 00:33:37.133 --> 00:33:40.622 The ground acceleration that you're gonna need to eventually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7173-1 00:33:40.622 --> 00:33:44.341 tip this rock over is gonna be G times the tangent of alpha, and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7173-2 00:33:44.341 --> 00:33:47.716 alpha is basically this angle here that you can see in the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7173-3 00:33:47.716 --> 00:33:51.320 figure is the angle between the center of mass and the rocking 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7173-4 00:33:51.320 --> 00:33:51.663 point. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7191-0 00:33:51.673 --> 00:33:54.257 And so, depending on which rocking point you're looking at, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7191-1 00:33:54.257 --> 00:33:55.463 the alpha will be different. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7239-0 00:33:55.693 --> 00:33:58.630 But in essence, if you are trying to push this rock over 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7239-1 00:33:58.630 --> 00:34:01.465 from the right, for example, the quasi static toppling 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7239-2 00:34:01.465 --> 00:34:04.815 acceleration would be G tangent, alpha and so people will go out 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7239-3 00:34:04.815 --> 00:34:07.752 in the field and they'll essentially measure these alpha 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7239-4 00:34:07.752 --> 00:34:08.113 values. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7261-0 00:34:08.233 --> 00:34:11.546 And so that can essentially put a bound of ground motion that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7261-1 00:34:11.546 --> 00:34:13.683 will be useful for testing hazard maps. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7278-0 00:34:13.693 --> 00:34:17.450 And so that's what people usually use, PBS or precariously 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7278-1 00:34:17.450 --> 00:34:18.533 balanced rocks 4. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7293-0 00:34:20.313 --> 00:34:22.523 That's actually not what we're gonna do in this study. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7334-0 00:34:22.533 --> 00:34:25.552 I'm not testing hazard maps at all, I'm just interested in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7334-1 00:34:25.552 --> 00:34:28.520 trying to understand what happened to the PBR's that were 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7334-2 00:34:28.520 --> 00:34:31.283 documented in the 1990s because we had an earthquake. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7341-0 00:34:31.293 --> 00:34:33.143 That happened very, very close to them. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7359-0 00:34:33.573 --> 00:34:37.323 And So what we did was I went out in September of 2022. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7369-0 00:34:37.333 --> 00:34:40.063 I resurveyed Meadow Cliff Canyon. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7411-0 00:34:40.073 --> 00:34:43.564 Just trying to look for all of the precarious rocks that were 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7411-1 00:34:43.564 --> 00:34:47.055 documented by Jim Bruene in the 1990s to see what happened to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7411-2 00:34:47.055 --> 00:34:50.433 them and what I found was a little bit of a surprise to me. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7418-0 00:34:50.703 --> 00:34:52.693 I went through Medical Cliff Canyon. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7432-0 00:34:52.703 --> 00:34:56.263 It's about a 2 kilometer by two kilometer study area. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7439-0 00:34:56.273 --> 00:34:57.643 There's a bunch of rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7467-0 00:34:58.103 --> 00:35:01.606 It's a pretty rugged terrain, but what I found was that I 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7467-1 00:35:01.606 --> 00:35:05.291 couldn't find evidence for a single precarious rock that Jim 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7467-2 00:35:05.291 --> 00:35:05.533 had. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7482-0 00:35:05.543 --> 00:35:08.869 Document documented that was on the ground and some of them are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7482-1 00:35:08.869 --> 00:35:10.273 actually rather precarious. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7498-0 00:35:10.283 --> 00:35:14.593 This is a photo of a precarious rock that Jim took in 1996. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7512-0 00:35:14.603 --> 00:35:16.731 You could see this guy's basically just balance on the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7512-1 00:35:16.731 --> 00:35:16.963 ledge. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7533-0 00:35:16.973 --> 00:35:19.769 You can see it's overhanging and it shouldn't take all that much 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7533-1 00:35:19.769 --> 00:35:21.103 ground motion to knock it over. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7554-0 00:35:21.633 --> 00:35:25.033 But if you go back in 2022, it's still there and it really hasn't 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7554-1 00:35:25.033 --> 00:35:25.703 moved at all. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7596-0 00:35:25.713 --> 00:35:28.855 And there's a bunch of examples of other rocks that I found in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7596-1 00:35:28.855 --> 00:35:31.299 the Canyon, and so I was interested in trying to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7596-2 00:35:31.299 --> 00:35:33.643 understand why these rocks were so precarious. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7601-0 00:35:33.653 --> 00:35:36.258 And you have a magnitude 6 earthquake that ruptures right 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7601-1 00:35:36.258 --> 00:35:36.663 under it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7610-0 00:35:36.853 --> 00:35:40.093 Why these rocks didn't fall over umm? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7631-0 00:35:40.333 --> 00:35:43.724 And so to do this, umm, we did a a pretty detailed and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7631-1 00:35:43.724 --> 00:35:46.808 multidisciplinary characterization of the rupture 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7631-2 00:35:46.808 --> 00:35:47.363 sequence. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7661-0 00:35:47.373 --> 00:35:50.196 I'm not gonna go through all the steps that we did, but it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7661-1 00:35:50.196 --> 00:35:52.827 involved high precision earthquake locations to try to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7661-2 00:35:52.827 --> 00:35:54.263 figure out the fault geometry. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7669-0 00:35:54.773 --> 00:35:56.903 We did some moment tensor analysis. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7692-0 00:35:56.913 --> 00:36:00.042 We did analysis of source Spectra to see if it was an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7692-1 00:36:00.042 --> 00:36:02.013 unusually high stress drop event. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7711-0 00:36:02.193 --> 00:36:04.980 We compared the ground motions at the local and regional 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7711-1 00:36:04.980 --> 00:36:06.643 stations to ground motion models. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7745-0 00:36:06.903 --> 00:36:10.016 We actually even did a site response survey, but we're 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7745-1 00:36:10.016 --> 00:36:12.904 really trying to introduce interested in trying to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7745-2 00:36:12.904 --> 00:36:16.470 understand why these rocks, if they were so precarious, didn't 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7745-3 00:36:16.470 --> 00:36:17.263 fall over umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7758-0 00:36:17.403 --> 00:36:19.483 So just to Orient you guys, this is where we are. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7764-0 00:36:19.493 --> 00:36:21.873 We're in the California, Nevada border area. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7790-0 00:36:22.603 --> 00:36:26.180 Umm, the the earthquake, it's called the Antelope Valley 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7790-1 00:36:26.180 --> 00:36:29.756 earthquake, but it's actually not on the Antelope Valley 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7790-2 00:36:29.756 --> 00:36:30.133 fault. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7806-0 00:36:30.653 --> 00:36:33.880 The the fault geometry actually agrees quite well with this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7806-1 00:36:33.880 --> 00:36:35.063 Slinkard Valley fault. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7818-0 00:36:35.293 --> 00:36:38.303 The epicenter you can see in this figure is here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7842-0 00:36:38.433 --> 00:36:42.466 The PBR site is a little bit to the north, but actually it turns 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7842-1 00:36:42.466 --> 00:36:45.383 out that the rupture is a NS striking rupture. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7866-0 00:36:45.473 --> 00:36:48.679 The basically it propagated from the epicenter to almost directly 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7866-1 00:36:48.679 --> 00:36:51.593 below the site, and I'll show you an image of that in a few 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7866-2 00:36:51.593 --> 00:36:51.933 slides. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7870-0 00:36:53.053 --> 00:36:53.403 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7918-0 00:36:54.293 --> 00:36:57.593 As you guys probably know, doing earthquake locations, especially 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7918-1 00:36:57.593 --> 00:37:00.643 at the California, Nevada border is particularly challenging 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7918-2 00:37:00.643 --> 00:37:03.943 because you got a mix of seismic networks that Crotts cross state 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7918-3 00:37:03.943 --> 00:37:06.893 lines, you've got a velocity model that's probably not the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7918-4 00:37:06.893 --> 00:37:07.393 right one. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-0 00:37:07.803 --> 00:37:10.945 If you're using a statewide average model, and So what we 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-1 00:37:10.945 --> 00:37:14.088 usually find is that if you're trying to study earthquake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-2 00:37:14.088 --> 00:37:17.067 source properties for earthquakes near the border, the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-3 00:37:17.067 --> 00:37:20.318 standard monitoring catalogs that you get from the Northern 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-4 00:37:20.318 --> 00:37:23.731 California data Center, or you get from our data center aren't 8ca14bac-4f56-40c1-9c1a-c4d258076e65/7982-5 00:37:23.731 --> 00:37:26.603 usually sufficient for detailed scientific purposes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8020-0 00:37:26.613 --> 00:37:29.811 So what we did was we systematically reprocessed the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8020-1 00:37:29.811 --> 00:37:33.070 process the data to ensure better quality control, so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8020-2 00:37:33.070 --> 00:37:36.329 quality control on the phase arrivals on the absolute 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8020-3 00:37:36.329 --> 00:37:38.743 locations and the relative relocations. