WEBVTT 00:00:00.000 --> 00:00:04.000 [Okie dokie. What does everybody remind us to do? Record.] 00:00:04.000 --> 00:00:09.000 Good morning, everyone, and good afternoon, good evening, and good night, depending on where you are. 00:00:09.000 --> 00:00:12.000 Thank you for joining us from wherever you are joining us. 00:00:12.000 --> 00:00:21.000 Welcome to Day 3 of three, the final finale day of the Northern California Earthquake Hazards Workshop. [Kermit wave] 00:00:21.000 --> 00:00:30.000 So just to get us started, our delightful host with the most, John Grindle, is going to give us a couple of welcome slides and then we are going to go to our first exciting session. 00:00:30.000 --> 00:00:31.000 John, please. 00:00:31.000 --> 00:00:41.000 All right. Day 3, here we go. The USGS strives to provide a diverse, inclusive, and respectful environment because it is essential to the integrity of our organization and our science. 00:00:41.000 --> 00:00:48.000 If anything fails to exemplify these ideals, please alert an organizer for immediate assistance. 00:00:48.000 --> 00:01:00.000 Views expressed by the speakers do not reflect those of the USGS or federal government. Presentations were pre-recorded in early January. Some of our ground rules, we ask everybody to stay on mute unless you are speaking. 00:01:00.000 --> 00:01:07.000 And we use the chat feature. So you are encouraged to ask questions, make comments, and be nice in the chat. 00:01:07.000 --> 00:01:11.000 If you don't like the chat feature, you can turn it off. 00:01:11.000 --> 00:01:20.000 Go down to the chat button in your Zoom control bar. There's a little arrow. Click on that and then uncheck show chat previews and the chats will go away. 00:01:20.000 --> 00:01:37.000 We also have closed captioning, which reminds me to turn on closed captioning. So we'll do that later. If you'd like to hide the captioning, there is a hide captions button that you can use as well. During our Q&A discussions. 00:01:37.000 --> 00:01:45.000 You're encouraged to raise your hand, your virtual hand using the react button, and then you can share your video and we'll bring you up onto stage 00:01:45.000 --> 00:01:53.000 to ask your questions verbally. Also, if you'd like to rename yourself with your full name and institution, that is fantastic. 00:01:53.000 --> 00:02:07.000 Here is our list of organizers. We won't go through everybody, but big thank you to all of our organizers once again for Day 3. And then finally, if you have any issues, you can chat me or you can send an email to Shane or myself anytime. 00:02:07.000 --> 00:02:13.000 That was short and sweet. And I think we are ready to go. 00:02:13.000 --> 00:02:21.000 Thank you. Well, the Bay Area, it is big. It covers many different kinds of settings, many different kinds of people and many different kinds of vulnerabilities. 00:02:21.000 --> 00:02:29.000 So let's take a tour of some of them today. And to lead us on this exciting tour, we have Jeff and Taka'aki Taira [Woohoo!] 00:02:29.000 --> 00:02:38.000 Thank you, Sarah. I do have to say I do many webinars, but not all of them are DJ'd as well as this one. So I appreciate the amp up this morning. 00:02:38.000 --> 00:02:46.000 Good morning, good afternoon, good evening all. My name is Jeff Bellasario. I lead the Bay Area Council Economic Institute. We are a think tank based in San Francisco. 00:02:46.000 --> 00:02:55.000 We study the economy and policy across Northern California. So I'm very excited for this discussion here this morning. 00:02:55.000 --> 00:03:11.000 I'm going to get us going right into it. So our first presentation is going to come from Dena Belzer from Strategic Economics and Andy Kosinski from Fehr & Peers. And their presentation is titled "Post-COVID Place-Based Implications of Bay Area Seismic Vulnerability— 00:03:11.000 --> 00:03:16.000 Looking at Travel Behaviors and Economic Development." So we'll let the video roll here. 00:03:16.000 --> 00:03:31.000 Good afternoon, everybody. We are here today to talk about post-COVID place-based implications of Bay Area seismic vulnerability travel behavior and economic development. I'm Dena Belzer from Strategic Economics, 00:03:31.000 --> 00:03:37.000 and I'm here today with my colleague Andy Kosinski from Fehr & Peers Associates. 00:03:37.000 --> 00:03:45.000 Andy will be talking today about Bay Area travel behavior and I will be talking about East Bay economic development. 00:03:45.000 --> 00:03:53.000 Andy. Thanks, Tina. I'm Andy Kaczynski, and I'm the Oakland Office Leader and Senior Associate with Fehr & Peers. 00:03:53.000 --> 00:04:02.000 A transportation consulting firm. I'm here to talk about travel changes since COVID and what that means 00:04:02.000 --> 00:04:17.000 for this industry. Much travel has returned to pre-pandemic levels here in the San Francisco Bay Area and nationally, but some have not, and there are some key implications of these trends, which include less of a focus on travel to downtowns. 00:04:17.000 --> 00:04:22.000 Less travel on Mondays and Fridays. Less travel during the peak rush hours. 00:04:22.000 --> 00:04:28.000 And a stronger rebound for certain types of trips over others. 00:04:28.000 --> 00:04:48.000 Starting with a look nationally and the Institution of Transportation Engineers presented some results of a national survey recently that showed travel generally for drivers and driving has returned to 2019 levels, in particular in urban areas where it's really kind of storming back. 00:04:48.000 --> 00:05:03.000 However, we are very clearly seeing less travel on Mondays and Fridays due to many companies initiating flexible remote work policies where the core in-office days tend to be in the middle of the week. 00:05:03.000 --> 00:05:13.000 Furthermore, we're seeing a phenomenon called peak spreading, where rather than concentrating travel in that 8 a.m. and 5 p.m. rush hour 00:05:13.000 --> 00:05:22.000 many more folks have that flexibility; they're traveling on the shoulders of the peak, which means immediately on either side, as well as traveling a lot more 00:05:22.000 --> 00:05:36.000 in the midday so it's like 3 p.m, we're seeing increases as folks who work from home are taking more discretionary trips, whereas grocery trips or school trips. 00:05:36.000 --> 00:05:54.000 Zooming into the San Francisco Bay Area the post-COVID recoveries are very different for driving versus transit, and so for driving using bridge traffic as a proxy for overall driving levels. It's almost back 00:05:54.000 --> 00:06:03.000 87% of recovery and even more on some certain bridges. However, for transit, there were levels of recovery are substantially lower 00:06:03.000 --> 00:06:21.000 especially for the transit agencies that historically have been very focused on getting people to and from key central business districts and downtown such as BART, which very much serves downtown San Francisco, and Oakland, and Caltrain. 00:06:21.000 --> 00:06:30.000 Dena and I were asked by to produce a report called "Role in the Region." 00:06:30.000 --> 00:06:40.000 Which tells BART's story of how their role in the region has changed since COVID and what they're doing to respond to some of the post-COVID challenges that they face. 00:06:40.000 --> 00:07:00.000 The chart on the left, which is from this report, shows just how closely BART's ridership rebound aligns, which is in blue, aligns with return to office and office occupancy, which is in orange, which really underscores how much the key of office workers are to long-term BART ridership recovery. 00:07:00.000 --> 00:07:12.000 And on the right, the chart shows that in orange during the commute hour in particular from downtown recovery is very low, 30%. 00:07:12.000 --> 00:07:34.000 Whereas they're seeing a lot more recovery in the evening and the weekend especially in areas that are away from the downtowns and that's shown in blue with 60% or 70% recovery. And BART is one of the things they're doing is investing more in evening and weekend service. 00:07:34.000 --> 00:07:40.000 To adapt to the new ridership profile. What does this mean for key infrastructure? 00:07:40.000 --> 00:07:45.000 There's been a lot of great progress recently, major investments in seismic retrofits. 00:07:45.000 --> 00:08:00.000 To now complete such as Presidio Parkway Project. BART themselves have a major earthquakes seismic retrofit program that was completed in 2024 the eastbound of the San Francisco Bay Bridge was completed several years ago. 00:08:00.000 --> 00:08:05.000 Which is meaning that our infrastructure is becoming more and more resilient. 00:08:05.000 --> 00:08:10.000 The fact that much of the workforce can now work from home for a few days or weeks is needed. 00:08:10.000 --> 00:08:26.000 Will make our recovery economically go a lot smoother after a big earthquake disturbance. Real-time communications such as pushing out updates and updating travel planners has come a long way. 00:08:26.000 --> 00:08:44.000 The concerns that remain are that essential workers at once who cannot work from home and many of those do rely on public transportation we saw that during COVID and BART is rapidly approaching a fiscal cliff, which is going to imperil 00:08:44.000 --> 00:08:55.000 BART and other transit agencies to their ability to be there as a redundancy during future disturbances to the transportation network. 00:08:55.000 --> 00:09:11.000 The chart on the right shows that BART's fair revenue and parking fee revenue in blue took a huge hit in COVID, was supplemented by a federal emergency assistance in purple for several years, which is running out and then the state's stopgap assistance in teal 00:09:11.000 --> 00:09:19.000 is running out next year, which will leave a pretty big hole in their finances, which if that's not filled, we'll have. 00:09:19.000 --> 00:09:35.000 major effects on getting the essential workers moving immediately after an earthquake and will have an effect on all the other ways that BART benefits the economy, such as getting people to and from culture and arts and sports events, shopping. 00:09:35.000 --> 00:09:40.000 So what should we do? We need to continue placing a dollar value on vulnerabilities. 00:09:40.000 --> 00:09:48.000 To help us continue to prioritize infrastructure investments and hardening such as seismic retrofits 00:09:48.000 --> 00:09:54.000 we need to invest in getting people to and from transit. It's called the first-last mile. 00:09:54.000 --> 00:10:03.000 For these emergency situations that way our transit systems such as BART and ferries can really provide great redundancy for freeways. 00:10:03.000 --> 00:10:09.000 We need to continue advancing our use of travel models to help scenario plan. 00:10:09.000 --> 00:10:14.000 So that we can anticipate what would happen after a major earthquake. 00:10:14.000 --> 00:10:28.000 And then finally, we need to invest in a robust transit network to boost the region's resilience so that BART and other agencies can be there and provide that essential services to get people to and from their jobs 00:10:28.000 --> 00:10:35.000 and other uses in the event of an earthquake. 00:10:35.000 --> 00:10:42.000 Okay, now I'm going to follow-up by talking about seismic risk, COVID and the East Bay economy. 00:10:42.000 --> 00:10:51.000 And the reason that I'm focusing on the East Bay economy today is because this is where, as shown in purple on this map. 00:10:51.000 --> 00:11:10.000 most of the lands that are zoned for production, distribution, repair kinds of activities in the Bay Area are located. And these kinds of workers should be considered essential workers, they cannot telecommute, they can't work from home 00:11:10.000 --> 00:11:14.000 and do their work on a computer, they have to be in place, 00:11:14.000 --> 00:11:24.000 and employment in these kinds of jobs is growing very quickly in the East Bay. It's growing more quickly than the East Bay economy as a whole. 00:11:24.000 --> 00:11:30.000 These industry sectors also help the East Bay diversify the region's economy. 