Well, the east side of the Sierra lives up to its reputation for being in earthquake country. From the July 2019 Ridgecrest Earthquake Sequence (reports here)to some shakers east of Mono Lake, to the May 2020 Monte Cristo Earthquake Sequence (report here) to some earthquakes in the Owens Lake area of California. Residents of Olancha, Lone Pine, and Keeler felt strong shaking from a magnitude M 5.8 earthquake, also preceded by about 2 days with a M 4.6 temblor.

https://earthquake.usgs.gov/earthquakes/eventpage/ci39493944/executive

The plate tectonics in the western US is overwhelmingly dominated by the plate boundary between the North America and Pacific plate. The North America plate moves south “relative” to the Pacific plate. Standing on the Pacific plate, looking across the fault, the North America plate moves to your right (a right-lateral strike-slip fault).

Here, both plates are moving “absolutely” in the northwestern direction, but the Pacific plate is moving slower. Therefore the relative sense of motion results in a right-lateral fault.

The plates move side-by-side at a velocity (speed) of about 50 mm per year (2 inches per year). In California, most of this relative motion is localized along the San Andreas fault system. But there are sub-parallel “sibling” faults that also share some of the “slip budget” (their proportion of the 50 mm/yr).

About 20% of the relative plate motion is found along faults on the east side of the Sierra Nevada, along the Eastern California Shear Zone and the Walker Lane system.

Further to the north, in northern California, Oregon, Washington, and Canada, the relative plate motion is compressive, forming the Cascadia subduction zone.

East of California, the plate boundary experiences relative extension, forming the geomorphic province called the Basin and Range. The faults in the Basin and Range are mostly normal faults (extensional faults).
Read more about the different fault types here.

On 26 March 1872 there was a large earthquake that ruptured faults from south of Owens Lake near Olancha, CA northwards to Big Pine, CA. This earthquake may be the largest historic earthquake in California with a magnitude of M 7.8 to 7.9 (Hough and Hutton, 2008).

This earthquake was the result of slip on the Owens Valley fault system (OVF). The majority of slip was right-lateral strike-slip, but because the OVF is not perfectly aligned with the relative plate motion, some of the slip on these faults was normal slip (i.e. extensional).

There are still preserved remains of structures damaged by the earthquake in Lone Pine, CA.

The OVF has been mapped and trenched across to learn about the prehistoric record of earthquakes on the fault.

Also, from measurements of features that have been offset along the fault during earthquakes, along with knowledge of the age of those features, we can estimate how fast the frust is moving relatively across the fault. Below are some figures that help us learn about this historty and activity of the OVF (e.g. Bacon and Pezzopane, 2007; Kirby et al, 2008; Haddon et al., 2013; Bacon et al., 2019).

Beth Haddon et al. (2013) conducted a very interesting study that compiled and updated previous slip estimates for the 1872 OVF earthquake. Their analysis vastly improved the estimate of how much the fault slipped at different locations along the fault (i.e. the fault slip distribution) and included a novel way to account for uncertainty (a.k.a. error) in the measurements of these offsets.

California Geological Survey Engineering Geologist Brian Olson was sent to the field to make observations of fault rupture, landslides, and liquefaction related to this earthquake. Some of his tweets from the field are included below in the social media section.

Below is my interpretive poster for this earthquake

• I plot the seismicity from the past month, with diameter representing magnitude (see legend). I include earthquake epicenters from 1920-2020.
• I plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.
• A review of the basic base map variations and data that I use for the interpretive posters can be found on the Earthquake Reports page.
• Some basic fundamentals of earthquake geology and plate tectonics can be found on the Earthquake Plate Tectonic Fundamentals page.

I include some inset figures. Some of the same figures are located in different places on the larger scale map below.

• In the upper left corner is a map that shows the earthquake faults and historic earthquake locations (epicenters) in the western US. Historic earthquake fault ruptures are mapped as red lines and labeled with their year and magnitude.
• In the lower right corner is a map that shows a comparison of the California Geological Survey Shakemap (a model of how strong the ground might shake during the M 5.8 earthquake) and results from online web surveys from peoples’ real observations (i.e. “Did You Feel It?” reports. The colored lines show the boundary between different levels of intensity using the Modified Mercalli Intensity (NNI) scale. The areas are colored relative to the DYFI reports, using the same MMI scale and colors shown on the legend).
• In the lower center is an illustration showing how earthquake intensity is higher closer to the earthquake. With distance, the intensity goes down. This is another comparison between the Shakemap models and the DYFI observations.
• In the upper right corner is a map that shows the liquefaction susceptibility, or the chance that an area may experience liquefaction during the earthquake. I present a map that also shows the chance that there will be landslides triggered by the earthquake lower in this report. Also, check out social media section to see videos of evidence of these landslides.

• Here is the map with a year’s seismicity plotted (and a century in the overview map).
• Something to note is that these Owens Lake earthquakes follow some triggered earthquakes that have been going on in the Coso Mountains and to the west of the reservoirs along the Owens River. Following the Ridgecrest Earthquake Sequence, the crust near the fault that slipped flexed like our elastic waist bands. This flexing caused the forces acting on faults withing the crust to increase and decrease in different places. These changes are called changes in static coulomb stress.
• According to some studies (see tweets and the Temblor reports related to Ridgecrest), the area to the northwest of Ridgecrest have increased static coulomb stress changes, which increases the chance that faults might slip in those areas.
• Guess where these Owens Valley earthquakes are happening? Yup, in an area tha has possibly experienced an increase in stress.

• Below is an updated map that shows the aftershocks (and foreshocks) related to the M 5.8 earthquake.
• There have only been two earthquakes in the past century that have magnitudes M ≥ 5. Some earthquakes can have aftershocks that last centuries (like the 1872 central Washington earthquake, which is still popping off aftershocks today). Because of the paucity of seismicity in this area, we may not be able to know if these two events in 2009 are aftershocks from 1872. The same is true for the M 5.8 sectence that is ongoing right now in Owens Valley. I suspect that these are unrelated to 1872 and are directly related to the Ridgecrest Earthquakes.
• This part of the OVF is at the end of the fault, where it is less organized, so fault lengths are shorter and misaligned. Based on the work of Haddon et al. (2013), the slip on these faults in 1872 was low. So, maybe these faults had more accumulated strain than the rest of the OVF faults, so we would not expect more earthquakes on the OVF system (?). Hard to really know…

I include some inset figures. Some of the same figures are located in different places on the larger scale map below.

• In the upper left corner is a map that shows historic earthquake locations (a century M ≥ 2 and a week M ≥ 0). I highlight areas of recent seismic unrest.
• In the upper right corner is a map from Bacon et al. (2019) that shows the different faults that they studied in this area. Each different fault is colored and labeled, along with symbology showing what type of relative motion is accommodated on those faults. These authors mapped and dated prehistoric shorelines, then used their location to evaluate slip rates for these faults over a very long time span.
• In the lower right corner are some cross sections showing how Bacon et al/ (20219) interpret how the tectonic structures are oriented in the subsurface beneath the Owens Valley. The locations for section A-A’ and B-B’ are shown on the main map as yellow-green lines.

• So what does all this mean about the future? We won’t know until the future becomes the present, and then the past.
• The Garlock fault south of Ridgecrest. Some of the most detailed paleoseismology studies have taken place along the Garlock fault. Yet, we don’t know if there will be an earthquake there tomorrow or a decade or century from now. Read more about the Garlock fault here.
• The Blackwater fault south of Ridgecrest. There are numerous faults in the Eastern California Shear Zone between the Ridgecrest Earthquake Sequence and the Landers and Hector Mine earthquakes from 1992 and 1999 respectively. How do changes in stress following the Ridgecrest earthquake affect the crust south of the Garlock fault? This is a place to watch, but it may take decades, or more, before there is an earthquake here.
• The Owens Valley fault north of Ridgecrest. This seems like a lesser likelihood. The average time between large earthquakes on the OVF is several thousands of years and 1972 was the last one. It is possible we don’t know everything about this system (as always, our knowledge about prehistoric earthquakes is a minimum estimate; we may find more evidence later).
• The area north of the 1972 OVF earthquake and south of the Cedar Mountain Earthquake or anywhere along the 395 corridor through Walker, Carson City, Reno, etc. The 2019 Pacific Cell Friends of the Pleistocene field trip reviewed some evidences for recent faulting in this region. So, this is a place to watch for sure.

Earthquake Triggered Landslides and Liquefaction

• Here is a suite of maps that use USGS earthquake products to help us learn about how earthquakes may affect the landscape: landslide probability and liquefaction susceptibility (a.k.a. the Ground Failure data products)..
• First I present the landslide probability model. This is a GIS data product that relates a variety of factors to the probability (the chance of) landslides as triggered by this earthquake. There are a number of assumptions that are made in order to be able to produce this model across such a large region, though this is still of great value (like other aspects from the USGS, e.g. the PAGER alert). Learn more about all of these Ground Failure products here.
• There are many different ways in which a landslide can be triggered. The first order relations behind slope failure (landslides) is that the “resisting” forces that are preventing slope failure (e.g. the strength of the bedrock or soil) are overcome by the “driving” forces that are pushing this land downwards (e.g. gravity). I spend more time discussing landslides and liquefaction in this recent earthquake report.
• This model, like all landslide computer models, uses similar inputs. I review these here:
1. Some information about ground shaking. Often, people use Peak Ground Acceleration, though in the past decade+, it has been recognized that the parameter “Arias Intensity” is a better measure of the energy imparted by the earthquake across the land and seascape. Instead of simply accounting for the peak accelerations, AI integrates the entire energy (duration) during the earthquake. That being said, PGA is a more common parameter that is available for people to use. For example, when I was modeling slope stability for the 2004 Sumatra-Andaman subduction zone earthquake, the only model that was calibrated to observational data were in units of PGA. The first order control to shaking intensity (energy observed at any particular location) is distance to the earthquake fault that slipped.
2. Some information about the strength of the materials (e.g. angle of internal friction (the strength) and cohesion (the resistance).
3. Information about the slope. Steeper slopes, with all other things being equal, are more likely to fail than are shallower slopes. Think about skiing. Beginners (like me) often choose shallower slopes to ski because they will go down the slope slower, while experts choose steeper slopes.
• I use the same color scheme that is presented by the USGS on their website. Note that the majority of areas that may have experienced earthquake triggered landslides are cream in color (0.3-1%). There are a few places with a slightly higher chance that there were triggered landslides. It is possible that there were no significant landslides from this earthquake. The lower bounds for earthquake triggered landslides on land is about M 5.5 and a M 6.4 releases much more energy than that.
• Landslide ground shaking can change the Factor of Safety in several ways that might increase the driving force or decrease the resisting force. Keefer (1984) studied a global data set of earthquake triggered landslides and found that larger earthquakes trigger larger and more numerous landslides across a larger area than do smaller earthquakes. Earthquakes can cause landslides because the seismic waves can cause the driving force to increase (the earthquake motions can “push” the land downwards), leading to a landslide. In addition, ground shaking can change the strength of these earth materials (a form of resisting force) with a process called liquefaction.
• Sediment or soil strength is based upon the ability for sediment particles to push against each other without moving. This is a combination of friction and the forces exerted between these particles. This is loosely what we call the “angle of internal friction.” Liquefaction is a process by which pore pressure increases cause water to push out against the sediment particles so that they are no longer touching.
• An analogy that some may be familiar with relates to a visit to the beach. When one is walking on the wet sand near the shoreline, the sand may hold the weight of our body generally pretty well. However, if we stop and vibrate our feet back and forth, this causes pore pressure to increase and we sink into the sand as the sand liquefies. Or, at least our feet sink into the sand.
• Below is the liquefaction susceptibility map. I discuss liquefaction more in my earthquake report on the 28 September 20018 Sulawesi, Indonesia earthquake, landslide, and tsunami here.
• I use the same color scheme that the USGS uses on their website. Note how the areas that are more likely to have experienced earthquake induced liquefaction are in the valleys. The fact that this earthquake happened in the summer time suggests that there may not have been any liquefaction from this earthquake.

