WEBVTT Kind: captions Language: en-US 00:00:00.148 --> 00:00:16.718 [music] 00:00:16.718 --> 00:00:22.430 … distinct pleasure to introduce Bill Ellsworth, my long-time 00:00:22.430 --> 00:00:26.242 colleague and one of my best friends at the Survey. 00:00:26.242 --> 00:00:33.639 For those of you who don’t know, Bill is one of a large group of 00:00:33.639 --> 00:00:40.050 eminent Earth scientists who came from Oklahoma. [laughs] 00:00:40.050 --> 00:00:43.240 From which he went to Stanford, where he got his bachelor’s and 00:00:43.240 --> 00:00:48.710 master’s degree. Then Rob Wesson, our colleague, 00:00:48.710 --> 00:00:53.500 was able to lure him to work here at the USGS in Menlo Park 00:00:53.500 --> 00:00:56.820 in the earthquake program. He became quickly indispensable, 00:00:56.820 --> 00:01:03.439 so he decided it was time to leave and get a Ph.D. Went to MIT and, 00:01:03.439 --> 00:01:07.550 in pretty record time, achieved that working with Kei Aki. 00:01:07.550 --> 00:01:11.870 He has been at the Survey ever since, and when I say “been,” 00:01:11.870 --> 00:01:17.070 I mean his desk is here. [laughter] 00:01:17.070 --> 00:01:22.150 He is – one of the things that I admire most about Bill is, as well as being 00:01:22.150 --> 00:01:28.420 a technically superb seismologist, he has been prescient on a number of 00:01:28.420 --> 00:01:34.200 really important developments in earthquake seismology, like 00:01:34.200 --> 00:01:39.909 identification of repeating earthquakes. Bill, I think, was the first to do that 00:01:39.909 --> 00:01:45.020 using the double-difference method to precisely relocate earthquakes, 00:01:45.020 --> 00:01:49.090 which has become kind of a standard tool in seismology, and Bill and his 00:01:49.090 --> 00:01:53.810 colleague, Felix Waldhauser, again, were the first to do that. 00:01:53.810 --> 00:01:58.491 And then, more recently – more recently, well, it depends on your age, 00:01:58.491 --> 00:02:07.899 I guess, in the last decade or so, has been a leader in using deep 00:02:07.899 --> 00:02:13.750 boreholes drilled for scientific purposes and put to use as very 00:02:13.750 --> 00:02:20.970 sensitive seismological observatories. He also, and this is the subject of 00:02:20.970 --> 00:02:28.750 his talk today, has been a leader in the field of – the emerging 00:02:28.750 --> 00:02:31.997 and important field of induced seismicity. 00:02:32.028 --> 00:02:35.620 He’ll talk about that today, but I want to flash up one image 00:02:35.620 --> 00:02:45.170 that is reminiscent of his and my early days in – as Survey – witless 00:02:45.170 --> 00:02:52.600 administrators, as someone put it. At a very – some meeting that was 00:02:52.600 --> 00:02:56.739 allegedly important, Bill and I, we were branch chiefs together, 00:02:56.739 --> 00:03:01.290 and we were sitting [laughter] at a table, and we both had beards 00:03:01.290 --> 00:03:04.689 that were considerably longer than they are now. 00:03:04.689 --> 00:03:10.550 And Rob Wesson looked at us and then, at a kind of a suitable 00:03:10.550 --> 00:03:17.079 silent moment, said, ZZ Top? [laughter] 00:03:17.079 --> 00:03:24.794 Those of you who may remember ZZ Top, my condolences. [laughter] 00:03:24.794 --> 00:03:28.620 But they’re still – they’re still at it, just as Bill and I are. 00:03:28.620 --> 00:03:34.570 And I got this image off the web about 10 minutes ago, to tell you the truth. 00:03:34.570 --> 00:03:40.768 But the latest news is they’re playing Moose Jaw tonight. [laughter] 00:03:40.768 --> 00:03:46.409 And Bill’s, of course, playing to a much more illustrious audience today. 00:03:46.409 --> 00:03:51.560 And he told me that I had to keep my presentation short, and I told him, 00:03:51.560 --> 00:03:55.354 you know, good luck, but now it’s time to turn it over to you, Bill. 00:03:55.385 --> 00:03:57.057 - All right. Thank you, Wayne. 00:03:57.057 --> 00:03:59.284 - [inaudible] - Yeah. 00:03:59.284 --> 00:04:02.359 So the part of the story Wayne hasn’t told you is there’s the other – 00:04:02.359 --> 00:04:05.079 there’s the ponytail version as well. [laughter] 00:04:05.079 --> 00:04:07.939 But we’ll talk about that later if questions come up. 00:04:07.939 --> 00:04:11.030 So back to more serious subjects here, I guess. 00:04:11.030 --> 00:04:13.400 First of all, thanks, everyone, for coming this afternoon. 00:04:13.400 --> 00:04:18.500 And I’m going to be talking today about a project that a number of us have been 00:04:18.500 --> 00:04:21.190 working on for a couple of years now trying to understand the 00:04:21.190 --> 00:04:24.440 recent changes in earthquake activity across the U.S. and 00:04:24.440 --> 00:04:27.170 how it may be related to energy activities. 00:04:27.170 --> 00:04:29.970 And let me say at the outset that all the science that I’m going to 00:04:29.970 --> 00:04:34.921 talk about today is strictly USGS or work of our colleagues. 00:04:34.921 --> 00:04:38.639 Anything that I say that might venture into the realm of policy 00:04:38.639 --> 00:04:43.340 or speculation is on me. It’s not either the official opinion of 00:04:43.340 --> 00:04:46.630 the Geological Survey, the Department of the Interior, or anybody else. 00:04:46.630 --> 00:04:50.050 Okay, that’s a disclaimer for people out there in television land. 00:04:50.050 --> 00:04:52.509 So let’s go ahead and get started. First of all, let me just acknowledge 00:04:52.509 --> 00:04:54.669 that there are a bunch of people that have contributed in various 00:04:54.669 --> 00:04:57.850 ways to this presentation. And, in particular, a number of people 00:04:57.850 --> 00:05:01.590 who are part of the USGS Powell Center project on induced seismicity. 00:05:01.590 --> 00:05:06.949 I’d particularly like to single out some of the non-USGS participants, including 00:05:06.949 --> 00:05:12.033 Lisa Brown, Wesley Block, Cliff Frohlich, Austin Holland, Steve Horton. 00:05:12.033 --> 00:05:14.770 So thanks to all of those who’s – be showing some of the work 00:05:14.770 --> 00:05:18.919 from these folks here along the way. So let’s get going. 00:05:18.919 --> 00:05:21.630 The outline is going to be as follows. We’re going to take a – first, we’re 00:05:21.630 --> 00:05:24.650 going to take a look at this issue of the recent increase in earthquake 00:05:24.650 --> 00:05:28.210 activity within the mid-continent. And this is really the thing that got 00:05:28.210 --> 00:05:31.670 us started a couple of years ago when we realized that things 00:05:31.670 --> 00:05:34.602 were changing, and we really want to understand why. 00:05:34.602 --> 00:05:38.060 I’d then like to talk a little bit about seismic hazard and risk and some of 00:05:38.060 --> 00:05:41.977 the challenges we face in these areas of unusual earthquakes. 00:05:41.977 --> 00:05:45.789 I feel it’ll be necessary to say a few words about kind of the mechanics 00:05:45.789 --> 00:05:49.569 of how we understand human activity can be inducing earthquakes. 00:05:49.569 --> 00:05:53.009 And then look at this rather contentious issue, perhaps, 00:05:53.009 --> 00:05:56.576 of is it fracking, wastewater disposal, or something else. 00:05:56.576 --> 00:06:00.780 And then we’ll look at four case studies that I think help illustrate some of these 00:06:00.780 --> 00:06:05.520 points, including some very recent activity, meaning last week, that was 00:06:05.520 --> 00:06:09.800 going on in the Fort Worth, Texas, area. And then finally, I’d like to finish 00:06:09.800 --> 00:06:13.010 with something I call think locally, act globally. And now, I didn’t get 00:06:13.010 --> 00:06:16.500 that backwards, and you’ll understand why when we get there. 00:06:16.500 --> 00:06:19.770 So let’s get going. This is a map that would be familiar, I think, 00:06:19.770 --> 00:06:23.479 to many of you. The colors here show the probability of earthquake 00:06:23.479 --> 00:06:28.380 shaking over a long exposure period, about 475 years. 00:06:28.380 --> 00:06:30.900 This is the information that goes into making the National Seismic 00:06:30.900 --> 00:06:35.430 Hazard Map. And that map is used to provide guidance 00:06:35.430 --> 00:06:39.229 on building structures to resist earthquakes at almost 00:06:39.229 --> 00:06:41.780 a trillion dollars’ worth of new construction per year. 00:06:41.780 --> 00:06:44.370 So it’s an important USGS product. 00:06:44.370 --> 00:06:46.540 The dots here represent the earthquakes that have happened 00:06:46.540 --> 00:06:49.810 just in the past few years. And you can see that, in general, 00:06:49.810 --> 00:06:51.710 there’s a pretty good correlation with the map. 00:06:51.710 --> 00:06:55.650 In these areas, particularly in the western U.S., there are lots of dots, 00:06:55.650 --> 00:06:59.599 lots of – lots of hot colors. In areas where there are cold colors, 00:06:59.599 --> 00:07:02.160 there are few dots. So this is indication that 00:07:02.160 --> 00:07:05.470 the map is generally doing what it’s supposed to. 00:07:05.470 --> 00:07:07.349 But we do want to think a little bit about how maps 00:07:07.349 --> 00:07:11.130 such as this get made and what happens if things change. 00:07:11.130 --> 00:07:14.740 In particular, there has been a change in earthquake activity within this middle 00:07:14.740 --> 00:07:18.889 section of the country from about here to here that began in about 2009. 00:07:18.889 --> 00:07:23.199 And you can see on this hockey stick plot, there’s a really rapid increase 00:07:23.199 --> 00:07:27.370 in earthquake activity, more than a doubling of rate, 00:07:27.370 --> 00:07:30.720 within the – within the mid-continent. And this is the thing that we began 00:07:30.720 --> 00:07:36.780 to investigate in 2011, and in fact, investigations continue. 00:07:36.780 --> 00:07:40.430 So just to go through some of the evidence that supports this, 00:07:40.430 --> 00:07:43.550 I’d like to show you a series of slides here that represent decadal 00:07:43.550 --> 00:07:47.600 views of earthquake activity. These maps are truncated at magnitude 3, 00:07:47.600 --> 00:07:52.169 so we don’t consider smaller events. And studies that have been done by 00:07:52.169 --> 00:07:55.810 the Nuclear Regulatory Commission and their contractors indicate that, 00:07:55.810 --> 00:07:59.240 within this area, we’re complete at magnitude 3 all the way back to 00:07:59.240 --> 00:08:04.530 1970 or before. So we’re not looking at changes in station density or other 00:08:04.530 --> 00:08:08.990 things that might affect detectability. So we can see here from this picture, 00:08:08.990 --> 00:08:13.340 ’70 to ’79, there’s a lot of earthquake activity in the – in the zone around 00:08:13.340 --> 00:08:16.150 New Madrid where the 1811-1812 earthquakes occurred. 00:08:16.150 --> 00:08:19.449 And kind of a smattering of earthquakes across the mid-continent. 00:08:19.449 --> 00:08:23.090 1980s, the patterns change. We see a persistence of activity 00:08:23.090 --> 00:08:27.150 in the region around New Madrid. There’s a swarm that picks up 00:08:27.150 --> 00:08:30.014 here in central Arkansas, a place near Enola. 