00:11:30.000 --> 00:11:50.000 If we become too dependent on our traditional tech sectors, then we are very vulnerable to the volatility in those tech industries, which we saw a lot of following the economic decline in 2000 following a 00:11:50.000 --> 00:11:59.000 2008 banking crisis and again, now we're seeing with some of the right sizing of these industries following COVID. 00:11:59.000 --> 00:12:14.000 And finally, these kinds of jobs offer an opportunity for people who don't have a college or advanced degree, but I only have a high school degree. So this really offers a working living wage for those kinds of people. 00:12:14.000 --> 00:12:19.000 Just to illustrate here is the Hayward fault. 00:12:19.000 --> 00:12:27.000 I want to say that these same industry lands also represent an ecosystem, so they work together. 00:12:27.000 --> 00:12:50.000 It's not about one business. For example, Tesla manufactures cars that are exported globally, but Tesla's suppliers are also located in the East Bay. So without those suppliers, Tesla couldn't produce its cars. We also have a lot of distribution and logistics of parts and other kinds of 00:12:50.000 --> 00:13:09.000 bits and pieces. This is not just about Amazon warehouses, but it's actually again, about the supply chain there is a lot of parts assembly that goes on. And finally, there are raw inputs and materials that are coming of this intraregional supply chain or ecosystem. 00:13:09.000 --> 00:13:19.000 And the reason that I am also really interested in this is because the U.S. Geological Survey 00:13:19.000 --> 00:13:36.000 did this work on the Hayward fault, the HayWired Scenario and asked us to take a spatial look at where the impacts would be most significant. So this is the first time that one of these scenarios has really looked at a place to understand what happened. 00:13:36.000 --> 00:13:57.000 We identified 180 census tracts that face the highest potential for total building damage. These are buildings that would be damaged beyond repair and about 150 of those tracks are just in Alameda County. You can see them in orange. There are a few tracks elsewhere in the Bay Area, but again, mostly 00:13:57.000 --> 00:14:12.000 in Alameda County, and this is central Alameda County and Northern Alameda County The U.S. Geological Survey HayWired Scenario showed that these two areas, northern and central Alameda County, are extremely vulnerable 00:14:12.000 --> 00:14:23.000 to 7.0 magnitude earthquake. For non-residential buildings, this includes these industrial buildings. 00:14:23.000 --> 00:14:37.000 We could lose as much as 58 million square feet of space and that's 3,700 commercial buildings and about 25 of those buildings are industrial, like this building here. 00:14:37.000 --> 00:14:45.000 Then we could lose 76 million square feet or about 35,000 homes and again, these are buildings that are damaged beyond repair 00:14:45.000 --> 00:15:10.000 And housing and work are interconnected. So again, going back to the East Bay economy post-COVID, what we've seen in terms of progress over the 10 years is we've had a robust recovery from the 2008 recession and that East Bay industrial jobs or jobs in these industrial lands grew 32% more quickly than the East Bay employment as a whole. 00:15:10.000 --> 00:15:30.000 But our concerns are that we're learning that we have a vulnerable power supply. There is increased demand for power and for road infrastructure in result to commercial vehicles and electrification. So these are light trucks, delivery trucks, trucks moving goods in and out of the port. 00:15:30.000 --> 00:15:47.000 We see different movement patterns for both goods and people and then again, we already have a lack of affordable housing. We have significant destruction of our housing stock this is going to create a further crunch on our workforce. 00:15:47.000 --> 00:16:01.000 Just to use Union City as a quick case study. This illustrates that we are seeing these trends of demographic change of aging population. In some cases, we're not seeing robust population growth. 00:16:01.000 --> 00:16:08.000 Incomes are going up as people are moving out of households, they're aging out or whatever. 00:16:08.000 --> 00:16:14.000 People with higher levels of educational attainment, so a college degree or higher, are moving in. 00:16:14.000 --> 00:16:22.000 And then this is also changing our commute patterns. 00:16:22.000 --> 00:16:36.000 So, a declining share of our workforce is able to live and work in our Alameda County cities and the people who are moving into our Alameda County cities such as Union City 00:16:36.000 --> 00:16:47.000 are taking that more diverse commute pattern. So again, changing commute patterns, not exactly the same as what Andy was showing, but they are changing. 00:16:47.000 --> 00:17:02.000 And finally, what are the policy implications of a major earthquake? Well, first of all, this could inhibit future Bay Area industrial trends that compounded problems that COVID created, but we were able to overcome. 00:17:02.000 --> 00:17:14.000 And also the East Bay economy may not be able to recover from an earthquake the way it could from COVID. We still had the buildings in place and we still had the people in place. 00:17:14.000 --> 00:17:20.000 If we have a significant earthquake, both the buildings and the people will be potentially gone. 00:17:20.000 --> 00:17:33.000 Again, damage to the housing stock would really disrupt the region's economy. People may not be able to return and finally, energy supply may be a bigger vulnerability than the road or transit network. 00:17:33.000 --> 00:17:39.000 So I'm going to stop there and we'll look forward to taking your questions when we have our conference session. 00:17:39.000 --> 00:17:43.000 Thank you very much. 00:17:43.000 --> 00:17:58.000 Okay. Thank you to Dena and Andy for that great presentation. I am supposed to remind you that you can use the chat to ask questions. We do have the presenters here, they'll do their best to answer those questions while the presentation is going. 00:17:58.000 --> 00:18:05.000 But also put in questions that we can use after the presentation for our live discussion. 00:18:05.000 --> 00:18:09.000 We're going to stay in the East Bay for this next presentation. 00:18:09.000 --> 00:18:16.000 It comes from Vicki Langenheim from USGS, and it's on the basin structure in the Concord, Walnut Creek, Livermore region. 00:18:16.000 --> 00:18:22.000 And she's looking at gravity studies. So we will roll the next video here, please. 00:18:22.000 --> 00:18:36.000 Hi, I'm Vicki Langenheim and I was asked to give a talk on gravity studies pertaining to the Walnut Creek, Concord, Livermore region east of San Francisco Bay. This image shows an oblique northward view of the gravity map overlaying on a 00:18:36.000 --> 00:18:45.000 Google image that shows Interstate 580 traversing the big gravity low shown by the blues reflecting the large deep Livermore Basin. 00:18:45.000 --> 00:18:53.000 So I'll be giving you a brief tour of what we've learned in this area and how they relate to earthquake hazards. 00:18:53.000 --> 00:19:00.000 First, where is this region and why is it of interest? So to orient ourselves, this is the population density map of the San Francisco Bay 00:19:00.000 --> 00:19:10.000 region from the 2020 census, the deeper the blue, the more densely populated. Our study area outlined in red contains locally dense populations in Livermore, Dublin, Concord, 00:19:10.000 --> 00:19:15.000 Walnut Creek, and Antioch. Note also that major infrastructure passes through this region. 00:19:15.000 --> 00:19:23.000 Let's now look at the geology of the region. Here's the study area outlined in red on the state geologic map 00:19:23.000 --> 00:19:33.000 with Livermore, Dublin, Concord, Walnut Creek. Note that many of these cities lie close to the active Calaveras fault. 00:19:33.000 --> 00:19:43.000 This area has recently been the subject of new geologic map compilations in conjunction with gravity, as well as updates to the seismic velocity model to better understand this area, 00:19:43.000 --> 00:19:50.000 and the Sacramento, San Joaquin Delta region to the northeast. So zooming into this area 00:19:50.000 --> 00:20:00.000 the Calaveras, Greenville, and Concord faults are all active to Holocene faults, strike-slip faults, but also note the lesser known Holocene active Las Positas fault, 00:20:00.000 --> 00:20:15.000 as well as the prevalence of folds shown by the magenta fold axes. That variance right from north-northwest parallel to the strike-slip faults to east-west, indicating complex patterns of compression and transgression in this part of the plate boundary. 00:20:15.000 --> 00:20:28.000 The geologic units in this map are greatly simplified, but are an appropriate first cut for assigning physical properties such as density or seismic velocity. The units here are ordered by age and increasing density. 00:20:28.000 --> 00:20:40.000 Bedrock consists of Mesozoic Franciscan Complex and the Jurassic Coast Range Ophelite, overlane by a marine latest Jurassic to Miocene sedimentary sequence and the non-marine late Miocene to Quaternary sequence. 00:20:40.000 --> 00:20:48.000 How does this compare with the gravity map, which we have processed so it shows us density variations in the upper to middle crust. 00:20:48.000 --> 00:21:02.000 The gravity map here shows the distribution of gravity measurements. The black dots are our new measurements concentrated along the Calaveras and Greenville faults, as well as the margins of Mount Diablo. These augment existing measurements shown by the white circles. 00:21:02.000 --> 00:21:20.000 Let's compare this map with the simplified geology. The gravity map on the right indicates that the Dublin Livermore area is marked by a large gravity low shown by the blues. The gravity low in general matches the distribution of yellow and browns in the geologic map on the left. 00:21:20.000 --> 00:21:39.000 So the Quaternary and Tertiary part of the sedimentary sequence. Not surprisingly, the highest gravity values, shown by the reds and magentas, coincide with the dense post-range ophiolite, gravity eyes also coincide with the Franciscan there and in the southeastern part of the map. 00:21:39.000 --> 00:21:58.000 The Cretaceous Great Valley sequence produces a gravity ridge shown by the yellows extending southeast of Mount Diablo which we interpret as resulting from shallow basement in the core of an aniform separated from the overlying Cretaceous rocks by a folded buttress unconformity 00:21:58.000 --> 00:22:02.000 The Livermore gravity low maps out the extent of a deep sedimentary basin. 00:22:02.000 --> 00:22:09.000 An oil test well, shown by the white star here, indicates that much of this basin fill is of Miocene age or younger. 00:22:09.000 --> 00:22:12.000 With the top of Miocene reported at a depth of 2.5 kilometers. 00:22:12.000 --> 00:22:20.000 And the well-bottoming at Miocene at about 5.3 kilometers, which is consistent with a seismic refraction profiled by Meltzer and others, 00:22:20.000 --> 00:22:26.000 which passed near the drill hole, indicating a basement depth of about 5.5 kilometers. 00:22:26.000 --> 00:22:36.000 We can use gravity gradients to map out the margins of this basin where we would also expect velocity boundaries. 00:22:36.000 --> 00:22:43.000 So maximum gradients are plotted as black dots in the map on the right. The larger dots mean larger horizontal gradients. 00:22:43.000 --> 00:23:05.000 We'll start where the basin bounding faults are relatively simple. The southern stretches of the Calaveras fault, which marks the southwest margin of the basin and the Greenville fault which marks the eastern margin of the basin. The locations of the map faults relative to the gravity gradient indicate that the Calaveras fault dips vertically to steeply to the west, 00:23:05.000 --> 00:23:14.000 and the Greenville fault dips steeply to the east. As both of these faults progress northward towards the big gravity high of Mount Diablo, 00:23:14.000 --> 00:23:22.000 the Calaveras fault appears to step over with gradients to the Concord fault. 