WEBVTT Kind: captions Language: en-US 00:00:01.520 --> 00:00:05.600 Hi, there. I’m Steve DeLong from the USGS Moffett Field. 00:00:05.600 --> 00:00:10.720 And I’m going to be reporting on some recent ongoing and future 00:00:10.720 --> 00:00:14.560 research in northern California. And the sort of thread that ties 00:00:14.560 --> 00:00:19.360 the talk together today is research that is maybe beyond our sort of 00:00:19.360 --> 00:00:25.040 bread-and-butter emphasis on paleoseismology and looking at 00:00:25.040 --> 00:00:28.216 secondary faults and creeping faults – that sort of thing. 00:00:28.240 --> 00:00:32.720 Lots of co-authors on the left there. Most of them are the USGS folks at 00:00:32.720 --> 00:00:35.600 Moffett Field – the geology group. Also Yann Gavillot from 00:00:35.600 --> 00:00:38.960 Oregon State who is a collaborator. And other collaborators and other folks 00:00:38.960 --> 00:00:41.600 who aren’t on this list have material in this talk as well. 00:00:41.600 --> 00:00:45.096 I’ve done my best to give them credit when I’ve included their work. 00:00:45.120 --> 00:00:49.760 So the sort of three things I’ll talk about are recent updates to the National 00:00:49.760 --> 00:00:54.320 Seismic Hazard Map fault model and the research questions that kind of 00:00:54.320 --> 00:00:57.440 came out from that process. And then I’ll zoom in a little bit 00:00:57.440 --> 00:01:01.680 on the San Joaquin-Sacramento Delta and talk about seismic hazard there 00:01:01.680 --> 00:01:06.080 and research that’s in that area. And then I’ll finish up by talking 00:01:06.080 --> 00:01:09.680 a little bit about sort of an update to our longstanding effort 00:01:09.680 --> 00:01:13.190 to understand creeping faults in northern California. 00:01:14.080 --> 00:01:18.936 So first, recent updates to the National Seismic Hazard Model, Hazfaults. 00:01:18.960 --> 00:01:21.920 This is the generalized fault model used in the National Seismic 00:01:21.920 --> 00:01:26.320 Hazard Map and UCERF models. This is a more general model 00:01:26.320 --> 00:01:30.480 than Qfaults or AP maps. And the fault geometries are 00:01:30.480 --> 00:01:33.680 not meant to be fully detailed or accurate, but the overall geometry 00:01:33.680 --> 00:01:37.096 has really important implications for fault connectivity, 00:01:37.120 --> 00:01:40.720 earthquake rupture propagation, and maximum earthquake magnitudes and 00:01:40.720 --> 00:01:44.240 how these things are handled in models. And there’s lots of discussion 00:01:44.240 --> 00:01:46.720 about how this is done. You can see, of course, 00:01:46.720 --> 00:01:49.840 the UCERF publications, and then sort of some discussions that have 00:01:49.840 --> 00:01:53.680 come up more recently include Dave Schwartz’s paper from 2018 00:01:53.680 --> 00:01:56.536 and Morgan Page’s paper from 2020. 00:01:56.560 --> 00:02:00.400 So this has been updated. And thanks to Alex Hatem 00:02:00.400 --> 00:02:04.880 out of USGS Golden for leading this national cat-herding effort. 00:02:04.880 --> 00:02:07.120 It was done really efficiently with, I think, 00:02:07.120 --> 00:02:11.896 a lot of participation from important folks. 00:02:11.920 --> 00:02:14.936 And that model is available at ScienceBase. 00:02:14.960 --> 00:02:18.696 You can contact Alex or me if you want to get that sent to you. 00:02:18.720 --> 00:02:21.920 So, over on the right here is northern California. 00:02:21.920 --> 00:02:25.840 Bay Area, Central Valley, Sierra, Mendocino Triple Junction. 00:02:25.840 --> 00:02:30.456 And the orange faults are unchanged from previous versions of this model. 00:02:30.480 --> 00:02:33.440 Red faults have been removed and refined. 