00:08:30.014 --> 00:08:32.940 And earthquake activity in a number of other states. 00:08:32.940 --> 00:08:36.080 1990s, again, the pattern stays pretty much constant here. 00:08:36.080 --> 00:08:38.080 They shift around elsewhere. 00:08:38.080 --> 00:08:40.669 And then we get to the 2000s, and things have really changed. 00:08:40.669 --> 00:08:45.830 There is a really large concentration of earthquakes, again, in Arkansas. 00:08:45.830 --> 00:08:49.500 Many earthquakes – more earthquakes than in the past occurring in Oklahoma. 00:08:49.500 --> 00:08:51.560 Earthquake concentrations in Texas, New Mexico, 00:08:51.560 --> 00:08:54.070 and on the Colorado border. So these are the things that 00:08:54.070 --> 00:08:57.440 are contributing to this increase in earthquake activity. 00:08:57.440 --> 00:09:03.240 If we look at their distribution in space, we find that, over a period, say, 00:09:03.240 --> 00:09:08.320 from 2001 to 2011, that decade, we would have expected 234 earthquakes, 00:09:08.320 --> 00:09:12.450 on average, based upon what had happened in the previous three decades. 00:09:12.450 --> 00:09:17.110 We had almost – we had 112 in Oklahoma alone; 56 in the Guy, 00:09:17.110 --> 00:09:21.350 Arkansas, area where that swarm was occurring; 93 in this region along 00:09:21.350 --> 00:09:25.590 the Colorado-New Mexico border, the Raton Basin; and as many as we 00:09:25.590 --> 00:09:29.459 would have expected everywhere in just the rest of the mid-continent – 245. 00:09:29.459 --> 00:09:33.630 So something unusual is going on – about twice the rate. 00:09:33.630 --> 00:09:37.329 We can see from this figure supplied by my colleague Austin Holland, 00:09:37.329 --> 00:09:40.110 in Oklahoma, that it’s not a matter of instrumentation. 00:09:40.110 --> 00:09:43.110 If we look at how many people were feeling earthquakes, 00:09:43.110 --> 00:09:46.390 beginning in the mid-1970s in Oklahoma, you can see that 00:09:46.390 --> 00:09:49.920 that increase correlates very well with what see instrumentally. 00:09:49.920 --> 00:09:52.570 So I think all the seismologists who have looked at this are fairly well 00:09:52.570 --> 00:09:56.350 convinced that this change is real. Something different is going on relating 00:09:56.350 --> 00:10:01.839 to many more earthquakes than we had seen in the recent historical past. 00:10:01.839 --> 00:10:06.140 So let’s now take a look at what some of the implications might be for this 00:10:06.140 --> 00:10:09.475 increase in earthquake activity. And I should that, in 2013, 00:10:09.475 --> 00:10:13.430 that rate has continued to be high. It isn’t like things are slowing down. 00:10:13.430 --> 00:10:16.160 They are continuing. One of the things we might 00:10:16.160 --> 00:10:23.020 want to know is how well such maps forecast future activity. 00:10:23.020 --> 00:10:26.329 Before we go at that, I’d like to look a little bit at who some of the audiences 00:10:26.329 --> 00:10:30.120 might be for this – for these questions. So first, let’s ask who might be 00:10:30.120 --> 00:10:33.320 concerned about getting answers. Well, first of all, there is industry. 00:10:33.320 --> 00:10:36.580 They are really quite concerned and interested in this. 00:10:36.580 --> 00:10:40.579 It would include the producers, those of who are drilling wells 00:10:40.579 --> 00:10:44.720 and extracting resources. The service providers who do 00:10:44.720 --> 00:10:47.410 a lot of the work for them and help provide guidance to them 00:10:47.410 --> 00:10:51.640 about how to perform the work. And also the wastewater disposers. 00:10:51.640 --> 00:10:55.079 Typically, small companies are the ones that are responsible 00:10:55.079 --> 00:11:01.531 for sequestering the byproducts of the extraction activities. 00:11:01.531 --> 00:11:07.586 In addition, we’ve got the regulators, who are – would include the oil and gas 00:11:07.586 --> 00:11:10.850 regulators, those who directly regulate what goes on in the industry, 00:11:10.850 --> 00:11:14.100 those who make the rules or provide the interpretation. 00:11:14.100 --> 00:11:18.010 But, in addition, there are other regulators that become involved. 00:11:18.010 --> 00:11:21.310 There are a lot of local land-use jurisdictions that also concerned. 00:11:21.310 --> 00:11:26.350 That they may be asking questions, what risk might we be putting a facility 00:11:26.350 --> 00:11:31.149 to if we allow certain activities to occur. And, even more generally, there will 00:11:31.149 --> 00:11:34.290 be the seismic safety regulators, those who would like to know 00:11:34.290 --> 00:11:36.650 what are the implications of these changing patterns of 00:11:36.650 --> 00:11:40.920 earthquakes in terms of building codes, for example. 00:11:40.920 --> 00:11:43.269 Public is also obviously a partner in this. 00:11:43.269 --> 00:11:48.220 And they are very – likely anyone who is concerned about their 00:11:48.220 --> 00:11:52.010 potential exposure, we’ll certainly hear from, as we do. 00:11:52.010 --> 00:11:56.050 And there will also be the owners of critical facilities, those who perhaps 00:11:56.050 --> 00:11:59.170 have dams, bridges, or other things – nuclear power plants – that would 00:11:59.170 --> 00:12:02.841 like to know, are they – are they exposed to a risk that they were 00:12:02.841 --> 00:12:07.502 not considering when the facility was being constructed or planned? 00:12:07.502 --> 00:12:09.560 And, of course, then there are the builders, the people who take the 00:12:09.560 --> 00:12:13.838 responsibility for actually executing the construction. 00:12:13.838 --> 00:12:15.820 Well, what are some of the things that they would want to 00:12:15.820 --> 00:12:18.450 know or need to know? Well, the industry, I think, 00:12:18.450 --> 00:12:20.529 in some ways, we can say simply, they’d like to know what 00:12:20.529 --> 00:12:23.240 the requirements are for getting on with business. 00:12:23.240 --> 00:12:27.610 They have a certain risk that’s being posed by all of these induced 00:12:27.610 --> 00:12:30.893 earthquakes, and for them, it’s largely a business risk. 00:12:30.925 --> 00:12:36.140 If they don’t get a license to operate, they lose the opportunity to make 00:12:36.140 --> 00:12:40.182 a profit, to extract a resource, to make it available to society. 00:12:40.182 --> 00:12:43.270 The regulators, they would like to make sure that any changes 00:12:43.270 --> 00:12:46.480 in regulation have a sound scientific basis. 00:12:46.480 --> 00:12:48.690 And there’s a lot of questions about that right now. 00:12:48.690 --> 00:12:51.110 The fact that we’re debating this, that there’ll be many sessions 00:12:51.110 --> 00:12:53.810 at the upcoming AGU meeting, I think indicates that there’s 00:12:53.810 --> 00:12:57.360 a lot of science that yet remains to be done. 00:12:57.360 --> 00:12:59.580 The public is interested in a couple of reasons. 00:12:59.580 --> 00:13:02.640 One is that they want assurances that regulations are sufficient 00:13:02.640 --> 00:13:05.820 and being followed. But they’re also concerned because 00:13:05.820 --> 00:13:10.459 they need information to understand the risk and understand the hazard and learn 00:13:10.459 --> 00:13:15.740 ways that they can mitigate the risk. I think we at the USGS can be rather 00:13:15.740 --> 00:13:19.829 proud of the job we do and, in terms of informing the public about earthquake 00:13:19.829 --> 00:13:24.339 hazards, we do a great job of that in areas where earthquakes occur naturally. 00:13:24.339 --> 00:13:27.279 I think maybe we need to think about doing more of this 00:13:27.279 --> 00:13:29.990 in areas where earthquakes are unusual. 00:13:29.990 --> 00:13:34.720 Well, earthquakes that are unusual are happening not only in the United States 00:13:34.720 --> 00:13:38.190 but other places in the world. And, if we turn back the clock and go to 00:13:38.190 --> 00:13:43.450 1967 in a – in a place called Blackburn, England, there was a concern about 00:13:43.450 --> 00:13:48.010 some holes that you may remember. And John Lennon’s famous song. 00:13:48.010 --> 00:13:51.709 There were 4,000 that they were concerned about in 1967. 00:13:51.709 --> 00:13:56.149 Today they’re only concerned about one. And that is a well that was drilled 00:13:56.149 --> 00:14:00.260 to develop shale gas resources. And, in 2011, when this hole 00:14:00.260 --> 00:14:04.500 was initially fracked, it produced a magnitude 2.3 earthquake. 00:14:04.500 --> 00:14:07.190 How many of you have felt a 2.3 earthquake? 00:14:07.190 --> 00:14:09.824 A few hands out there. Okay. 00:14:09.824 --> 00:14:13.320 This actually has shut down fracking in Great Britain. 00:14:13.320 --> 00:14:15.598 So this is a serious issue for them. 00:14:15.598 --> 00:14:20.839 And there are lots of partners in this, including the Anglican Church, 00:14:20.839 --> 00:14:25.720 as you can see here. But there are also the humorous and the editorial 00:14:25.720 --> 00:14:30.130 cartoonists are involved as well. And this one says, what a relief. 00:14:30.130 --> 00:14:33.150 I thought they said that Cuadrilla, the fracking company, 00:14:33.150 --> 00:14:37.649 was coming to ruin our village, but it’s only Godzilla. 00:14:37.649 --> 00:14:39.790 So we have some holes to fill in our scientific 00:14:39.790 --> 00:14:41.639 understanding of induced earthquakes. 00:14:41.639 --> 00:14:45.850 And first of these is really an improved fundamental understanding of process. 00:14:45.850 --> 00:14:49.410 As I’ll discuss, I think we know the outlines of what’s going on, 00:14:49.410 --> 00:14:53.120 but translating that into things that we can apply on a local scale 00:14:53.120 --> 00:14:56.899 present many challenges. We’d really like to develop 00:14:56.899 --> 00:15:00.320 a predictive understanding of the conditions that may induce earthquakes 00:15:00.320 --> 00:15:03.480 so that something might be said before an activity begins. 00:15:03.480 --> 00:15:06.398 Right now, it’s really kind of shooting in the dark. 00:15:06.398 --> 00:15:09.740 Sometimes wells and activity lead earthquakes, 00:15:09.740 --> 00:15:12.728 and most times, they do not. 00:15:12.728 --> 00:15:16.220 We’d also like to help develop the scientific basis for induced seismicity 00:15:16.220 --> 00:15:19.626 risk management. What do you do when induced earthquakes begin? 00:15:19.626 --> 00:15:23.370 That, again, is one of the big challenges. And finally, where we would like to 00:15:23.370 --> 00:15:28.519 end up is with a probabilistic model for induced seismic hazard assessment. 00:15:28.519 --> 00:15:32.110 We currently don’t have that. And, as the U.S. National Seismic 00:15:32.110 --> 00:15:36.720 Hazard Map gets revised, it’s likely that the issue of induced earthquakes 00:15:36.720 --> 00:15:40.720 is going to be set to the side, at least for this round. 