00:23:22.000 --> 00:23:36.000 Whereas the Greenville fault breaks up into multiple fault splays with the map the most prominent gradient associated with the southern edge of basement, 00:23:36.000 --> 00:23:47.000 towards, again, the Concord fault. The northern part of the basin is marked by folding and reflected by slightly higher gravity values in this area. 00:23:47.000 --> 00:23:54.000 And lastly, the southeast margin locally coincides with the Las Positas fault at its northeast end. 00:23:54.000 --> 00:24:07.000 But the gravity gradients indicate that the basin margin here probably also consists of another fault to the southeast that is concealed beneath Plio-Quaternary deposits. 00:24:07.000 --> 00:24:12.000 So we'll examine a couple of integrated geologic and geophysical models that Russ Graymer and I did. 00:24:12.000 --> 00:24:20.000 Along the white lines that illustrate the complicated structures that mark this basin. 00:24:20.000 --> 00:24:25.000 The first cross-section is shown by the red line in the gravity map. On the right, 00:24:25.000 --> 00:24:45.000 the geologic section on the bottom panel density and magnetizations assigned to those units in the middle panel and the observed and predicted response from those physical properties. Let me overlay the basement boundary shown by the thick pink line 00:24:45.000 --> 00:24:56.000 and one point is that these geologic units are rarely flat lying in the basin between the Calaveras and Pleasanton faults, the strata dips deeply to the northeast. 00:24:56.000 --> 00:25:14.000 In the main part of the basin units are folded and overthrust with steep west dips. So a simple rule of attributing density and velocity that increases with depth may actually increase laterally because of these steep dips. Another point is that the basin is 00:25:14.000 --> 00:25:20.000 about 8 kilometers deep, but note that the sediments are pretty dense in this simplified model. 00:25:20.000 --> 00:25:32.000 Mainly because of the uplifted and folded Livermore gravels. So gravity suggests that the gravels may be dense or even denser than some of the older units such as the Miocene Neroli 00:25:32.000 --> 00:25:40.000 Formation. The second cross-section crosses from the Calaveras fault, cross Mount Diablo. 00:25:40.000 --> 00:25:51.000 where the Greenville fault splays around Mount Diablo in that big restraining bend. The basement boundary here is shown in pink. 00:25:51.000 --> 00:26:09.000 So note also that we've assumed that Franciscan lies beneath the basin here. In this interpretation, the Greenville fault splays into the Diablo fault here and up towards the Concord fault as well into the Mount Diablo thrust fault. Again, the basin sediments are folded 00:26:09.000 --> 00:26:23.000 even overturned in the fold and thrust belt southwest of Mount Diablo, whereas to the northeast, the Cretaceous strata truncate downward onto the basement at the base of a northeast dipping Tertiary section. 00:26:23.000 --> 00:26:40.000 So how does this relate to seismic hazard? Well, first of all, the interpretation that slip on the Greenville fault is transferred west to the Concord fault, something that has happened in the last two to three million years in this big restraining band. 00:26:40.000 --> 00:27:00.000 Based on the age of the folded Livermore gravels suggests that this step over is responsible for the uplift of Mount Diablo and folding and thrusting north deliver value. This also argues against a huge thrust fault that underlies Mount Diablo that extends east of the Greenville fault and into the Central Valley has been 00:27:00.000 --> 00:27:07.000 earlier inferred. Second, the basin structure has implications for ground motion shaking. 00:27:07.000 --> 00:27:15.000 So let's now focus on the Livermore Basin area. Marked by the brown box here. 00:27:15.000 --> 00:27:23.000 So a seismic array that Hartzell and others in 2016 analyzed is plotted here on the state geologic map in the center. 00:27:23.000 --> 00:27:36.000 Showed that ground motions are greatly amplified in Livermore Valley, as shown by the panels on the left. And the strongest amplifications coincides with the lowest gravity values of the Livermore Basin. 00:27:36.000 --> 00:27:41.000 Threads here are greater amplification and the contours here are of gravity. 00:27:41.000 --> 00:27:47.000 Amplification is up to eight times for frequencies of one hertz or less. 00:27:47.000 --> 00:27:56.000 They also inverted for shear wave velocities and found Vs30 values that range from as low as about 160 to 320 meters a second. 00:27:56.000 --> 00:28:00.000 A bit slower than the actual borehole measurement here on the red dot. 00:28:00.000 --> 00:28:15.000 But considerably slower than in the version of the San Francisco Bay velocity model at the time. Hirokawa and Aagaard updated the velocity model by adjusting and lowering in an ad hoc way, their words and not mine. 00:28:15.000 --> 00:28:18.000 P-wave and corresponding S-wave velocities in the upper 6 kilometers. 00:28:18.000 --> 00:28:28.000 This helped with matching arrival times, but not always match the cumulative absolute displacement, a measure of the amplitude of the ground motions. 00:28:28.000 --> 00:28:36.000 Well, one way forward to refine this is to compare the updated ad hoc velocity rules with velocity logs in the Livermore Valley. 00:28:36.000 --> 00:28:47.000 For example, in that area the deep drill hole, Sonic Log span from 450 to 450 meters to 5.3 kilometers depth. 00:28:47.000 --> 00:28:54.000 As well as use her shear wave inversions that Hartzell presented in that 2016 paper. 00:28:54.000 --> 00:29:11.000 Perhaps use the geologic cross-sections that inform our where basin sediments deviate from being horizontally stratified, as well as utilize updated geologic maps that are more detailed than the state geologic map to capture some of the variability we know exists at the surface. 00:29:11.000 --> 00:29:26.000 So the map in the upper right here highlights recently published compilation of geology for this region that breaks up the units in more detail than shown in the geologic map. 00:29:26.000 --> 00:29:32.000 The compilation also includes the gravity anomaly shown by the blue lines and gradients as the red dots. 00:29:32.000 --> 00:29:41.000 Note that the Livermore gravels here had been broken out in this map where they are just one big Pliocene mass on the state geologic map. 00:29:41.000 --> 00:29:46.000 And note also that the Quaternary is broken out into more units than shown on the state map. 00:29:46.000 --> 00:29:57.000 That could be useful in fine tuning the 3D geologic model that underpins the San Francisco Bay seismic velocity model which of course is used for simulating ground motions from scenario earthquakes. 00:29:57.000 --> 00:30:10.000 I'd also like to point out some of the lessons from a recently published paper by Steve Hartzell and others, including me, with another seismic array to the northwest in the Concord fault. 00:30:10.000 --> 00:30:14.000 So we'll now focus on the area shown by the red box. 00:30:14.000 --> 00:30:28.000 The upper left shows a static gravity map with a seismic array shown by the white triangles and maximum gradients, gravity gradients shown by the black dots, the contours from that map are superposed on the maps on the right as light-blue lines. 00:30:28.000 --> 00:30:36.000 The maps on the right show site response based on a reference site spectral ratio method and the reference is located on Great Valley sequence 00:30:36.000 --> 00:30:52.000 near Mount Diablo and the circles on this map show amplification relative to that site. The spokes are amplifications that point back to the earthquake that was recorded at that site. So at all frequencies, you can see that there is significant amplification 00:30:52.000 --> 00:31:00.000 near the Concord fault or southwest of the Concord fault. 00:31:00.000 --> 00:31:06.000 And this is along that prominent gravity gradient that bounds the gravity high of Mount Diablo. 00:31:06.000 --> 00:31:15.000 Note also that many of the longer spokes point are oriented north-northwest, so from the Calaveras related fault ruptures. 00:31:15.000 --> 00:31:22.000 Note also that the lowest gravity values here coincide with folded tertiary sediments. 00:31:22.000 --> 00:31:30.000 And that amplifications are not as high. This lack of a large gravity low between the Franklin and the Concord faults 00:31:30.000 --> 00:31:47.000 suggest that the right step being transtentional transferral slip across these faults is either very recent very low slip rate happens farther south or is obscured by the large restraining bend from the Greenville to the Concord fault. 00:31:47.000 --> 00:31:54.000 Well, this paper also shows maps of amplification 00:31:54.000 --> 00:32:13.000 from source site spectral inversion with amplification at amplifications of 3 to 4 times at frequencies of 2 hertz or lower. And this pattern of higher amplifications is similar to the other method that shows higher amplification down the basin axis and near the southeast part 00:32:13.000 --> 00:32:29.000 the Concord fault. Lastly, I think this was an interesting result that shows the importance of topography composed of dense bedrock in modulating ground motions they simulated two earthquakes, one on the Hayward fault, 00:32:29.000 --> 00:32:38.000 the other on the Greenville fault using the velocity model version 21.1 discussed in Hirokawa and Aagaard 00:32:38.000 --> 00:32:57.000 2022 paper. In the Walnut Creek Concord area highlighted by the white circles sne sees higher peak velocities from the Hayward fault with a sharp break at the Concord fault where higher gravity values indicate shallow bedrock to the northeast of the fault, whereas the Greenville 00:32:57.000 --> 00:33:08.000 Source results in lower velocities attributed to topographic shadowing of now, Diablo. 00:33:08.000 --> 00:33:27.000 So in conclusion, gravity and geologic maps and cross-sections help understand how slip is partitioned east of the Hayward fault and can also help in further refinement of 3D geologic and seismic velocity models. Thank you. 00:33:27.000 --> 00:33:49.000 Thank you so much, Vicki, for the very exciting talk. So ideally enjoying to see the mini discussion ongoing chat and then looks like some question can be answered next talk. So I just wondering move to the next presentation which are given by the Chad Trexler from USGS, 00:33:49.000 --> 00:33:57.000 Earthquake Science Center. His talk is more about the active fault in the Sacrament-San Joaquin Delta. Please go ahead to start to the video. 00:33:57.000 --> 00:34:02.000 Hi, everyone. My name is Chad Trexler and I'm a geologist with the Earthquake Science Center. 00:34:02.000 --> 00:34:07.000 I'd like to talk to you all today about our ongoing research in the Sacramento-San Joaquin Delta. 00:34:07.000 --> 00:34:15.000 Where we're using a variety of techniques to further our understanding of active faults that are relatively poorly constrained compared to many of the better known faults in Northern California. 00:34:15.000 --> 00:34:25.000 This is work that I've been spearheading along with help from Belle Philibosian, Jesse Vermeer, and a variety of other folks who've been involved in the past 40 years or so. 00:34:25.000 --> 00:34:35.000 Because I'm a structural geologist by training, I'd like to start us off with the regional geologic map of the Bay Area and surrounding areas. This is a map that many of us are likely familiar with, 00:34:35.000 --> 00:34:46.000 and from the perspective of earthquake scientists, it's dominated by a system of north-west south-southeast striking dextral faults that make up the Pacific North America plate boundary at this latitude. 00:34:46.000 --> 00:34:52.000 In this context, the Sacramento-San Joaquin Delta, outlined here in purple, is unique. 00:34:52.000 --> 00:35:05.000 The delta occupies something of a structural gap where the structural architecture is relatively prominent in the coast ranges, both to the north and to the south, is not obviously continuous through the Delta itself. 00:35:05.000 --> 00:35:15.000 I'd like to focus in on the Delta now with the black box showing the extent of the next few slides where north will be to the upper left corner of the figures. 