Other Report Pages

Some Relevant Discussion and Figures

• Here is a figure from Rinke et al. (2012) that shows the global and regional tectonics here. I include the figure captions below as blockquotes. The first map shows the plate boundary scale tectonic regions. This is a generalized map (e.g. don’t pay attention to where the San Andreas and Cascadia faults are located).




Simplified tectonic map of the western U.S. Cordillera showing the modern plate boundaries and tectonic provinces. Basin and Range Province is in medium gray; Central Nevada seismic belt (CNSB), eastern California shear zone (ECSZ), Intermountain seismic belt (ISB), and Walker Lane belt (WLB) are in light gray; Mina deflection (MD) is in dark gray.

• Here is the Amos et al. (2013) plate tectonic map. Check out the location of the historic surface rupturing earthquakes. Their figure caption is below (as for other figures here).




Overview of active faults and regional topography of the Eastern California shear zone (ECSZ) and southern Walker Lane belt. Labeled faults are abbreviated as follows: ALF—Airport Lake fault, BF—Blackwater fault, GF—Garlock fault, KCF—Kern Canyon fault, LLF—Little Lake fault, OVF—Owens Valley fault, SNFF—Sierra Nevada frontal fault. OL—Owens Lake, IWV—Indian Wells Valley. Major historical earthquake surface ruptures in the Eastern California shear zone and Walker Lane belt are outlined in white, with stars denoting epicentral locations: OV—1872 Owens Valley, L—Landers 1992, HM—1999 Hector Mine. Active fault traces are taken from the U.S. Geological Survey Quaternary fault and fold database, with the exception of the Kern Canyon fault, taken from Brossy et al. (2012).

• This map extends a little farther to the east (Frankel et al., 2008). This map shows nicely how the Sierra Nevada and Owens Valley faults (the Pacific-North America plate boundary) and Eastern California Shear Zone, aka ECSZ (the maps south of the Garlock fault, 35.5N°) interact with east-west trending left-lateral strike-slip faults like the Garlock fault. The ’92 Landers and ’99 Hector Mine Earthquakes are on faults in the ECSZ.




Shaded relief index map of Quaternary faults, roads, towns, and fi eld trip stops in the eastern California shear zone. Most faults are from the U.S. Geological Survey Quaternary fault and fold database (http://earthquake.usgs.gov/regional/qfaults). Arrows indicate relative fault motion for strike slip faults. Bar and circle indicates the hanging wall of normal faults. Field trip stop location numbers are tied to site descriptions in the fi eld guide section. AHF—Ash Hill fault; ALF—Airport Lake fault; B—Bishop; BF—Blackwater fault; BLF—Bicycle Lake fault; BM—Black Mountains; BP—Big Pine; Br—Baker; Bw—Barstow; By—Beatty; CA—California; CF—Cady fault; CLF—Coyote Lake fault; CoF—Calico fault; CRF—Camp Rock fault; DSF—Deep Springs fault; DV-FLVF—Death Valley–Fish Lake Valley fault; EPF—Emigrant Peak fault; EV— Eureka Valley; FIF—Fort Irwin fault; FM—Funeral Mountains; GF—Garlock fault; GFL—Goldstone Lake fault; GM—Grapevine Mountains; HF—Helendale fault; HLF—Harper Lake fault; HMSVF—Hunter Mountain–Saline Valley fault; I—Independence; LF—Lenwood fault; LLF— Lavic Lake fault; LoF—Lockhart fault; LP—Lone Pine; LuF—Ludlow fault; LV—Las Vegas; M—Mojave; MF—Manix fault; NV—Nevada; O—Olancha; OL—Owens Lake; OVF—Owens Valley fault; P—Pahrump; PF—Pisgah fault; PV—Panamint Valley; PVF—Panamint Valley fault; R—Ridgecrest; S—Shoshone; SAF—San Andreas fault; SDVF—southern Death Valley fault; SLF—Stateline fault; SPLM—Silver Peak–Lone Mountain extensional complex; SNF—Sierra Nevada frontal fault; SP—Silver Peak Range; T—Tonopah; TF—Tiefort Mountain fault; TMF—Tin Mountain fault; TPF—Towne Pass fault; WMF—White Mountains fault; YM—Yucca Mountain.

• This is also from Amos et al. (2013) that shows how some northeast striking normal faults are related to the Little Lake fault, in the northern part of Indian Wells Valley. The Little Lake fault connects to the Sierra Nevada frontal fault.




Simplified geologic map of the Little Lake fault, highlighting Quaternary volcanic and alluvial deposits bearing on the Pleistocene drainage of Owens River through the Little Lake area. Map units are named and modified from Duffield and Bacon (1981). The 30 m elevation contours are taken from the National Elevation Database (NED). The ⁴⁰Ar/³⁹Ar dates are labeled as in Table 1. SNFF—Sierra Nevada frontal fault.

• Here is the Frankel et al. (2008) larger scale fault map, also focusing on the northern Indian Wells Valley.




Northward branching of the Holocene-active Airport Lake fault zone in northern Indian Wells Valley, Rose Valley, the Coso Range, and Wild Horse Mesa. AL—Airport Lake playa; BR— basement ridge; CB—Central branch; CWF—Coso Wash fault; EB—Eastern branch; GF—geothermal field; HS— Haiwee Spring; LCF—Lower Cactus Flat; MF—McCloud Flat; UCF—Upper Centennial Flat; WB—Western branch; WHA—White Hills anticline; WHM—Wild Horse Mesa; WHMFZ— Wild Horse Mesa fault zone. Faults with especially prominent scarps in Wild Horse Mesa are highlighted in bold. Late Quaternary faults modified from Duffield and Bacon (1981) and Whitmarsh (1998), with additional original mapping. A and B indicate two faults that display evidence for late Quaternary dextral offset.

• This is the Stevens et al. (2013) map that shows the sedimentary basins in the region.




Map showing interpreted thickness of Cenozoic deposits and major faults outlining the deep basins, based on inversion of gravity data [56]. Connection between West Inyo and Southwest Argus faults from Pluhar et al. [58]. ALFZ = Airport Lake Fault Zone; CWF = Coso Wash Fault; EIF = East Inyo Fault; LLF = Little Lake Fault. A-A’ to H-H’ indicate lines of cross sections and gravity profiles shown in Figure 10.

• Here are the fault blocks presented by Stevens et al. (2013).




Map showing deep basins, relatively shallow down-dropped blocks, extended mountain blocks, and structural zones in the ESVS, which is bounded by largely unextended mountain blocks. CB = Chalfant Basin; NBB = North Bishop Block; RVB = Round Valley Basin

• Here is a great overview map of the faults in the region from Oskin et al. (2008). Their paper is about their research to quantify the tectonic loading of faults in the Eastern California shear zone. Note that they use about 12 mm per year of Pacific-North America relative plate motion across this region.




A: Index map of southwest North America showing geodetic provinces from Bennett et al. (2003) and location of Mojave block. Velocities of geodetically stable regions are shown relative to Colorado Plateau. ECSZ—eastern California shear zone in Mojave block. Shear zone continues northward into western Great Basin province. GF—Garlock fault. B: Index map of the Mojave block with active faults and locations of recent earthquake ruptures. Circles show localities of slip-rate measurements that sum to ≤6.2 ± 1.9 mm/yr across the ECSZ. GPS—global positioning system.

• Here is another good overview map, showing the faults for which Petersen and Wesnousky (1994) reviewed slip rates in that publication. They present an excellent review of all slip rate and paleoseismic investigations at the time that paper was published.




Map showing sites of slip rate studies in southern California for the San Andreas (SAI-14), San Jacinto (SJI-13), Elsinore-Whittier (El-8), Newport- Inglewood (N1-3), Palos Verdes (N4-6), Rose Canyon (N7), Transverse Ranges (T1-50), Mojave (MI-6), and Garlock (G1-9) faults.

• Oskin and Iriondo studied the Blackwater fault, the right-lateral strike-slip fault system that extends from the south into the region of the Ridgecrest Earthquake Sequence. The Blackwater fault is connected to the south with the Calico fault (a fault between the 1992 and 1999 earthquakes). This appears to be the major Eastern California Shear zone fault that extends towards the Airport Valley and Little Lake faults (which ruptured during the Ridgecrest Earthquake Sequence).