00:15:40.720 --> 00:15:44.230 So let’s go back now to this question of seismic hazard and risk. 00:15:44.230 --> 00:15:48.560 As I mentioned, most of the risk is associated on the West Coast 00:15:48.560 --> 00:15:51.022 or in the deforming Intermountain West. 00:15:51.022 --> 00:15:53.639 I think all of you know lots about plate tectonics, 00:15:53.639 --> 00:15:56.220 so I don’t need to explain why that’s the case. 00:15:56.220 --> 00:16:01.060 But, when we look at how we assess risk in an area like data-rich California, 00:16:01.060 --> 00:16:04.579 we can make models such as the just recently completed Uniform California 00:16:04.579 --> 00:16:08.930 Earthquake Rupture Forecast Version 3. This is kind of a snapshot that 00:16:08.930 --> 00:16:12.380 summarizes what was found in this study. The red faults here 00:16:12.380 --> 00:16:15.170 are the ones that are going to be the most active over the large period. 00:16:15.170 --> 00:16:18.920 And, as the colors fade to cooler, it lowers the risk of earthquakes 00:16:18.920 --> 00:16:21.010 happening on individual structures. 00:16:21.010 --> 00:16:24.930 To build this model, we have lots of our geologic tools to stand on. 00:16:24.930 --> 00:16:28.752 We can begin with descriptions of where the faults are located. 00:16:28.752 --> 00:16:31.860 Information about how fast the faults are moving determined both from 00:16:31.860 --> 00:16:35.699 paleoseismology and geodesy. That can be then folded into the 00:16:35.699 --> 00:16:38.860 physics that we understand to develop earthquake rate models and eventually 00:16:38.860 --> 00:16:42.079 end up with probability models. That works well when we 00:16:42.079 --> 00:16:46.133 understand not only the mechanics, but have the data to go with it. 00:16:46.133 --> 00:16:48.470 In most of the mid-continent and the eastern U.S., 00:16:48.470 --> 00:16:51.300 we don’t have that information. And what we really rely upon 00:16:51.300 --> 00:16:54.519 is the rate at which earthquakes have happened in the past. 00:16:54.519 --> 00:16:59.720 So this map is largely based – east of the Rockies is based upon 00:16:59.720 --> 00:17:02.500 how many earthquakes are in the earthquake catalogs. 00:17:02.500 --> 00:17:05.651 And that information is used to spread across and to forecast 00:17:05.651 --> 00:17:09.910 the possibility that larger earthquakes may occur. 00:17:09.910 --> 00:17:12.920 Now that there’s been a change in earthquake activity within this region, 00:17:12.920 --> 00:17:16.280 how should we respond in remaking a map? 00:17:16.280 --> 00:17:18.860 So one question we might ask about this map that was made 00:17:18.860 --> 00:17:23.030 in 2008 is, how well does it forecast things going forward? 00:17:23.030 --> 00:17:26.140 We can – we can ask that map how many earthquakes were expected 00:17:26.140 --> 00:17:30.360 to occur in the next four years. And we can compare that with 00:17:30.360 --> 00:17:33.400 the number that actually did occur, and then determine how likely 00:17:33.400 --> 00:17:35.750 it was this would happen by chance. 00:17:35.750 --> 00:17:38.610 And this is an exercise that Andrea Llenos and Andy Michael have 00:17:38.610 --> 00:17:42.450 been working on. This is one of the results from their study. 00:17:42.450 --> 00:17:46.780 The blue areas here on the map indicate that the map works pretty well. 00:17:46.780 --> 00:17:49.440 As the colors become hotter, it works less well. 00:17:49.440 --> 00:17:53.190 And, in particular, I draw your attention to central Oklahoma, 00:17:53.190 --> 00:17:58.150 earthquakes in the Dallas/Forth Worth area, some in western Texas, and again, 00:17:58.150 --> 00:18:00.270 earthquakes on the Colorado-New Mexico border. 00:18:00.270 --> 00:18:03.630 These are places where earthquakes were unlikely to occur in the numbers 00:18:03.630 --> 00:18:07.020 that they did over these years. So this is one of the lines evidence, 00:18:07.020 --> 00:18:09.670 I think, that leads us to think that there’s more going on 00:18:09.670 --> 00:18:13.850 than just natural variations in activity. 00:18:13.850 --> 00:18:16.320 Let me talk a little bit now about how there can be changes 00:18:16.320 --> 00:18:20.700 in earthquake activity that are related to things that people do. 00:18:20.700 --> 00:18:23.650 There are two basic mechanisms that we think of in terms of induced 00:18:23.650 --> 00:18:29.260 earthquakes. On the left is the direct fluid pressure effects. 00:18:29.260 --> 00:18:33.320 This is where fluid pressure is changed underground, perhaps due to the 00:18:33.320 --> 00:18:38.740 injection of water in the well or from, say, the percolation of water from 00:18:38.740 --> 00:18:43.120 a deep reservoir into underground formations. 00:18:43.120 --> 00:18:47.050 That pressure, if it reaches a fault, can increase the fluid pressure acting 00:18:47.050 --> 00:18:50.670 within the fault and weaken it through the effective stress mechanism. 00:18:50.670 --> 00:18:54.170 So this is kind of an indirect method in which the earthquake is releasing 00:18:54.170 --> 00:18:57.170 stresses that are already present in the ground, but the fault is 00:18:57.170 --> 00:19:00.980 being destabilized by the effect of fluid pressure. 00:19:00.980 --> 00:19:04.690 The other way that it can happen is by actually changing the solid – 00:19:04.690 --> 00:19:08.190 the solid stresses in the Earth. And that could happen, say, 00:19:08.190 --> 00:19:13.940 for example, in the case of either injection or depletion of an oil reservoir. 00:19:13.940 --> 00:19:16.460 That will changes stresses in the far-field. 00:19:16.460 --> 00:19:19.140 Similar things happen in geothermal reservoirs. 00:19:19.140 --> 00:19:23.310 And it’s through this mechanism that we can also bring a fault to failure. 00:19:23.310 --> 00:19:27.390 The mechanism that most of us are thinking about these days is this one, 00:19:27.390 --> 00:19:30.650 however, in which there is the effect of fluid pressure, which, as we’ll see, 00:19:30.650 --> 00:19:35.550 can act at considerable distance from the point of injection. 00:19:35.550 --> 00:19:39.730 So one of the challenges is knowing what will be activated if we change 00:19:39.730 --> 00:19:42.530 the fluid pressures underground. And I think the first thing to remember 00:19:42.530 --> 00:19:46.230 is that faults occur at all – on a wide variety of scales, and they’re found 00:19:46.230 --> 00:19:49.690 in virtually all geologic settings. A number of the faults that we’ve seen 00:19:49.690 --> 00:19:53.330 activated recently are ancient faults. They’re not ones that were likely 00:19:53.330 --> 00:19:56.820 to move anytime soon, maybe not in a billion years. 00:19:56.820 --> 00:20:02.030 But if they’re in the right orientation, and the state of stress is sufficient, 00:20:02.030 --> 00:20:05.540 it can bring those faults to failure. The other thing we know is that the 00:20:05.540 --> 00:20:08.330 state of stress is not – is not hydrostatic. 00:20:08.330 --> 00:20:12.980 And it depends upon the tectonic setting. Three examples of the classical 00:20:12.980 --> 00:20:18.550 Andersonian faulting environments here shown in this figure from Rick Sibson. 00:20:18.550 --> 00:20:22.660 And it’s when – it’s when the fault is well-oriented in the contemporary stress 00:20:22.660 --> 00:20:28.710 field with appropriate stresses acting on it that it can be re-activated when the 00:20:28.710 --> 00:20:32.270 failure condition that’s governed by the Coulomb failure law is brought to bear. 00:20:32.270 --> 00:20:36.900 And that law very simply says that the critical shear stress at which a fault will 00:20:36.900 --> 00:20:40.920 nucleate an earthquake is equal to the coefficient of friction times 00:20:40.920 --> 00:20:44.100 the effective normal stress. The solid body normal stress 00:20:44.100 --> 00:20:47.840 minus the pore pressure. So that, by injecting water underground, 00:20:47.840 --> 00:20:51.910 we raise the pore pressure, we reduce this term, and that can bring a fault 00:20:51.910 --> 00:20:56.080 to failure without changing the actual shear stress acting on it. 00:20:56.080 --> 00:20:58.980 So a lot of the questions we really should be addressing are, 00:20:58.980 --> 00:21:00.640 what is the state of stress underground? 00:21:00.640 --> 00:21:03.430 What is its orientation? How does it vary spatially? 00:21:03.430 --> 00:21:05.203 These are things we don’t know and I think are 00:21:05.203 --> 00:21:09.380 some of the really key research questions moving forward. 00:21:09.380 --> 00:21:11.680 So this is what we call the effective stress relationship. 00:21:11.680 --> 00:21:14.200 Just to give an example of how this works, I’m showing 00:21:14.200 --> 00:21:17.230 a Mohr’s circle diagram. I know this is familiar to some of you, 00:21:17.230 --> 00:21:22.310 but this is a way of displaying the stresses that act upon any plane 00:21:22.310 --> 00:21:26.491 in a simple 2D diagram. These circles here go from the 00:21:26.491 --> 00:21:31.120 greatest principal stress to the least and intermediate principal stresses. 00:21:31.120 --> 00:21:35.230 Planes that are in the Earth fall within this field, and if we consider just a 00:21:35.230 --> 00:21:38.710 random population of planes here, which could be in hydraulic 00:21:38.710 --> 00:21:41.970 communication with the source of additional pressure that I’m talking 00:21:41.970 --> 00:21:45.470 about. Let’s see what happens if we increase the pressure. 00:21:45.470 --> 00:21:48.690 Now, if we increase the pressure, what it’s going to do, it’s going to 00:21:48.690 --> 00:21:53.930 shift this entire field to the left. And it can bring some of these planes 00:21:53.930 --> 00:21:57.990 through the stability line, in this case for a static coefficient of 0.8. 00:21:57.990 --> 00:22:01.560 So these are events that we would call to be in the hydroshear regime, 00:22:01.560 --> 00:22:04.580 ones in which the earthquake can be nucleated simply by the 00:22:04.580 --> 00:22:09.532 increase in pore pressure, again releasing pre-existing stress. 00:22:09.532 --> 00:22:13.850 Well, one good example of this is from a very famous paper that was 00:22:13.850 --> 00:22:17.830 put together here at the USGS by Jack Healy and his colleagues, 00:22:17.830 --> 00:22:23.410 published in Science magazine in 1968, their study of the Denver earthquakes. 00:22:23.410 --> 00:22:27.630 This is really the eureka moment, the discovery of how fluid injection 00:22:27.630 --> 00:22:31.610 can induce earthquakes. As many of you know, there was 00:22:31.610 --> 00:22:34.330 a deep well drilled on the Rocky Mountain Arsenal, 00:22:34.330 --> 00:22:38.650 where they were injecting some rather nasty stuff into the ground. 00:22:38.650 --> 00:22:42.160 The idea of drilling a well into the Precambrian basement, this seemed like, 00:22:42.160 --> 00:22:46.220 at the time, to be a good way to get rid of chemical warfare agents. 00:22:46.220 --> 00:22:51.170 And, within a short period of time after injection began, people began to notice 00:22:51.170 --> 00:22:54.070 earthquakes in the Denver area. So we’re looking at the correlation 00:22:54.070 --> 00:22:58.030 here between the volume injected and the earthquakes occurring. 