00:02:33.440 --> 00:02:35.440 And green faults are new additions to the model. 00:02:35.440 --> 00:02:38.160 So you can see not big structural changes to the model, 00:02:38.160 --> 00:02:42.696 but there are some details that are interesting to talk about, I think. 00:02:42.720 --> 00:02:47.920 So, north of the Bay Area, northern California really worked mostly by 00:02:47.920 --> 00:02:52.400 folks not in the Moffett Field office, include the offshore San Andreas 00:02:52.400 --> 00:02:56.536 Fault – just a little refinement there just to kind of sandwich the map trace 00:02:56.560 --> 00:03:00.800 inboard of where marine surveys basically didn’t find it. 00:03:00.800 --> 00:03:05.280 And how this fault, as it comes offshore from Point Arena, interacts with the 00:03:05.280 --> 00:03:10.776 rapidly deforming uplifting King Range and the Mendocino Triple Junction 00:03:10.800 --> 00:03:16.400 is not super well-understood. So this is a slightly more likely 00:03:16.400 --> 00:03:19.416 alignment of the fault, but there’s still work to be done up there. 00:03:19.440 --> 00:03:22.720 Northern Central Valley – I think this is largely due to Steve Angster, 00:03:22.720 --> 00:03:26.560 USGS, from his thesis work. Added the Red Bluff Fault 00:03:26.560 --> 00:03:30.240 and the Inks Creeks folds. And I believe he’s got a recent – well, 00:03:30.240 --> 00:03:33.360 he does have a recent geology paper where you can get some of the details 00:03:33.360 --> 00:03:37.496 that led to these changes in the model. So you can reach out to him. 00:03:37.520 --> 00:03:42.880 And then northern California – or, northeastern California, way up here, 00:03:42.880 --> 00:03:46.536 sort of south of Mount Shasta, northern Walker Lane. 00:03:46.560 --> 00:03:49.120 Added the Pondosa Fault Zone. If you want to learn about that – 00:03:49.120 --> 00:03:51.680 if that’s not something you’ve heard about, Jessie Thompson Jobe 00:03:51.680 --> 00:03:55.120 will be describing that is a lightning talk in this meeting. 00:03:55.120 --> 00:03:58.480 And then lots of other refinement thanks to PG&E, consulting groups, 00:03:58.480 --> 00:04:03.920 and other researchers on Hat Creek fault, McArthur Fault, faults in the 00:04:03.920 --> 00:04:07.200 Big Valley, Honey Lake, and just a – sort of a large number 00:04:07.200 --> 00:04:11.642 of faults in this area have been added to the model. 00:04:14.160 --> 00:04:17.200 Zooming in now on the Bay Area – so here we are, San Francisco. 00:04:17.200 --> 00:04:20.456 Here’s the bay. Here’s the edge of the delta. 00:04:20.480 --> 00:04:23.200 You know, really – a few faults have been added. Most refinements. 00:04:23.200 --> 00:04:27.576 And lots of folks were involved in this – Tim Dawson, Jeff Unruh, 00:04:27.600 --> 00:04:32.480 Vicki Langenheim, and Russ Graymer, largely via their forthcoming Mount 00:04:32.480 --> 00:04:38.296 Diablo work – paper that’s coming out in a GSA special paper soon. 00:04:38.320 --> 00:04:40.880 And our collaborator Yann Gavillot as well. 00:04:40.880 --> 00:04:46.720 So Contra Costa shear zone has always been this enigmatic area 00:04:46.720 --> 00:04:50.640 of faulting and map lineaments. And we’ve just basically simplified 00:04:50.640 --> 00:04:54.560 this into the – what is this – the Southampton and the Franklin Faults, 00:04:54.560 --> 00:04:59.840 trying to put likely traces of where the faulting moves forward – 00:04:59.840 --> 00:05:03.576 moves northward into Napa Valley. 00:05:03.600 --> 00:05:06.400 Still not well-constrained. The old version’s not in here, 00:05:06.400 --> 00:05:10.800 but it was a little bit more complex in how it connects down 00:05:10.800 --> 00:05:13.360 from the Calaveras or up from the Calaveras. 