00:35:15.000 --> 00:35:27.000 Here's the Delta again, this time shown with a hillshade in the background. Remember the north is to the upper left. The Coast Ranges north of Delta are on the left-side of the map and Mount Diablo is in the lower right. 00:35:27.000 --> 00:35:37.000 The colored lines here are the USGS Quaternary fold database and the yellow arrows show GNSS velocity relative to a station on Mount Diablo. 00:35:37.000 --> 00:35:44.000 The data set is relatively sparse, in part because of the difficulty in installing monuments in a river Delta and tidal slough. 00:35:44.000 --> 00:35:52.000 But it does show that the region is broadly experiencing plate boundary parallel strain, similar to what we see further west in the Bay Area, 00:35:52.000 --> 00:35:58.000 With a handful of millimeters per year accommodated within the Delta. 00:35:58.000 --> 00:36:02.000 Seismicity data sets also suggest that structures in the Delta are active. 00:36:02.000 --> 00:36:09.000 Though a few patterns emerge that are interesting. First, most of the seismicity is small, attitudes of less than three. 00:36:09.000 --> 00:36:15.000 And quite deep. Most seismicity is between 10 and 30 kilometers below the surface. 00:36:15.000 --> 00:36:23.000 This roughly east-west profile through the central Delta from Parsons et al., 2002 illustrates this nicely. 00:36:23.000 --> 00:36:33.000 While the relative lack of shallow earthquakes is interesting. The focal mechanisms from the deep earthquakes that we do see are more or less what we would expect based on tectonic context. 00:36:33.000 --> 00:36:41.000 Dextral on subvertical north-south striking planes and reverse on moderately dipping east-west tracking planes. 00:36:41.000 --> 00:36:48.000 The notable exception to this pattern of small and deep seismicity is, of course, the 1892 Winter's Vacaville earthquake sequence. 00:36:48.000 --> 00:36:58.000 Which was highlighted by a pair of magnitude 6.0 earthquakes two days apart in April of 1892. 00:36:58.000 --> 00:37:04.000 Well, the Delta as a whole is quite low relief. There are a few regions of locally prominent topography. 00:37:04.000 --> 00:37:14.000 These include the Potrero, Kirby, and Montezuma Hills, outlined here in white, all of which coincide broadly with the locations of mapped Quaternary faults. 00:37:14.000 --> 00:37:35.000 So given the somewhat incomplete picture from geodesy and seismicity can we use the geomorphology that we see in these regions and the structural geology to help develop a better picture of the Tertiary fault activity in the Delta. I'd like to think we can. And to dig into this question a bit further, I'm going to focus specifically on the Pittsburgh-Kirby Hills Fault System, 00:37:35.000 --> 00:37:46.000 which runs approximately north-south through the Western Delta from just east of Fairfield and Travis Air Force Base at its north-end southward to the Sacramento River and the cities of Pittsburgh and Antioch 00:37:46.000 --> 00:37:54.000 at its southend. Note that we've rotated map orientation again. North is back to the top of the frame here. 00:37:54.000 --> 00:38:06.000 The Pittsburgh-Kirby Hills fault highlighted in red follows the general pattern within the Delta of striking north-northeast subparallel with dextral plate boundary faults to the west. 00:38:06.000 --> 00:38:13.000 Given its orientation, we expect that this fault should broadly accommodate dextral displacement. 00:38:13.000 --> 00:38:28.000 However, the topography within the Delta, specifically the uplift of the Montezuma Hills east of the Pittsburgh-Kirby Hills fault, suggests that there may be some component of dip slip displacement as well and the east side is moving up relative to the west side of the fault, 00:38:28.000 --> 00:38:50.000 if you go by the topography. Meanwhile, cross-sections constructed using interpreted regional seismic reflection surveys suggested the Pittsburgh-Kirby Hills fault is a steeply east dipping structure and displacement of Eocene and older strata is east-side down opposite what is suggested by the geomorphology on the surface. 00:38:50.000 --> 00:39:09.000 So let's take a closer look at the Montezuma Hills and dive into the LIDAR data a little bit. This is a figure produced from a 2018 LIDAR data set of the region. And one of the things you notice right away as the Montezuma Hills contain a large number of wind and water gaps. 00:39:09.000 --> 00:39:30.000 These are geomorphically through-going channels shown with the black dashed arrows that cross the drainage divide shown on this figure with the black and white dashed line. We also notice remnants of an apparently intact preserved surface particularly in the Southern Montezuma Hills here outlined in purple. 00:39:30.000 --> 00:39:35.000 Both of these geomorphic features are often considered indicators of active surface uplift. 00:39:35.000 --> 00:39:41.000 In addition, the geomorphology is rather asymmetric from one side of the drainage divide to the other. 00:39:41.000 --> 00:39:47.000 This profile shows channel elevation across one of those wind gaps, highlighted in light-blue on the map. 00:39:47.000 --> 00:39:52.000 With local relief shown in gray and the multicolored lines showing tributary channels. 00:39:52.000 --> 00:40:04.000 The channels are colored by normalized channel steepness, which is a metric used by tectonic geomorphologists to show how steep a channel is relative to what we might expect based on where we are located along its profile. 00:40:04.000 --> 00:40:09.000 The warmer colors indicate a channel that is over-steepened, which can be an indication of uplift. 00:40:09.000 --> 00:40:26.000 I want to specifically point out that both channel steepness and relative relief are greater southwest of the drainage divide. On the left of the profile, then to the northeast, suggesting that uplift signal might be stronger in the southwest than the northeast. 00:40:26.000 --> 00:40:42.000 We've also made some excavations within the water gaps in the Montezuma Hills, which have led us to our current model of the preserved surface and channels of the Montezuma Hills represents an uplifted Delta or estuarine system, something analogous to the modern Delta, but now located about 100 meters above sea level. 00:40:42.000 --> 00:40:48.000 Our efforts to date these deposits are ongoing, but Tephrachronology from the Montezuma Formation, which makes up the bedrock 00:40:48.000 --> 00:41:04.000 of the preserved surface constrains a minimum uplift rate of greater than about 0.1 millimeters a year, which isn't much, but based on the fact that these features are preserved at all, we suspect the rate may be somewhat higher than that. 00:41:04.000 --> 00:41:09.000 Maybe on the order of millimeters per year. 00:41:09.000 --> 00:41:14.000 So to explain the juxtaposition of kinematics that we see of west-side up displacement of Eocene units. 00:41:14.000 --> 00:41:24.000 An east-side up displacement of Quaternary units, we're going to turn our attention southward across the Sacramento to the flanks of Mount Diablo, where structures might provide a useful analog. 00:41:24.000 --> 00:41:37.000 The Kirker, Clayton, and Marsh Creek faults highlighted on this map in red are interpreted as structures associated with an extensional basin that formed in the Paleogene atop the Farallon subduction forearc. 00:41:37.000 --> 00:41:45.000 These faults have then been both folded and reactivated by the modern dextral transform tectonic regime. 00:41:45.000 --> 00:42:00.000 Similar extension structures within the Tertiary section have been documented in seismic reflection data throughout the Delta, including in the Montezuma Hills, shown here in a figure modified from work by Jeff Unruh. 00:42:00.000 --> 00:42:15.000 So if we apply a similar model to the Pittsburgh-Kirby Hills Fault System, the structures we are investigating within the Delta largely formed as a part of the Farallon Forearm, and more recently, they've been deformed and reactivated in the modern dextral plate boundary setting. 00:42:15.000 --> 00:42:26.000 So this is starting to come together into a relatively coherent story where the Montezuma Hills block is interpreted as an inverted extensional basin, which is uplifted and preserved an older version of the modern Delta estuary. 00:42:26.000 --> 00:42:32.000 So with this in mind, can we improve constraints on late Quaternary activity of the Pittsburgh- 00:42:32.000 --> 00:42:38.000 Kirby Hill's fault in ways that can test this model. We can do that in two ways. 00:42:38.000 --> 00:42:44.000 First, we've undertaken study with sediment cores. 00:42:44.000 --> 00:42:50.000 Preliminary results already in hand. 00:42:50.000 --> 00:42:57.000 Where we're looking at a transect across the fault system near Means Landing, which is west of the Montezuma Hills. 00:42:57.000 --> 00:43:09.000 In sort of the eastern part of Sassoon Marsh. These cores seem to document a pretty dramatic change in peat thickness across a strand of the Pittsburgh-Kirby Hills Fault. 00:43:09.000 --> 00:43:17.000 From less than 2 meters on one side of the fault to greater than 6 meters of peat on the other side of the fault. 00:43:17.000 --> 00:43:20.000 This is across a single strand of the fault system, not the system as a whole. 00:43:20.000 --> 00:43:31.000 In tidal marsh settings, peat deposits can record paleo sea level so this potentially is providing a horizontal datum that we can compare across the fault. 00:43:31.000 --> 00:43:39.000 We're going to need to do some more work here fully explore the extent to which this change in thickness might indicate fault displacement. 00:43:39.000 --> 00:43:46.000 But the preliminary results are intriguing. We also compared the ages and depths of peat samples we collected to peat samples from elsewhere in the Delta. 00:43:46.000 --> 00:43:54.000 That's what's shown in this plot with depth relative to mean state of low on the vertical axis and age on the horizontal axis. 00:43:54.000 --> 00:44:05.000 Our samples are shown in color and the regional data set is in black and white. Note that the peat ages from both sides of the fault are consistently younger than samples from similar depths elsewhere in the Delta. 00:44:05.000 --> 00:44:16.000 Which is potentially consistent with uplift of the entire sample set, although more work is needed to tease out the details here. 00:44:16.000 --> 00:44:31.000 The second thing we've been working on in the Delta recently is on the flank of the Montezuma Hills. I'd like to return to this profile of the Montezuma Hills, which so nicely shows that southwest to northeast asymmetry. 00:44:31.000 --> 00:44:47.000 The topographic scarp that defines the southwest margin of the Montezuma Hills has in the past been inconsistently attributed to a fault. This potential structure, which we I've been referring to as the Montezuma Hills fault is somewhat oblique to and several kilometers east of 00:44:47.000 --> 00:44:53.000 the Pittsburgh-Kirby Hills fault system, though it may be reasonable to consider it a secondary strand of that system. 00:44:53.000 --> 00:44:59.000 This potential fault has been previously described, but is not currently included in state or USGS active fault databases 00:44:59.000 --> 00:45:08.000 and the topographic scarp along the southwest Montezuma Hills has alternatively been interpreted as a large [indiscernible] bank from an ancestral meander of the Sacramento River. 00:45:08.000 --> 00:45:17.000 So to test between these two models for scarp formation. Last fall, we opened a trench across the scarp near Collinsville at the southwest corner of the Montezuma Hills. 00:45:17.000 --> 00:45:21.000 We're still working up the results from this trench and we don't have any age control yet, 00:45:21.000 --> 00:45:29.000 but here's the preliminary trench log with an orthophoto on top and an interpreted log beneath. 