00:22:58.030 --> 00:23:00.710 And you can see there’s a generally good correlation here. 00:23:00.710 --> 00:23:03.320 What’s really fascinating is that the earthquakes continue 00:23:03.320 --> 00:23:07.480 for some time after injection stopped, and including the largest earthquakes, 00:23:07.480 --> 00:23:10.623 which occurred more than a year later. 00:23:11.487 --> 00:23:15.870 Studies done, again by the USGS group, was able to show that the earthquakes 00:23:15.870 --> 00:23:19.490 were occurring on a fault deep in the basement, and careful relocations 00:23:19.490 --> 00:23:24.200 by Herrmann and Park showed that, by the time, in 1967, the earthquakes 00:23:24.200 --> 00:23:28.110 had migrated more than 5 kilometers away from the injection well. 00:23:28.110 --> 00:23:33.731 Now, this doesn’t fit the general kind of models of homogeneous 00:23:33.766 --> 00:23:37.650 layers and uniform diffusion. Paul Hsieh and John Bredehoeft 00:23:37.650 --> 00:23:40.990 wrote a very classic paper on this explaining about how 00:23:40.990 --> 00:23:44.510 a channelized system, basically a fault zone, 00:23:44.510 --> 00:23:49.315 could allow fluid pressure to be transmitted over large distances. 00:23:50.244 --> 00:23:55.980 Well, I think more amazingly, to me, is the fact that the USGS not only 00:23:55.980 --> 00:23:59.510 was able to bring the study together, but we actually were able to test it 00:23:59.510 --> 00:24:02.840 in a field experiment that began in the late 1960s. 00:24:02.840 --> 00:24:06.950 I can’t imagine doing such an active experiment today, but Barry Raleigh, 00:24:06.950 --> 00:24:11.410 Jack Healy, and John Bredehoeft, and many others were successful 00:24:11.410 --> 00:24:15.180 in conducting an earthquake control experiment in an oil field in western 00:24:15.180 --> 00:24:18.160 Colorado – the Rangely Field. This was a field that had been 00:24:18.160 --> 00:24:23.120 in secondary recovery for some time and was inducing earthquakes. 00:24:23.120 --> 00:24:26.460 The operator gave them permission to work with four wells in which 00:24:26.460 --> 00:24:29.770 they could vary the fluid pressure. And, after having made laboratory 00:24:29.770 --> 00:24:34.030 measurements on the earthquakes, they were able to modulate the fluid pressure 00:24:34.030 --> 00:24:39.535 within the reservoir and to basically turn the earthquakes on and off. 00:24:39.535 --> 00:24:43.570 I do want to depart here from the – what’s written on the slide here to 00:24:43.570 --> 00:24:47.120 tell you a little story that I heard about the day that they decided to 00:24:47.120 --> 00:24:50.620 turn the pumps on for the first time to begin to pressure the reservoir. 00:24:50.620 --> 00:24:55.550 So, at the end of a long day, Barry and John say to Jack, Jack, it’s been 00:24:55.550 --> 00:24:59.360 a long day in the field. The pumps are going. Let’s go get a beer. 00:24:59.360 --> 00:25:01.800 And Jack said, nope, we can’t go get a beer until we’ve gone 00:25:01.800 --> 00:25:04.730 to the monitoring well. I think this was the only time that 00:25:04.730 --> 00:25:08.870 Jack Healy refused to go get a beer in his life. [laughter] 00:25:08.870 --> 00:25:13.880 But, after a lot of jawboning, I think Barry and John decided to mollify Jack, 00:25:13.880 --> 00:25:16.800 and we’ll go take a look at this. The calculations suggested 00:25:16.800 --> 00:25:19.620 it’s going to be a week or so before anything shows up. 00:25:19.620 --> 00:25:23.750 They walk there, and the little old analog Heise gauge is already going up. 00:25:23.750 --> 00:25:27.706 So this was a really very important result because it means that the fluid 00:25:27.706 --> 00:25:31.840 pressure transmission can occur very rapidly through fractures in the Earth. 00:25:31.840 --> 00:25:35.370 And I think this is one of the keys that we have to continue to think about, 00:25:35.370 --> 00:25:38.280 that fluid pressure can get very quickly transmitted 00:25:38.280 --> 00:25:42.307 over long distances if they’re open pathways. 00:25:42.307 --> 00:25:47.320 Well, so we know about Rangely. We know about the 00:25:47.320 --> 00:25:50.500 Rocky Mountain Arsenal case. Many other case have been studied. 00:25:50.500 --> 00:25:52.660 There’s a great compendium of them put together 00:25:52.660 --> 00:25:57.580 by Craig Nicholson and Rob Wesson in a USGS Bulletin 1951 that 00:25:57.580 --> 00:26:00.580 I could remember to any of you who want to read more about this. 00:26:00.580 --> 00:26:03.930 But what’s really come to the fore now is this whole issue about how 00:26:03.930 --> 00:26:08.363 earthquakes may be related to this change in oil field activity. 00:26:08.363 --> 00:26:11.810 The big change has been a new way of recovering resources through 00:26:11.810 --> 00:26:14.910 horizontal drilling. And, in this example here, 00:26:14.910 --> 00:26:21.450 a typical fracking well will drill down until it reaches the target formation, 00:26:21.450 --> 00:26:26.380 typically a rock that has either gas or oil in it, but it won’t flow out 00:26:26.380 --> 00:26:29.620 unless you break it up. It’s broken up by drilling 00:26:29.620 --> 00:26:33.220 a long horizontal well, sometimes 2 or 3 kilometers long, 00:26:33.220 --> 00:26:36.900 and then breaking the rock through hydraulic fracturing in stages. 00:26:36.900 --> 00:26:39.990 This basically is a process in which a small section of the well is 00:26:39.990 --> 00:26:43.573 over-pressured, leading to the failure, either through hydroshear or through 00:26:43.573 --> 00:26:47.850 hydrofrack, creating a connected network of fractures that allow 00:26:47.850 --> 00:26:51.680 the resource to be extracted. Well, as you do that, you may end up 00:26:51.680 --> 00:26:54.700 with wastes that need to be disposed. Typically, that’s brought to a 00:26:54.700 --> 00:26:59.420 wastewater well where fluids are injected much deeper underground. 00:26:59.420 --> 00:27:05.150 And these wells are very carefully sited. They’re regulated by a 1974 law 00:27:05.150 --> 00:27:07.779 that protects drinking water. It doesn’t say anything about 00:27:07.779 --> 00:27:13.100 earthquakes, but it is designed to keep these fluids, typically salty waters, well 00:27:13.100 --> 00:27:17.710 out of the environment, and certainly well away from any potable aquifers. 00:27:17.710 --> 00:27:21.340 So the big question that people have been asking, and really, I think the 00:27:21.340 --> 00:27:25.680 public discussion often focuses on the earthquakes and the fracking wells. 00:27:25.680 --> 00:27:27.660 We don’t think that’s the case. 00:27:27.660 --> 00:27:30.090 There have been literally hundreds of thousands of frack jobs 00:27:30.090 --> 00:27:33.530 just in the United States alone. Only a handful have produced 00:27:33.530 --> 00:27:37.627 felt events, and none as large as magnitude 4. 00:27:37.627 --> 00:27:41.250 I was at a meeting with Art McGarr last week in Canada where we 00:27:41.250 --> 00:27:45.340 heard about possibly a magnitude 4.2 that was associated with fracking, 00:27:45.340 --> 00:27:47.879 but that certainly would be the world record. 00:27:47.879 --> 00:27:51.170 Wastewater wells, on the other hand, I think we can clearly associate 00:27:51.170 --> 00:27:54.770 with much larger earthquakes, but they’re relatively rare. 00:27:54.770 --> 00:27:57.360 There are something like 30,000 of these deep wastewater wells 00:27:57.360 --> 00:28:00.740 in the United States. Many have very large volumes – more than 00:28:00.740 --> 00:28:04.850 a million cubic meters that have been induced, but very few of them 00:28:04.850 --> 00:28:07.980 have seismicity that we can associate with them. 00:28:07.980 --> 00:28:11.350 The earthquakes go as large as magnitude 5.6 if we accept the 00:28:11.350 --> 00:28:13.920 case in Oklahoma that I’ll discuss in a minute. 00:28:13.920 --> 00:28:16.360 So that really brings things now into the range in which we’re going to 00:28:16.360 --> 00:28:22.215 be concerned about the effects of earthquakes on people and on structures. 00:28:22.215 --> 00:28:25.830 Well, let’s talk a little bit more about fracking and earthquakes. 00:28:25.830 --> 00:28:30.300 There are very few studies in the public literature that go into this in any detail. 00:28:30.300 --> 00:28:34.160 One very nice report was released last year by the British Columbia 00:28:34.160 --> 00:28:37.540 Oil and Gas Commission. And they worked with the operators to 00:28:37.540 --> 00:28:42.230 collect some rather detailed information during fracking operations in a rather 00:28:42.230 --> 00:28:46.720 remote part of northeastern British Columbia – the Horn River Basin. 00:28:46.720 --> 00:28:49.640 And typically, what they found from the microseismic studies were that 00:28:49.640 --> 00:28:53.460 these typically negative magnitude earthquakes were contained within 00:28:53.460 --> 00:28:57.420 the target formation, but occasionally they would see a larger earthquake. 00:28:57.420 --> 00:29:00.860 And, in this case, you can see that the fault that ruptured in this 00:29:00.860 --> 00:29:04.120 large earthquake is well-outlined. Many of these were faults that they 00:29:04.120 --> 00:29:07.680 could identify on their seismic data, but not all of them. 00:29:07.680 --> 00:29:11.445 So it would appear that, again, this mechanism of increasing the fluid 00:29:11.445 --> 00:29:15.910 pressure is allowing pressure to rise within a pre-existing fault, and if the 00:29:15.910 --> 00:29:20.171 stress conditions are correct, it will fail and produce an earthquake. 00:29:20.171 --> 00:29:23.280 I took a look at what might have been happening in Pennsylvania, 00:29:23.280 --> 00:29:25.510 the Marcellus Shale Play. This is an area where it’s been 00:29:25.510 --> 00:29:28.230 very contentious, as I’m sure many of you know, about the 00:29:28.230 --> 00:29:31.810 development of shale gas. And we don’t have such 00:29:31.810 --> 00:29:34.160 detailed records, although we do have generally good 00:29:34.160 --> 00:29:37.250 earthquake catalogs prepared by Lamont. 00:29:37.250 --> 00:29:41.360 And shown in this map is the area of the Marcellus Shale. 00:29:41.360 --> 00:29:43.940 So we’re looking at the part of Pennsylvania which is largely 00:29:43.940 --> 00:29:46.520 in the west, where the development has occurred. 00:29:46.520 --> 00:29:50.570 And shown in blue are the earthquakes that are found in the Lamont catalog 00:29:50.570 --> 00:29:56.180 for the 25 years between – 35 years between 1970 and 2004. 00:29:56.180 --> 00:30:00.070 And then the earthquakes that have happened since development in red. 00:30:00.070 --> 00:30:03.850 Prior to 2004, there were just three earthquakes larger than magnitude 2. 00:30:03.850 --> 00:30:05.510 Since then, there were six. 00:30:05.510 --> 00:30:09.030 Well, none large as magnitude 3. So maybe there’s a correlation 00:30:09.030 --> 00:30:11.850 with increase, but I think it’d be safe to say that there were 00:30:11.850 --> 00:30:15.740 no consequences of importance from the thousands of frack treatments 00:30:15.740 --> 00:30:19.790 that were done, at least from a seismic safety standpoint. 