A: Index map of Pacific–North America plate boundary through southwest North America. Principal faults are shown as thick black lines. Tectonically stable areas are outlined by dotted lines. Walker Lane and Eastern California shear zone, shown as dark gray band encompassing network of active faults, together absorb 9%–23% of total plate boundary shear (Dixon et al., 2000; Dokka and Travis, 1990a). JDF—Juan de Fuca; MTJ— Mendocino triple junction. B: Index map of Eastern California shear zone showing fault slip rates (in parentheses, mm/yr) determined by paleoseismic studies (Klinger and Piety, 2000; Lee et al., 2001; McGill and Sieh, 1993; Rockwell et al., 2000; Zhang et al., 1990). Heavy dark gray lines outline historic earthquake ruptures (Beanland and Clark, 1994; Sieh et al., 1993; Treiman et al., 2002). Heavy, medium gray band highlights Blackwater–Calico fault system. Light gray band surrounding Blackwater fault and passing north of Garlock fault is zone of localized 1.2 6 0.5 mm/yr strain accumulation documented by radar interferometry (Peltzer et al., 2001). C: Neotectonic map of Blackwater fault, showing type and orientation of fault line scarps with ticks on downthrown side. Dark patterned areas are lava flows cut by Blackwater fault (Dibblee, 1968, 1967; Smith, 1964)

• Peltzer et al. (2001) evaluate the amount of tectonic strain that has accumulated over time (see geodesy section to learn more about strain). First I present their tectonic map.




Tectonic map of southern California. Solid lines are active faults (Jennings, 1975). Yellow dots are relocated earthquakes between 1981 and 2000 (Hauksson, 2000). Dashed-line box is area covered by Earth Resource Satellite (ERS) data used in this study. White dashed line shows location of concentrated shear observed in synthetic aperture radar (SAR) data. Black stars indicate epicenters of recent earthquakes: OV—1872 Owens Valley, JT—1992 Joshua Tree, L—1992 Landers, BB—1992 Big Bear, N—1994 Northridge, RC—1994 and 1995 Ridgecrest, HM—1999 Hector Mine. Heavy solid lines depict surface ruptures of Landers (Sieh et al., 1993), Hector Mine (U.S. Geological Survey and California Division of Mines and
Geology, 2000; Peltzer et al., 2001), and Owens Valley (Beanland and Clark, 1994; only southern half of rupture is shown) earthquakes. Black dots and arrows show locations and observed velocities of 11 stations of Yucca GPS array (Gan et al., 2000).
* Faults are listed in the paper

• Here is the Guest et al. (2003) map showing their interpretation of how these faults developed over time.




In this model the Owlshead and southern Panamint blocks are hypothesized to have undergone sinistral transtension in response to a clockwise rotation of their southern confining boundary (Garlock fault zone).
RTR—Radio Tower Range, SOM—Southern Owlshead Mountains, WWFZ—WingateWash fault zone, BMF—Brown Mountain fault, OLF—Owl Lake fault, GF—Garlock fault, MSS—Mule Springs strand, LLZ—Leach Lake fault zone, SDVFZ—Southern Death Valley fault zone.

Background Literature – Geodesy

• Gan et al. (2003) present a summary of geodetic data where they show that the Owens Valley, Little Lake, and Helendale faults form the generalized western boundary of the Eastern California shear zone (there are additional right-lateral faults to the west however).




Map showing the location of the ECSZ, the GPS arrays, the station velocities (relative to the fixed North America), and the principal faults in southern California (from Jennings [1992]). The thick dashed lines directed N23°W show the boundaries of the assumed parallel-sided ECSZ. The thin dashed lines extended from the segments of the Garlock fault show the trends of the segments.

• One of the challenges with interpreting geodetic data is comparing earthquake fault slip rates inferred from geodetic methods with rates calculated using geologic data (either from long term offsets of bedrock, or from more recent rates using fault trenches).
• Chuang and Johnson (2011) present their comparisons of GPS slip rates with geologic rates.
• Blue = geologic rate
• Black = geodetic rate
• Magenta = block model rate from their analyses




Comparison of geologic fault slip rates (blue, mm/yr) used in model, range of estimates from elastic block models (black) of Becker et al. (2005) and Meade and Hager (2005), and estimates from our block model (magenta) along major faults. Negative is left lateral. Light red lines are surface fault traces, and white thick lines are model blocks. Blue arrows are Southern California Earthquake Center (SCEC) crustal motion map 3 (Shen et al., 2003) velocities with respect to stable North America.
*See their paper for fault abbreviations.

• Here is an interesting figure showing their (Chuang and Johnson, 2011) estimate of the relative position in the earthquake cycle for these faults. This is based on published recurrence intervals for these faults (the average time between earthquakes given paleoseismic investigation data).




Summary of assumed geologic rates, recurrence interval (T), and time since last earthquake (teq) in Southern California. (For further discussion of sources of T and teq, see footnote 1). Blue numbers are expert opinion slip rates from Working Group on California Earthquake Probabilities (2008) and red numbers are rates from other paleoseismology data.
Color of rupture segment represents ratio of time since last earthquake and recurrence interval. Hot (red) colors show segments are in early earthquake cycle, and cold (blue) colors show late earthquake cycle.

• This is the summary of the Chuang and Johnson (2011) slip rate comparison.




A: Geologic fault slip rates versus slip rates inferred from geodetic data. Geologic rates are summarized in Table DR1 (see footnote 1). Blue bars are slip rate comparisons from Meade and Hager (2005) and red bars are from this study. B: Normalized velocity across Garlock fault (blue), Mojave segment of San Andreas fault (red), and eastern California shear zone (ECSZ, green) from our cycle model. Black line is normalized velocity derived from elastic model.

• Here is an earlier analysis comparing geodetic rates with geologic rates (Dixon et al., 2003). First we see a map showing the faults from which the fault comparisons are shown.




Sketch map of study area, modified from Dixon et al. (1995). Bar marks approximate location of Global Positioning System transect (Gan et al., 2000). GF— Garlock fault. Labeled faults of Eastern California shear zone: ALF— Airport Lake fault zone; OVF—Owens Valley fault zone; HMF—Hunter Mountain–Panamint Valley fault zone; DVF— Death Valley–Furnace
Creek fault zone; FLV— Fish Lake Valley fault zone.

• Here is the east west profile from Dixon et al. (2003). The horizontal axis is distance and the vertical axis is the rate that each site moves in mm per year. Their fault modeling is represented by the dark black line.




Global Positioning System velocity (triangles) and one standard error (bars) from Gan et al. (2000) compared to prediction of viscoelastic coupling model (heavy solid line), representing summed velocity contributions from four parallel faults (light dashed lines). SAF—San Andreas fault; DVF—Death Valley–Furnace Creek fault zone; HMF—Hunter Mountain–Panamint Valley fault zone; OVF—Owens Valley fault zone. Inset shows model rheology for Eastern California shear zone. SNB—Sierra Nevada block;B&R— Basin and Range Province; h is fault depth (depth of elastic layer) for three faults (a, b, or c), m is rigidity, h is viscosity. Arrows mark location of major shear-zone faults.

• Peltzer et al. (2001) use synthetic aperture radar interferometry (see my second update report for more on InSAR anslysis) to measure tectonic deformation that accumulated between 1992-2000.
• The Coso Geothermal Field is the rainbow area in the northernmost part of the map. Indian Wells Valley is the green area to the south of the Coso Field. This is an area of elevated strain. The Garlock fault is the ~east-west black line in the center of the white inset box.




Surface velocity map obtained by averaging 25 interferograms of Los Angeles–Mojave region. One color cycle depicts 10 mm/yr of surface displacement along radar line of sight (at lat N348; ERS [Earth Resource Satellite] descending track trends S13.68W, radar looking westward at 238 off vertical incidence angle in middle of imaged swath). Gray areas are zones of low phase coherence that have been masked in processing. Black lines are active faults (Jennings, 1975). White box indicates subset of synthetic aperture radar (SAR) data that was used for profile in Figure 4. Note conspicuous shear strain along San Andreas fault and shear zone parallel to Blackwater–Little Lake fault system. Large deformation signal in northwest corner of frame is ground subsidence related to Coso volcanic and geothermal field (Fig. 1). Surface displacement associated with 1994 and 1995 Ridgecrest earthquakes is visible south of Coso area. Other patterns of surface deformation include ground subsidence due to groundwater withdrawal in Los Angeles and Lancaster areas (Fig. 1) and to seasonal change of water table level around dry lakes.

• Peltzer et al. (2001) plot observations from their radar data showing relative plate motion associated with dislocation along the Blackwater-Little Lake fault system.




Profiles of observed and modeled line-of-sight displacement projected on vertical plane perpendicular to shear zone. Gray dots are individual data points for all radar-image pixels included in box shown in Figure 3. Solid line shows 2 km running mean of observed displacement along profile length. Note that apparent standard deviation of projected data relative to average profile reflects in part displacement gradient parallel to fault strike and not only error in data. Groups of dots that deviate from dense part of profile are due to ground subsidence near lake shores and to surface displacement associated with Ridgecrest earthquakes (Figs. 1, 3). Short-dash line is profile predicted by long-term velocity model used to estimate interferometric baseline (Shen et al., 1996). Long-dash line is profile predicted by velocity model, including additional buried dislocation along Blackwater–Little Lake fault system. Parameters of added fault are given in text. Black dots and error bars (2s) are line-of-sight projections of horizontal velocities observed by GPS at stations of Yucca transect (Gan et al., 2000).

Background Literature – Owens Valley fault

• Kylander-Clark et al. (2005) use the lateral offset of plutonic dikes (igneous rocks) to constrain a long term slip rate across the Owens Valley fault. This map shows one of the dike pairs used in their analysis. By knowing the age of these dieks, and the distance that they have been offset, we can obtain a slip rate.




Locations of the Golden Bear and Coso dikes, adjacent to Owens Valley. Main figure shows the Golden Bear and Coso dikes striking into the valley, where they intrude 102 Ma plutons. Both the dikes and the plutons provide distinctive markers that can be matched across the valley and are consistent with 65 km of dextral displacement since 84 Ma. Inset shows other markers across Owens Valley that earlier workers suggested indicate from 0 to 65 km of dextral offset across the valley. Also shown are the traces of the Tinemaha fault (Stevens et al., 1997; Stevens and Stone, 2002) and intrabatholithic break 3 (IBB3; Kistler, 1993), which are hypothesized to accommodate offset of these markers. Note that the section of IBB3 between 38°N and 36.5°N is correlative with the eastern intrabatholithic break (EIB) of Saleeby and Busby (1993). Not all known locations of Independence dikes are indicated. Instead, patterned areas show only the densest parts of the dike swarm as defi ned by Glazner et al. (2003). AR—Argus Range; CR—Coso Range; IR—Inyo Range; WM—White Mountains

• Bacon and Pezzopane used trench excavations across earthquake faults to construct a prehistoric earthquake history for the Owens Valley fault. Below is their tectonic map for the region.