00:45:29.000 --> 00:45:43.000 In the trench walls, we see young, poorly consolidated bedrock at the uphill eastern end, shown in yellow, truncated by fault. The colluvial package on the west side of the fault highlighted in pink appears to be slightly deformed and has a gentle 00:45:43.000 --> 00:45:51.000 westward dip in his capped and overprinted by what appears to be several generations of soil development shown in blue. 00:45:51.000 --> 00:46:00.000 We're still working on interpreting the results from this trench. So stay tuned for more results from this study in the coming months. 00:46:00.000 --> 00:46:13.000 To summarize, the preliminary results from our ongoing studies on the Pittsburgh-Kirby Halts fault system, both our peak course study and our paleoseismic trench give us indications that the Pittsburgh-Kirby's fault is an active fault that is deforming the surface in the Quaternary, 00:46:13.000 --> 00:46:20.000 on two separate strands. Further analyses will give us a better sense of the rate of deformation on each strand. 00:46:20.000 --> 00:46:30.000 To wrap things up, I want to put our refined understanding of structures in the Delta into its context as a part of an evolving tectonic margin. 00:46:30.000 --> 00:46:42.000 Prior to about 10 million years ago, the plate boundary at this latitude was a convergent margin, and many of the structures we see today formed in that stretch regime, including structures in the Delta like the Pittsburgh-Kirby Hills fault. 00:46:42.000 --> 00:46:45.000 After the passage of the Triple Junction at about 10 million years ago, 00:46:45.000 --> 00:46:57.000 the plate boundary began evolving as a dextral transform boundary and the modern active faults are reactivating and or overprinting on inherited fault geometries. 00:46:57.000 --> 00:47:10.000 So these inherited geometries lead to the unexpected and sometimes inconsistent kinematics that we see in the various data sets we've explored today. 00:47:10.000 --> 00:47:22.000 So some conclusions for you just to sum it all up. The bedrock geology and Tertiary geologic history in the Delta provide important context and explanation for seemingly inconsistent evidence of active deformation within the Delta. 00:47:22.000 --> 00:47:38.000 Relatively complex Tertiary history plays a fundamental rule in the way that modern strain is accommodated within the Delta and is important in understanding the data sets that we we have collected. So if you want more detail on this exhaustive amounts of detail. 00:47:38.000 --> 00:47:42.000 Please see our recent paper in Tectonica it came out about a year ago. 00:47:42.000 --> 00:47:56.000 Special thanks to Steve DeLong, Austin Elliott. Nick Cunetta, Harrison Gray, and Morena Hammer, Maddie Doyle, Alex Morelan, and many others for your help on this work and as I said, stay tuned for more results hopefully coming soon. 00:47:56.000 --> 00:48:01.000 Thank you very much. 00:48:01.000 --> 00:48:15.000 Thank you so much, Chad. It's a very fantastic talk with geomorphology data set to map it out to the detailed active vote. Very exciting. Many, many discussion in the chat is great. 00:48:15.000 --> 00:48:33.000 So the next speaker, yes, next speaker is Don Hoirup, California Department of Water Resource. His talk is more about the seismic hazard for his research, the state water project. Please go ahead to the recording. 00:48:33.000 --> 00:48:39.000 Hi everyone, this is Don Hoirup with the California Department of Water Resources Project geology section. 00:48:39.000 --> 00:48:46.000 I'm going to present seismic hazard risk to the California State Water Project in and around the Bay Area. 00:48:46.000 --> 00:48:53.000 DWR manages California's water resources, systems, and infrastructure, including the California State Water Project. 00:48:53.000 --> 00:48:59.000 The State Water Project has its origin in the Upper Feather River Basin of Northern California. 00:48:59.000 --> 00:49:11.000 Water is conveyed down through rivers to the Oroville Thermolito Dam Complex where it flows into the Sacramento River and south into the Sacramento-San Joaquin River Delta area. 00:49:11.000 --> 00:49:16.000 Water's taken up by the North Bay Aqueduct. And South Bay Aqueduct and the California Aqueduct. 00:49:16.000 --> 00:49:30.000 From the California Aqueduct, water flows south towards Southern California. In 1957, the California Water Plan And in 1960, Burns-Porter Act authorized construction of the State Water Project. 00:49:30.000 --> 00:49:38.000 Also known as the Feather River Project. The State Water Project was planned, constructed, and is operated and maintained by DWR. 00:49:38.000 --> 00:49:54.000 The water project is the nation's largest state-built power user-financed water conveyance system its designed to deliver about 4.2 million acre feet of water per year and supplies water to about 27 million Californians and 750,000 acres of farmland. 00:49:54.000 --> 00:50:07.000 Sixty-six percent of that water is residential, municipal, and industrial use; 34% agricultural use. The state water project spans from Northern California and Plumas County to Southern California, 00:50:07.000 --> 00:50:12.000 Riverside County. It includes 705 miles of canals, tunnels, and pipelines, 00:50:12.000 --> 00:50:18.000 36 reservoirs, 28 dams, 21 pumping plants, 5 hydroelectric power plants, 00:50:18.000 --> 00:50:26.000 4 pumping power generating plants, all built based on investigative work done by engineering geologists in the 50s up through the 1980s. 00:50:26.000 --> 00:50:32.000 There are 29 total state water project water contractors; 5 water contractors around the Bay Area, 00:50:32.000 --> 00:50:40.000 serving 3.2 million people alone. County flood and solar care 00:50:40.000 --> 00:50:47.000 water agents, but about area there. 00:50:47.000 --> 00:50:54.000 Served by the Bay which supports 40% of the 00:50:54.000 --> 00:51:24.000 as long as about 00:53:10.000 --> 00:53:19.000 [Okay, unfortunately, we're having audio difficulties with this. Don, how do you feel about talking live to your video that's playing? 00:53:19.000 --> 00:53:24.000 Yeah, don't you know it. Absolutely. John, whatever you need. If you want to… Just go back to what kind of, you know.] 00:53:24.000 --> 00:53:27.000 21 pumping plants, 5 hydroelectric power plants around the Bay Area, serving over 3.2 million people alone. 00:53:27.000 --> 00:53:34.000 Yes. That's good. [Can you hear me okay, John? 00:53:34.000 --> 00:53:35.000 Okay. Let's just see how it goes. And when it cuts out, I'll pick up. 00:53:35.000 --> 00:53:36.000 Yes.] 00:53:36.000 --> 00:53:38.000 The Napa County Flood Control and Water Conservation District and Solano County Water Agency both serve about 500,000 in the Napa and Solano County area. 00:53:38.000 --> 00:53:39.000 [Perfect. Thanks, Don.] 00:53:39.000 --> 00:53:43.000 Okay. 00:53:43.000 --> 00:53:51.000 They are both served by the North Bay Aqueduct, which supplies about 40 to 50% of the total water use in the area. 00:53:51.000 --> 00:53:56.000 The Solano County Water Agency serves about 500,000 people. That's Napa and Solana counties. 00:53:56.000 --> 00:54:01.000 State water percentage of their total water use is 40 to 50%. 00:54:01.000 --> 00:54:07.000 The Alameda County Flood Control and Water Conservation District Zone 7 is served by the South Bay Aqueduct. 00:54:07.000 --> 00:54:15.000 South Bay Aqueduct supplies about 260,000 people, 80% of their total water use in the area. 00:54:15.000 --> 00:54:19.000 The Alameda County Water District is also served by the South Bay Aqueduct. 00:54:19.000 --> 00:54:29.000 The Aqueduct services about 344,000 people. With the state water project percentage of their total water use being about 40%. 00:54:29.000 --> 00:54:53.000 Lastly, the Santa Clara Valley Water District is served by the South Bay Aqueduct as well, servicing about 1.9 million people which accounts for about 40% of the total water use in that area. 00:54:53.000 --> 00:55:05.000 [All right, I'll jump in here in case it kicks in.] When the State Water Project was designed The best available information for faults was the state map at a 1:500,000 scale. 00:55:05.000 --> 00:55:14.000 So the blue line represents what the initial design of the state water project looked like in consideration of major faults throughout California. 00:55:14.000 --> 00:55:18.000 Basically, the State Water Project was designed to withstand up to about 0.1 g. 00:55:18.000 --> 00:55:28.000 Although dams were built with a much higher factor of safety. 00:55:28.000 --> 00:55:38.000 All right. So the state water project is 60 years old and we've somehow managed to dodge multiple earthquakes throughout California. 00:55:38.000 --> 00:55:44.000 Somehow. So we've never experienced a damaging earthquake that includes the 1975 Oroville event and the 1994 Northridge event. 00:55:44.000 --> 00:55:53.000 Damaging earthquakes that includes the 1970 event. 00:55:53.000 --> 00:56:01.000 So I basically said most everything there. 00:56:01.000 --> 00:56:16.000 All right, so this presentation focuses on the North Bay Aqueduct, South Bay Aqueduct, and the river Sacramento-San Joaquin River Delta and a little bit of the State Water Project Aqueduct. So we're going to shift gears and get more focused. 00:56:16.000 --> 00:56:28.000 This is the overall relative shake intensity map from USGS-CGS showing earthquake shaking potential from 2016. Of course, as you see, 2% in 50 years. 00:56:28.000 --> 00:56:43.000 A one-second period, but you get the idea that state water projects expect big ground motions. This is familiar probably to most everybody. The 72% probability of one or more magnitude 6.7 by 2043. 00:56:43.000 --> 00:56:48.000 As you can see, we have multiple fault crossings, major fault crossings along North Bay, South Bay. 00:56:48.000 --> 00:57:00.000 And then, of course, the blind thrust in the California Aqueduct 00:57:00.000 --> 00:57:14.000 Of course, I didn't speak that fast during the recording. All right. Yes, so check this out. The construction of South Bay and North Bay Aqueduct specifically were in the late 1950s and 1960s. 00:57:14.000 --> 00:57:19.000 During kind of a quiet period of earthquake activity in the Bay Area and throughout California. 00:57:19.000 --> 00:57:43.000 Really, I think everyone's pretty familiar with that effect. DWR utilizes California Geological Survey's hazard maps to serve as kind of a proxy or have been since about the 2000s of where to really look for potential hazards. So we've used those 00:57:43.000 --> 00:58:09.000 AP maps and liquefaction zone maps, landslide zone maps, and the combination of them to kind of help guide us where we need to maybe focus more resources for evaluating vulnerability, exposure to risk, and mitigation. 00:58:09.000 --> 00:58:20.000 This is showing that the North Bay area is a bit devoid of the liquefaction-landslide hazard zone maps, but does have the AP zone maps. 00:58:20.000 --> 00:58:45.000 Right now, we're putting resources into North Bay Aqueduct because we haven't paid a lot of attention in its lifespan to evaluate exposure to risk, exposure to hazard and evaluate overall risk. 00:58:45.000 --> 00:59:05.000 For South Bay, we have a little bit better coverage We have some of the 7.5' quads have liquefaction landslide hazard. Other areas don't. So those areas, the South Bay Aqueduct's actually been fairly well studied. We've had a lot of help from our consultants like Lettuce Consulting International 00:59:05.000 --> 00:59:29.000 for doing overall hazard assessment from the Delta area all the way down to the terminal tank in San Jose. 00:59:29.000 --> 00:59:51.000 So this slide, basically we're talking about increasing growth in the Bay Area, population growth. But actually what we found looking at Napa County's population may decrease somewhat by 2030 and that's for a variety of reasons, but in the overall scheme of things in the Bay Area, we're looking at a general population increase. 00:59:51.000 --> 00:59:56.000 That's from the sources of Department of Finance and actually from the various counties 00:59:56.000 --> 01:00:25.000 websites that indicate an overall growth. 