00:30:19.790 --> 00:30:22.530 The same can’t be said for wastewater. 00:30:22.530 --> 00:30:24.700 Most of the wastewater in Pennsylvania has to be 00:30:24.700 --> 00:30:28.140 trucked out of state for disposal. And one place that it went was 00:30:28.140 --> 00:30:33.870 a well in Youngstown, Ohio. On New Year’s Eve in 2011, 00:30:33.870 --> 00:30:38.110 an earthquake of about magnitude 4 occurred beneath this well. 00:30:38.110 --> 00:30:42.110 And studies by Won-Young Kim and others now have, I think fairly 00:30:42.110 --> 00:30:45.060 conclusively, shown that this was an earthquake that was triggered 00:30:45.060 --> 00:30:48.010 by wastewater injection. This well happened to go in 00:30:48.010 --> 00:30:51.190 the Precambrian basement and may have had direct communication 00:30:51.190 --> 00:30:57.856 with this fault that became re-activated by the – in the earthquake. 00:30:57.856 --> 00:31:01.660 Others have taken a broader look at this. My colleague Cliff Frohlich at the 00:31:01.660 --> 00:31:05.621 University of the Texas-Austin has used the transportable array 00:31:05.621 --> 00:31:08.800 when it was in Texas to examine earthquake activity within the 00:31:08.800 --> 00:31:14.680 Barnett Shale in north-central Texas. And so this is the Dallas-Fort Worth 00:31:14.680 --> 00:31:19.670 airport here. This is an area where earthquakes were associated with injection. 00:31:19.670 --> 00:31:23.560 And, by taking a broader view, looking at the period of time when 00:31:23.560 --> 00:31:28.290 the transportable array was in the area, Cliff was able to show that most of 00:31:28.290 --> 00:31:32.050 the high volume that – where there were earthquakes, they were spatially 00:31:32.050 --> 00:31:35.110 associated with high-volume injection wells. 00:31:35.110 --> 00:31:37.980 So the hypothesis here is there’s something either about high rate of 00:31:37.980 --> 00:31:41.150 injection or total cumulative volume which makes things 00:31:41.150 --> 00:31:45.041 more likely that earthquakes will occur. 00:31:45.041 --> 00:31:48.450 We’ll come back and take a look at this slide here in a little bit. 00:31:48.450 --> 00:31:52.830 So moving on now to another case that’s been well-studied in Guy, Arkansas. 00:31:52.830 --> 00:31:59.420 Steve Horton and his colleagues at the Arkansas Survey were able to capture 00:31:59.420 --> 00:32:02.960 an earthquake sequence shortly after it began that was associated with, 00:32:02.960 --> 00:32:07.011 again, wastewater injection. These are their results here for the 00:32:07.011 --> 00:32:10.420 hypocenters of the earthquakes, and you can see they very clearly 00:32:10.420 --> 00:32:13.570 delineate a near-vertical strike-slip fault. 00:32:13.570 --> 00:32:17.360 It was well-oriented in terms of movement. This was a fault that 00:32:17.360 --> 00:32:20.010 wasn’t known beforehand. People were concerned about 00:32:20.010 --> 00:32:23.290 these faults, which were poorly oriented, so unlikely to move. 00:32:23.290 --> 00:32:26.700 But this basement fault turned out to be well-oriented. 00:32:26.700 --> 00:32:30.800 This resulted in both of these wells being shut down 00:32:30.800 --> 00:32:33.820 So let me go now briefly through four case studies that bring things 00:32:33.820 --> 00:32:36.270 a little bit more up to date. We’re going to look first at the 00:32:36.270 --> 00:32:40.403 Paradox Basin, where there is a long- term injection project underway. 00:32:40.403 --> 00:32:43.320 We’ll then go look at one of these unusual earthquakes – the one 00:32:43.320 --> 00:32:46.920 at east Texas near Timpson. We’ll then look at Oklahoma 00:32:46.920 --> 00:32:49.330 to see what’s been going on there over this period of time. 00:32:49.330 --> 00:32:52.170 And then finally, we’ll finish with some earthquakes that are 00:32:52.170 --> 00:32:56.500 in the Fort Worth area that have just been happening this past month. 00:32:56.500 --> 00:32:59.770 So the first of these studies looks at the Bureau of Reclamation’s 00:32:59.770 --> 00:33:04.650 Paradox Valley project. This is a location where a tributary of 00:33:04.650 --> 00:33:10.690 the Colorado River, the Delores River, is crossing a salt dome, basically. 00:33:10.690 --> 00:33:14.650 And we need to keep the salt out of the river to make the water useful. 00:33:14.650 --> 00:33:19.480 We have to do this forever, basically, to satisfy treaty obligations with Mexico. 00:33:19.480 --> 00:33:24.920 So the approach that was adopted in the late 1980s and early ’90s was to drill 00:33:24.920 --> 00:33:31.250 a series of shallow wells to depress the salty shallow surface water 00:33:31.250 --> 00:33:34.850 to allow the river to flow across without becoming contaminated, 00:33:34.850 --> 00:33:38.700 and then take the brine and inject it in a deep well. 00:33:38.700 --> 00:33:42.710 This was a place where something was – there were some measurements made 00:33:42.710 --> 00:33:46.060 beforehand, in particularly, the least principal stress was known. 00:33:46.060 --> 00:33:49.300 We know the vertical stress. So we can look at how well – 00:33:49.300 --> 00:33:52.500 what actually happened compared with our theoretical estimate. 00:33:52.500 --> 00:33:55.970 They estimated a coefficient of friction based upon the rock types. 00:33:55.970 --> 00:34:01.880 And, in fact, when the initial injection tests began, 00:34:01.880 --> 00:34:04.450 earthquakes began to occur at the right pressure. 00:34:04.450 --> 00:34:09.700 So this, again, validates this idea of pressure being the main moderator that 00:34:09.700 --> 00:34:16.584 is allowing a fault to fail when the effective stress rises to the critical point. 00:34:16.584 --> 00:34:20.349 During production, however, it’s necessary to pump much harder. 00:34:20.349 --> 00:34:22.313 And they actually have to pump high enough that they’re 00:34:22.349 --> 00:34:25.540 continuously hydrofracking. This has led to the development 00:34:25.540 --> 00:34:28.480 of a cloud of earthquakes which has spread well away from the well. 00:34:28.480 --> 00:34:30.580 This is shown in cross-section. 00:34:30.580 --> 00:34:36.300 And this is from a paper published by John Ake and others in 2005. 00:34:36.300 --> 00:34:39.140 And so this has been an ongoing issue. The Bureau of Reclamation has studied 00:34:39.140 --> 00:34:42.370 this area very carefully for a long period of time, established that there were 00:34:42.370 --> 00:34:47.320 no natural earthquakes occurring in the region for many years beforehand, 00:34:47.320 --> 00:34:50.840 and continued to monitor. Today we see a pattern of earthquakes 00:34:50.840 --> 00:34:55.439 extending well away from the injection well – 8 or 9 kilometers in this direction, 00:34:55.439 --> 00:34:57.540 and the possibility that some of these earthquakes 00:34:57.540 --> 00:35:00.850 on the far side of the valley may also be connected. 00:35:00.850 --> 00:35:03.580 So things were going along pretty well until January of this year 00:35:03.580 --> 00:35:07.350 when a magnitude 3.9 earthquake occurred at this – at this far end. 00:35:07.350 --> 00:35:10.450 And that has caused everyone to rethink things. 00:35:10.450 --> 00:35:14.000 That was larger than an earthquake that was allowed in their design. 00:35:14.000 --> 00:35:16.980 It’s interesting. This is 8 kilometers from the injection point, 00:35:16.980 --> 00:35:20.150 so some distance away. And, even though small-magnitude 00:35:20.150 --> 00:35:23.830 activity here began within a year of injection, it took 16 years 00:35:23.830 --> 00:35:26.740 before this earthquake occurred. So there’s a lot that we have yet to, 00:35:26.740 --> 00:35:30.950 I think, really fully understand about how these systems work. 00:35:30.950 --> 00:35:35.410 And we need the kind of data that was collected beforehand at Paradox 00:35:35.410 --> 00:35:37.520 to really understand things, where they know the state of stress, 00:35:37.520 --> 00:35:41.110 but we think we have to do more, particularly in terms of monitoring 00:35:41.110 --> 00:35:44.040 where pressures are going underground. 00:35:44.040 --> 00:35:47.230 The second case I’d like to look at briefly are some earthquakes that have 00:35:47.230 --> 00:35:50.690 been happening in east Texas, an area that doesn’t have 00:35:50.690 --> 00:35:55.160 no earthquakes, but earthquakes of this magnitude are without precedent. 00:35:55.160 --> 00:35:58.450 This shows the Did You Feel It? map for the earthquakes here. 00:35:58.450 --> 00:36:01.894 Work being done with co-authors in Texas. 00:36:01.894 --> 00:36:05.340 There have been five principal earthquakes since May of last year. 00:36:05.340 --> 00:36:09.370 Began with a 3.9, followed by a magnitude 4.8 that did 00:36:09.370 --> 00:36:12.920 a fair amount of damage to unreinforced masonry buildings. 00:36:12.920 --> 00:36:15.090 Followed by an earthquake in January of this year and 00:36:15.090 --> 00:36:19.070 then two more in September. So this is an ongoing sequence. 00:36:19.070 --> 00:36:23.540 The regulator in Texas – the Texas Railroad Commission is somewhat 00:36:23.540 --> 00:36:28.370 aware of our studies, but at this point, they’ve chosen not to take any action. 00:36:28.370 --> 00:36:31.490 To actually begin to zero in on things, we had to go back to do some kind of 00:36:31.490 --> 00:36:34.770 old-fashioned seismology to do some intensity surveys to figure out 00:36:34.770 --> 00:36:37.780 where things were going on. The red dots here indicate 00:36:37.780 --> 00:36:40.940 the area of highest intensity. And when they were identified, 00:36:40.940 --> 00:36:45.200 it became clear that there were a couple of high-volume wells, 00:36:45.200 --> 00:36:47.970 which we’re calling North and South, that were located in the area. 00:36:47.970 --> 00:36:52.710 So much of our later activity was really focused on identifying where 00:36:52.710 --> 00:36:56.590 the earthquakes were occurring and what the association may be. 00:36:56.590 --> 00:36:59.580 These are some results from the temporary network that we put out. 00:36:59.580 --> 00:37:02.720 The best locations are the ones shown here in red. 00:37:02.720 --> 00:37:06.440 And, along with the green ones, all based on portable earthquake data, 00:37:06.440 --> 00:37:10.550 they define a fault trending to the northwest that agrees with the focal 00:37:10.550 --> 00:37:15.270 mechanism solution and quite close to both the North and the South wells. 00:37:15.270 --> 00:37:19.360 These other two wells are lower volume and we don’t think were associated. 00:37:19.360 --> 00:37:23.480 I would point out that the earthquake location by the national network 00:37:23.480 --> 00:37:26.770 is about 10 kilometers off. That actually doing pretty well. 00:37:26.770 --> 00:37:29.650 That’s about what we expect for the NEIC. 00:37:29.650 --> 00:37:32.820 So we can’t use the kind of information we’re typically available 00:37:32.820 --> 00:37:36.990 to zero in on this level. We really have to get in and do very detailed 00:37:36.990 --> 00:37:42.014 local studies to really understand what the associations may be. 00:37:42.014 --> 00:37:46.010 So, on the left here shows, again, this map of the epicenters. 