00:05:13.360 --> 00:05:18.616 Refined the – Mount Diablo is these two green arcuate thrusts. 00:05:18.640 --> 00:05:23.840 And added this little Midway Fault and the West Tracy Fault, which we are 00:05:23.840 --> 00:05:29.336 confident have Quaternary activity – Holocene activity, most likely. 00:05:29.360 --> 00:05:33.360 And made some other refinements to geometries based on things like where 00:05:33.360 --> 00:05:36.930 creep is mapped out and looking at Lidar and that sort of thing. 00:05:38.000 --> 00:05:40.856 And you can see those refinements are sort of up and down here. 00:05:40.880 --> 00:05:45.921 So no big changes to the principal San Andreas, Hayward, etc., etc. 00:05:47.840 --> 00:05:54.160 So this all sort of inspired us to talk about current research and 00:05:54.160 --> 00:05:58.456 future research interests. Some of this stuff, of course, is ongoing. 00:05:58.480 --> 00:06:02.400 And so I will talk about the things in bold – San Joaquin-Sacramento Delta. 00:06:02.400 --> 00:06:06.240 But other things that have been going on, Belle Philibosian and Mike Oskin 00:06:06.240 --> 00:06:10.080 and the Davis group have both independently been working 00:06:10.080 --> 00:06:13.120 in Napa for quite some time. Mike was – Mike was out there 00:06:13.120 --> 00:06:17.176 before the 2014 earthquake. He knew something. 00:06:17.200 --> 00:06:22.376 So fault mapping updates are forthcoming for Napa, for sure. 00:06:22.400 --> 00:06:25.920 Rodgers Creek-Maacama connectivity – oh, I’ve got some 00:06:25.920 --> 00:06:30.056 ovals to show you here. There’s Napa. 00:06:30.080 --> 00:06:33.440 And so the connectivity to the Maacama and the Rodgers Creek, 00:06:33.440 --> 00:06:35.840 Suzanne Hecker is working on this, and there will be forthcoming 00:06:35.840 --> 00:06:38.080 mapping that gives some more details on that. 00:06:38.080 --> 00:06:42.536 Nothing’s been including in the fault update, but that’s happening. 00:06:42.560 --> 00:06:45.280 Farther north, we’re interested in the northern Maacama, and I mostly put 00:06:45.280 --> 00:06:48.640 this in because there’s a whole session on this issue in this meeting, 00:06:48.640 --> 00:06:51.600 and it’s something I’ve spent a little time looking at, and it’s interesting to 00:06:51.600 --> 00:06:54.720 see how these faults become more complex as you move northward 00:06:54.720 --> 00:06:58.160 towards the Mendocino Triple Junction. And its recent seismicity really 00:06:58.160 --> 00:07:02.320 indicates that the faulting is complex, which others have observed as well. 00:07:02.320 --> 00:07:07.416 So it’d be nice to – there is ongoing work to better understand that. 00:07:07.440 --> 00:07:10.320 Connections between the Greenville Fault, which – 00:07:10.320 --> 00:07:12.680 you know, the Greenville Fault is here east of Livermore – 00:07:12.680 --> 00:07:14.696 had an earthquake in 1980. 00:07:14.720 --> 00:07:17.760 And we don’t really know what happens to the slip as it moves 00:07:17.760 --> 00:07:21.360 north from Livermore Valley. Does it stay to the east of Mount 00:07:21.360 --> 00:07:24.720 Diablo, where there’s not really great evidence for active faulting? 00:07:24.720 --> 00:07:26.960 Or does it move through Mount Diablo up onto the Concord, 00:07:26.960 --> 00:07:29.656 which we know is a pretty active fault? 00:07:29.680 --> 00:07:31.880 Still an open question. 00:07:33.280 --> 00:07:36.136 More work can be done there. 00:07:36.160 --> 00:07:39.840 We have ongoing – oh, yeah, so also the connection for 00:07:39.840 --> 00:07:43.336 the Calaveras – so here’s the Calaveras Fault. 