01:00:25.000 --> 01:00:37.000 All right. Delta Conveyance Project. So what you're going to see here shortly is a video, that would be nice to have the audio for, so I won't be able to reproduce that, but it has to do with what's called the Delta Tunnel 01:00:37.000 --> 01:01:05.000 or the Delta Conveyance Project now. It's the idea of bypassing the Delta has been around for a very long time from the peripheral canal days back in the 1940s up into 1982, the Bay Delta Conveyance Plan up to 2014 California water effects fix and currently Delta Conveyance. The whole idea is constructing and diverting 6,000 cubic feet of water per second in a about 35 foot wide tunnel from the Sacramento area near Hood 01:01:05.000 --> 01:01:18.000 down to Bethany Reservoir, which is near Clifton Court Reservoir down by Tracy. She has to be about 150 feet deep, 40 miles of tunnel total 01:01:18.000 --> 01:01:25.000 at a cost of about $18 billion and about 10 years to construct. 01:01:25.000 --> 01:01:37.000 And what I said in this slide is that, you know, obviously the Delta is very vulnerable to seismic. There's levees. You break levees, you have likely saltwater intrusion. This video here, it's really quite good. 01:01:37.000 --> 01:01:57.000 I'll kind of muscle through it here a little bit, but it's a DWR production saying that, you know, we've got the Delta. We're exposed to seismic vulnerabilities and we're addressing that hazard by the idea of the Delta Tunnel. Originally, it was going to be two tunnels. 01:01:57.000 --> 01:02:11.000 From near Hood down to Clifton Court for Bay. Now it's just the one tunnel and that's Bethany Reservoir where the water would dump into and from there, you've got the South Bay Aqueduct in the distance at the headwaters there. And then to the left is the California Aqueduct. 01:02:11.000 --> 01:02:20.000 We're just talking about seismic activity in the Bay Area. That's the Loma Prieta. I think that's Napa, West Napa event there. 01:02:20.000 --> 01:02:27.000 More Loma Prieta. 01:02:27.000 --> 01:02:55.000 Yeah, failure to infrastructure, you know, mostly highways took the hit from Loma Prieta but our spokesperson here is discussing seawater intrusion from a levee failure. So the levees are being fortified now every day. But overall, here's what happens. You break levees, you get an influx of seawater into a what's now predominantly freshwater, brackish water, 01:02:55.000 --> 01:03:11.000 situation. The reds representing higher concentrations of salinity. So not only do you damage farmlands, but you bring it up that lowest orange was Clifton Court Four Bay, really the headwaters to the bulk of the California Aqueduct. 01:03:11.000 --> 01:03:24.000 So tests have been done. I think folks have seen this video before. I think this was by UC Davis. Sorry if I'm wrong on that, but it's basically a shake and they're looking at what the response is from peats, 01:03:24.000 --> 01:03:31.000 and these are some of the levees that have been moderately fortified. You can still see a little bit of erosion. 01:03:31.000 --> 01:03:36.000 But one of the things that we're doing is fortifying levees. 01:03:36.000 --> 01:03:46.000 We see the multiple and various fault strands that are in and around the East Bay and through the Delta. 01:03:46.000 --> 01:03:56.000 He's talking about the Kirby Hills. He references the Kirby Hills fault through into Pittsburgh and referencing a big event that happened there in the 1800s, I believe. 01:03:56.000 --> 01:04:09.000 The original Delta and the levee construction and what some of the fortified levees look like today. 01:04:09.000 --> 01:04:17.000 This was the Jones track failure from spring rains back in 2005, I believe. 01:04:17.000 --> 01:04:23.000 That wasn't from seismic, obviously it was just from a big spring melt. 01:04:23.000 --> 01:04:33.000 And run off and had a lot of problems there. Talking about seismic here and vulnerability to the levees and failure of the levees and what they do. 01:04:33.000 --> 01:04:45.000 What it can look like. This is talking about the conveyance, the tunnel, and that having infrastructure underground is less vulnerable to strong ground motions than it is at the surface. 01:04:45.000 --> 01:04:51.000 And why it makes sense to go underground and not just put resources into levee fixes. 01:04:51.000 --> 01:05:07.000 So when breaches happen, DWR's mass stockpiles of reserves of boulders to do fixes so it's not like we have to go out and get materials. They're strategically placed throughout the Delta to fix locations that do breach. 01:05:07.000 --> 01:05:14.000 That's Clifton Court in the background. 01:05:14.000 --> 01:05:37.000 And he's basically showing the shake intensity map in the Delta area, Bay Area. 01:05:37.000 --> 01:05:48.000 That's the end of the video. And this part's the same where you can get more information. If you have any interest in what is going on in the Delta, recommend you go to the DWR's website. 01:05:48.000 --> 01:06:12.000 There's a host of videos. They're all shorts. They're 4 or 5 minutes long, but touch on all aspects of the Delta and of the Delta Conveyance option we have here and a lot about what the levees are all about out there. 01:06:12.000 --> 01:06:23.000 All right. That pretty much wraps it up. I think there's one slide after this. 01:06:23.000 --> 01:06:29.000 Yeah. Great. Thanks. And sorry, everybody. Not sure what happened there. 01:06:29.000 --> 01:06:35.000 Thank you so much. It's all really an exciting project. Delta is a very big project, yes. 01:06:35.000 --> 01:06:51.000 What is very important. And thank you so much again for jumping into the live presentation which may be more energetic. So I think, Sarah, I think we're going to bring up all speaker for the discussion section and then we're going to try to be called to talk about it. 01:06:51.000 --> 01:07:10.000 But I'm just wondering to a little bit some moment because Don's presenting to his presentation on live, he may not have a time to see the chat so i'm just wondering if somebody particularly want to have a question you put it to the chat but don't have a chance to see it so if somebody want to talk you know 01:07:10.000 --> 01:07:23.000 question for Don, raise their hand. Somebody can spot you and then we can start the discussion section. 01:07:23.000 --> 01:07:34.000 Let me just check if somebody raised their hand or particularly in the chat 01:07:34.000 --> 01:07:40.000 Thanks, Julian. 01:07:40.000 --> 01:07:46.000 It looks like we are all good. So I think, again, thank you so much, Don. 01:07:46.000 --> 01:08:03.000 Again so that all the speaker if you have some question we have very diverse topic so it's maybe difficult I have some you know my own question but i just deserve it in case I have to jump in. So anybody from the okay sorry keys please go ahead. 01:08:03.000 --> 01:08:10.000 Thanks, Taka. Don, can you summarize the advantages of a tunnel to the current system 01:08:10.000 --> 01:08:16.000 with respect to earthquake hazards, I'll let you do that. Thanks. 01:08:16.000 --> 01:08:34.000 Yeah, and the short answer, Keith is engineers have felt that the seismic exposure is less, or I should say the risk of damage is less going underground than it is to fortify levees. There's about 1,100 miles of levee 01:08:34.000 --> 01:08:50.000 out there and in the presentation says it's a couple hundred miles have been fortified to help withstand but there's about a thousand miles of levees that are just, you know, built in the late 1800s and in through the 1900s and beyond 01:08:50.000 --> 01:09:03.000 and the reliability of having a tunnel is a longer term fix than than having a fortification of the levees. 01:09:03.000 --> 01:09:07.000 Thanks. 01:09:07.000 --> 01:09:16.000 Thank you. 01:09:16.000 --> 01:09:23.000 Okay, I guess I see that. Laura, thank you. I'm sorry. I'm maybe pronounced it right, but please go ahead. 01:09:23.000 --> 01:09:35.000 Hi, good morning. Thank you all. This was just an excellent panel. I was just curious how, especially the last presenters, but Dena as well. 01:09:35.000 --> 01:09:42.000 How you guys have, whether you've been following the proposed N ewtown, California Forever, 01:09:42.000 --> 01:09:58.000 because Chad, certainly your work is in that area. Don, you know, projections you mentioned around water needs would be vastly different if that city, which anticipates being 400,000 population, 01:09:58.000 --> 01:10:09.000 came into being there near the Montezuma Hills. So just curious what thoughts you guys have had or have raised or been part of so far with that 01:10:09.000 --> 01:10:13.000 proposal. 01:10:13.000 --> 01:10:29.000 Well, I'm not sure about Dena, but from the transportation perspective, we've been working directly with the developer on the plans and I know that the theme here is more in terms of resilience but there's been a focus on trying to 01:10:29.000 --> 01:10:37.000 minimize the extent possible the people needing to rely on cars to get around for mainly environmental reasons, social reasons. 01:10:37.000 --> 01:10:51.000 So a big part of that has been sort of planning what the transit might be to connect people to nearby train lines that said the area, but knowing that it's on the edge of the region it's going to be fairly suburban in nature. 01:10:51.000 --> 01:11:09.000 Car ownership will probably be pretty high. On the water side, yeah, less of my remit there but definitely a challenge given it's a pretty remote area. 01:11:09.000 --> 01:11:19.000 I mean, I can speak to the employment side of that, which I think the idea of creating an isolated jobs, housing, 01:11:19.000 --> 01:11:31.000 node like that is unrealistic because it does not allow would not allow the employment to draw on a much wider and deeper labor pool. 01:11:31.000 --> 01:11:44.000 So that's just talking to the economic vulnerability and not to the seismic or water. 01:11:44.000 --> 01:11:56.000 Yeah, we've had to work with the folks behind California Forever directly to do field work out there are our paleoseismic trench site is on land owned by them. 01:11:56.000 --> 01:12:02.000 And actually, it's gotten a lot easier in the last year and a half since that whole plan became public. 01:12:02.000 --> 01:12:13.000 They were cagey and hard to get a hold of. And now they're much more willing to communicate. But they've actually been totally willing to work with us and are interested in our findings. 01:12:13.000 --> 01:12:31.000 Yeah, there was some talk in the chat about in Aquist Priola on this structure, we obviously need age to control And need to refine our our understanding of what's going on, but It's definitely something we're thinking about. 01:12:31.000 --> 01:12:35.000 Thank you so much. It's okay to move on, I guess. 01:12:35.000 --> 01:12:39.000 Okay, thank you, Christine. They're waiting for long. So could you go ahead? 01:12:39.000 --> 01:12:50.000 Hey, thank you. I have a couple of questions. One for Don. I was wondering about what they do with the tunnels when they cross a fault. I've been looking at the Lake Elizabeth tunnel and it's like such an interesting array of problems. 01:12:50.000 --> 01:12:51.000 Yeah. 01:12:51.000 --> 01:13:08.000 And then that kind of ties together with what Vicki was showing, just that there's buried structures, there's more structures than we've identified at the surface, and we have this kind of I mean, maybe in the area of the Northern Calavera area, so we've got this sort of start of all these linkages and handovers that then propagate across Garquinas and 01:13:08.000 --> 01:13:22.000 San Pablo Bay. And then they simplify again. To the north but um those are Like it's true already in the established areas where there are major aqueducts and it's even more true if you put in a 40 mile tunnel. 01:13:22.000 --> 01:13:40.000 Yeah, yeah. Great question, Christine. Thank you. Yes, so fall crossings are highly considered and as part of the construction And the way it's being approached is that there'll be multiple portals that access the tunnel at depth. 01:13:40.000 --> 01:14:05.000 Along the length of the 40. So there'll be access points for when an event happens and ruptures The lining, it can be repaired. So, you know, because it's basically housed by Delta, you know, Delta based sediments We're not too worried about the effectiveness. You can still draw 40 feet. You wouldn't pinch it off. You'd need 40 feet of displacement. 