00:37:46.010 --> 00:37:49.810 This is a cross-section indicating a fault that’s dipping up toward the North well, 00:37:49.810 --> 00:37:52.654 the injection points here are at the bottom of these wells. 00:37:52.654 --> 00:37:55.530 And then shown on the right are some histograms showing 00:37:55.530 --> 00:37:59.660 the monthly total of injection for these four wells. 00:37:59.660 --> 00:38:03.390 South is the higher-volume well. The North is a little bit lower volume. 00:38:03.390 --> 00:38:06.720 And I think what’s caught a number of our eyes is that, 00:38:06.720 --> 00:38:10.800 while the South volume is declining, the pressure is staying very steady. 00:38:10.800 --> 00:38:14.330 As the North volume is declining, the pressure is going up. 00:38:14.330 --> 00:38:18.320 And this suggests perhaps they’re getting to the point that pressure or 00:38:18.320 --> 00:38:23.470 water is being forced into new areas. So perhaps there’s a connection here. 00:38:23.470 --> 00:38:27.200 Seismicity we’ve been able to show actually began as early as 2008, 00:38:27.200 --> 00:38:30.510 although the record is really pretty spotty until 2013. 00:38:30.510 --> 00:38:33.600 So it may take a long time to build up to the point at which 00:38:33.600 --> 00:38:37.090 injection will lead actually to the triggering of earthquakes. 00:38:37.090 --> 00:38:43.270 So, for this particular case, we could ask, is it natural, or is it induced? 00:38:43.270 --> 00:38:47.110 Well, the sequences located near these two high-volume injections wells, 00:38:47.110 --> 00:38:51.580 there’s an increase with the pressure with the occurrence of the earthquakes. 00:38:51.580 --> 00:38:54.600 And the region has known subsurface faults with previous activity. 00:38:54.600 --> 00:39:00.310 I think the argument against it being anything by natural is the fact that there 00:39:00.310 --> 00:39:03.300 is previous activity known in this area. I think this just illustrates how 00:39:03.300 --> 00:39:08.650 difficult it is to come to a firm conclusion in these cases. 00:39:08.650 --> 00:39:11.640 Let me come back now to this question of the unusual earthquakes. 00:39:11.640 --> 00:39:14.360 And we’re now going to look at Oklahoma to take a look at what’s 00:39:14.360 --> 00:39:17.891 been happening there in recent years. Just to remind you, the earthquake 00:39:17.891 --> 00:39:23.217 activity took off in 2009 and has really continued unabated to the present time. 00:39:23.217 --> 00:39:26.450 So, in 2009, when things began, there were some earthquakes 00:39:26.450 --> 00:39:30.380 in the central part of the state and a few other places. 00:39:30.380 --> 00:39:34.210 By 2010, that level of activity had intensified. 00:39:34.210 --> 00:39:38.780 This is an area of shale gas development in the southeastern part of the state. 00:39:38.780 --> 00:39:42.426 A lot going on in the central part of the state that we don’t fully understand. 00:39:42.426 --> 00:39:45.980 2011, the pattern continues to be much the same. 00:39:45.980 --> 00:39:49.220 That included the magnitude 5.7 earthquake near Prague, 00:39:49.220 --> 00:39:52.500 probably the largest injection-induced earthquake. 00:39:52.500 --> 00:39:56.300 In 2012, the pattern, again, looks pretty much the same, 00:39:56.300 --> 00:39:58.860 and then in 2013, something changed. 00:39:58.860 --> 00:40:02.120 There’s a new area of activity which has been excited here 00:40:02.120 --> 00:40:06.620 along the Kansas border. So what’s going on here? 00:40:06.620 --> 00:40:09.181 Some of you probably know the answer. It’s the development of the 00:40:09.181 --> 00:40:12.300 Mississippi Lime Play. This is a location in which 00:40:12.300 --> 00:40:16.220 shallow drilling has – with these deviated wells is beginning to 00:40:16.220 --> 00:40:21.620 produce oil from this horizon. It’s what we call low-cut oil, so there’s 00:40:21.620 --> 00:40:25.370 lots of water that has to be disposed. And, as part of the development process, 00:40:25.370 --> 00:40:29.090 they use these deep injection wells to get rid of the water. 00:40:29.090 --> 00:40:32.440 What we don’t know at this point is whether the earthquakes are related to 00:40:32.440 --> 00:40:36.900 the fracking process or they’re related to the injection process. 00:40:36.900 --> 00:40:38.350 And this is, again, one of these things 00:40:38.350 --> 00:40:41.536 where it’s very difficult working with inadequate data. 00:40:41.536 --> 00:40:44.080 So, in some sense, we missed an opportunity here to really 00:40:44.080 --> 00:40:46.580 get ahead of the game. And I think this is one thing we’ve 00:40:46.580 --> 00:40:50.840 been missing is to be there before activity begins, to have a chance to 00:40:50.840 --> 00:40:54.800 look at what the initial pressures are and the state of stress, to learn 00:40:54.800 --> 00:40:57.260 something about the formation hydrology, and to identify 00:40:57.260 --> 00:41:01.140 what faults may be activated. And then to monitor things using 00:41:01.140 --> 00:41:04.410 not only better seismic data than we typically have in this part of the world, 00:41:04.410 --> 00:41:07.800 but also better information about injection. 00:41:07.800 --> 00:41:10.070 So now let’s take a look at what’s been happening recently 00:41:10.070 --> 00:41:15.940 in the area around Fort Worth. Since November 6th of this year, 00:41:15.940 --> 00:41:19.120 there have been a series of earthquakes as large as magnitude 3.6 that have 00:41:19.120 --> 00:41:24.000 been widely felt in the area northwest of Fort Worth. 00:41:24.000 --> 00:41:27.550 And here’s an example of a Did You Feel It? map from the area. 00:41:27.550 --> 00:41:32.650 So people are concerned about these. Lots of discussion in the local media 00:41:32.650 --> 00:41:35.460 about these earthquakes and what they may mean. 00:41:35.460 --> 00:41:38.320 Here’s an example here of one of the reports recently. 00:41:38.320 --> 00:41:43.740 This is from the – from someone in the sheriff’s office, and they say that, 00:41:43.740 --> 00:41:47.180 despite the frequency, this woman is still surprised by the shaking 00:41:47.180 --> 00:41:49.010 and thankful she knows the cause. 00:41:49.010 --> 00:41:54.630 She says, hopefully it’s not Godzilla. He comes back. [laughs] 00:41:54.630 --> 00:41:57.700 So here’s a map that shows the earthquake locations that have been 00:41:57.700 --> 00:42:02.700 determined by the NEIC. The nearest station is 100 kilometers away. 00:42:02.700 --> 00:42:07.980 We know from our results in Timpson, Texas, that 10 kilometers is probably 00:42:07.980 --> 00:42:11.330 a good circle of uncertainty. So undoubtedly, these earthquakes 00:42:11.330 --> 00:42:14.330 are coming from a smaller region that’s shown here. 00:42:14.330 --> 00:42:16.260 So it occurred to me, we might be able to do 00:42:16.260 --> 00:42:18.403 something with the Did You Feel It? information. 00:42:18.403 --> 00:42:21.705 I suspect a number of you have made Did You Feel It? reports, and you 00:42:21.705 --> 00:42:24.550 kind of wonder what becomes of them other than make these maps. 00:42:24.550 --> 00:42:28.119 Turns out they’re very useful for doing science. 00:42:28.119 --> 00:42:33.191 Thanks to Vince Quitoriano, I was able to get the geocoded Did You Feel It? 00:42:33.191 --> 00:42:36.950 information for these earthquakes that actually says – when somebody says, 00:42:36.950 --> 00:42:40.280 this is my house number, we can geocode that. And so we can begin 00:42:40.280 --> 00:42:43.853 to make maps that show precisely where things were collected. 00:42:43.853 --> 00:42:46.790 And so here’s an example of the first earthquake in the sequence. 00:42:46.790 --> 00:42:49.440 This shows the Did You Feel It? reports that were received. 00:42:49.440 --> 00:42:53.940 And these are low levels of shaking – MMI II is just people who are 00:42:53.940 --> 00:42:56.885 sitting down or lying in bed will feel it. 00:42:56.885 --> 00:43:00.210 MMI III means just about everyone is going to feel it, but we’re not 00:43:00.210 --> 00:43:03.390 at the point of rattling dishes or swinging chandeliers. 00:43:03.390 --> 00:43:07.050 So you can see here that things are – at least for this event, are kind of 00:43:07.050 --> 00:43:09.880 concentrated within this box. Keep an eye on the box. 00:43:09.880 --> 00:43:17.650 We’ll step through some more. Here’s a 2.9, 2.8, a 3.0, 2.8. 00:43:17.650 --> 00:43:20.460 Here’s the largest – 3.6. So now we’re getting to the area 00:43:20.460 --> 00:43:22.460 where there’s some things moving around. 00:43:22.460 --> 00:43:25.640 Again, everything is really concentrated in this one area. 00:43:25.640 --> 00:43:29.951 A 2.9, 3.0, and then finally, these are the earthquakes that were 00:43:29.951 --> 00:43:32.840 too small to be located. People felt them, and they still report them. 00:43:32.840 --> 00:43:34.140 So these are the really tiny guys. 00:43:34.140 --> 00:43:36.320 And, in some ways, they may be the most instructive. 00:43:36.320 --> 00:43:40.390 They, again, point to this one area as being where things are coming from. 00:43:40.390 --> 00:43:43.610 So what’s going on in that area? Well, there are a lot of wells. 00:43:43.610 --> 00:43:48.050 This is a map from the database from the Texas Railroad Commission, 00:43:48.050 --> 00:43:51.760 the regulator, and every one of these little lines here represents a horizontal 00:43:51.760 --> 00:43:55.860 well that’s been drilled into the Barnett Shale to produce gas. 00:43:55.860 --> 00:44:00.630 So possibly there’s some new fracking going on, but we don’t know. 00:44:00.630 --> 00:44:04.110 It turns out there’s only one high- volume wastewater well in this area. 00:44:04.110 --> 00:44:07.480 It’s at this location here. So I think it would be a suspect – 00:44:07.480 --> 00:44:10.230 something that would be worth looking into. 00:44:10.230 --> 00:44:14.440 This was a well that was identified in Cliff Frohlich’s 2012 study, and he 00:44:14.440 --> 00:44:17.420 did note that there was one earthquake that he found that was nearby. 00:44:17.420 --> 00:44:21.520 So I think there’s more to learn here from these Did You Feel It? reports. 00:44:21.520 --> 00:44:24.550 And hopefully we will get at that. 00:44:24.550 --> 00:44:29.040 One thing we don’t see is, at least through mid-April, when the last data 00:44:29.040 --> 00:44:33.030 was available, this well seems to be producing at a – injecting at 00:44:33.030 --> 00:44:35.720 a fairly steady rate, although it’s a pretty big volume – 00:44:35.720 --> 00:44:38.280 3 million cubic meters have been injected to date. 00:44:38.280 --> 00:44:43.410 Again, the one earthquake identified back in 2010 00:44:43.410 --> 00:44:47.230 and now the recent upturn in earthquake activity. 