(A) Map of major Quaternary faults in the northern Eastern California shear zone and southern and central Walker Lane, as well as the locations of the Owens Valley fault. Faults are modified from Reheis and Dixon (1996) and Wesnousky (2005)
(B) Generalized fault and geology map of south-central Owens Valley, showing the A.D. 1872 Owens Valley fault rupture and major fault zones in the valley (modified from Hollett et al. [1991] and Beanland and Clark [1994]).
(For fault abbreviations, see their paper.)

• This map shows a more detailed view of the Owens Valley fault and the Owens Lake topography (Bacon and Pezzopane, 2007).




Shaded relief map of southern Owens Valley showing fault zones and the ages of the most recent prominent highstands and recessional shorelines of Owens Lake during the latest Quaternary (modified from Bacon et al., 2006).

• This map shows the Bacon and Pezzopane (2007) field sites.




Map of the field area and locations of paleoseismic study sites in relation to the A.D. 1872 Owens Valley earthquake fault trace near Lone Pine. Study sites are located on the Alabama Hills (AHS), Diaz Lake (DLS), and Manzanar (MZS) sections of the Owens Valley fault zone mapped by Bryant (1988) and Beanland and Clark (1994) from 1:12,000 aerial photographs.

• An essential part of any earthquake fault investigation is knowledge about the geologic units that are offset by the fault. Bacon and Pezzopane (2007) also described and interpreted the sediment stratigraphy in southern Owens Valley as part of their research.




Schematic composite stratigraphic column. The generalized stratigraphic and geochronologic relations, developed from exposures at the Alabama Gates and Quaker paleoseismic sites and Owens River bluffs near Lone Pine (Bacon et al., 2006), show the positions of radiocarbon dates, sequence boundaries, and event chronologies as discussed in the text.

• The geologic method (McCalpin, 1996) is based on the offset of geologic materials like sedimentary deposits or bedrock lithologic units. Below are trench logs showing the geologic units that Bacon and Pezzopane (2007) use to infer an earthquake history. Geologic evidence is “primary” evidence for earthquakes.

• Here is a time series showing the sedimentary and earthquake history as interpreted by Bacon and Pezzopane (2007).




Schematic depiction of stratigraphy and structural relations at the Quaker paleoseismic site prior to the penultimate event and after the A.D. 1872 earthquake (depictions A–H). The stratigraphy and structure exposed in trench T5 (Fig. 7) was retrodeformed and reconstructed one event at a time (while also accounting for other stratigraphic and
paleoseismic relations exposed in adjacent fault trenches and stratigraphic pits). The locations of sequence boundaries (SB0–SB4) are shown and can be referenced on Figure 5.

• Haddon et al. (2013) compiled fault offset measurements and presented a summary here, showing the slip distribution along the fault (along strike). The measurements plotted below represent measurements of offsets of features as measured in high resolution LiDAR topographic data. They separate data into lateral offset (the amount of strike-slip relative motion) and throw offset (the amount of normal relative motion, from extension).
• We can see that the fault has both strike-slip and normal offsets, with strike-slip the dominant relative motion.




Compilation of small geomorphic offsets measured from lidar using LaDiCaoz_v2 along average OVF strike (3408) (supporting information Tables S2 and S3). Data include confidence ratings of low-moderate to high and omit net values determined by summing. Gray error bars show uncertainty limits determined visually from back-slipping. (a) The spatial distribution of OVF scarps (red lines) mapped from EarthScope lidar and classified by Owens Valley fault section (orange and black points), following previous mapping by Beanland and Clark [1994], Bryant [1984a, 1984b], and Slemmons et al. [2008]. Nearby faults are taken from the U.S. Geological Survey Quaternary fault and fold database. From south to north: DS, Dirty Socks; OL, Owens Lake; LP, Lone Pine fault; DL, Diaz Lake; IS, southern Independence; MF, Manzanar fault; I, Independence; T, Tinemaha; TW, western Tinemaha; FS, Fish Springs; BP, Big Pine; K, Keough section of Sierra Nevada frontal fault (SNNF), KLF, Klondike Lake fault; KSF, Klondike Springs fault; WMF, White Mountain fault. (b) Right-lateral offset measurements symbolized by fault section include previously reported values (orange diamonds) from Bateman [1961], Lubetkin and Clark [1988], Beanland and Clark [1994], Lee et al. [2001a], Zehfuss et al. [2001], and Slemmons et al. [2008]. (c) Along-strike compilation of measured vertical throw. Throw is predominantly east-down, with negative values indicative of downward motion to the west.

• This is a spectacular plot showing the along-strike variation in offset measurements.




Frequency distributions and cumulative offset probability density (COPD) plots for lateral and vertical offsets, compiled using bin sizes of 1 and 0.25 m, respectively (supporting information Tables S2 and S3). Histograms omit uncertainties, whereas COPD plots incorporate PDFs generated by the cross-correlation routine and truncated based on the range of uncertainty from back-slipping. Data are color-coded according to major sections of the OVF. (a) Scarps along the southern, central, and northern sections of the OVF relative to volcanic flows (purple) and a few representative elevation contours, generally corresponding to recognized pluviallacustrine features (#1–4) [Bacon et al., 2006; Jayko and Bacon, 2008; Bacon et al., 2013; Bacon et al., 2014]. Age estimates for features documented near (1) 1180 m, (2) 1162 m, (3) 1131 m, and (4) 1101 m are 160632 ka [Jayko and Bacon, 2008], 23,230–26,250 cal yr BP [Bacon et al., 2006], 15,870–16,230 cal yr BP [Bacon et al., 2014], and 300630 to 400630 yr BP [Bacon et al., 2013], respectively. Green points mark surface slip measurements based on geomorphic features. CM, Crater Mountain. Volcanic flows are from the California Geological Survey. (b–e) Optimum offset values for the southern (yellow), central (blue), and northern (red) sections are grouped and shaded by confidence rating. COPD plots use moderate to high confidence offsets and incorporate summed values.

• Here is the plot from Haddon et al. (2013) that shows a summary of their displacement measurements from the Owens Valley and Lone Pine faults. The lower panel shows these measurements combined.




Net 1872 surface slip derived from moderate to high confidence displacements plotted along subparallel strands. Gray bars reflect aggregated uncertainties from back-slipping of lidar imagery. (a) Along-strike compilation of displacement values for main traces of the OVF, as predicted by binned COPD plots. (b) Along-strike compilation of Lone Pine fault displacements. (c) Summed distributions (red lines) for possible net 1872 surface slip along a simplified
fault plane striking 3408 and dipping 808 northeast. The maximum implied displacement is between 7 and 11 m and reflects the average of four high values. The net slip averages 4.461.5 m based on a 5-km binned average that incorporates graphical values for gaps between higher confidence data.

• Here is their summary map showing slip rates for each of the faults used in their study (Haddon et al., 2013).




Compilation of reported slip rates in mm/yr on active faults in the southern Walker Lane (modified from Foy et al. [2012]) with rspect to the geodetic rate across the zone derived from the global positioning system and the relative motion of the Sierra Nevada– Great Valley microplate [Lifton et al., 2013]. Geologic slip rate studies, from south to north: Amos et al. [2013b], (this study), Oswald and Wesnousky [2002], Frankel et al. [2007a,b], Lubetkin and Clark [1988], Reheis and Sawyer [1997], Lee et al. [2001b], Ganev et al. [2010], Kirby et al. [2006], and Nagorsen-Rinke et al. [2013]. Faults listed alphabetically: AHF, Adobe Hills fault; ALF, Airport Lake fault; BMF, Black Mountain fault; DSF, Deep Springs fault; FCF, Furnace Creek fault; FLVF, Fish Lake Valley fault; HMF, Hunter Mountain fault; LLF, Little Lake fault; OVF, Owens Valley fault; NDVF, Northern Death Valley fault; PVF, Panamint Valley fault; QVF, Queen Valley fault; SAF, San Andreas fault; SNFF, Sierra Nevada frontal fault; SVF, Saline Valley fault; WMF, White Mountain fault.

• Dr. Steve Bacon was first infected with the quest for knowledge about the tectonics of the Owens Valley when he attended the 1997 Pacific Cell Friends of the Pleistocene field trip to Owens Valley. IF anyone has a scan of the 1997 Owens Valley guidebook, please contact me.
• Dr. Bacon chose to study the Owens Valley fault for his Masters Thesis work at Humboldt State University, Department of Geology. I was lucky enough to help him do some of this work as I was also attending HSU at the time. I also remembering how another researcher had failed to listed to Steve, yet they published a paper where they measured post-earthquake features as it they were offset during the earthquake. The peer review process is imperfect sometimes.
• Being a sediment stratigrapher, I appreciate the fact that the key preface to consducting a paleoseismic investigation is developing knowledge about the stratigraphy in the region. This was a major part of Dr. Bacon’s research. Please read more about his analysis of the lake level variations for the past 50,000 years in the Owens Lake in his recently published article (Bacon et al., 2020) listed in the references.
• Here is the Bacon et al. (2019) overview map that shows the spatial extent of the 1872 Owens Valley fault earthquake rupture.




Map of primary faults and rocks of the Big Pine volcanic field in south-central Owens Valley. The A.D. 1872 Owens Valley fault rupture and fault segments of the OVF and SNFF are shown (modified from Bacon and Pezzopane, 2007). Faults: CFF—Centennial Flat fault; KF—Keeler fault; ORF—Owens River fault; SFF—Sage Flat fault. Numbers show sites on OVF referred to in text of: 1—Kirby et al. (2008); 2—Lee et al. (2001); and 3—Bacon and Pezzopane (2007).

• Here is a map showing the detailed faults in the Owens Lake area, which is the focus of their study (Bacon et al., 2019). These authors used the geometric position of geomorphic features (like shorelines), along with numerical ages of those features (the time that they formed), to calculate long term slip rates for these faults.