01:14:05.000 --> 01:14:09.000 But it would certainly be able to handle a couple of feet. 01:14:09.000 --> 01:14:34.000 And then water would be shut, drained. And then repaired. So yeah, it's a consideration. I'll tell you what was real interesting during early design is, I think most know that that's big oil and gas area and that a TBM, a tunnel boring machine, as it propagates through, our biggest concern was running into old standpipe at depth because that'll seize up 01:14:34.000 --> 01:14:49.000 Tbm. I think you guys know that up in Washington and Seattle, that's pretty much what happened. It stopped their progress of their tunnel up there because of these pipes. So folks are certainly concerned, but the man-made hazards are worse. 01:14:49.000 --> 01:14:50.000 Sure. 01:14:50.000 --> 01:14:57.000 Wow. Okay. Thank you. Yeah, just the second half of my question was for Vicki. 01:14:57.000 --> 01:15:10.000 Looking at the splaying of faults and the different ages of faults there, you know, we focus on AP and pretty recent faulting for For surface hazard, but like for a project like this, you need to go back farther in time probably. 01:15:10.000 --> 01:15:12.000 Is there… 01:15:12.000 --> 01:15:32.000 Yeah, I think you would have to do that and always the specter of reactivation on these older structures. And if they're only cutting pre-quaternary rocks, it makes it very difficult to assess their earthquake history. So I don't have an answer for that, but it's definitely 01:15:32.000 --> 01:15:49.000 Something to be considered. And of course, blind thrusts have been a have been problematic for a long time because they also tend to break up and as you get close to the surface. So how do you mitigate that and i guess 01:15:49.000 --> 01:16:03.000 I have a question for Dawn about tunnel ed, have they actually started tunneling or have they done little boreholes to check for Suitability, because you might find some additional faults that we might not have known about. 01:16:03.000 --> 01:16:18.000 Right. So back starting around 2005 and up until 2010 or so A whole DWR Delta program was underway led by Mark Pegenkopf with GWR Project Geology. 01:16:18.000 --> 01:16:35.000 And everything from barge drilling to on land drilling was done along the alignments and the alternative alignments. So a lot of drill hole work was done and then research on existing data out there, including geophysical data available. 01:16:35.000 --> 01:16:57.000 But as of right now, the whole process of the delta conveyance has been shifted from within DWR to what's called delta conveyance authority and delta conveyance office kind of a separate entity outside of DWR. They are actively looking at things like the West Tracy fault 01:16:57.000 --> 01:17:03.000 The Midway Fault, those are coincidentally and just purely by coincidentally faults that I'm looking at right now. 01:17:03.000 --> 01:17:22.000 For activity. And so I'm working close with the Delta Conveyance office and feeding them information as it comes in to help support what their final version of the outlet structures are going to look like at Bethany. 01:17:22.000 --> 01:17:35.000 Thank you. So Kat, do you want to say add something? Because you also ideally amazing to say you're geomorphology staff. So I just wondering, do you want to add something for this question? 01:17:35.000 --> 01:17:40.000 I'm trying to remember where we started with that question. 01:17:40.000 --> 01:17:45.000 Okay, so go ahead. Just so you know you and the big keys talk is somehow you know 01:17:45.000 --> 01:17:51.000 Yeah, well. I think Vicki said it best. Geology matters. 01:17:51.000 --> 01:18:00.000 And at least in the Delta, it seems like it's really dictating how things are behaving in the modern setting. 01:18:00.000 --> 01:18:18.000 I think partly because of the strain rates are low. So, you know, there isn't enough strain going through the system to really reset things. So we're activating pre-existing things and stuff is distributed And it's all moving pretty slowly. 01:18:18.000 --> 01:18:21.000 So yeah, Don, if you find more faults in your boreholes, let us know. 01:18:21.000 --> 01:18:27.000 I'm sure there are many out there. There are some amazing figures. 01:18:27.000 --> 01:18:45.000 Vicki's talk mentioned that the 2021 GSA special volume on diablo There are a bunch of papers in that volume that have some really incredible figures i'm thinking Jeff Unru has one. There's one of the F paper in there that have some 01:18:45.000 --> 01:18:48.000 Yeah. 01:18:48.000 --> 01:19:01.000 Some really impressive data sets. For sort of the extent of the complexity of the the inherited geology that we're like trying to interpret active structures through so 01:19:01.000 --> 01:19:11.000 Some of the chat, I might add to that, some of the more interesting things that were found during drilling efforts and exploration out there were intact redwood trees. 01:19:11.000 --> 01:19:32.000 At depth and volcanic ash, tephra. We work pretty closely with our consultants at LCI when that when those things showed up. And I think when you mentioned Jeff's work, Jeff Unruh's work, I think they helped us with the Tefer chronology 01:19:32.000 --> 01:19:43.000 As I recall, I think we had a couple of postdocs who were working on some of those ashes to try and look at deformation. 01:19:43.000 --> 01:19:55.000 Great, thank you. Just to move on to a different topic about before that, Jeff, do you have something? From your perspective because you are slightly different way so i'm just wondering we want to cover your angle too. 01:19:55.000 --> 01:20:06.000 Well, I guess my question would be for Dina, most likely you brought up the energy infrastructure and the vulnerabilities there. I think there was maybe a question in the chat to expand on that a little bit. 01:20:06.000 --> 01:20:24.000 So I do think it's interesting. As the Bay Area grows, as California grows we are increasingly moving into places that are more at risk, right? We're seeing that with wildfires, you see that with earthquakes and just kind of I'm going to touch on that and how you view the growth of the state vis-a-vis those risks, right? 01:20:24.000 --> 01:20:38.000 Well, yeah. And I think also responding to those risks is taking away from resources that could otherwise be invested in upgrading the grid that's serving existing areas. So I think that's part of the challenge both part of the challenge both 01:20:38.000 --> 01:20:45.000 Economically and in terms of planning and strategy. So, um. 01:20:45.000 --> 01:20:52.000 It's not just about the population growth, but it's about serving. And in a way, this is to Lori's question. 01:20:52.000 --> 01:20:57.000 When I saw Laura click on, I'm like, oh, here's going to be a smart question. 01:20:57.000 --> 01:21:16.000 That if we continue to grow in places where we have no infrastructure, then again, we're sucking away from the opportunity to really think about upgrade and improve the infrastructure we do have. And that's true in both transportation and utilities, both wet and dry. 01:21:16.000 --> 01:21:29.000 So I think that's really… where these conversations should align in some ways is how we protect our existing areas that are vulnerable to all kinds of risk. 01:21:29.000 --> 01:21:30.000 Thank you. 01:21:30.000 --> 01:21:31.000 If that makes sense. 01:21:31.000 --> 01:21:37.000 Thank you. Andy, do you want to add something? 01:21:37.000 --> 01:21:44.000 Yeah, I think that I think investment in seismic resilience has actually been a pretty big priority. 01:21:44.000 --> 01:22:02.000 In the Bay Area, as evidenced by pretty major like the eastbound bay bridge clearly was a $6 billion project that was ultimately completed There are countless others, but that's always a trade-off is For an agency like BART. 01:22:02.000 --> 01:22:16.000 That you're balancing investment in a possible future scenario that may not play out for another 60 years against like investing in operations right now in the face of big budget cuts. 01:22:16.000 --> 01:22:25.000 These are questions that are really being handled at the state legislator level in terms of where this money goes. 01:22:25.000 --> 01:22:33.000 Great. Thank you so much. So I think we have five minutes and is there any from audience raise their hand. 01:22:33.000 --> 01:22:54.000 If not, I just want to be a little bit My side, I'm sorry. I'm just to see the, you know, chat, some comment in the chat is more talk about the velocity structure Thank you so much. You have put up to the many questions for the structure. So I think the big picture is more like an energetic discussion hubbing is especially big key show that her desired. 01:22:54.000 --> 01:23:20.000 How this data new kind of gravity data which could be incorporating to the USGS apparel state model you know many people here it's interesting to how we're going to be updating or improve the velocity model so i guess that's a very important topic so Vicky, you put some comment back and forth but could you tell me a little bit how it's the best way to move forward to including your data set or to improve the Bay Area? 01:23:20.000 --> 01:23:22.000 Data set. 01:23:22.000 --> 01:23:33.000 Well, first of all, the Livermore Basin has been known about from gravity and that deep drill hole for a long time and that that first part is in the Bay Area. 01:23:33.000 --> 01:23:58.000 Geologic and seismic velocity model. Gravity isn't very good per se in telling you what is actually within those basin sediments. And it's not always a direct relationship between density and shear wave velocity so I think incorporating geologic insights working with the geologists who 01:23:58.000 --> 01:24:18.000 Who have access to geologic reasoning and data sets that Some geophysicists may not be aware of in terms of trying to flesh out what the basin fill is might be really useful and and and doing some of this integrated modeling of 01:24:18.000 --> 01:24:23.000 Different data sets to come up with a more complete picture of the geology. 01:24:23.000 --> 01:24:37.000 Brad Agard said, is it feasible to incorporate this into the seismic velocity model and it is if you have dedicated resources to do that. 01:24:37.000 --> 01:24:50.000 And then my question is, and this is something that could be looked at to see if that additional geologic detail really makes a difference in matching the seismic waveforms. 01:24:50.000 --> 01:25:08.000 So maybe looking at a certain area and doing a much more detailed geologic model in assigning seismic velocities to see if that really does a better job adding that detail to matching the waveforms. 01:25:08.000 --> 01:25:12.000 And of course, there's all sorts of different uncertainties. The geology is uncertain. 01:25:12.000 --> 01:25:32.000 The source is uncertain. That's one way forward. And then I think another way to look at some of the variability in the VS30 values that you know one way of doing is just taking the geologic map and saying, okay, looking at the slope and looking at 01:25:32.000 --> 01:25:57.000 Relative age of those. In fact, I see Alan is raising his hand but also to um to maybe incorporate models of how alluvial fan systems work or fluvial systems so that you might be able to put some variability in some of that in perhaps an informed way, especially if we have a lot of data points to work with. 01:25:57.000 --> 01:25:58.000 And maybe Alan can talk more about it. 01:25:58.000 --> 01:26:05.000 Thank you. Yes. Please go ahead, Alan. Thank you. 01:26:05.000 --> 01:26:23.000 And turn myself on. Can you hear me? Great, great. So I want to echo everything that Vicki said, but I also want to emphasize that you know without uh earthquake recordings This is basically just an academic exercise. 01:26:23.000 --> 01:26:39.000 That's the proof of the pudding is we have to have earthquakes and how well does the state-of-the-art approach Or do all of these approaches match up to the Holy Grail? Are we able to predict those wiggles? 