00:44:47.230 --> 00:44:49.080 The state still doesn’t quite know what to do. 00:44:49.080 --> 00:44:53.540 As of Friday, the regulator said that they don’t think there’s a connection. 00:44:53.540 --> 00:44:58.900 So finally, let me get to the last topic – think locally, act globally. 00:44:58.900 --> 00:45:01.600 We have a lot to learn. We can do that through studies 00:45:01.600 --> 00:45:04.620 that are really very carefully focused on trying to understand 00:45:04.620 --> 00:45:09.209 the mechanics and the setting in which induced earthquakes occur. 00:45:09.241 --> 00:45:12.380 The Prague earthquake is one that is – we were fortunate to be able to 00:45:12.380 --> 00:45:15.310 get there beforehand. Elizabeth Cochran has been working 00:45:15.310 --> 00:45:18.690 with Kade Keranen and others to study this earthquake, and they’ve 00:45:18.690 --> 00:45:22.320 really put together a really, I think, very important piece of work published 00:45:22.320 --> 00:45:27.100 in Geology that describes one model for how injection 00:45:27.100 --> 00:45:30.680 at the north end of this earthquake sequence may have induced 00:45:30.680 --> 00:45:35.927 a series of earthquakes, including this magnitude 5.7. 00:45:35.927 --> 00:45:39.160 Well, the magnitude 5.7 in Oklahoma did some 00:45:39.160 --> 00:45:42.990 serious damage to a few homes. It did disrupt some unreinforced 00:45:42.990 --> 00:45:46.777 masonry buildings and sent a couple people to the hospital, but on the whole, 00:45:46.777 --> 00:45:50.269 it wasn’t too serious, and I don’t think its the kind of earthquake that, 00:45:50.294 --> 00:45:53.880 in most places in the United States, we’re going to expect major consequences. 00:45:53.880 --> 00:45:58.230 But, if we move that earthquake to the developing world, we can 00:45:58.230 --> 00:46:01.810 compare it with the earthquake that happened in San Salvador in 1986. 00:46:01.810 --> 00:46:06.126 This is one that Randy White and Dave Harlow studied in some detail. 00:46:06.126 --> 00:46:11.060 The same magnitude 5.7 earthquake, similar depth, produced over 00:46:11.060 --> 00:46:15.750 1,500 fatalities, 10,000 injuries, and 100,000 were put out of their homes. 00:46:15.750 --> 00:46:18.330 So this is a serious problem is the technologies that are 00:46:18.330 --> 00:46:21.680 being developed today get carried elsewhere in the world. 00:46:21.680 --> 00:46:24.741 And surely they will be. This is a map from the U.S. Energy 00:46:24.741 --> 00:46:28.710 Information Agency showing the distribution of shale oil and shale gas 00:46:28.710 --> 00:46:31.900 resources across the world. I think there’s no question that these 00:46:31.900 --> 00:46:35.560 resources are going to be developed, maybe even in England sometime 00:46:35.560 --> 00:46:41.540 if they can get over Godzilla. But I think this is really our opportunity 00:46:41.540 --> 00:46:47.840 to really help set the science that can be used to guide the regulators and 00:46:47.840 --> 00:46:51.870 provide both the public and the industry assurance that solid science will 00:46:51.870 --> 00:46:56.090 back regulations that make sense in terms of making sure 00:46:56.090 --> 00:46:59.711 that developments are done in a safe and responsible way. 00:46:59.711 --> 00:47:04.950 So, with that, I’ll just close by saying that currently we are stuck 00:47:04.950 --> 00:47:07.740 with a lot of open questions. We have uncertainties about the state 00:47:07.740 --> 00:47:11.030 of stress, the pore pressure, we don’t know the flow paths very well, 00:47:11.030 --> 00:47:14.422 although many of us think faults are involved. We don’t know 00:47:14.422 --> 00:47:18.400 where the capable faults are. We don’t really have the best results 00:47:18.400 --> 00:47:21.760 for most of the country with earthquake networks. 00:47:21.760 --> 00:47:24.420 Difficulty predicting how large earthquakes go once initiated 00:47:24.420 --> 00:47:27.400 is a key problem for probabilistic seismic hazards, 00:47:27.400 --> 00:47:30.840 as is the uncertainty in the strength of shaking. 00:47:30.840 --> 00:47:34.360 So we’ve got a lot to do. We need to work on making 00:47:34.360 --> 00:47:38.130 more and better measurements of the pre-injection underground 00:47:38.130 --> 00:47:40.910 conditions to understand where the faults are. 00:47:40.910 --> 00:47:43.900 To monitor and report not only what’s happening with injection 00:47:43.900 --> 00:47:46.970 but also to accurately detect the earthquakes. 00:47:46.970 --> 00:47:49.370 And also to be able to make the measurements of the earthquakes 00:47:49.370 --> 00:47:52.110 that are going to help guide the development of seismic safety maps. 00:47:52.110 --> 00:47:54.190 So, with that, I want to thank you for your attention. 00:47:54.190 --> 00:47:56.713 I’d be happy to answer any questions. 00:47:56.713 --> 00:48:04.119 [applause] 00:48:05.416 --> 00:48:22.401 [silence] 00:48:22.401 --> 00:48:25.890 - Thank you, Bill, for that fantastic talk. 00:48:25.890 --> 00:48:30.480 The question I have has to do with the fact that we inject 00:48:30.480 --> 00:48:36.241 large volumes of water when we do hydrofracking at very high pressures. 00:48:36.241 --> 00:48:40.840 And yet, there are very few cases where there are earthquakes induced 00:48:40.840 --> 00:48:44.490 from that activity, whereas there are a lot of earthquakes induced 00:48:44.490 --> 00:48:48.780 from injecting fluids that come out and then injecting later on. 00:48:48.780 --> 00:48:52.650 What is the real explanation for that? - Well, that’s a good question, Yousef. 00:48:52.650 --> 00:48:55.590 I think there are probably three factors involved. 00:48:55.590 --> 00:48:59.840 One is the volumes involved in hydrofracks are actually quite small, 00:48:59.840 --> 00:49:04.160 maybe a few thousand cubic meters, as opposed to millions of cubic meters. 00:49:04.160 --> 00:49:07.540 The second is that the pressure is in the well only a very – for a short period 00:49:07.540 --> 00:49:11.260 of time, that each stage is only pressurized for hours, and then 00:49:11.260 --> 00:49:14.410 it’s relieved, and you move on to the next stage. 00:49:14.410 --> 00:49:18.100 And the third reason, I think, is that hydrofracking is occurring at 00:49:18.100 --> 00:49:21.980 relatively shallow depths, typically. And the earthquakes that we’re 00:49:21.980 --> 00:49:24.270 most concerned about are ones that actually involve the basement. 00:49:24.270 --> 00:49:28.040 So, unless there’s a connection reaching the basement, I think 00:49:28.040 --> 00:49:31.120 the earthquake potential at very shallow depth tends to be small. 00:49:31.120 --> 00:49:34.405 So I think those are the three factors that contribute. 00:49:36.230 --> 00:49:41.472 [silence] 00:49:41.472 --> 00:49:48.236 - Bill, great summary. This is probably not within your field, 00:49:48.236 --> 00:49:52.030 necessarily, but I wanted to ask it. What is the economic motivation 00:49:52.030 --> 00:49:56.230 for all of this? In other words, what is the production out of these 00:49:56.230 --> 00:50:00.430 wells compared to standard oil company production? 00:50:00.430 --> 00:50:02.279 Do you have any feeling for that? 00:50:02.279 --> 00:50:06.630 - Yeah. It’s really revolutionized the energy industry in the United States. 00:50:06.630 --> 00:50:11.180 We have gone from a net importer to a net exporter. 00:50:11.180 --> 00:50:14.490 We have terminals that were built to receive LNG from 00:50:14.490 --> 00:50:16.450 overseas that they’re now looking at converting into 00:50:16.450 --> 00:50:20.670 the export terminals for liquified natural gas. 00:50:20.670 --> 00:50:24.460 The U.S. is emitting a lot less carbon into the atmosphere 00:50:24.460 --> 00:50:32.037 as natural gas has replaced coal in power plants. 00:50:32.037 --> 00:50:34.630 But, at the same time, it has to be said, that’s made the 00:50:34.630 --> 00:50:38.250 price of coal low and now – so U.S. coal is being burned in Europe, 00:50:38.250 --> 00:50:42.840 so the net effect is one that one has to think about globally. 00:50:42.840 --> 00:50:46.280 I think what has also caught people’s attention is the development 00:50:46.280 --> 00:50:53.570 of the oils – the liquids, in other words, either – say from North Dakota, 00:50:53.570 --> 00:50:56.460 for example, we’ve been talking about some now here, and of course, 00:50:56.460 --> 00:50:59.070 California and the Monterey is the next one on the horizon 00:50:59.070 --> 00:51:03.750 that’s going to be a big discussion. So I think there’s a lot of interest in this. 00:51:03.750 --> 00:51:07.510 There’s a very nice editorial by Marcia McNutt in Science a week ago 00:51:07.510 --> 00:51:11.602 that I could recommend that goes into some of these issues. 00:51:13.846 --> 00:51:19.870 [silence] 00:51:19.895 --> 00:51:25.119 - Is there any attempt to conduct the re-injection 00:51:25.119 --> 00:51:29.275 in a way that’s similar to the original fracking? 00:51:29.275 --> 00:51:31.790 Since that doesn’t seem to cause a problem? 00:51:31.790 --> 00:51:36.190 - Yeah. So you’re – it’s really a question of numbers. 00:51:36.190 --> 00:51:42.410 And typically, the wastewater is concentrated for injection in a specific 00:51:42.410 --> 00:51:47.400 location where geology is favorable for what is thought to be injection 00:51:47.400 --> 00:51:50.840 of very large volumes. And, as we’ve seen, with 30,000 wells, 00:51:50.840 --> 00:51:55.110 and few of them problematic, it probably works pretty well on average. 00:51:55.110 --> 00:52:00.910 I think the oil shale is another story because there, you are – through 00:52:00.910 --> 00:52:04.050 a dewatering process, you’re maybe bringing up 19 barrels 00:52:04.050 --> 00:52:09.080 of saltwater with one barrel of oil. And so you’ve got 19 barrels you 00:52:09.080 --> 00:52:12.190 need to dispose of somewhere else. And, in many ways, 00:52:12.190 --> 00:52:15.020 perhaps that’s what’s driving things in Oklahoma. 00:52:15.020 --> 00:52:18.669 But it is – it is a numbers game. Drilling a deep disposal well 00:52:18.669 --> 00:52:22.130 is expensive, and I think people want to get the maximum use 00:52:22.130 --> 00:52:24.742 out of them once they have one. 00:52:26.852 --> 00:52:31.950 - Bill, is there any basic physics that is not understood now? 00:52:31.950 --> 00:52:36.260 Is this all just a matter of data collection to improve the understanding, 00:52:36.260 --> 00:52:38.770 or is it really more basic research to go … 00:52:38.770 --> 00:52:41.880 - I think there’s a lot of basic research to do. 00:52:41.880 --> 00:52:45.510 One is – relates to the state of stress. How does the state of stress 00:52:45.510 --> 00:52:48.920 vary spatially? I don’t think we know very much about that. 00:52:48.920 --> 00:52:52.320 It’s difficult to measure. But that’s something that we 00:52:52.320 --> 00:52:55.740 really could do some research on to figure out new and better ways, 00:52:55.740 --> 00:52:58.160 perhaps, of gathering that type of information. 