Map of primary faults in Owens Lake basin and elevations of deformed shoreline features (∼1156–1166 m) used to estimate the magnitude of ground deformation and slip rates across faults in the lake basin. Faults are modified after Bacon et al. (2005) and Slemmons et al. (2008). Faults: CFF—Centennial Flat fault; COLF—Central Owens Lake fault; IMF—Inyo Mountains fault; KF—Keeler fault; ORF—Owens River fault; OVF—Owens Valley fault; SIMF—southern Inyo Mountains fault; and SNFF—Sierra Nevada frontal fault. The location of the Sage Flat fault (SFF) after Jayko (2009) and Amos et al. (2013a) is also shown. Plunging anticlines from Frankel et al. (2008). Reference elevation contours at 1096 and 1160 m represent the margin of Owens Lake playa and the approximate location of ca. 40.0 ka shoreline features, respectively. Modern sill is also shown relative to the 1160 m elevation that defines the overflow channel of the basin. Sediment lake core OL92 of Smith and Bischoff (1997) is shown relative to the depocenter area of the lake basin. Approximate location of transect for repeat leveling surveys near Lone Pine of Savage and Lisowski (1980, 1995) is also shown. K—town of Keeler; S—Swansea embayment; O—town of Olancha.

• This is a summary of fault characteristics as presented by Bacon et al. (2019). Dip-slip rate is the slip rate as measured up and down along the fault (in the direction that water would drip if it were placed on the fault). The extension rate is the slip rate measured horizontally in the same direction.

• Here is another map of the Owens Lake area, showing these slip rates and cross section locations for sections shown below (Bacon et al., 2019).




Generalized fault map of Owens Lake basin showing slip rates from this study and previous investigations. Faults: CFF—Centennial Flat fault; COLF—Central Owens Lake fault; IMF—Inyo Mountains fault; KF—Keeler fault; ORF—Owens River fault; OVF—Owens Valley fault; SFF—Sage Flat fault; SIMF—southern Inyo Mountains fault; SNFF—Sierra Nevada frontal fault. Extension direction at N72°E normal to Owens Valley is shown with geologic extension rate from this study and geodetic extension rates from trilateration networks in the valley (Savage and Lisowski, 1995) and GPS arrays across northern Owens Valley (Ganev et al., 2010a). The location of transects A–A′, B–B′, and C–C′ used in cross sections are shown. K—town of Keeler; S—Swansea embayment.

• Here are the cross sections showing the faults as these authors (Bacon et al., 2019) interpret their geometry in the subsurface.




Cross sections showing orientation of faults and sense of slip, and reconstructed water levels of the ca. 40 ka highstand pluvial lake in Owens Lake basin. Faults: CFF—Centennial Flat fault; COLF—Central Owens Lake fault; IMF—Inyo Mountains fault; KF—Keeler fault; ORF—Owens River fault; OVF—Owens Valley fault; SFF—Sage Flat fault; SIMF—southern Inyo Mountains fault; SNFF—Sierra Nevada frontal fault. Fault orientations are apparent dip based on fault strike across transects. Inferred locations of IMF and SIMF on transect A–A′ are from Pakiser et al. (1964) and Bacon et al. (2005).

• Here is a figure that shows a summary of their analysis (Bacon et al., 2019). Read the caption below to help yourself to understand this figure. It is complicated, but simple at the same time. Read their paper to learn more about this comprehensive and amazing research.




Plots showing the elevation of: (A) deformed ca. 40 ka shoreline features and lowstand beach ridge deposits, and (B) ca. 15 cal k.y. B.P. shorelines features and deformed fluvial-deltaic deposits. The elevation of shoreline features and deposits are projected onto transect B–B′ and shown in relation to the generalized location of faults in Owens Lake basin (Fig. 9). Magnitude of ground deformation shown is ∼10 m subsidence relative to the ca. 40 ka reconstructed water level (i.e., paleohorizontal datum) and ∼3.6 m fault separation on the Keeler fault of the ca. 40 ka beach ridge crests. The elevation and age of fluvial deltaic deposits on the hanging wall of the Owens Valley fault are from paleoseismic fault trench data (Bacon and Pezzopane, 2007). Faults: CFF—Centennial Flat fault; COLF— Central Owens Lake fault; KF—Keeler fault; ORF—Owens River fault; OVF—Owens Valley fault; SIMF—southern Inyo Mountains fault; NFF—Sierra Nevada frontal fault. Actual dips of faults are not shown. Vertical sense of slip is indicated by arrows. Lateral slip is indicated by crosses (away) and dots (toward). The elevation errors from GPS survey of shoreline features and deposits are less than width of symbols.

Background Literature – Earthquake History

• Here are the results of the paleoseismic (prehistoric earthquake history) investigation for the Owens Valley fault (Bacon and Pezzopane, 2007).




Fault segmentation and section map of central and southern Owens Valley showing overlap and possible distributive faulting and linkage between the northern segment of the Owens Valley fault (OVF) and southern White Mountains fault (WMF) near Big Pine. The trace of the A.D. Owens Valley fault rupture and section boundaries of Beanland and Clark (1994) and segment boundaries of dePolo et al. (1991) are shown in relation to the central and southern White Mountains fault and the location of the Black Mountain rupture of dePolo (1989). RRF—Red Ridge fault; LP—Lone Pine; I—Independence; BP—Big Pine; OSL—optically stimulated luminescence; PE—Penultimate event; APE—antepenultimate event; MRE—most recent event.

San Andreas plate boundary

General Overview

• 1906.04.18 M 7.9 San Francisco

Earthquake Reports

Northern CA

• 2017.12.14 M 4.3 Laytonville
• 2016.11.06 M 4.1 Laytonville, CA
• 2016.11.03 M 3.8 Laytonville, CA
• 2016.08.10 M 5.1 Lake Pillsbury, CA
• 2016.08.04 M 4.5 Honey Lake, CA
• 2015.08.30 M 3.6 Mendocino County, CA
• 2015.07.27 M 3.5 Point Arena, CA

Central CA

• 2018.07.30 M 3.7 San Pablo Bay
• 2018.01.04 M 4.4 Berkeley
• 1989.10.18 M 6.9 Loma Prieta

Southern CA

• 2020.06.24 M 5.8 Lone Pine
• 2019.07.04 M 6.4 Ridgecrest
• 2019.07.05 M 6.4 / 7.1 Ridgecrest Update #1
• 2019.07.18 M 6.4 / 7.1 Ridgecrest Update #2
• 2019.07.20 M 6.4 / 7.1 Ridgecrest Update #3
• 2019.06.05 M 4.3 San Clemente Island
• 2018.04.05 M 5.3 Channel Islands
• 2018.04.05 M 5.3 Channel Islands Update #1
• 2016.02.23 M 4.9 Bakersfield
• 2015.12.30 M 4.4 San Bernardino, CA
• 2015.05.03 M 3.8 Los Angeles, CA
• 2015.04.13 M 3.3 Los Angeles, CA
• 2014.04.01 M 5.1 La Habra p-3
• 2014.03.29 M 5.1 La Habra p-2
• 2014.03.28 M 5.1 La Habra p-1
• 1994.11.17 M 6.7 Northridge, CA
• 1971.02.09 M 6.7 Sylmar, CA

Social Media

#EarthquakeReport for M5.8 Owens Valley fault zone#Earthquake #Terremoto#Landslide #Liquefaction #Aftershocks

prob (?) related to static coulomb stress changes following #RidgecrestEarthquake Sequence
prob (?) not aftershock from 1872 M7.8-9 OVF EQhttps://t.co/Ux1s5W1Dph pic.twitter.com/KY22aJLFU4

— Jason "Jay" R. Patton (@patton_cascadia) June 28, 2020

Deslizamientos de Tierra en las Montañas de Lone Pine, tras Terremoto de M6.1 en California, #US. (24.06.2020). #Earthquake #Nevada #Owens #Alico #Keeler #MT #Whitney #Sismo #Temblor #Landslide #zabedrosky

By: Steven Wheeler ✓. pic.twitter.com/YdtWiOdjVF

— ⚠David de Zabedrosky🌎 (@deZabedrosky) June 24, 2020

https://t.co/KDLTpayYhr

— Jason "Jay" R. Patton (@patton_cascadia) June 24, 2020

The 2019 M 7.1 Ridgecrest earthquake struck 50 mi to the south of today's quake. Temblor's forecast (Toda & Stein, BSSA, in press) suggests that stress transfer from the Ridgecrest events primed Lone Pine, and other areas, for subsequent quakes. pic.twitter.com/KHDNsckIOb

— temblor (@temblor) June 24, 2020

pic.twitter.com/SyDYUzFbQB

— John Chrissinger (@JChrissinger) June 25, 2020

Auto solution FMNEAR (Géoazur/OCA) with regional records for the 2020-06-24 17:40:48.8 UTC M6.8 CENTRAL CALIFORNIA, USA (Loc EMSC used to trigger inversion).https://t.co/UHDsc1hVXA (not on mobile version)
Thanks to the seismic records provided by NCEDC, SCEC, and IRIS pic.twitter.com/wO6bKkbxwx

— Bertrand Delouis (@BertrandDelouis) June 24, 2020

When I got to the lower trailhead parking lot I saw this scar in the asphalt and an illegally parked boulder. “Something is *afoot*!”, I whispered to myself. #OwensLakeEarthqauke 4/ pic.twitter.com/1BeW9qEMOW

— Brian OLSON-19 (@mrbrianolson) June 25, 2020

Recent Earthquake Teachable Moment | M5.8 earthquake near Lone Pine, CA

IRIS Teachable Moments contains interpreted USGS regional tectonic maps and summaries, computer animations, seismograms, AP photos, and other event-specific information.https://t.co/GqGHSc2CA7 pic.twitter.com/zpQmFWHIvD

— IRIS Earthquake Sci (@IRIS_EPO) June 25, 2020

Amazing that there are no documented injuries or missing people following yesterday’s 5.8 magnitude quake and resulting rockslide at Whitney Portal.