00:07:43.360 --> 00:07:45.600 Where does this go? It probably doesn’t go through the 00:07:45.600 --> 00:07:50.480 Contra Costa shear zone up to Napa. It just doesn’t seem like this is 00:07:50.480 --> 00:07:54.800 the most active faulting area. But the Concord is certainly more 00:07:54.800 --> 00:07:58.720 active, so perhaps it actually – slip is transferred to the Concord 00:07:58.720 --> 00:08:02.240 somehow through this area. So that’s an area lots of folks 00:08:02.240 --> 00:08:04.675 are working on and thinking about. 00:08:06.240 --> 00:08:09.416 Farther north – Bartlett Springs Fault. We want to understand creep, 00:08:09.440 --> 00:08:14.296 slip rate, event chronology. So we’re pushing forward on that 00:08:14.320 --> 00:08:17.760 as well as – we have a plan to update fault mapping as well 00:08:17.760 --> 00:08:22.398 now that we have Lidar. The last real effort was photo-based. 00:08:23.200 --> 00:08:26.960 And then I’ll talk a little bit about this issue of maybe possible fault 00:08:26.960 --> 00:08:31.520 connectivity from these sort of Mount Diablo-Great Valley thrust systems 00:08:31.520 --> 00:08:36.080 through the Midway Fault and farther up, and this question of where – 00:08:36.080 --> 00:08:39.760 how does this all work kinematically? And, more generally, we’re interested 00:08:39.760 --> 00:08:42.640 in the distributions and implications of fault creep. 00:08:42.640 --> 00:08:45.200 And I’ll talk about that as well. 00:08:45.920 --> 00:08:51.096 So in the delta, Chad Trexler is leading a lot of this work, but I’m involved. 00:08:51.120 --> 00:08:55.096 Yann Gavillot is involved. Belle Philibosian is involved. 00:08:55.120 --> 00:08:57.120 And we’ve got lots of – a list of things to do once 00:08:57.120 --> 00:08:58.880 we can get back out in the field, for sure. 00:08:58.880 --> 00:09:00.720 So the Montezuma Hills are an area of interest. 00:09:00.720 --> 00:09:05.680 This is the sort of actively deforming low range of hills north of the delta. 00:09:05.680 --> 00:09:09.040 We know there’s these geomorphically interesting wind gaps where streams 00:09:09.040 --> 00:09:11.200 used to go through, and now they don’t. 00:09:11.200 --> 00:09:16.400 And so this is certainly a likely indication of active deformation 00:09:16.400 --> 00:09:19.176 in this area. So we’d like to better understand that. 00:09:19.200 --> 00:09:22.280 And then Chad is really working – and he’s got a lightning talk, 00:09:22.280 --> 00:09:26.160 and he can give you the details. I’m using a combination of the bedrock 00:09:26.160 --> 00:09:31.360 geology and the geomorphology, including things like zones of possibly 00:09:31.360 --> 00:09:35.096 active uplift and how that interacts with a fluvial system. 00:09:35.120 --> 00:09:37.920 And he’s identified all sorts of interesting stuff there that can 00:09:37.920 --> 00:09:41.765 indicate tectonic activity and faulting. 00:09:43.200 --> 00:09:46.160 Zooming in just a bit – Yann Gavillot is going to give a lightning talk on 00:09:46.160 --> 00:09:49.680 sort of the trenching – most recent trenching in this area, 00:09:49.680 --> 00:09:52.960 but we’re also working on looking at – so starting here. 00:09:52.960 --> 00:09:57.200 This is the Diablo Range, zooming into the Black Butte Fault and San Joaquin 00:09:57.200 --> 00:10:00.160 Fault in this area and some active structures to the north of that. 00:10:00.160 --> 00:10:05.496 Then zooming in a bit more, we can see that there are these places where 00:10:05.520 --> 00:10:09.680 faults offset these alluvial surfaces. So there’s a – you know, we’ve done 00:10:09.680 --> 00:10:14.560 a bunch of mapping of this suite of alluvial fan and fluvial terrace surfaces 00:10:14.560 --> 00:10:20.456 at both Lone Tree Creek and Corral Hollow and analyzing those. 