00:52:58.160 --> 00:53:01.050 I think there are also questions about what happens once you begin to 00:53:01.050 --> 00:53:04.790 develop a channel through which pressure and fluid is flowing. 00:53:04.790 --> 00:53:08.740 How does that evolve with time? Are there chemical interactions 00:53:08.740 --> 00:53:11.860 between the fluid that’s being injected in the formation, for example, 00:53:11.860 --> 00:53:15.820 that may enhance that? I think there are also questions of – 00:53:15.820 --> 00:53:19.660 kind of related to more theoretical things like rate-and-state friction 00:53:19.660 --> 00:53:23.500 about how that may evolve as a – as a fault begins – that is currently 00:53:23.500 --> 00:53:26.540 locked begins to move. How does that evolve over time? 00:53:26.540 --> 00:53:30.119 So I think there’s a lot yet to do, both in the field and 00:53:30.119 --> 00:53:33.510 on the blackboard and in the laboratory. 00:53:38.388 --> 00:53:41.085 I think Rick’s got a question. Yeah. 00:53:43.509 --> 00:53:45.622 - [inaudible] 00:53:47.298 --> 00:53:56.459 [silence] 00:53:56.459 --> 00:54:00.871 Great. I was wondering, is there wastewater injection going on 00:54:00.871 --> 00:54:05.210 on a large scale in California, and what’s happening there? 00:54:05.210 --> 00:54:09.780 - Yeah, there are thousands of wastewater wells in California. 00:54:09.780 --> 00:54:15.000 I’ve taken a brief look at that, and, by and large, they’re pretty uncorrelated 00:54:15.000 --> 00:54:17.610 with the earthquake activity. There are places where you see 00:54:17.610 --> 00:54:22.110 a correlation, but correlation is not causation. So it requires, 00:54:22.110 --> 00:54:27.560 I think, more examination. One example is the – a field which is 00:54:27.560 --> 00:54:31.090 under secondary recovery at San Ardo, which is a very old oil field. 00:54:31.090 --> 00:54:34.030 We’ve known for decades there are earthquakes right there, 00:54:34.030 --> 00:54:36.921 but they’re 10 kilometers deep. I think most people think it’s 00:54:36.921 --> 00:54:41.030 coincidence. So there’s a lot to do. But I think there’s an opportunity here 00:54:41.030 --> 00:54:46.830 to get ahead of things because, if the Monterey is developed, as is likely, 00:54:46.830 --> 00:54:51.170 we have the kind of seismic coverage that we wish for in other parts of the 00:54:51.170 --> 00:54:54.990 country here, and it’s really a question of gathering the rest of the information 00:54:54.990 --> 00:55:00.764 to understand how conditions may change as the process proceeds. 00:55:02.702 --> 00:55:08.889 [silence] 00:55:08.889 --> 00:55:15.090 - Hey, Bill. So you mentioned the issue of maximum magnitude for 00:55:15.090 --> 00:55:20.859 these events, and for tectonic events, usually the attempt to measure the fault 00:55:20.859 --> 00:55:23.990 dimensions and make some sort of estimate for the maximum magnitude 00:55:23.990 --> 00:55:28.580 based on that, do you think that same sort of logic applies here? 00:55:28.580 --> 00:55:32.020 And, if so, how do we figure out how big these structures are 00:55:32.020 --> 00:55:35.440 deep underground? - I do. And I think some people 00:55:35.440 --> 00:55:38.410 would like to say, well, they can only go up to a certain size. 00:55:38.410 --> 00:55:41.590 But every time someone has said that size, they got bigger. 00:55:41.590 --> 00:55:46.280 There was a report by the National Research Council published in 2012 00:55:46.280 --> 00:55:49.610 in which they pointed to the Denver earthquakes as the largest at about 4.8. 00:55:49.610 --> 00:55:52.040 And, of course, then we had the Oklahoma earthquake that 00:55:52.040 --> 00:55:56.930 moved it out to 5.6 or 5.7. So I think we have to assume that 00:55:56.930 --> 00:56:02.750 kind of regular frequency magnitude statistics apply on the network of faults. 00:56:02.750 --> 00:56:05.109 And so it’s really going to be the fault dimensions that are 00:56:05.109 --> 00:56:08.450 going to control it in the end. Perhaps the earthquakes in central 00:56:08.450 --> 00:56:11.170 Oklahoma near Prague were as large as they were because they were on 00:56:11.170 --> 00:56:14.970 the Wilzetta Fault, a large structure. Maybe that in these other areas, 00:56:14.970 --> 00:56:17.850 there just simply aren’t faults that are large enough to be much larger than 00:56:17.850 --> 00:56:19.800 a magnitude 3 or magnitude 4. 00:56:19.800 --> 00:56:24.081 So I think that understanding where the faults are is going to be one of the keys. 00:56:26.128 --> 00:56:31.435 [silence] 00:56:31.460 --> 00:56:33.840 - So injection is nothing new in that part of the world. 00:56:33.840 --> 00:56:37.619 Perhaps the volume or rates are different over the last decade. 00:56:37.619 --> 00:56:41.200 Is there – do you have any ideas of, you can determine whether that 00:56:41.200 --> 00:56:45.790 background rate is itself a reflection of induced activity? 00:56:45.790 --> 00:56:50.540 - That’s a really good question. And, in this USGS Bulletin by 00:56:50.540 --> 00:56:54.440 Nicholson and Wesson, they raised the possibility that all the earthquakes 00:56:54.440 --> 00:56:59.080 in Oklahoma are induced, not natural. And so we don’t know. 00:56:59.080 --> 00:57:01.330 We don’t have good records that go back in time. 00:57:01.330 --> 00:57:04.970 I think what we can say is that, within the central part of the state, 00:57:04.970 --> 00:57:12.240 where the seismicity kind of initiated in 2009, this was an area that had 00:57:12.240 --> 00:57:16.120 been under very heavy injection for a few years before then. 00:57:16.120 --> 00:57:22.820 2005, 2006 is when kind of very heavy dewatering of fractured reservoirs began 00:57:22.820 --> 00:57:27.990 to get this low-cut oil and subsequent injection of the fluids back underground. 00:57:27.990 --> 00:57:33.180 So this may be a case in which it’s the – it’s the time factor. 00:57:33.180 --> 00:57:36.440 Getting enough fluid into the reservoir, which has moved pressure into places 00:57:36.440 --> 00:57:40.244 that can induce earthquakes. That may be what’s operating. 00:57:40.244 --> 00:57:44.740 But, again, we’re kind of in a data-poor environment, not knowing enough about 00:57:44.740 --> 00:57:50.033 where those earthquakes really occurred back in the early 2000s. 00:57:53.371 --> 00:57:55.934 Patrick has a question. 00:57:57.957 --> 00:58:01.574 [silence] 00:58:01.574 --> 00:58:04.700 - I’m intrigued at the spatial distribution here. 00:58:04.700 --> 00:58:08.010 There’s a state shown on the map that’s dimly up there called 00:58:08.010 --> 00:58:14.990 North Dakota that – is there any incidence of disposal wells and 00:58:14.990 --> 00:58:17.990 this sort of phenomenon up there? Or is this a function of the fact 00:58:17.990 --> 00:58:21.270 that that’s a very low-seismicity area to begin with? 00:58:21.270 --> 00:58:24.750 - Yeah. This is a – that’s a really good question, Patrick, and important 00:58:24.750 --> 00:58:29.740 observation, that this is the area of the Bakken Shale Play, which is 00:58:29.740 --> 00:58:34.490 one of these – a development of liquids rather than gas. 00:58:34.490 --> 00:58:37.520 So there’s a lot of water being produced, co-produced, with the oil that is 00:58:37.520 --> 00:58:41.040 being re-injected. We’ve not seen detectable changes 00:58:41.040 --> 00:58:43.500 in seismicity, although the magnitude threshold there 00:58:43.500 --> 00:58:46.240 is probably about magnitude 3. 00:58:46.240 --> 00:58:48.450 But it may – you know, it may tell us something about 00:58:48.450 --> 00:58:51.570 stress conditions as well. It may be that in that part of 00:58:51.570 --> 00:58:54.215 the mid-continent, the rocks are further from failure. 00:58:54.246 --> 00:58:58.359 And so we haven’t raised the fluid pressure to the level it’s a problem. 00:58:58.359 --> 00:59:00.980 But that’s really a speculation at this point. 00:59:00.980 --> 00:59:03.190 But I think there was something fundamentally different about the 00:59:03.190 --> 00:59:06.590 conditions that are either here or, say, here in Oklahoma. 00:59:06.590 --> 00:59:08.960 So something really important to look at. 00:59:08.960 --> 00:59:13.891 Look at the places the earthquakes are not occurring as well as where they are. 00:59:13.930 --> 00:59:16.914 - Actually, Wayne, can I make one comment? 00:59:16.914 --> 00:59:20.020 In terms of Dave’s question about whether or not it’s really a background 00:59:20.020 --> 00:59:23.560 rate in Oklahoma, I mean, Andrea and I have a paper that was in BSSA 00:59:23.560 --> 00:59:26.840 recently where, not only does the rate change in Oklahoma and also 00:59:26.840 --> 00:59:31.400 in Arkansas, but the physics of the – the statistics of the clustering changes. 00:59:31.400 --> 00:59:33.730 And that would argue that something really new is going on, 00:59:33.730 --> 00:59:37.330 not just more induced seismicity, but actually probably the 00:59:37.330 --> 00:59:40.343 old stuff is really background. 00:59:44.944 --> 00:59:49.240 - Well, I’d like to ask just a final question, Bill. 00:59:49.240 --> 00:59:57.590 As you’ve emphasized, the orientation of potential failure planes with respect 00:59:57.590 --> 01:00:02.970 to the regional stress field is one of the most important criteria in 01:00:02.970 --> 01:00:06.460 deciding whether there’s going to be – determining whether there’s going to 01:00:06.460 --> 01:00:11.070 be induced seismicity and how large it can be. 01:00:11.070 --> 01:00:15.860 Can seismic imaging help us in that regard so that if there’s, say, 01:00:15.860 --> 01:00:24.250 a proposal for a big injection well, then a 3D seismic survey could locate 01:00:24.250 --> 01:00:27.780 potential faults and their dimensions? - Yeah, very definitely, Wayne. 01:00:27.780 --> 01:00:31.160 And actually, there’s a project that’s just getting underway in Oklahoma 01:00:31.160 --> 01:00:36.270 to do that, to try to take industry data to bring together kind of a statewide 01:00:36.270 --> 01:00:40.650 view of where the faults are located. You can see it in seismic data. 01:00:40.650 --> 01:00:42.830 Seismic data is not going to be available. 01:00:42.830 --> 01:00:46.380 Typically it’s owned by many parties. But the fault interpretations are 01:00:46.380 --> 01:00:49.810 the things that may be available. So the hope is that maybe by building 01:00:49.810 --> 01:00:54.940 out from Oklahoma, we’ll be able to see a new standard set for identifying 01:00:54.940 --> 01:00:57.100 where there are potentially active structures. 01:00:57.100 --> 01:01:00.300 And I think we’re going to need to go with that the seismic data to see if, 01:01:00.300 --> 01:01:03.269 in fact, these are the ones that are being activated. 01:01:06.394 --> 01:01:11.306 Okay. Well, if there aren’t any other questions, formal questions, 01:01:11.306 --> 01:01:17.900 any of you want to hear more about ZZ Top and beards and ponytails, 01:01:17.900 --> 01:01:21.843 Bill and I will be ready to answer those. Thanks, again, to Bill for a terrific talk. 01:01:21.843 --> 01:01:24.945 [applause]