Fingers crossed it stays that way. pic.twitter.com/4wm9ZCBxxP

— Jacob Margolis (@JacobMargolis) June 25, 2020

The 5 Hz GPS velocities from yesterdays M5.8 Lone Pine earthquake show good correspondence with the existing ShakeMap. The triangles are the nearby seismic sites. @UNAVCO pic.twitter.com/Vbz6JdLnTR

— Brendan Crowell (@bwcphd) June 25, 2020

Surface deformation revealed by Sentinel-1 interferogram of the Mw 5.8 #LonePine #earthquake . pic.twitter.com/N7AZLm0nwj

— Kang Wang (@kjellywang) June 27, 2020

M5.8 Lone Pine, CA (2020.06.24)https://t.co/SIueo6em6W
Sentinel Path 144 (2020.06.21-2020.06.27)
v1:
Centroid lon/lat:-117.975/ 36.488
Centroid depth (km): 13.24
Depth range (km): 7.98-18.5
Geodetic Mag: Mw5.8
Slip mag (m): 0.297
Str/Dip/Rake: 339/67/132
Len/Wid (km): 5.67/11.40 pic.twitter.com/qw3Ovjp1bO

— gCent (@gCentBulletin) June 27, 2020

The cumulative stress change caused by the 2019 Ridgecrest sequence (Mw6.4 and Mw7.1) show a positive stress loading (in red) on the Mw 5.8 Lone Pine earthquake (orange circle). pic.twitter.com/R1IuVUu2pN

— Jugurtha Kariche (@JkaricheKariche) June 25, 2020

Lone Pine is well worth the visit. And the 1872 event is memorialized there with a plaque in town and the group grave just north of town where 27 people who died in the quake were buried. pic.twitter.com/7m11lu98jw

— Dan Brekke (@danbrekke) June 24, 2020

Today's T64 #Sentinel1 interferograms for the M5.8 Lone Pine / Owens Lake Ca #earthquake were really bad – so let's stick to the first one (T144) from yesterday. 2-3cm of LOS ground displacement over Owens Lake area. #InSAR proc. at @esa_gep. Epicenters, faults & FM from USGS 1/2 pic.twitter.com/N9syXVzVm9

— Sotiris Valkaniotis (@SotisValkan) June 28, 2020

A 3D of the rock fall/debris location in the Lone Pine slope over Whitney Portal. #landslides triggered from the M5.8 June 24 earthquake. #Sentinel2 image from June 27 2020. pic.twitter.com/nt1bIqeWEm

— Sotiris Valkaniotis (@SotisValkan) June 28, 2020

References:

Basic & General References

• Frisch, W., Meschede, M., Blakey, R., 2011. Plate Tectonics, Springer-Verlag, London, 213 pp.
• Hayes, G., 2018, Slab2 – A Comprehensive Subduction Zone Geometry Model: U.S. Geological Survey data release, https://doi.org/10.5066/F7PV6JNV.
• Holt, W. E., C. Kreemer, A. J. Haines, L. Estey, C. Meertens, G. Blewitt, and D. Lavallee (2005), Project helps constrain continental dynamics and seismic hazards, Eos Trans. AGU, 86(41), 383–387, , https://doi.org/10.1029/2005EO410002. /li>
• Jessee, M.A.N., Hamburger, M. W., Allstadt, K., Wald, D. J., Robeson, S. M., Tanyas, H., et al. (2018). A global empirical model for near-real-time assessment of seismically induced landslides. Journal of Geophysical Research: Earth Surface, 123, 1835–1859. https://doi.org/10.1029/2017JF004494
• Kreemer, C., J. Haines, W. Holt, G. Blewitt, and D. Lavallee (2000), On the determination of a global strain rate model, Geophys. J. Int., 52(10), 765–770.
• Kreemer, C., W. E. Holt, and A. J. Haines (2003), An integrated global model of present-day plate motions and plate boundary deformation, Geophys. J. Int., 154(1), 8–34, , https://doi.org/10.1046/j.1365-246X.2003.01917.x.
• Kreemer, C., G. Blewitt, E.C. Klein, 2014. A geodetic plate motion and Global Strain Rate Model in Geochemistry, Geophysics, Geosystems, v. 15, p. 3849-3889, https://doi.org/10.1002/2014GC005407.
• Meyer, B., Saltus, R., Chulliat, a., 2017. EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) Version 3. National Centers for Environmental Information, NOAA. Model. https://doi.org/10.7289/V5H70CVX
• Müller, R.D., Sdrolias, M., Gaina, C. and Roest, W.R., 2008, Age spreading rates and spreading asymmetry of the world’s ocean crust in Geochemistry, Geophysics, Geosystems, 9, Q04006, https://doi.org/10.1029/2007GC001743
• Pagani,M. , J. Garcia-Pelaez, R. Gee, K. Johnson, V. Poggi, R. Styron, G. Weatherill, M. Simionato, D. Viganò, L. Danciu, D. Monelli (2018). Global Earthquake Model (GEM) Seismic Hazard Map (version 2018.1 – December 2018), DOI: 10.13117/GEM-GLOBAL-SEISMIC-HAZARD-MAP-2018.1
• Silva, V ., D Amo-Oduro, A Calderon, J Dabbeek, V Despotaki, L Martins, A Rao, M Simionato, D Viganò, C Yepes, A Acevedo, N Horspool, H Crowley, K Jaiswal, M Journeay, M Pittore, 2018. Global Earthquake Model (GEM) Seismic Risk Map (version 2018.1). https://doi.org/10.13117/GEM-GLOBAL-SEISMIC-RISK-MAP-2018.1
• Zhu, J., Baise, L. G., Thompson, E. M., 2017, An Updated Geospatial Liquefaction Model for Global Application, Bulletin of the Seismological Society of America, 107, p 1365-1385, https://doi.org/0.1785/0120160198

Specific References

• Amos, C.B., Bwonlee, S.J., Hood, D.H., Fisher, G.B., Bürgmann, R., Renne, P.R., and Jayko, A.S., 2013. Chronology of tectonic, geomorphic, and volcanic interactions and the tempo of fault slip near Little Lake, California in GSA Bulletin, v. 125, no. 7-8, https://doi.org/10.1130/B30803.1
• Astiz, L. and Allen, C.R., 1983. Seismicity of the Garlock Fault, California in BSSA v. 73, no. 6, p. 1721-1734
• Bacon, S.N. and Pezzopane, S.K., 2007. A 25,000-year record of earthquakes on the Owens Valley fault near Lone Pine, California: Implications for recurrence intervals, slip rates, and segmentation models in GSA Bulletin, v. 119, no. 7/8, p. 823-847, https://doi.org/10.1130/B25879.1
• Bacon, S.N., Bullard, T.F., Keen-Zebert, A.K., Jayko, A.S., and Decker, D.L., 2019. Spatiotemporal patterns of distributed slip in southern Owens Valley indicated by deformation of late Pleistocene shorelines, eastern California in GSA Bulletin, https://doi.org/10.1130/B35247.1
• Bason, S.N., Jaylo, A.S., Owen, L.A., Lindvall, S.C., Rhodes, E.J., Shumer, R.A., and Decker, D.L., 2010. A 50,000-year record of lake-level variations and overflow from Owens Lake, eastern California, USA in Quaternary Science Reviews, v. 238, https://doi.org/10.1016/j.quascirev.2020.106312
• Bakun, W.H., Ralph A. Haugerud, Margaret G. Hopper, Ruth S. Ludwin, 2002. The December 1872 Washington State Earthquake in BSSA, v. 92, no. 8., https://doi.org/10.1785/0120010274
• Brocher, T., Margaret G. Hopper, S.T. Ted Algermissen, David M. Perkins, Stanley R. Brockman, and Edouard P. Arnold, 2048. Aftershocks, Earthquake Effects, and the Location of the Large 14 December 1872 Earthquake near Entiat, Central Washington in BSSA, v. 108, no. 1., https://doi.org/10.1785/0120170224
• Chuang, R.Y. and Johnson, K.M., 2011. Reconciling geologic and geodetic model fault slip-rate discrepancies in Southern California: Consideration of nonsteady mantle flow and lower crustal fault creep in Geology, v. 39, no. 7, p. 627630, https://doi.org/10.1130/G32120.1
• Dawson, T. E., S. F. McGill, and T. K. Rockwell, Irregular recurrence of paleoearthquakes along the central Garlock fault near El Paso Peaks, California, J. Geophys. Res., 108(B7), 2356, https://doi.org/10.1029/2001JB001744, 2003.
• Dixon, T.H., Norabuena, E., and Hotaling, L., 2003. Paleoseismology and Global Positioning System: Earthquake-cycle effects and geodetic versus geologic fault slip rates in the Eastern California shear zone in Geology, v. 31, no. 1., p. 55-58,
• Frankel, K.L., Glazner, A.F., Kirby, E., Monastero, F.C., Strane, M.D., Oskin, M.E., Unruh, J.R., Walker, J.D., Anandakrishnan, S., Bartley, J.M., Coleman, D.S., Dolan, J.F., Finkel, R.C., Greene, D., Kylander-Clark, A., Morrero, S., Owen, L.A., and Phillips, F., 2008, Active tectonics of the eastern California shear zone, in Duebendorfer, E.M., and Smith, E.I., eds., Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada: Geological Society of America Field Guide 11, p. 43–81, doi: 10.1130/2008.fl d011(03).
• Frankel, K.L., Glazner, A.F., Kirby, E., Monastero, F.C., Strane, M.D., Oskin, M.E., Unruh, J.R., Walker, J.D., Anandakrishnan, S., Bartley, J.M., Coleman, D.S., Dolan, J.F., Finkel, R.C., Greene, D., Kylander-Clark, A., Morrero, S., Owen, L.A., and Phillips, F., 2008, Active tectonics of the eastern California shear zone, in Duebendorfer, E.M., and Smith, E.I., eds., Field Guide to Plutons, Volcanoes, Faults, Reefs, Dinosaurs, and Possible Glaciation in Selected Areas of Arizona, California, and Nevada: Geological Society of America Field Guide 11, p. 43–81, doi: 10.1130/2008.fl d011(03).
• Gan, W., Zhang, P., Shen, Z-K., Prescott, W.H., and Svarc, J.L., 2003. Initiation of deformation of the Eastern California Shear Zone: Constraints from Garlock fault geometry and GPS observations in GRL, v. 30, no. 10, https://doi.org/10.1029/2003GL017090
• Guest, B., Pavlis, T.L., Goldberg, H., and Serpa, L., 2003. Chasing the Garlock: A study of tectonic response to vertical axis rotation in Geology, v. 31, no. 6, p. 553-556
• Haddon, Elizabeth K.; Amos, Colin B.; Zielke, O.; Jayko, A. S.; and Bürgmann, R., “Surface Slip During Large Owens Valley Fault Earthquakes” (2016). Geology Faculty Publications. 99. https://cedar.wwu.edu/geology_facpubs/99
• Kylander-Clark, A.R.C., Coleman, D.S., Glazner, A.F., and Bartley, J.M., 2005. Evidence for 65 km of dextral slip across Owens Valley, California, since 83 Ma in GSA Bulletin, v. 117, no. 7/8, https://doi.org/10.1130/B25624.1
• Oskin, M. and Iriondo, A., 2004. Large-magnitude transient strain accumulation on the Blackwater fault, Eastern California shear zone in Geology, v. 32, no. 4, https://doi.org/10.1130/G20223.1
• Oskin, M., L. Perg, D. Blumentritt, S. Mukhopadhyay, and A. Iriondo, 2007. Slip rate of the Calico fault: Implications for geologic versus geodetic rate discrepancy in the Eastern California Shear Zone, J. Geophys. Res., v. 112, B03402, https://doi.org/10.1029/2006JB004451
• Oskin, M., Perg, L., Shelef, E., Strane, M., Gurney, E., Singer, B., and Zhang, X., 2008. Elevated shear zone loading rate during an earthquake cluster in eastern California in Geology, v. 36, no. 6, https://doi.org/10.1130/G24814A.1
• Peltzer, G., Crampe, F., Hensely, S., and Rosen, P., 2001. Transient strain accumulation and fault interaction in the Eastern California shear zone in geology, v. 29, no. 11
• Petersen, M.D. and Wesnousky, S.G., 1994. Review Fault Slip Rates and Earthquake Histories for Active Faults in Southern California in BSSA, v. 84, no. 5, p. 1608-1649
• Stein, R.S., Earthquake Conversations, Scientific American, vol. 288, 72-79, January issue, 2003. Republished in: Our Ever Changing Earth, Scientific American, Special Edition, v. 15 (2), 82-89, 2005.
• Toda, S., Stein, R. S., Richards-Dinger, K. & Bozkurt, S. Forecasting the evolution of seismicity in southern California: Animations built on earthquake stress transfer. J. Geophys. Res. 110, B05S16 (2005) https://doi.org/10.1029/2004JB003415