01:26:39.000 --> 01:26:53.000 That's all I want to say. I think it's very obvious to everybody here that you know There are multiple methods. They're great no matter how how conscientious you are, you know. 01:26:53.000 --> 01:26:59.000 Pushing the limit. That's fantastic but Without comparing it to earthquakes. 01:26:59.000 --> 01:27:03.000 It's just an academic exercise. And you see this all over the literature. 01:27:03.000 --> 01:27:09.000 Right. Anyway, that's 01:27:09.000 --> 01:27:12.000 Thank you so much. Please go ahead. Please, please, please, please. 01:27:12.000 --> 01:27:32.000 May I just say one thing? These geologic models that we're developing are not just for seismic hazard. They're also for groundwater modeling so i mean it is going to depend on the questions you ask of these models. 01:27:32.000 --> 01:27:41.000 And of course, yes, we need more earthquakes. And more seismometers. 01:27:41.000 --> 01:27:51.000 But in lieu of what we have now, this is what we have we have to work with. 01:27:51.000 --> 01:28:09.000 Thank you. Sorry. Okay. So one thing I just want to touch because there are many questions there, but especially for the keys from keys to the uh Dina and Andy, because especially It's how the two be get to you guys come in to this group. So I just want to be touched. So his question is. 01:28:09.000 --> 01:28:17.000 Further explain the statement about energy infrastructure being vulnerable and seemingly in the big concern. Did you see his comment? 01:28:17.000 --> 01:28:18.000 Would you mind to answer a little bit? Yes, thank you. 01:28:18.000 --> 01:28:39.000 Right. Yeah, so and maybe Anne has more to say on this subject, but mostly the work that we did for Haywired focused on buildings. And then other people looked at roads and transit. And I'm just looking at more recent work I've done for these East Bay industrial lands. 01:28:39.000 --> 01:28:54.000 And how the building the challenges that buildings are facing today for reuse or that these industrial areas of the East Bay are facing for redevelopment, again for industrial activities. 01:28:54.000 --> 01:29:01.000 And expanded economic activity. Are very constrained by power supply. It's a huge issue. 01:29:01.000 --> 01:29:14.000 And it really does reflect PG&E's attention elsewhere. Their investment, and as Andy said, it reflects his trade-offs between where do we invest our money And how do we plan for the future? 01:29:14.000 --> 01:29:37.000 And to the extent that the electrical grid might be vulnerable to seismic activity, it would exacerbate or really compound a problem we're already seeing as a result of response to other incidents that we've had recently, mostly the wildfires here in Northern California, because we haven't had 01:29:37.000 --> 01:29:49.000 An earthquake lately to back up the data the soils. So that's more so what I'm responding to. 01:29:49.000 --> 01:29:56.000 Thank you. Andy, it's okay. Do you want to add more while we can move on? Okay, thank you. 01:29:56.000 --> 01:30:07.000 Okay, so I'm just looking at that time a little bit over the am so just try to be scroll to the session. Jeff, do you want to add something Okay. 01:30:07.000 --> 01:30:12.000 No, I was going to say we could take one more question from the audience if it exists. If not. 01:30:12.000 --> 01:30:13.000 We don't want to cut into the break. 01:30:13.000 --> 01:30:21.000 Right. Yes, from people from the speaker do you have something forget to say, okay, okay, I get it. Thank you. Please. 01:30:21.000 --> 01:30:23.000 Eric gets the last word. 01:30:23.000 --> 01:30:28.000 Yeah. So I did ask a question very early in the chat. 01:30:28.000 --> 01:30:37.000 And I am still curious about The reason why the faults don't match across the between the north and the south of the East Bay. 01:30:37.000 --> 01:30:52.000 Chad got a bit mentioned something about inherited structures and is it just that the inherited structures are different to the north and south or Does anyone have any thoughts? And this, I guess, would be for Vicky as well. 01:30:52.000 --> 01:30:59.000 That was sort of what I was alluding to uh in my somewhat glib response to your question in the chat. 01:30:59.000 --> 01:31:18.000 I think that the at least for the delta, the inherited structures are a huge part of the story and are sort of interfering with or dictating how the modern strain is accommodated through their And the stream rates aren't just aren't high enough 01:31:18.000 --> 01:31:25.000 To blow through it and make it look like the rest of the plate boundary. 01:31:25.000 --> 01:31:29.000 But that's probably, I mean, that's definitely an overly symbolistic take. 01:31:29.000 --> 01:31:35.000 Yeah, I'm curious if Vicki has other thoughts here. 01:31:35.000 --> 01:31:45.000 Well, I do remember seeing a paper where someone had mentioned something modeling of the delta region as being fairly unique. 01:31:45.000 --> 01:31:58.000 I've got to dig it up. It was a paper that Bob Simpson, maybe you've seen it, Chad, but it was by a russian And it might be worthwhile to revisit that. 01:31:58.000 --> 01:32:14.000 Also, there is this big gravity low over the delta that you would think that low would continue to the north and to the south in Sacramento and San Joaquin Valley because you do still have a lot of this very thick Great Valley sequence but 01:32:14.000 --> 01:32:24.000 Delta is kind of different in terms of perhaps the crust under there. 01:32:24.000 --> 01:32:25.000 I have a big sore thumb. 01:32:25.000 --> 01:32:40.000 Well, and Diablo is different too, right? And… And the Great Valley Fault System comes like from the north it looks pretty normal and it projected the delta disappears and it comes from the south and it projects into the delta and disappears. But they aren't a long strike from one another. 01:32:40.000 --> 01:32:41.000 Yeah. 01:32:41.000 --> 01:32:50.000 There's a step. And the delta and Diablo are in that that step. So so yeah inherited structures but also it's It's special. 01:32:50.000 --> 01:32:59.000 There's something weird going on there. And I don't know if Russ is Russ Gramer is on, but he's also thought about this quite a bit. 01:32:59.000 --> 01:33:04.000 So it's an interesting question. 01:33:04.000 --> 01:33:13.000 All right, we've covered a lot of ground here in 90 minutes so I just want to thank all the panelists, Dina, Don, Andy, Vicki, Chad. 01:33:13.000 --> 01:33:18.000 For your presentations. Thank you to the audience for the great questions. And I think with that. 01:33:18.000 --> 01:33:24.000 There's still more to come. So let me turn it back to John and Sarah to talk about the agenda for the rest of the day. 01:33:24.000 --> 01:33:37.000 Okay, well, thank you to all of our wonderful speakers and moderators. But can we give Don an extra big hand for dealing with all these technical difficulties? Thank you, Don. 01:33:37.000 --> 01:33:48.000 Okay, so we have a 15 minute break on the calendar, but if you are giving a thunder talk in the next session, please stick around so we can get you set up and get you your slides set up. 01:33:48.000 --> 01:34:04.000 So everybody go enjoy 15 minutes and come back at 1115 Pacific, except For grace, Mike Blanpied, Michael Ball, or the Michaels, Ruth, Julian, Christy, Travis. 01:34:04.000 --> 01:34:19.000 We're going to play Don's talk. This is not the formal meeting, but we're going to put this into formal the actual recording. So everybody mute yourselves for the next little bit while I start doing this. Okay, I'm going to start the recording right now. 01:34:19.000 --> 01:34:37.000 Hello and welcome to another episode in our Delta Conveyance Quick Question video series where we answer questions about the proposed Delta conveyance project Often referred to as the Delta Tunnel. Our question in this episode is, how would the Delta Conveyance Project make California's primary water supply system 01:34:37.000 --> 01:34:46.000 More resilient against a major earthquake. To live in California is to live with earthquakes. According to the California Earthquake Authority. 01:34:46.000 --> 01:34:56.000 The state experiences more than 100 small earthquakes every day. But because it can be many years between major seismic events, it's easy to forget that the question is always when. 01:34:56.000 --> 01:35:06.000 And not if the next big one will happen. When we think about the destruction wrought by major earthquakes, we probably think first of the damage to buildings, roads, and bridges. 01:35:06.000 --> 01:35:12.000 But here in California, one of the most devastating impacts could originate right here in the Delta. 01:35:12.000 --> 01:35:18.000 That's because Delta levees have been shown to be vulnerable to collapse during earthquake simulations. 01:35:18.000 --> 01:35:25.000 Extensive levee failure in the delta could result in the inundation of saltwater from San Francisco Bay into the delta. 01:35:25.000 --> 01:35:34.000 And the contamination of the fresh water supply that 27 million Californians and hundreds of thousands of acres of farmland depends on. 01:35:34.000 --> 01:35:39.000 The potential scale of the social and economic impacts is hard to imagine. 01:35:39.000 --> 01:35:47.000 But why are Delta levees so vulnerable? Studies have found that the soft soil under levees in the delta is susceptible to liquefaction. 01:35:47.000 --> 01:35:55.000 Meaning the soil becomes less stable and loses its strength as a result of shaking caused by an earthquake. 01:35:55.000 --> 01:35:59.000 Other factors, including subsidence and the constant pressure from water in the channels. 01:35:59.000 --> 01:36:04.000 Increase the chances of levee collapse during a major seismic event. 01:36:04.000 --> 01:36:11.000 The delta is traversed by a series of seismic faults that make up the eastern part of the San Andreas Fault system. 01:36:11.000 --> 01:36:18.000 One of them, the Kirby Hills Fault. Passes under the Sacramento River right here near Pittsburgh. 01:36:18.000 --> 01:36:25.000 And is an active fault line believed to have been the source of a magnitude 6 earthquake in 1889. 01:36:25.000 --> 01:36:30.000 Back then, the process of building the Delta's vast system of levees had barely begun. 01:36:30.000 --> 01:36:35.000 Today, there's more than 1,100 miles of them protecting Delta farmland and communities. 01:36:35.000 --> 01:36:47.000 As well as the state's primary supply of fresh water. Seismologists estimate that the Kirby Hills fault has the potential to generate an earthquake large enough to cause some levees to fail. 01:36:47.000 --> 01:36:53.000 The proposed Delta Tunnel would be much more earthquake resistant than surface infrastructure such as levees. 01:36:53.000 --> 01:37:00.000 Canals or pipelines. Ground motion at depth is actually much less than the motion at the surface. 01:37:00.000 --> 01:37:04.000 This is because of the way shock waves propagate in an earthquake. 01:37:04.000 --> 01:37:12.000 Therefore, a tunnel at the depth proposed in the Delta Conveyance Project is at far less risk of damage. 01:37:12.000 --> 01:37:21.000 Dwr has been planning for many years to address the risk of earthquakes and has developed detailed plans to guide our response and recovery efforts. 01:37:21.000 --> 01:37:30.000 Strategies include enormous stockpiles of rock and flood fight materials that can be distributed throughout the delta to repair potential levee breaches. 01:37:30.000 --> 01:37:43.000 But as effective as these measures would be in dealing with the aftermath of a major earthquake, the Delta Tunnel would provide the most effective way to preserve that crucial link between where water is and where it's needed. 01:37:43.000 --> 01:37:56.000 Probability models have shown that there is a 72% likelihood of at least one earthquake of a 6.7 magnitude or greater, striking somewhere in the San Francisco region before 2043. 01:37:56.000 --> 01:38:07.000 This fact alone emphasizes the importance of acting now to invest in modernizing California's infrastructure to protect our critical water supplies. 01:38:07.000 --> 01:38:16.000 To learn more about the Delta Conveyance Project, visit DWR online at water.ca.gov slash delta conveyance. 01:38:16.000 --> 01:38:39.000 You'll find many links to informative articles and videos about the project. Thanks for watching.