00:10:20.480 --> 00:10:23.840 Getting – we’re starting to get ages – luminescence and cosmogenic ages. 00:10:23.840 --> 00:10:26.160 More are forthcoming. But initially, you know, 00:10:26.160 --> 00:10:28.480 correct for geometry, and we can see that these faults are probably 00:10:28.480 --> 00:10:32.376 deforming at something like that 1.5 to 3.5 millimeters per year. 00:10:32.400 --> 00:10:36.400 And this has implications for seismic hazard to the delta, which we know 00:10:36.400 --> 00:10:41.939 is ecologically and, in terms of infrastructure, vulnerable. 00:10:43.120 --> 00:10:45.040 And then how these faults sort of interact. 00:10:45.040 --> 00:10:50.480 So here we are in – here’s Tracy, and this is the Qfaults and Hazfaults 00:10:50.480 --> 00:10:53.840 and how these – how the faulting works on the range front and how that 00:10:53.840 --> 00:10:58.960 might transfer through the Black Butte anticline up here onto the Midway Fault 00:10:58.960 --> 00:11:04.320 and then possibly, from the Midway Fault, does this slip actually transfer 00:11:04.320 --> 00:11:07.360 on the east side of Mount Diablo? Or does it work through this network 00:11:07.360 --> 00:11:10.240 of faults southeast of Mount Diablo and even onto Mount Diablo? 00:11:10.240 --> 00:11:14.560 So the larger-scale kinematics in this area are interesting to the think about, 00:11:14.560 --> 00:11:18.160 and we’re just trying to understand those, as well as 00:11:18.160 --> 00:11:22.296 the activity of the Midway Fault here. 00:11:22.320 --> 00:11:27.120 So just wrapping up, so creeping faults are something that we have studied for 00:11:27.120 --> 00:11:30.480 a long time in northern California. And recently, we’ve really been 00:11:30.480 --> 00:11:34.640 aided by our geodetic friends. Gareth Funning and his group, 00:11:34.640 --> 00:11:37.440 in particular, but lots of other folks as well who have helped us 00:11:37.440 --> 00:11:40.080 understand the distribution of fault creep. 00:11:40.080 --> 00:11:44.080 So this is information that we really like to receive so we can guide our 00:11:44.080 --> 00:11:48.160 geologic studies and help us interpret our observations in light of what 00:11:48.160 --> 00:11:53.040 the remote sensing work tells us. And so recently, they’ve highlighted 00:11:53.040 --> 00:11:55.520 zones on the Rodgers Creek Fault that are creeping. 00:11:55.520 --> 00:12:00.720 And this is from things like spaceborne SAR – InSAR – 00:12:00.720 --> 00:12:03.840 and repeating earthquakes. Down here, we see evidence 00:12:03.840 --> 00:12:05.040 from repeating earthquakes. 00:12:05.040 --> 00:12:09.360 Looking at seismicity, we can get at fault creep and geometry of structures 00:12:09.360 --> 00:12:12.800 and all sorts of interesting things over on the right as well. 00:12:12.800 --> 00:12:19.200 So creep rates in the colored boxes from repeating earthquakes as well. 00:12:19.200 --> 00:12:22.560 And then, of course, the satellite SAR has really been great for 00:12:22.560 --> 00:12:26.000 showing us where faults creep. So what kind of stuff do geologists 00:12:26.000 --> 00:12:29.120 do with fault? Well, quite a bit. Because we want to understand 00:12:29.120 --> 00:12:32.536 how much moment and slip rate is taken up aseismically. 00:12:32.560 --> 00:12:34.480 We want to understand how we distinguish creep 00:12:34.480 --> 00:12:37.920 in the paleoseismic record. And we want to think about what 00:12:37.920 --> 00:12:41.040 the implications are for fault rupture propagation, especially when you think 00:12:41.040 --> 00:12:46.056 about big players like the central San Andreas and the Hayward. 00:12:46.080 --> 00:12:48.720 And so, you know, I mentioned InSAR and seismicity. 