Return to the Earthquake Reports page.

• Sorted by Magnitude
• Sorted by Year
• Sorted by Day of the Year
• Sorted By Region

• Summary of Reports for the Ridgecrest Earthquake Sequence
The original Earthquake Report for this widely felt sequence is here.
The update #1 Earthquake Report for this widely felt sequence is here.
The update #2 Earthquake Report for this widely felt sequence is here.
The update #3 Earthquake Report for this widely felt sequence is here.

Well Well Well
Here is a commercial from Sony for Sony Discman following the 1995-96 Ridgecrest Earthquake (from which we have usurped this name for this July 2019 sequence).

The story continues to unfold.

• Here is a graphic from the USGS that summarizes our observations as of 16 July.

• The The Geotechnical Extreme Events Reconnaissance (GEER) Association report for the Ridgecrest Earthquake Sequence is now online.

Field Work Narrative

Last week I was lucky enough to spend a week in the field with my coworkers (California Geological Survey) and colleagues (U.S. Geological Survey) making observations of surface rupture from the Ridgecrest Earthquake Sequence (RES). It was initially termed the Searles Valley Earthquake Sequence, but we have since changed the name. Just check out #RidgecrestEarthquake on social media. Our work will be presented in several publications in the coming future. Stay tuned.
Many of us were granted rare access to the Naval Air Weapons Station China Lake. This emergency earthquake response effort was an unprecedented collaborative effort between the Navy, the CGS, and the USGS. We worked together as a team and accomplished our mission goals with due diligence. The CGS/USGS team is out in the field again this week, working off base. We plan to continue doing additional field work for weeks to come. (Though I need to get back to my tsunami stuff as we have deadlines to prepare new tsunami hazard products in the next few weeks to months.)
These collaborative efforts were based on a mutual respect between team agencies and team members. The field team members all appreciated the very special access we were granted. The commanding officer, Captain Paul Dale, is very supportive of scientific research and his support of our mission was evidence of this.
We were granted permission to take photos of the geologic evidence of the earthquake and ground shaking. We reviewed our images with the Public Affairs Officer to ensure that we did not take photos of any facilities or equipment that was on the base. This was important and we were very careful about this. We even double checked the images after we got back from the field.
I will add some photos to this page tomorrow.

Remote Sensing Narrative

There has also been a large number of Earth scientists using remote sensing data to evaluate the RES. These data are primarily from satellite images of different types (spectral imagery (another word for what we used to call air photos), RADAR, Global Positioning Systems (GPS), seismometer observations, etc.).
For most of these methods, pre-earthquake data are compared with post-earthquake data for a comparison. The methods used for these comparisons is advancing at a lightning pace. Every year, these models get better and better.
These remote sensing methods allow us to infer how the ground moved and slipped during and after the earthquake. We can get estimates of the slip on the fault from this type of analysis.
Combining different sources of remote sensing data also allows us to make estimates of the faults, where they moved, and how much they moved (in the subsurface).
I will present some of these observations below.

USGS Data Products

I prepared some interpretive posters for the M 7.1 earthquake shortly after it happened. The USGS earthquake pages are a source of great information as evidenced by how hard they are hit by web visitors following events as significant as the M 7.1. The website was unusable for periods of time. This demonstrates that the USGS is doing something right.
Last weekend, I spent Saturday preparing the same types of interpretive posters that I presented here, but as comparisons between the M 6.4 and M 7.1 temblors.

• Here is an updated seismicity map. There are two main types of earthquakes on this map. I present this map both with aerial imagery and with a topographic (“hillshade”) basemap. I outline the general area of Ridgecrest in purple.
1. First, there are an abundance of aftershocks aligned with the two main faults that ruptured during this sequence (the northwest trending M 7.1 fault and the northeast trending M 6.4 fault). Part of the northwest striking fault ruptured during the M 6.4 event.
2. Second, there are several areas that show earthquakes that were triggered by this sequence. There are some triggered earthquakes along the Coso Range (where the Coso Geothermal Field is located), some events along the Garlock fault, and some temblors along the Ash Hill fault (in Panamint Valley, to the north of Searles Valley).






• This is a seismicity comparison for the two earthquakes. on the left are earthquakes (USGS) from prior to the M 7.1 earthquake and on the right are quakes after and including the M 7.1 temblor. I plot the USGS Quaternary fault and fold database on the left as black lines.




• Here is a map with landslide probability on it. Please head over to that report for more information about the USGS Ground Failure products (landslides and liquefaction). Basically, earthquakes shake the ground and this ground shaking can cause landslides. We can see that there is a low probability for landslides. However, we have already seen photographic evidence for landslides and the lower limit for earthquake triggered landslides is magnitude M 5.5 (from Keefer 1984-ish).




• Here is a map showing liquefaction susceptibility. I explain more about this type of map in my original report for the M 6.4 earthquake. Scroll down a bit to find the landslide and liquefaction maps for that event.




• Finally, here is a map that shows the shaking intensity for the M 6.4 and M 7.1 earthquakes. As I mention in my original report, this is based on a model that relates earthquake shaking intensity with earthquake magnitude and distance from the earthquake. Note that there was violent shaking from the M 7.1 event (MMI IX).

NASA JPL ARIA Data Products

• NASA Jet Propulsion Laboratory (JPL) prepares Advanced Rapid Imaging and Analysis (ARIA) data products for major events worldwide. Their data are presented online here. I used the data from this event in a GIS computer program, but the data are prepared in Google Earth files too (so everyone can use them if they have a modern computer with an internet connection). This is a valuable government service.
• This first map shows the results of modeling Synthetic Aperture Radar Interferometry data. Basically, Radar satellite imagery data from before and from after the earthquake are compared to model the amount of ground deformation that occurred between the satellite acquisitions. Each color band represents a certain amount of motion. This is referred to as the wrapped image.
• Here are a series of sources of background information about InSAR analysis.
• Wikimedia
• Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics
• Geoscience Australia
• USGS
• Webinar for InSAR Analysis: NASA




• This map is made using the same basic data, though it has been processed in a way to show the overall ground motion with just two colors, instead of color bands. This is called the unwrapped image.




• Below is the first in a series of videos that explains more about SAR and InSAR analyses.

Dr. Sotiris Valkaniotis

• Dr. Valkaniotis is a Greek geologist who has a great set of remote sensing skills who studies earthquake geology and paleoseismology. I include lots of social media posts below where people share their analyses. However, I select two images from Dr. Valkaniotis for this earthquake. Contact him for more information about his processing. As embedded below in the social media section, here is the tweet that is the source of these two maps.
• These images are similar to the NASA JPL ARIA unwrapped maps above. I include his description below in blockquote.




Gradient render from unwrapped LOS displacement map (higher quality 20m from SNAP). Surface ruptures (major & minor) are easily visible as dark linear features (high displacement gradient). Processing in @esa_gep. Descending pair from #Sentinel1, #Ridgecrestearthquake




And the ascending pair from #Sentinel1, #Ridgecrestearthquake. Gradient render from unwrapped LOS displacement map (higher quality 20m from SNAP). Processing in @esa_gep.

• Here is a map that Dr. Valkaniotis prepared showing fault lines he has interpreted from his model results.




Complex and detailed pattern of co-seismic ruptures for the #RidgecrestEarthquake sequence. Red lines are primary & secondary surface ruptures, together with small triggered ruptures away from main faults. Previously mapped Quaternary Faults with yellow, for comparison.

PBS News Hour: 2019.07.08

Death Valley at Devil’s Hole

The clip shows water violently sloshing around, rising and falling 10 to 15 feet, according to a park estimate. The video captures two angles, one looking into the cave and the other underwater inside it.
Devils Hole is a part of the desert uplands and spring-fed oases that make up the Ash Meadows complex, a national wildlife refuge.

Temblor Articles

Ross Stein (Ph.D.), Volkan Sevilgan (M.Sc.), Tiegan Hobbs (Ph.D.), Chris Rollins (Ph.D.), Geoffrey Ely, (Ph.D.), and Shinji Toda (Ph.D.) are coauthors to a suite of 5 articles presented on Temblor.net. Temblor is a National Science Foundation funded organization that promotes earthquake insurance and seismic retrofits for people in earthquake country. I wrote several articles for Temblor prior to starting work at the California Geological Survey. (My efforts at earthjay.com are purely volunteer and do not reflect endorsement nor review from or by CGS.)
These reports are excellent sources of interpretive information at the detail for non experts (sometimes my reports are at a detail more aimed towards undergraduate geology students, though I attempt to make them available to a broad audience as well). I include a few figures from their reports that I find most interesting, but please check out their articles for more information!