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8061-0 00:37:38.753 --> 00:37:42.355 So we've basically took our phase arrivals from our network 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8061-1 00:37:42.355 --> 00:37:46.198 database and then we redid the absolute locations using a local 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8061-2 00:37:46.198 --> 00:37:49.981 velocity model and then we did relative relocations using this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8061-3 00:37:49.981 --> 00:37:52.503 grow class package that I helped develop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8083-0 00:37:53.233 --> 00:37:55.576 So I'm not going to get into the details of the methodology, I 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8083-1 00:37:55.576 --> 00:37:57.213 just want to show you what the results are. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8085-0 00:37:58.283 --> 00:37:58.523 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8111-0 00:37:58.703 --> 00:38:02.261 And so here's our earthquake catalog in map view, just so you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8111-1 00:38:02.261 --> 00:38:05.073 can get a sense for the geometry of the problem. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8123-0 00:38:05.543 --> 00:38:08.713 Basically what we have is a nice dipping normal fault. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8143-0 00:38:08.723 --> 00:38:11.798 The hypocenter of the main shock is actually at the base of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8143-1 00:38:11.798 --> 00:38:12.423 normal fault. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8203-0 00:38:12.603 --> 00:38:15.524 It maps well to the Slinker Valley fault that's in the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8203-1 00:38:15.524 --> 00:38:18.869 Quaternity fault database, but what's most important is if you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8203-2 00:38:18.869 --> 00:38:21.684 look at this in map view, basically all this BLOB of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8203-3 00:38:21.684 --> 00:38:24.817 earthquakes that you see, this is aftershocks that are all 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8203-4 00:38:24.817 --> 00:38:26.623 along the main shock fault plane. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8213-0 00:38:26.633 --> 00:38:28.813 So this is basically the extent of the main shock. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8220-0 00:38:28.963 --> 00:38:29.523 What plane? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8237-0 00:38:29.693 --> 00:38:33.315 And the precariously balanced rock site is right on top of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8237-1 00:38:33.315 --> 00:38:34.983 northern part of the rupture. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8244-0 00:38:34.993 --> 00:38:35.983 So you've got a rupture. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8256-0 00:38:35.993 --> 00:38:39.503 That was kind of bilateral, at least in its aftershock pattern. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8270-0 00:38:39.773 --> 00:38:42.543 And it went to right below this rock site. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8305-0 00:38:42.673 --> 00:38:46.944 And so we're really just looking at a site that's four or five 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8305-1 00:38:46.944 --> 00:38:51.283 kilometers in elevation above, but in map view directly aligned 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8305-2 00:38:51.283 --> 00:38:52.843 with the rupture plane. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8316-0 00:38:54.123 --> 00:38:56.453 And so we can actually get the geometry better. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8351-0 00:38:56.463 --> 00:39:00.232 UM, if we look at this in 3D, So what I've done is I've I'm 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8351-1 00:39:00.232 --> 00:39:04.191 plotting the aftershocks here and the best fit of the plane to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8351-2 00:39:04.191 --> 00:39:05.573 the mainshock rupture. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8371-0 00:39:05.833 --> 00:39:08.754 And then the precariously balanced rock side is actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8371-1 00:39:08.754 --> 00:39:10.753 this square that I'm drawing up there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8399-0 00:39:10.903 --> 00:39:13.799 And So what you can see is that it's actually well above the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8399-1 00:39:13.799 --> 00:39:16.790 rupture plane, but in map view, it's almost directly on top of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8399-2 00:39:16.790 --> 00:39:16.933 it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8406-0 00:39:16.943 --> 00:39:18.093 And so the distance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8442-0 00:39:18.283 --> 00:39:21.500 If you measure things like our Rup, which is the distance from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8442-1 00:39:21.500 --> 00:39:24.871 the site to the closest point on the rupture surface, you go to a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8442-2 00:39:24.871 --> 00:39:27.781 value of about 6.4 kilometers, and that's basically just 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8442-3 00:39:27.781 --> 00:39:28.803 completely vertical. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8451-0 00:39:28.813 --> 00:39:31.023 It has no sort of horizontal effect to it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8498-0 00:39:32.063 --> 00:39:36.044 Umm, we did try to characterize the stress drop and the source 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8498-1 00:39:36.044 --> 00:39:40.089 properties of this earthquake, with the idea being that if it's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8498-2 00:39:40.089 --> 00:39:44.007 a high stress drop event, it might have unusually high ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8498-3 00:39:44.007 --> 00:39:44.513 motions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8529-0 00:39:44.563 --> 00:39:47.559 Or if it's a low stress drop event, it might have unusually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8529-1 00:39:47.559 --> 00:39:50.605 low ground motions and that might help explain what happened 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8529-2 00:39:50.605 --> 00:39:51.903 to the rocks in this case. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8564-0 00:39:51.913 --> 00:39:55.949 What we get this is basically a figure where I'm showing fits to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8564-1 00:39:55.949 --> 00:39:59.303 the Spectra and then also posterior distributions for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8564-2 00:39:59.303 --> 00:40:02.843 things like corner frequency and moment and stress drop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8585-0 00:40:03.373 --> 00:40:06.998 What we ended up getting is a stress drop value of about 17 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8585-1 00:40:06.998 --> 00:40:07.723 megapascals. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8601-0 00:40:07.733 --> 00:40:10.650 So it's kind of, it's not an unusually high stress drop 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8601-1 00:40:10.650 --> 00:40:10.963 event. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8643-0 00:40:11.033 --> 00:40:14.569 It's not like 50 or anything like that, but it's kind of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8643-1 00:40:14.569 --> 00:40:18.291 moderate to high and so it doesn't really help us solve our 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8643-2 00:40:18.291 --> 00:40:21.765 problem of why those rocks aren't standing or are still 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8643-3 00:40:21.765 --> 00:40:22.323 standing. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8679-0 00:40:22.513 --> 00:40:25.274 If it were a very low stress drop event, that might help us, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8679-1 00:40:25.274 --> 00:40:28.217 but in this case it's a moderate to high, so that isn't really a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8679-2 00:40:28.217 --> 00:40:29.213 plausible explanation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8724-0 00:40:31.193 --> 00:40:34.676 Interestingly, we can measure stress drops for the aftershocks 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8724-1 00:40:34.676 --> 00:40:37.772 and what we notice is that in this case it appears that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8724-2 00:40:37.772 --> 00:40:41.145 there's a trend of stress drops to increase with depth, just 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8724-3 00:40:41.145 --> 00:40:42.583 like we saw in California. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8766-0 00:40:42.593 --> 00:40:46.051 But the depth trend is actually quite a bit larger in this case, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8766-1 00:40:46.051 --> 00:40:48.658 and I'm not sure if that's because these are all 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8766-2 00:40:48.658 --> 00:40:51.425 aftershocks along the same normal fault, or if it's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8766-3 00:40:51.425 --> 00:40:53.553 something peculiar about this data set. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8794-0 00:40:53.873 --> 00:40:56.772 But in any case, it is interesting that the higher 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8794-1 00:40:56.772 --> 00:41:00.239 stress drop events in this case end up coming from the lower 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8794-2 00:41:00.239 --> 00:41:00.523 part. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8815-0 00:41:00.533 --> 00:41:03.379 The deeper part of the rupture zone be interesting to see if 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8815-1 00:41:03.379 --> 00:41:05.853 that generalizes to other normal faulting sequences. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8870-0 00:41:07.113 --> 00:41:11.124 Umm, another interesting aspect of this earthquake is that if 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8870-1 00:41:11.124 --> 00:41:15.071 you look at the the station that's closest by in the town of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8870-2 00:41:15.071 --> 00:41:19.018 Walker, it basically clipped during the main shock, which so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8870-3 00:41:19.018 --> 00:41:23.030 it was completely useless in terms of characterizing the main 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8870-4 00:41:23.030 --> 00:41:24.583 shock source properties. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8900-0 00:41:24.793 --> 00:41:28.611 But if you look on the day of the event, just on that station, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8900-1 00:41:28.611 --> 00:41:32.127 you can pick out all these really tiny 4 shocks that were 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8900-2 00:41:32.127 --> 00:41:32.733 happening. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8918-0 00:41:32.743 --> 00:41:35.514 And so there's an uptick in seismicity that really was only 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8918-1 00:41:35.514 --> 00:41:36.623 visible on this station. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8948-0 00:41:37.133 --> 00:41:39.594 So if we had a bunch of other stations nearby, we actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8948-1 00:41:39.594 --> 00:41:42.097 maybe could have seen something interesting happening right 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8948-2 00:41:42.097 --> 00:41:43.223 before the rupture started. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8985-0 00:41:43.233 --> 00:41:46.716 In this case, it's basically limited to this one station, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8985-1 00:41:46.716 --> 00:41:50.439 UMM, and the main shock itself actually also triggered a very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8985-2 00:41:50.439 --> 00:41:54.162 large aftershock that happened within about 30 seconds of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/8985-3 00:41:54.162 --> 00:41:55.063 main shock ohm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9007-0 00:41:55.233 --> 00:41:58.359 These are waveforms taken from two of the nearest strong motion 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9007-1 00:41:58.359 --> 00:42:00.753 stations, and they're plotted on the same scale. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9028-0 00:42:00.763 --> 00:42:03.848 So you can see this is a main shock magnitude 6 and this guy 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9028-1 00:42:03.848 --> 00:42:05.163 is actually an aftershock. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9061-0 00:42:05.173 --> 00:42:08.331 It's not something that's happening in its coda, and so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9061-1 00:42:08.331 --> 00:42:11.658 the fact that can actually see it on this scale means it's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9061-2 00:42:11.658 --> 00:42:13.293 something like a magnitude 5. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9078-0 00:42:13.303 --> 00:42:17.272 So this is actually rather large, but is very near in time 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9078-1 00:42:17.272 --> 00:42:18.483 to the main shock. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9116-0 00:42:18.493 --> 00:42:21.269 And so again, this is kind of an interesting progression that I'm 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9116-1 00:42:21.269 --> 00:42:23.877 not sure what it means in terms of normal faulting sequences, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9116-2 00:42:23.877 --> 00:42:26.358 but it's something that's worth studying a little bit more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9116-3 00:42:26.358 --> 00:42:26.653 detail. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9118-0 00:42:27.763 --> 00:42:28.043 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9134-0 00:42:28.303 --> 00:42:31.593 What we're most interested for this research is focusing on the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9134-1 00:42:31.593 --> 00:42:32.313 ground motion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9147-0 00:42:32.623 --> 00:42:36.610 And So what I'm plotting here are predictions from ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9147-1 00:42:36.610 --> 00:42:37.573 motion models. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9165-0 00:42:37.583 --> 00:42:41.477 So this is basically the NGA W active crustal combination of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9165-1 00:42:41.477 --> 00:42:43.073 foreground motion models. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9178-0 00:42:43.343 --> 00:42:47.853 I'm plotting PGA and PGV versus rupture distance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9188-0 00:42:47.863 --> 00:42:49.693 Both of these are on log log scales. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9243-0 00:42:50.283 --> 00:42:54.938 The red is the model predictions and the one Sigma uncertainty 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9243-1 00:42:54.938 --> 00:42:59.520 and the black is the recordings from regional stations and So 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9243-2 00:42:59.520 --> 00:43:04.175 what you can see is that these models actually seem to fit the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9243-3 00:43:04.175 --> 00:43:07.870 data pretty well at at the distances that we have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9243-4 00:43:07.870 --> 00:43:08.683 recordings. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9262-0 00:43:08.993 --> 00:43:12.339 Unfortunately, the closest station here is is about 18 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9262-1 00:43:12.339 --> 00:43:14.043 kilometers rupture distance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9270-0 00:43:14.453 --> 00:43:16.683 This is the station SJC. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9293-0 00:43:17.053 --> 00:43:20.597 But at least that gives us some intuition into what we might see 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9293-1 00:43:20.597 --> 00:43:22.723 at the precarious rock site the rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9324-0 00:43:22.733 --> 00:43:25.617 If we had any sort of measurements, the rocks would be 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9324-1 00:43:25.617 --> 00:43:28.712 all the way up here on the log log scale about three times 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9324-2 00:43:28.712 --> 00:43:30.023 closer than this station. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9357-0 00:43:30.263 --> 00:43:33.443 But at this station, we already starting to get a ground motion 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9357-1 00:43:33.443 --> 00:43:36.475 of point 2G, which should be reportedly high enough to knock 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9357-2 00:43:36.475 --> 00:43:38.413 over a lot of the rocks in the Canyon. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9367-0 00:43:39.183 --> 00:43:40.953 So we're still left with this mystery. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9408-0 00:43:40.963 --> 00:43:44.996 If we if we believe this ground motion model to be more or less 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9408-1 00:43:44.996 --> 00:43:48.902 correct, and while calibrated for this event what we get is a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9408-2 00:43:48.902 --> 00:43:51.423 PGA of point 3G right at our site. Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9436-0 00:43:51.483 --> 00:43:54.549 And so that's a high enough value that it should have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9436-1 00:43:54.549 --> 00:43:58.069 knocked down all the PBR's at least per this report from your 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9436-2 00:43:58.069 --> 00:43:58.353 2000. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9457-0 00:43:58.363 --> 00:44:02.645 So we're still left with this mystery about why the rocks are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9457-1 00:44:02.645 --> 00:44:03.543 standing umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9475-0 00:44:04.213 --> 00:44:10.106 And so if we take those models at face value, it it really is a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9475-1 00:44:10.106 --> 00:44:11.303 is a mystery. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9505-0 00:44:11.773 --> 00:44:16.410 These rocks, this one has a reported fragility, for example 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9505-1 00:44:16.410 --> 00:44:20.583 of about .2 G .18 to .2 G just based on its geometry. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9529-0 00:44:20.593 --> 00:44:22.463 And there's a bunch of other ones in the Canyon. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9539-0 00:44:22.473 --> 00:44:25.578 So even if this one somehow had some weird cohesion going on, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9539-1 00:44:25.578 --> 00:44:27.983 there's something interesting that's happening. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9589-0 00:44:28.403 --> 00:44:32.380 And So what we ended up doing was try to do a little bit more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9589-1 00:44:32.380 --> 00:44:36.101 detailed modeling into PBR fragility to try to understand 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9589-2 00:44:36.101 --> 00:44:40.270 what the relationship is between the dynamics of the problem and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9589-3 00:44:40.270 --> 00:44:42.323 whether or not the rocks topple. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9632-0 00:44:43.653 --> 00:44:46.852 And so we know this kind of heuristic of using the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9632-1 00:44:46.852 --> 00:44:50.803 slenderness of the rock and G tangent alpha comes from a quasi 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9632-2 00:44:50.803 --> 00:44:54.629 static analysis where you're kind of slowly pushing over the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9632-3 00:44:54.629 --> 00:44:55.633 rock to failure. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9641-0 00:44:55.863 --> 00:44:57.933 That's really not how ground motion works. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9650-0 00:44:57.943 --> 00:45:00.653 The shaking from seismic waves is a dynamic process. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-0 00:45:00.663 --> 00:45:03.644 What you're getting is essentially a sequence of sharp 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-1 00:45:03.644 --> 00:45:07.114 impulses that are averaged over some finite pulse duration, and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-2 00:45:07.114 --> 00:45:10.312 it turns out that if you look at some of the more detailed 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-3 00:45:10.312 --> 00:45:13.131 engineering studies of precarious rocks, there's an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-4 00:45:13.131 --> 00:45:16.492 important dynamic effect that goes on, and especially for the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-5 00:45:16.492 --> 00:45:19.907 large rocks like the ones that you're seeing in these figures, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-6 00:45:19.907 --> 00:45:23.430 for to knock over a large rock, it's not sufficient just to have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9730-7 00:45:23.430 --> 00:45:24.623 a strong acceleration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9747-0 00:45:24.633 --> 00:45:28.160 What you need is both a strong acceleration and a long enough 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9747-1 00:45:28.160 --> 00:45:29.013 pulse duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9756-0 00:45:29.023 --> 00:45:30.663 Essentially, it's an impulse effect. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9781-0 00:45:30.673 --> 00:45:34.117 You really need to average that acceleration over a long enough 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9781-1 00:45:34.117 --> 00:45:37.292 duration to knock over a big rock like the ones that we're 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9781-2 00:45:37.292 --> 00:45:37.723 showing. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9783-0 00:45:38.603 --> 00:45:38.803 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9830-0 00:45:39.043 --> 00:45:42.328 And so there's been a few different modeling efforts that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9830-1 00:45:42.328 --> 00:45:45.669 are developed to be able to analyze this with a little bit 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9830-2 00:45:45.669 --> 00:45:49.181 more detail to try to better take into account both the pulse 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9830-3 00:45:49.181 --> 00:45:52.013 duration effect and the peak ground acceleration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9877-0 00:45:52.283 --> 00:45:55.751 And so for this study, we adapted this these codes 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9877-1 00:45:55.751 --> 00:45:59.356 developed by per Vance and others that were based on 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9877-2 00:45:59.356 --> 00:46:03.300 numerical modeling and also experiments from shake tables 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9877-3 00:46:03.300 --> 00:46:07.313 that they developed here at UNR and in other universities. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9907-0 00:46:07.723 --> 00:46:12.082 And so the inputs this model are basically the rock geometry, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9907-1 00:46:12.082 --> 00:46:16.231 peak ground acceleration and actually this ratio of PGV to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9907-2 00:46:16.231 --> 00:46:18.903 PGA, which it turns out at least for. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9924-0 00:46:19.043 --> 00:46:22.611 Earthquake seems to be a pretty good proxy for the actual pulse 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9924-1 00:46:22.611 --> 00:46:23.113 duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9957-0 00:46:23.123 --> 00:46:26.937 This is just a schematic where they're plotting the ratio of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9957-1 00:46:26.937 --> 00:46:30.939 PGV over PGA to the actual pulse duration measured from several 8ca14bac-4f56-40c1-9c1a-c4d258076e65/9957-2 00:46:30.939 --> 00:46:34.253 large earthquakes, and they're very well correlated. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10000-0 00:46:34.683 --> 00:46:37.779 The reason why people use PDB over PGA is that this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10000-1 00:46:37.779 --> 00:46:41.269 basically something that could be computed from a hazard map, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10000-2 00:46:41.269 --> 00:46:44.647 whereas upholstery action is not something that is commonly 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10000-3 00:46:44.647 --> 00:46:46.223 extracted from a hazard map. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10022-0 00:46:47.493 --> 00:46:50.580 But in any case, what we can do with our study is actually 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10022-1 00:46:50.580 --> 00:46:52.883 measure pulse durations at nearby stations. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10058-0 00:46:53.193 --> 00:46:56.080 This is basically a collection of the three closest stations, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10058-1 00:46:56.080 --> 00:46:58.828 both horizontal components and what you'll see is that the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10058-2 00:46:58.828 --> 00:47:01.343 ground motion here is actually really high frequency. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10083-0 00:47:01.553 --> 00:47:04.549 Any of the strongest acceleration pulses that you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10083-1 00:47:04.549 --> 00:47:08.324 derive from these stations are very short, anywhere from .1 to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10083-2 00:47:08.324 --> 00:47:08.983 .2 seconds. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10106-0 00:47:09.173 --> 00:47:12.680 And so that's actually really short compared to the models 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10106-1 00:47:12.680 --> 00:47:16.543 that people are usually working on for precarious balance rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10141-0 00:47:17.703 --> 00:47:20.686 Essentially, hazard maps are controlled by the dynamics of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10141-1 00:47:20.686 --> 00:47:23.365 the magnitude 7 and the magnitude 8 earthquakes, and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10141-2 00:47:23.365 --> 00:47:26.500 those have much longer pulse durations than what we're seeing 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10141-3 00:47:26.500 --> 00:47:26.753 here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10161-0 00:47:27.223 --> 00:47:30.957 So in essence, at the site of interest, we're having rather 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10161-1 00:47:30.957 --> 00:47:33.633 large PGA, but it's a very high frequency. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10168-0 00:47:33.643 --> 00:47:35.323 So a very short pulse duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10209-0 00:47:35.623 --> 00:47:38.955 So if we plug in this numerical model, that actually accounts 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10209-1 00:47:38.955 --> 00:47:41.427 for both the peak ground acceleration and the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10209-2 00:47:41.427 --> 00:47:44.973 acceleration pulse operation, we actually get an answer that none 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10209-3 00:47:44.973 --> 00:47:47.123 of those rocks should be on the ground. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10224-0 00:47:47.133 --> 00:47:49.856 And so that's what I'm kind of plotting here with this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10224-1 00:47:49.856 --> 00:47:51.193 complicated looking figure. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10270-0 00:47:51.313 --> 00:47:54.539 Peak ground acceleration on the X axis, acceleration pulse 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10270-1 00:47:54.539 --> 00:47:57.875 duration on the Y axis and then I'm color coding by top link 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10270-2 00:47:57.875 --> 00:48:01.376 probability and so essentially the way to read this is that the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10270-3 00:48:01.376 --> 00:48:04.493 red colors here are the rocks that are likely to topple. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10301-0 00:48:05.103 --> 00:48:08.192 Blue is rocks that are unlikely to topple, so if you have a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10301-1 00:48:08.192 --> 00:48:11.282 combination of High Peak ground acceleration and long pulse 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10301-2 00:48:11.282 --> 00:48:13.393 duration, it's easy to knock over rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10328-0 00:48:13.893 --> 00:48:17.382 Here we're actually in this regime where the the expectation 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10328-1 00:48:17.382 --> 00:48:19.613 for our model is actually at the star. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10383-0 00:48:19.623 --> 00:48:22.787 And I've tried to draw in error bars, but essentially our error 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10383-1 00:48:22.787 --> 00:48:25.951 bars are all in the blue regime, so if you account for both the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10383-2 00:48:25.951 --> 00:48:28.572 pulse duration and the peak ground acceleration, you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10383-3 00:48:28.572 --> 00:48:31.637 actually get a very different answer than just accounting for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10383-4 00:48:31.637 --> 00:48:33.763 the peak ground acceleration in isolation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10416-0 00:48:34.583 --> 00:48:38.596 And I should say this figure is drawn for, umm, a rock that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10416-1 00:48:38.596 --> 00:48:42.542 looks very much like, umm this one, the classic PBR that's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10416-2 00:48:42.542 --> 00:48:44.683 standing on the the ledge there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10460-0 00:48:46.273 --> 00:48:49.408 But we can actually repeat this for rocks of different 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10460-1 00:48:49.408 --> 00:48:53.057 geometries, and what you'll find is that, somewhat intuitively, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10460-2 00:48:53.057 --> 00:48:56.592 the really slender rocks are easy to topple and smaller rocks 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10460-3 00:48:56.592 --> 00:49:00.184 are easy to topple, essentially because of that pulse duration 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10460-4 00:49:00.184 --> 00:49:00.583 effect. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10484-0 00:49:00.773 --> 00:49:03.713 But most of the large PBR's, which are the ones that are 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10484-1 00:49:03.713 --> 00:49:06.343 documented in the studies, are unlikely to topple. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10527-0 00:49:08.183 --> 00:49:11.850 And so this is kind of an interesting finding because what 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10527-1 00:49:11.850 --> 00:49:15.889 it means is that if you actually wanna use PBR's as a data point 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10527-2 00:49:15.889 --> 00:49:19.618 for testing hazard maps, you actually have to take a little 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10527-3 00:49:19.618 --> 00:49:20.613 bit more nuance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10553-0 00:49:20.783 --> 00:49:23.985 You really have to consider this post duration effect, especially 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10553-1 00:49:23.985 --> 00:49:26.799 if you're including smaller earthquakes that are close to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10553-2 00:49:26.799 --> 00:49:27.333 the source. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10593-0 00:49:27.783 --> 00:49:30.610 In trying to understand whether or not they can knock down 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10593-1 00:49:30.610 --> 00:49:33.581 ruptures, if you have a large earthquake, it's likely to have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10593-2 00:49:33.581 --> 00:49:36.552 a long enough pulse duration that you might be able to ignore 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10593-3 00:49:36.552 --> 00:49:37.223 it its effect. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10628-0 00:49:37.633 --> 00:49:40.953 But if you're looking at very near source ground motions or, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10628-1 00:49:40.953 --> 00:49:44.382 umm, the effects from smaller earthquakes like magnitude 5 and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10628-2 00:49:44.382 --> 00:49:47.539 magnitude 6, then this pulse duration effect becomes very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10628-3 00:49:47.539 --> 00:49:48.083 important. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10661-0 00:49:48.093 --> 00:49:51.143 And so these classical rules of thumb are these engineering 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10661-1 00:49:51.143 --> 00:49:54.294 heuristics might not apply to real world problems, especially 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10661-2 00:49:54.294 --> 00:49:56.683 if you're focused on near field ground motion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10663-0 00:49:57.833 --> 00:49:58.073 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10678-0 00:49:58.373 --> 00:50:02.023 And so there's a lot of ways to try to expand this study. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10714-0 00:50:02.033 --> 00:50:04.781 I think the first thing is to try to understand whether this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10714-1 00:50:04.781 --> 00:50:07.484 earthquake sequence is a typical one for the range bounding 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10714-2 00:50:07.484 --> 00:50:10.277 normal fault, or whether there's something special about this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10714-3 00:50:10.277 --> 00:50:10.683 sequence. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10747-0 00:50:11.013 --> 00:50:14.277 And there's also a whole lot of work to do to try to figure out 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10747-1 00:50:14.277 --> 00:50:17.083 how you can generalize this line of analysis for using 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10747-2 00:50:17.083 --> 00:50:19.123 precariously rocks to test hazard maps. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10800-0 00:50:19.173 --> 00:50:22.432 Because obviously that's one of the most useful things that we 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10800-1 00:50:22.432 --> 00:50:25.691 can do as a size monologist in this data set is very useful in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10800-2 00:50:25.691 --> 00:50:29.002 providing constraints on ground motion, but being able to apply 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10800-3 00:50:29.002 --> 00:50:32.312 the data set takes a whole lot of care, as we've seen with this 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10800-4 00:50:32.312 --> 00:50:32.623 study. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10803-0 00:50:33.563 --> 00:50:33.973 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10825-0 00:50:34.363 --> 00:50:37.971 So yeah, I wanna thank you guys for your time in listening to my 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10825-1 00:50:37.971 --> 00:50:38.693 presentation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10847-0 00:50:38.863 --> 00:50:42.112 If you're interested in either of these papers, I included QR 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10847-1 00:50:42.112 --> 00:50:44.523 codes so you can quickly look them up on our. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10858-0 00:50:44.533 --> 00:50:47.733 I'm happy to take questions here or after the presentation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10860-0 00:50:49.103 --> 00:50:49.543 Thank you. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10866-0 00:50:55.583 --> 00:50:56.813 Daniel, I stuck. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10870-0 00:50:57.393 --> 00:50:58.373 People have questions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10877-0 00:50:58.383 --> 00:50:59.363 Please raise your hands. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10892-0 00:50:59.373 --> 00:51:03.573 Raise any questions in here or maybe something in the chat. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10901-0 00:51:06.973 --> 00:51:08.053 Margaret, you have a question? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10905-0 00:51:08.063 --> 00:51:09.153 Why do I ask? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10938-0 00:51:09.663 --> 00:51:14.293 You should be like, OK, I had a question about the bolster 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10938-1 00:51:14.293 --> 00:51:18.923 ration of like how it was measured, was it the OR maximum? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10929-0 00:51:16.163 --> 00:51:16.403 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10934-0 00:51:19.873 --> 00:51:20.543 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10948-0 00:51:20.713 --> 00:51:25.293 Actually, for this study I measured pulse duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10965-0 00:51:25.523 --> 00:51:28.495 I was trying to measure pulse duration in the way that was 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10965-1 00:51:28.495 --> 00:51:29.553 defined by Purviance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10985-0 00:51:29.563 --> 00:51:32.451 So it would be directly applicable to his model, and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10985-1 00:51:32.451 --> 00:51:35.503 there's other ways of trying to measure pulse duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/10992-0 00:51:35.513 --> 00:51:36.123 So it's important. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11002-0 00:51:36.133 --> 00:51:38.633 That's the pulse duration of the acceleration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11044-0 00:51:39.643 --> 00:51:43.338 That's the the relevant parameter here, and so how it 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11044-1 00:51:43.338 --> 00:51:47.376 was defined in this study that developed the probabilistic 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11044-2 00:51:47.376 --> 00:51:51.140 toppling model is basically looking at peaks of ground 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11044-3 00:51:51.140 --> 00:51:54.493 motion that are within 75% of the maximum value. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11055-0 00:51:54.623 --> 00:51:57.953 And then just measuring the zero crossing pulse duration. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11070-0 00:51:57.963 --> 00:51:59.493 So it's actually a pretty simple measurement. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11083-0 00:51:59.503 --> 00:52:02.933 In this case, I think there's there's areas to explore. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11105-0 00:52:02.943 --> 00:52:06.508 Whether that's exactly the the correct measurement that you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11105-1 00:52:06.508 --> 00:52:10.133 need for this model, but I was trying to be consistent here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11124-0 00:52:13.273 --> 00:52:15.737 So yeah, you can actually kind of see it on this figure, but 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11124-1 00:52:15.737 --> 00:52:16.383 it's very small. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11139-0 00:52:16.393 --> 00:52:20.833 Basically the this little red line is the pulse duration in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11139-1 00:52:20.833 --> 00:52:21.573 each case. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11158-0 00:52:22.773 --> 00:52:25.208 Umm, you can see by eye the wiggles are you know this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11158-1 00:52:25.208 --> 00:52:26.703 very high frequency ground motion. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11165-0 00:52:29.923 --> 00:52:33.503 From graves diving question. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11171-0 00:52:35.833 --> 00:52:36.763 Yes. Thanks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11179-0 00:52:37.273 --> 00:52:39.563 Very, very good talk to Daniel. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11187-0 00:52:39.573 --> 00:52:41.943 Very interesting, very comprehensive. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11230-0 00:52:42.093 --> 00:52:46.730 I'm I have a question on the first part and it one of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11203-0 00:52:45.833 --> 00:52:46.043 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11230-1 00:52:46.730 --> 00:52:51.447 things that I've been looking at is is source scaling like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11230-2 00:52:51.447 --> 00:52:56.403 rupture area for these smaller well you know magnitude 5 type 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11230-3 00:52:56.403 --> 00:52:56.963 events. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11276-0 00:52:56.973 --> 00:53:01.803 And I'm curious if you know how rupture area that obviously 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11276-1 00:53:01.803 --> 00:53:06.392 enters into your analysis, but is it explicitly, are you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11247-0 00:53:02.143 --> 00:53:02.393 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11276-2 00:53:06.392 --> 00:53:11.223 explicitly solving for that or is it just kind of implicit? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11270-0 00:53:11.633 --> 00:53:12.073 No. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11285-0 00:53:12.083 --> 00:53:15.243 Yeah, in this case I'm umm, it's it's completely implicit. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11301-0 00:53:15.253 --> 00:53:18.828 The only way it actually enters in here directly is a measure of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11301-1 00:53:18.828 --> 00:53:19.983 the corner frequency. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11332-0 00:53:20.113 --> 00:53:23.047 So you have a measure of a corner frequency, and then you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11332-1 00:53:23.047 --> 00:53:26.335 can make some sort of assumption about what that means for fault 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11334-0 00:53:25.883 --> 00:53:26.163 OK. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11332-2 00:53:26.335 --> 00:53:27.043 area you have. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11348-0 00:53:27.053 --> 00:53:31.217 You have a moment measurements as well, so there's but you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11348-1 00:53:31.217 --> 00:53:31.993 you're not. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11399-0 00:53:32.043 --> 00:53:36.495 It's not explicitly solving for a fault geometry in this case, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11399-1 00:53:36.495 --> 00:53:40.948 so again, like the stress drop values that you see on this map 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11399-2 00:53:40.948 --> 00:53:45.188 are stress drops under the assumption of a circular source, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11399-3 00:53:45.188 --> 00:53:48.863 and so this this may not be the actual stress drop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11427-0 00:53:48.873 --> 00:53:52.053 So I think it's actually a lot of room for trying to understand 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11427-1 00:53:52.053 --> 00:53:55.183 what what this stress drop means in terms of role stress drop. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11425-0 00:53:53.713 --> 00:53:54.143 Right. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11439-0 00:53:56.103 --> 00:53:56.503 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11436-0 00:53:57.053 --> 00:53:58.003 Yeah, yeah, that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11446-0 00:53:58.013 --> 00:54:00.083 And that's the kind of the caveat here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11460-0 00:54:00.093 --> 00:54:02.723 I think you know in a relative sense you can say, yeah, hi. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11468-0 00:54:02.353 --> 00:54:02.493 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11472-0 00:54:02.773 --> 00:54:03.943 High or low and so. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11512-0 00:54:04.073 --> 00:54:07.796 But taking these say as an absolute measure, and then, you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11512-1 00:54:07.796 --> 00:54:11.140 know, backing out rupture, you might be a little bit 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11512-2 00:54:11.140 --> 00:54:14.043 problematic or or a lot of uncertainty there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11503-0 00:54:14.613 --> 00:54:14.883 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-0 00:54:14.893 --> 00:54:18.129 And I think that's a, you know, a lot of the areas for future 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-1 00:54:18.129 --> 00:54:21.052 direction, just trying to understand what the strengths 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-2 00:54:21.052 --> 00:54:23.609 and limitations of this spectral, don't you know 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-3 00:54:23.609 --> 00:54:26.845 frequency domain approach is compared to you know some of the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-4 00:54:26.845 --> 00:54:30.186 more because these are starting to get large enough earthquakes 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-5 00:54:30.186 --> 00:54:33.578 large enough that you could make finite fault models of them and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11580-6 00:54:33.578 --> 00:54:35.823 you know those have their own limitations. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11591-0 00:54:35.833 --> 00:54:39.041 But you can try to compare stress drop measurements from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11591-1 00:54:39.041 --> 00:54:39.323 that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11610-0 00:54:39.333 --> 00:54:42.502 You're just getting from Spectra to other ways of trying to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11610-1 00:54:42.502 --> 00:54:43.823 constrain the problem so. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11611-0 00:54:44.603 --> 00:54:45.473 OK, great. Thanks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11615-0 00:54:48.203 --> 00:54:48.833 Really. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11623-0 00:54:48.453 --> 00:54:48.653 So. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11617-0 00:54:49.343 --> 00:54:49.623 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11627-0 00:54:49.633 --> 00:54:50.433 Thanks so much, Danielle. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11635-0 00:54:50.513 --> 00:54:52.313 And those are really fantastic talk. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11639-0 00:54:52.323 --> 00:54:52.913 I loved it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11644-0 00:54:52.963 --> 00:54:53.453 All of it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11664-0 00:54:53.533 --> 00:54:57.967 And I have a lot of questions, but since you're on this on lot 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11668-0 00:54:56.583 --> 00:54:56.853 I'm sure. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11664-1 00:54:57.967 --> 00:54:59.093 2 question here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11675-0 00:54:59.143 --> 00:55:01.483 So you found that for the most part, they show. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11724-0 00:55:03.163 --> 00:55:06.503 Unilateral directivity, and I'm wondering if that's if you might 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11686-0 00:55:04.763 --> 00:55:05.013 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11724-1 00:55:06.503 --> 00:55:09.689 think that's magnitude dependent and perhaps related to Rob's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11724-2 00:55:09.689 --> 00:55:12.566 question related to the finiteness of the fault and the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11724-3 00:55:12.566 --> 00:55:14.673 resolution at which you're seeing these. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11734-0 00:55:14.683 --> 00:55:18.103 They're they're basically all low magnitude 5, right? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11749-0 00:55:18.003 --> 00:55:18.883 Right, yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11760-0 00:55:18.383 --> 00:55:21.714 It captured the Ridge Crest events and you're observing them 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11760-1 00:55:21.714 --> 00:55:22.643 at some distance. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11771-0 00:55:22.653 --> 00:55:26.543 That's obviously larger than the the fault dimension, right? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11782-0 00:55:27.193 --> 00:55:27.353 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11803-0 00:55:27.263 --> 00:55:32.009 So do you have an idea of like what the resolution have to be 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11803-1 00:55:32.009 --> 00:55:34.383 to observe a bilateral rupture? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11796-0 00:55:34.073 --> 00:55:34.923 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11800-0 00:55:35.053 --> 00:55:35.323 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11812-0 00:55:35.333 --> 00:55:39.153 One thing I didn't discuss, so there's two things to to really. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11845-0 00:55:42.803 --> 00:55:45.830 To really get at the directivity problem, it's very important to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11845-1 00:55:45.830 --> 00:55:48.717 have good azimuthal coverage, and we actually don't have them 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11845-2 00:55:48.717 --> 00:55:50.813 like in general the azimuthal coverage down. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11858-0 00:55:50.823 --> 00:55:52.903 Here, let me see if I can get to the right side. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11860-0 00:55:53.803 --> 00:55:54.173 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11880-0 00:55:54.183 --> 00:55:58.965 The station coverage in the area where we're seeing strong 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11880-1 00:55:58.965 --> 00:56:03.099 evidence for ruptured directivity is better, maybe 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11880-2 00:56:03.099 --> 00:56:03.423 not. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11907-0 00:56:03.483 --> 00:56:07.738 Not for the ocotillo one, but at least in this area is better 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11907-1 00:56:07.738 --> 00:56:11.033 than like for example lone pine like Lone Pine. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11925-0 00:56:11.043 --> 00:56:14.351 I think the model roughly thinks it's bilateral, but I'm not sure 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11925-1 00:56:14.351 --> 00:56:15.253 the station cover. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11974-0 00:56:15.263 --> 00:56:18.909 If you drew error bars, it'd be very large for this one, so you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11974-1 00:56:18.909 --> 00:56:22.383 have to have good azimuthal coverage in any case, regardless 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11974-2 00:56:22.383 --> 00:56:25.972 of the earthquake size, whether there's a magnitude dependence 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11974-3 00:56:25.972 --> 00:56:29.447 on the directivity, I think is an interesting problem that I 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11974-4 00:56:29.447 --> 00:56:29.903 haven't. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/11985-0 00:56:30.293 --> 00:56:32.173 Ohm gotten a chance to work on yet? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12004-0 00:56:32.183 --> 00:56:35.191 It's definitely in the next steps of trying to push this to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12004-1 00:56:35.191 --> 00:56:36.043 lower magnitudes. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12010-0 00:56:36.763 --> 00:56:38.553 UM, in essence, you might. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12047-0 00:56:38.563 --> 00:56:42.420 You might expect that you could see a clearer separation between 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12047-1 00:56:42.420 --> 00:56:46.100 the you know what's happening in the forward direction versus 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12047-2 00:56:46.100 --> 00:56:49.779 what's happening in the backward direction as earthquake size 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12047-3 00:56:49.779 --> 00:56:50.373 increases. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12070-0 00:56:50.383 --> 00:56:53.399 But I think that's something that could be done with 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12070-1 00:56:53.399 --> 00:56:55.903 synthetic tests to see if that is the case. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12095-0 00:56:56.823 --> 00:56:59.938 I'm gonna definitely look at smaller earthquakes than that, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12095-1 00:56:59.938 --> 00:57:02.793 but I'm actually not entirely sure what the answer is. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12145-0 00:57:03.353 --> 00:57:06.387 Intuitively, you might you think you could see a stronger 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12145-1 00:57:06.387 --> 00:57:09.578 directivity affect with larger earthquakes than with smaller 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12145-2 00:57:09.578 --> 00:57:12.560 earthquakes, but I know there's been a lot of studies in 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12145-3 00:57:12.560 --> 00:57:15.909 California measuring trying to measure rupture directivity from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12145-4 00:57:15.909 --> 00:57:18.943 small earthquakes and claiming they've seen a signal. So. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12170-0 00:57:20.503 --> 00:57:23.243 I I'm not sure I have any direct insight at this point. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12221-0 00:57:23.853 --> 00:57:26.810 Yeah, I guess I'm just thinking that it seems like the more we 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12221-1 00:57:26.810 --> 00:57:29.720 look at smaller earthquakes and the more detailed that we can 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12221-2 00:57:29.720 --> 00:57:32.771 look at this one quakes, they're just as complex as larger space 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12210-0 00:57:32.253 --> 00:57:32.413 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12221-3 00:57:32.771 --> 00:57:35.729 when the back and you observe it regional distances, they look 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12221-4 00:57:35.729 --> 00:57:36.433 simpler, right? 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12224-0 00:57:37.103 --> 00:57:38.733 Umm yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12261-0 00:57:38.743 --> 00:57:42.751 And I I mean, I think it's, you know, one of the issues is that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12261-1 00:57:42.751 --> 00:57:46.759 like the the action in this case is probably happening at lower 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12261-2 00:57:46.759 --> 00:57:49.953 frequencies and so is less subject to attenuation. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12293-0 00:57:51.353 --> 00:57:54.328 So you could see a a very, you know, on a on a large earthquake 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12293-1 00:57:54.328 --> 00:57:56.885 you can see a very clear directivity signal at a lower 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12293-2 00:57:56.885 --> 00:57:57.583 frequency band. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12318-0 00:57:57.593 --> 00:58:01.923 Then you would be able to see for a small earthquake UM. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12327-0 00:58:01.993 --> 00:58:06.505 And so that helps in terms of trying to, UM, uh, look at that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12327-1 00:58:06.505 --> 00:58:08.543 from the data point of view. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12365-0 00:58:08.873 --> 00:58:12.123 Umm, but you know, if you have infinite bandwidth, I'm not sure 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12365-1 00:58:12.123 --> 00:58:15.424 exactly why you wouldn't be able to see rupture directivity from 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12365-2 00:58:15.424 --> 00:58:18.573 a small earthquake, but we don't have infinite bandwidth, so. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12366-0 00:58:19.363 --> 00:58:19.613 Right. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12384-0 00:58:22.173 --> 00:58:24.873 So umm in the. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12376-0 00:58:22.343 --> 00:58:23.193 There's two. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12385-0 00:58:24.273 --> 00:58:24.923 I'll read the question. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12389-0 00:58:26.223 --> 00:58:27.643 Umm, thanks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12395-0 00:58:27.653 --> 00:58:30.443 Good Oliver Boyd said. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12398-0 00:58:30.453 --> 00:58:30.673 Great. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12432-0 00:58:30.683 --> 00:58:33.771 Talk to Daniel or any of the PBR's instrumented so that you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12432-1 00:58:33.771 --> 00:58:36.602 could compare measured and predicted ground motions to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12432-2 00:58:36.602 --> 00:58:38.043 account for slight response. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12433-0 00:58:38.633 --> 00:58:39.823 Yeah, it's a good question I. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12443-0 00:58:41.293 --> 00:58:43.643 None of the PBR's were instrumented. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12453-0 00:58:44.393 --> 00:58:45.953 I don't know if anyone's gone out and actually. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12457-0 00:58:46.833 --> 00:58:47.503 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12474-0 00:58:48.053 --> 00:58:52.814 Instrumented PBR with a seismometer and hoping and a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12474-1 00:58:52.814 --> 00:58:53.443 larger. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12510-0 00:58:53.453 --> 00:58:57.113 This was kind of this is one of the only cases that I've seen 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12510-1 00:58:57.113 --> 00:59:00.949 where someone's gone out and met and documented the PBS and then 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12510-2 00:59:00.949 --> 00:59:03.783 gone out again to see whether they got toppled. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12518-0 00:59:03.793 --> 00:59:04.763 I think there's one. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12529-0 00:59:04.773 --> 00:59:08.463 There's also a case study in Ridgecrest with the trona 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12529-1 00:59:08.463 --> 00:59:09.403 pinnacles ohm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12549-0 00:59:09.413 --> 00:59:12.493 It's a slightly different problem, but yeah, I think 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12549-1 00:59:12.493 --> 00:59:14.063 that's an interesting idea. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12570-0 00:59:14.073 --> 00:59:18.712 The the PBR's are a little bit of a delicate data set because 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12570-1 00:59:18.712 --> 00:59:22.303 people are worried about essentially vandalism. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12604-0 00:59:22.653 --> 00:59:25.949 If you have some big open public database of all these rocks that 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12604-1 00:59:25.949 --> 00:59:28.896 you could in principle knock down without too much hassle, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12604-2 00:59:28.896 --> 00:59:31.243 then people might actually go out and do that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12627-0 00:59:31.973 --> 00:59:35.760 But that said, I know they're developing a PBR database as 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12627-1 00:59:35.760 --> 00:59:38.713 part of scac that I submitted these rocks to. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12660-0 00:59:39.153 --> 00:59:43.117 I don't know what the status is of that now, but it could be an 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12660-1 00:59:43.117 --> 00:59:47.144 interesting future experiment to go out and umm put seismometers 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12660-2 00:59:47.144 --> 00:59:48.073 by these rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12682-0 00:59:48.083 --> 00:59:51.021 But then you're kind of still hoping for an earthquake to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12682-1 00:59:51.021 --> 00:59:54.163 happen, so could be one of those very long lived experiments. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12716-0 00:59:58.273 --> 01:00:02.838 I think in the interest of time, we're just going to let Tom and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12716-1 01:00:02.838 --> 01:00:07.263 Ben Devin ask their questions and then turn off the recording. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12723-0 01:00:07.273 --> 01:00:08.573 And then people can stick around. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12724-0 01:00:09.383 --> 01:00:09.563 Sure. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12739-0 01:00:12.053 --> 01:00:13.733 The time you wanna meet yourself. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12740-0 01:00:14.503 --> 01:00:14.893 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12744-0 01:00:14.903 --> 01:00:16.243 Let me DeMuth here. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12747-0 01:00:17.333 --> 01:00:17.713 Uh. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12750-0 01:00:17.973 --> 01:00:19.163 Hey, fantastic. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12775-0 01:00:19.233 --> 01:00:24.007 Talk Daniel and I've spent a lot of time with precarious rocks 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12775-1 01:00:24.007 --> 01:00:25.523 that Yucca Mountain. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12782-0 01:00:26.063 --> 01:00:26.263 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12795-0 01:00:26.963 --> 01:00:33.370 As Jim knows well, so and and prevents his calculations as 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12785-0 01:00:28.743 --> 01:00:28.913 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12795-1 01:00:33.370 --> 01:00:33.913 well. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12830-0 01:00:34.303 --> 01:00:39.830 I'm interested in in if you could go back to your very first 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12830-1 01:00:39.830 --> 01:00:45.629 slide of of the precarious rocks at Antelope Valley or Slinkard 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12824-0 01:00:42.583 --> 01:00:42.803 Mm-hmm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12830-2 01:00:45.629 --> 01:00:46.263 Valley. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12833-0 01:00:47.103 --> 01:00:47.603 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12836-0 01:00:47.183 --> 01:00:47.363 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12873-0 01:00:48.103 --> 01:00:54.773 And I'm interested in those rocks that are erosional 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12873-1 01:00:54.773 --> 01:01:01.820 remnants versus those that top of down from some higher 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12851-0 01:00:54.913 --> 01:00:55.153 Hmm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12873-2 01:01:01.820 --> 01:01:07.483 elevation and are just precariously perched. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12878-0 01:01:08.073 --> 01:01:08.323 Mm-hmm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12893-0 01:01:08.673 --> 01:01:15.113 Ohh like the two on the right, they they may. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12933-0 01:01:15.533 --> 01:01:20.010 Nevertheless, unless you go out there and try and rock them, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12933-1 01:01:20.010 --> 01:01:24.855 which may have been a little bit dicey for some of these, the two 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12933-2 01:01:24.855 --> 01:01:29.112 on the right could well be erosional remnants with fairly 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12933-3 01:01:29.112 --> 01:01:29.773 uh stiff. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12936-0 01:01:31.003 --> 01:01:31.573 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12950-0 01:01:32.203 --> 01:01:35.795 Connections to the rock below it, even though they're not very 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12950-1 01:01:35.795 --> 01:01:36.023 big. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12984-0 01:01:37.343 --> 01:01:41.267 That's I think that's less likely to be the case for ohh 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12961-0 01:01:38.573 --> 01:01:38.683 You. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12984-1 01:01:41.267 --> 01:01:45.467 the two in the middle, which I guess are the same same wrong 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12981-0 01:01:44.993 --> 01:01:45.343 Umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/12984-2 01:01:45.467 --> 01:01:46.293 later dates. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13015-0 01:01:47.153 --> 01:01:53.758 And umm, but also a lot of the the rocks on the left are, you 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13015-1 01:01:53.758 --> 01:02:00.151 know, well connected to their foundation and are not freely 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13015-2 01:02:00.151 --> 01:02:01.003 rocking. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13017-0 01:02:01.343 --> 01:02:01.543 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13038-0 01:02:02.343 --> 01:02:07.289 And so then you gotta be a little bit careful to separate 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13038-1 01:02:07.289 --> 01:02:09.933 those that you can freely rock. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13054-0 01:02:09.943 --> 01:02:14.362 So you get some estimate of the rocking points and and the the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13054-1 01:02:14.362 --> 01:02:14.853 alphas. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13059-0 01:02:15.693 --> 01:02:15.863 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13086-0 01:02:15.703 --> 01:02:21.360 Ohh from those that may yet have a connection to what's beneath 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13086-1 01:02:21.360 --> 01:02:26.930 them because they didn't come down from some remote place, but 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13086-2 01:02:26.930 --> 01:02:28.963 they're just erosional. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13112-0 01:02:29.783 --> 01:02:35.967 Uh, remnants of the erosion process as it eats away at the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13112-1 01:02:35.967 --> 01:02:38.483 the mountains here. Ohh. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13106-0 01:02:38.013 --> 01:02:38.963 Yeah, exactly. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13115-0 01:02:38.973 --> 01:02:39.903 That's a really good point. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13153-0 01:02:39.913 --> 01:02:43.600 The you know the analysis like the the modeling code is both 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13153-1 01:02:43.600 --> 01:02:47.106 the classic you know, rule of thumb and the you know, the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13153-2 01:02:47.106 --> 01:02:50.551 dynamic toppling, assuming they're free to rock, there's 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13153-3 01:02:50.551 --> 01:02:52.123 like no cohesion in there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13157-0 01:02:52.133 --> 01:02:52.623 There's not. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13175-0 01:02:52.633 --> 01:02:57.481 There's no pinning in there and so it is important to to 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13175-1 01:02:57.481 --> 01:02:59.693 recognize that assumption. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13221-0 01:02:59.703 --> 01:03:03.189 And also you know the erosional history, it doesn't matter so 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13221-1 01:03:03.189 --> 01:03:06.337 much for this study, but how long they've been in there 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13221-2 01:03:06.337 --> 01:03:09.880 currently precarious state makes a whole lot of difference for 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13221-3 01:03:09.880 --> 01:03:11.173 testing and hazard map. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13215-0 01:03:11.513 --> 01:03:12.183 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13268-0 01:03:12.273 --> 01:03:18.017 And and that will depend on the the erosional rates or when they 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13268-1 01:03:18.017 --> 01:03:23.231 fell down from where whatever spot they fall down and they 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13254-0 01:03:22.633 --> 01:03:23.073 Yeah, this. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13268-2 01:03:23.231 --> 01:03:26.943 fell down from some higher elevation and. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13274-0 01:03:26.673 --> 01:03:29.513 Exactly this guy in the middle is real hard to get to. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13298-0 01:03:29.523 --> 01:03:33.832 This guy on the right, you can walk up to it and there doesn't 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13298-1 01:03:33.832 --> 01:03:37.183 seem to be anything sticking it, but it doesn't. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13334-0 01:03:37.193 --> 01:03:40.735 I don't think anyone like really drilled into it to try to test 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13334-1 01:03:40.735 --> 01:03:42.783 that, although make as I don't know. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13327-0 01:03:41.523 --> 01:03:41.783 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13336-0 01:03:43.423 --> 01:03:45.563 Leave the one in the middle alone. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13346-0 01:03:46.023 --> 01:03:47.103 You don't want to go there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13345-0 01:03:47.663 --> 01:03:47.843 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13349-0 01:03:48.493 --> 01:03:49.363 OK. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13381-0 01:03:50.453 --> 01:03:54.856 But that that's that just adds a little bit, perhaps a lot of 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13381-1 01:03:54.856 --> 01:03:58.763 complexity depending on which rocks you're talking to. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13376-0 01:03:56.493 --> 01:03:56.693 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13390-0 01:03:58.773 --> 01:04:04.033 But well, thanks again for a really nifty talk. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13420-0 01:04:04.043 --> 01:04:11.315 Because it's really important that we we we test the you know 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13420-1 01:04:11.315 --> 01:04:18.939 the basic understanding and the validity of all these precarious 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13420-2 01:04:18.939 --> 01:04:19.643 rocks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13426-0 01:04:20.053 --> 01:04:22.623 Umm, thank you. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13425-0 01:04:20.763 --> 01:04:21.823 So great. Thanks. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13437-0 01:04:25.683 --> 01:04:28.123 Devin Mcphillips, you have the last question. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13446-0 01:04:29.903 --> 01:04:31.243 Hey, thanks for a great talk, Daniel. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13455-0 01:04:31.833 --> 01:04:31.953 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13462-0 01:04:32.773 --> 01:04:35.263 I just wanted to follow up a couple on a couple of questions. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13489-0 01:04:35.353 --> 01:04:39.585 One is that in terms of instrumenting the PBR's Tom 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13489-1 01:04:39.585 --> 01:04:44.143 Pratt in Reston has a a manuscript in review right now. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13513-0 01:04:44.153 --> 01:04:48.914 Now I believe that, umm, where he's instrumented, I think 5 or 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13513-1 01:04:48.914 --> 01:04:51.483 6 PBR's in the on the East Coast. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13534-0 01:04:51.493 --> 01:04:55.507 Coast just recording environmental noise but and and 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13534-1 01:04:55.507 --> 01:04:59.143 also a a little push that he gave them himself. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13545-0 01:04:59.153 --> 01:05:00.683 But it's an earthquake. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13547-0 01:05:00.693 --> 01:05:01.263 But it's a start. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13549-0 01:05:01.863 --> 01:05:02.263 That's cool. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13572-0 01:05:03.193 --> 01:05:10.423 And then there were two things that I might be worth mentioning 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13572-1 01:05:10.423 --> 01:05:14.603 about the PBR's one is that it just. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13599-0 01:05:14.613 --> 01:05:18.468 Yeah, it's it's maybe worth mentioning that probably the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13599-1 01:05:18.468 --> 01:05:22.796 standard of practice for PBR's right now is to use the prevents 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13599-2 01:05:22.796 --> 01:05:23.473 equations. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13661-0 01:05:23.483 --> 01:05:28.412 So so that that tan alpha relation is is sort of, yeah, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13612-0 01:05:27.633 --> 01:05:27.823 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13661-1 01:05:28.412 --> 01:05:33.780 used as a rule of thumb, but in sort of recent publications, 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13661-2 01:05:33.780 --> 01:05:39.237 umm, looking at infrastructure, people have tended to use the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13661-3 01:05:39.237 --> 01:05:44.606 use the permits equations to incorporate that pulse duration 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13661-4 01:05:44.606 --> 01:05:49.183 into the uncertainty or into the hazard curve, umm. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-0 01:05:49.643 --> 01:05:54.125 And then the other thing is just in terms of following up on Tom 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-1 01:05:54.125 --> 01:05:57.917 Hanks comment that that, that Brune data set is really 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-2 01:05:57.917 --> 01:06:01.847 interesting, but it it really should be updated probably 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-3 01:06:01.847 --> 01:06:05.984 before it's used further because there's really very little 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-4 01:06:05.984 --> 01:06:10.190 information in there about the actual size of these rocks or 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-5 01:06:10.190 --> 01:06:14.258 yeah or any any description of what their basal contact is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13733-6 01:06:14.258 --> 01:06:14.603 like. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13768-0 01:06:14.943 --> 01:06:18.317 It was sort of was a foundational study, but it but 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13768-1 01:06:18.317 --> 01:06:21.496 it it didn't take advantage of modern tools like 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13752-0 01:06:19.063 --> 01:06:19.253 Yeah. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13768-2 01:06:21.496 --> 01:06:23.313 photogrammetry, for example. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13806-0 01:06:23.833 --> 01:06:27.788 Yeah, I think there's, I mean, I'm not a, I don't claim to be a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13806-1 01:06:27.788 --> 01:06:31.558 PBR expert, but I think the people that really are are going 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13806-2 01:06:31.558 --> 01:06:35.081 out in the field and doing 3D models of these rocks with 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13806-3 01:06:35.081 --> 01:06:35.823 imagery and. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13832-0 01:06:35.893 --> 01:06:38.306 And I think that could be, you know, we've got all the the 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13832-1 01:06:38.306 --> 01:06:40.637 tabulation of sites and the rocks are probably all still 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13832-2 01:06:40.637 --> 01:06:40.883 there. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13842-0 01:06:40.893 --> 01:06:43.743 So people could go out and and do that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13860-0 01:06:43.753 --> 01:06:47.615 And you know, incorporate that information into a, you know, a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13860-1 01:06:47.615 --> 01:06:48.903 PBR database if that. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-0 01:06:49.013 --> 01:06:53.045 If that happens, and yeah, and and on your first point, I think 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-1 01:06:53.045 --> 01:06:56.951 and and then try to make this point in the paper that this is 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-2 01:06:56.951 --> 01:07:00.479 kind of the the study that we did is actually kind of a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-3 01:07:00.479 --> 01:07:04.322 validation of making sure that you use the you know the full 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-4 01:07:04.322 --> 01:07:08.039 you know at least some sort of dynamic toppling model when 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13936-5 01:07:08.039 --> 01:07:09.173 you're testing it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13950-0 01:07:09.183 --> 01:07:13.069 And it's actually the the that model predicts exactly what we 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13950-1 01:07:13.069 --> 01:07:13.633 observed. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13974-0 01:07:13.643 --> 01:07:17.047 And so it's just kind of a validation of using that as a 8ca14bac-4f56-40c1-9c1a-c4d258076e65/13974-1 01:07:17.047 --> 01:07:20.033 port as opposed to more of the simple heuristics. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14006-0 01:07:20.043 --> 01:07:23.622 So I yeah, I agree with you entirely and I maybe should have 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14006-1 01:07:23.622 --> 01:07:26.263 framed that a little better in the talk, so. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14007-0 01:07:25.923 --> 01:07:26.843 Well, like I enjoyed it. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14012-0 01:07:33.763 --> 01:07:33.963 OK. 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14060-0 01:07:33.973 --> 01:07:37.251 Well, let's thank Daniel again and finish up and I think Daniel 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14060-1 01:07:37.251 --> 01:07:40.580 might stick around in the teams chat in the teams for a few more 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14060-2 01:07:40.580 --> 01:07:43.755 minutes, you know, wants to say hello, but stop the recording 8ca14bac-4f56-40c1-9c1a-c4d258076e65/14060-3 01:07:43.755 --> 01:07:44.933 and thank thanks again.