00:12:48.720 --> 00:12:52.880 In our group, we use alignment array re-occupation, repeat terrestrial Lidar, 00:12:52.880 --> 00:12:57.200 UAV surveys, repeat airborne Lidar, image analysis using things like 00:12:57.200 --> 00:12:59.680 COSI-Corr, and, of course, direct observation, which you 00:12:59.680 --> 00:13:02.880 have a couple examples of here. This is Suzanne Hecker’s trench – 00:13:02.880 --> 00:13:06.240 recent trench on the Rodgers Creek. She’ll have a lightning talk about that. 00:13:06.240 --> 00:13:11.200 And our – the crew did a trenching investigation, and then, as we were 00:13:11.200 --> 00:13:14.720 wrapping up, the area burned. We lost a lot of gear, but it was 00:13:14.720 --> 00:13:18.080 interesting to go back out after the fire and observe that what is 00:13:18.080 --> 00:13:21.920 most likely the creeping trace of the fault has these opening cracks. 00:13:21.920 --> 00:13:28.800 And here’s Ali in the latest post-fire apocalyptic field gear surveying out 00:13:28.800 --> 00:13:32.320 those cracks. And then this is just an example of re-occupation 00:13:32.320 --> 00:13:34.640 of an alignment array that Belle Philibosian and 00:13:34.640 --> 00:13:37.360 Dan Mongovin worked on on the Sargent Fault. 00:13:37.360 --> 00:13:40.572 And we’ve looked at these elsewhere, of course. 00:13:43.200 --> 00:13:46.400 And just a quick update. You know, our longstanding 00:13:46.400 --> 00:13:52.536 monitoring of the northern California alignment array system. 00:13:52.560 --> 00:13:55.200 Jim Lienkaemper recently retired, and we’re carrying this on. 00:13:55.200 --> 00:13:58.720 We’ve got new instrumentation. This is, you know, driven by San Francisco 00:13:58.720 --> 00:14:04.936 State and Jim in the past, and now Austin Elliott is picking this up. 00:14:04.960 --> 00:14:06.880 And so we’ll be continuing to monitor all this. 00:14:06.880 --> 00:14:09.280 And then we’ve got – of course, always trying to figure out 00:14:09.280 --> 00:14:14.160 new fancy ways to measure creep. And to learn about this cool figure 00:14:14.160 --> 00:14:17.600 in the lower left, check out Chelsea Scott’s talk, which I believe is just 00:14:17.600 --> 00:14:20.480 after this one, or a few after this one. 00:14:20.480 --> 00:14:24.456 And you can learn all about using Lidar to measure creep. 00:14:24.480 --> 00:14:26.776 So I’ll tie this all together. 00:14:26.800 --> 00:14:30.960 You know, updating the Hazfaults model indicated areas in which fault activity 00:14:30.960 --> 00:14:33.416 and connectivity needs to be better understood. 00:14:33.440 --> 00:14:35.200 These secondary low-slip-rate, 00:14:35.200 --> 00:14:38.776 long-recurrence faults are particularly challenging to study. 00:14:38.800 --> 00:14:42.720 Understanding kinematics from, not just faults, but folds and, you know, 00:14:42.720 --> 00:14:46.216 things apparent in geomorphic analysis can be a way forward. 00:14:46.240 --> 00:14:50.160 And examples are, like, interactions between the thrust faults adjacent to 00:14:50.160 --> 00:14:52.960 Mount Diablo and the strike-slip faults – the Greenville, 00:14:52.960 --> 00:14:56.320 the Calaveras, etc., etc., may help us eliminate 00:14:56.320 --> 00:14:59.336 more complex kinematics and fault connectivity. 00:14:59.360 --> 00:15:04.240 Fault creep detection really helps us observe creep evidence in paleoseismic 00:15:04.240 --> 00:15:09.256 investigations and are good indication of where the active faulting is. 00:15:09.280 --> 00:15:12.880 And we’re going to continue creep monitoring and measurement 00:15:12.880 --> 00:15:15.840 using proven, like, alignment arrays and survey instruments 00:15:15.840 --> 00:15:19.496 and emerging methods like I described. 00:15:19.520 --> 00:15:22.400 Thanks for listening.