• Dr. Stein begins by presenting an hypothesis that these earthquakes are in a region of increased tectonic stress following the 1872 Owens Valley Earthquake, estimated to have a magnitude of M 7.6 (though it happened prior to modern seismometer instrumentation, so magnitude estimates have considerable uncertainty).
• When earthquake faults slip, the surrounding crust is squished and squashed. This deformation changes the tectonic stresses in the crust. In some places this change causes an increase in the amount of stress on earthquake faults and in some places it decreases the tectonic stress. In places where the stress increases, the fault is brought closer to having an earthquake, and vice versa for places where the stress is diminished.
• These stress changes are very small, so for a fault to be triggered by these changes in “static coulomb stress,” the fault had to be almost ready to slip before these changes happened. More can be found in Stein (2003) and Toda et al. (2005) linked below in the references.
• In the map below, warm colors represent areas with an increase in (static coulomb stress) and cool colors represent a decrease in stress. I include their figure caption in blockquote below the figure (as for all their figures).




he site of the July 4th shock was likely brought closer to failure in the 1872 M~7.6 shock. Notice that the (red) stress trigger zones of the this 148-year-old quake are all seismically active today, whereas the (blue) stress shadows are generally devoid of shocks.

• The Owens Valley fault triggering is speculative of course, since that earthquake was so long ago. However, there are other cases where aftershocks or triggered earthquakes are happening a long time after the main event. For example, there are ongoing aftershocks following an 1872 earthquake near Lake Chelan (Bakun et al., 2002; Brocher et al., 2018).
• Stein and his colleagues calculated “static coulomb” stress changes imparted by the Ridgecrest Earthquake Sequence onto a series of other faults in the area. Read more about their analyses here.




Here we calculate stress transferred to the principal mapped faults, using the USGS slip model for the 7.1 and a model based on University of Nevada Reno GPS displacements for the 6.4 (not shown here for simplicity, but included). Most of the stress change is from the 7.1: it was several times larger than the 6.4 and torqued the surrounding crust far more. This fault inventory might be woefully incomplete, of course: the 7.1 itself struck on an unmapped fault. Nevertheless, the most striking result is the >2-bar stress increase on a 30-km (20-mile) section of the Garlock Fault. An end-to-end rupture on the Garlock, if (still) possible, would be in the magnitude 7.6-7.8 range.

• In my interpretive posters above, I mention the areas where there have been triggered earthquakes (e.g. the Coso Geothermal Field, the Garlock fault, the Ash Hill fault). Turns out, Stein and his colleagues were thinking the same thing.
• They prepared a figure in their report here where they show changes in “static coulomb” stress. They label the same areas I mention (except the Ash Hill fault in Panamint Valley). Take a look at the areas of increased stress compared to these three regions (even the Ash Hill fault is in an area of increased stress).




Faults in the red lobes are calculated to be brought closer to failure; those in the blue ‘stress shadows’ are inhibited from failure. The calculation estimates what the dominant fault orientations are around the earthquakes by interpolating between major mapped faults (shown in red lines). So, we would expect strong stressing in the Coso Volcanic Field to the north (where the aftershocks lie), and along the Garlock Fault to the south (but not where most of them lie).

• Hobbs and Rollins speculate that the San Andreas fault may also have changes in (static coulomb) stress imparted by the Garlock fault if that were to slip. Read more in their article here.




If the western and central Garlock were to rupture, it would load the section of the San Andreas just north of Los Angeles. The jog in the San Andreas under the S in “Source” is at Palmdale. Figure from McAuliffe et al. [2013].

	2019.07.04 Southern California M 6.4 earthquake stressed by two large historic ruptures
	2019.07.05 Earthquake early warning system challenged by the largest SoCal shock in 20 years
	2019.07.06 Magnitude 7.1 earthquake rips northwest from the M6.4 just 34 hours later
	2019.07.06 M 7.1 SoCal earthquake triggers aftershocks up to 100 mi away: What’s next?
	2019.07.09 The Ridgecrest earthquakes: Torn ground, nested foreshocks, Garlock shocks, and Temblor’s forecast

• Here are the references for these Temblor articles.
• Stein, R. S., and Sevilgen, V., (2019), Southern California M 6.4 earthquake stressed by two large historic ruptures, Temblor, http://doi.org/10.32858/temblor.034
• Hobbs, T.E. and Rollins, C., (2019), Earthquake early warning system challenged by the largest SoCal shock in 20 years, Temblor, http://doi.org/10.32858/temblor.035
• Ross S. Stein, Tiegan Hobbs, Chris Rollins, Geoffrey Ely, Volkan Sevilgen, and Shinji Toda, (2019), Magnitude 7.1 earthquake rips northwest from the M6.4 just 34 hours later, Temblor, http://doi.org/10.32858/temblor.037
• Ross S. Stein, Chris Rollins, Volkan Sevilgen, and Tiegan Hobbs, (2019), M 7.1 SoCal earthquake triggers aftershocks up to 100 mi away: What’s next?, Temblor, http://doi.org/10.32858/temblor.038
• Chris Rollins, Ross S. Stein, Guoqing Lin, and Deborah Kilb (2019), The Ridgecrest earthquakes: Torn ground, nested foreshocks, Garlock shocks, and Temblor’s forecast, Temblor, http://doi.org/10.32858/temblor.039

Field Photos

• Below are some field photos I took. I cannot tell anyone where they were taken (at least not yet) as we don’t have clearance. I may post more later, but wanted to post some to show people the type of observations we were making.
• This is Dr. Chris DuRoss (USGS) as we walked across the scarp at our first site working together.




• Here is a great one of Dr. Jessie T. Jobe (USGS, soon to be USBR) taking notes at that same scarp (DuRoss’ boots for scale).




• This is a portion of a road where the fault crossed. There were several dm of lateral offset on either side of the road, but the road itself had an imperceptible amount of lateral offset (i.e. 1 ± 1 cm offset). There was some amount of compression here.




• Here we were projecting the ground surface across the fault to estimate the amount of vertical displacement. Dr. Ryan Gold (USGS) is measuring while a Navy Base geologist is holding the profile stick along the ground surface.




• Here is a photo very similar to Mr. Brian Olson’s tweeted photo, but I took this one instead. Dr. Belle Philibosian (USGS) is on the left and Kelly (NAWCL geologist) is on the right. This shows right-lateral strike-slip displacement of 420 cm. We thought nobody would believe us, so we made another measurement nearby to confirm.




• I located some beautiful slickenlines (grooves in the fault surface created when the fault slips) and this is Dr. Beth Haddon (USGS) collecting strike, dip and rake data for these lines. We collected many photos of this site so that we can create a 3-D model (using structure from motion).




• Here is Dr. Belle Philibosian looking spectacular as usual, providing scale to help us understand the amount of vertical separation across the fault in this location.




• We located some evidence for liquefaction too. Here is a sand volcano, where lots of the sediment got washed away by the fluid that possibly shot up through this hole.




• This was a great opportunity to show the compass orientation of these conjugate fault offsets in the road. The road material properties probably controlled the location of the faults here (there were pre-existing planes of weakness as evidenced by the tar patches, but some of the pavement faulting was new).

San Andreas fault

General Overview

• 1906.04.18 M 7.9 San Francisco

Earthquake Reports

Northern CA

• 2017.12.14 M 4.3 Laytonville
• 2016.11.06 M 4.1 Laytonville, CA
• 2016.11.03 M 3.8 Laytonville, CA
• 2016.08.10 M 5.1 Lake Pillsbury, CA
• 2015.08.30 M 3.6 Mendocino County, CA
• 2015.07.27 M 3.5 Point Arena, CA

Central CA

• 2018.07.30 M 3.7 San Pablo Bay
• 2018.01.04 M 4.4 Berkeley

Southern CA

• 2019.07.04 M 6.4 Ridgecrest
• 2019.07.05 M 6.4 / 7.1 Ridgecrest Update #1
• 2019.07.18 M 6.4 / 7.1 Ridgecrest Update #2
• 2019.07.20 M 6.4 / 7.1 Ridgecrest Update #3
• 2016.02.23 M 4.9 Bakersfield
• 2015.12.30 M 4.4 San Bernardino, CA
• 2015.05.03 M 3.8 Los Angeles, CA
• 2015.04.13 M 3.3 Los Angeles, CA
• 2014.04.01 M 5.1 La Habra p-3
• 2014.03.29 M 5.1 La Habra p-2
• 2014.03.28 M 5.1 La Habra p-1

Eastern CA

• 2016.08.04 M 4.5 Honey Lake, CA

Southern CA

Earthquake Reports

• 2019.06.05 M 4.3 San Clemente Island
• 2018.04.05 M 5.3 Channel Islands
• 2018.04.05 M 5.3 Channel Islands Update #1
• 1994.11.17 M 6.7 Northridge, CA
• 1971.02.09 M 6.7 Sylmar, CA

Social Media

Here's some context for the M7.1 #earthquake today in California and its foreshock/aftershock sequence. It is well off the San Andreas Fault and north of the Garlock fault in the Eastern California Shear Zone. Read more from @Temblor about this area here: https://t.co/thInzw8ghF pic.twitter.com/NpLvDpyn1y

— Dr. Kasey Aderhold (@kaseyaderhold) July 6, 2019

SLIPNEAR model along the aftershocks of the M6.4 mainshock. Slip inversion carried out with 2 different fault planes, one SE dipping (strike 45) from FMNEAR, and the other NW dipping from GCMT (strike 228). Slip distribution is quite similar in both cases (main slip zone stable) pic.twitter.com/gegZ9BSqR9

— Bertrand Delouis (@BertrandDelouis) July 7, 2019

Cumulative stress change caused by 4 July 2019 M=6.4 and the 7 July 2019 M=7.1 earthquakes on nearby strike slip faults, the red color represents increase seismic hazard Dr Kariche@IPGS2019 #RidgecrestEarthquake @DrLucyJones pic.twitter.com/jpGfqKhdzD

— Jugurtha Kariche (@JkaricheKariche) July 7, 2019

Pixel tracking of @Planetlabs satellite images reveals the northern termination of the Mw 7.1 July 5th #earthquake. Result shows only ~16 km of rupture, with a minor transtensional splay in lower right. Slip profile, exhibits classic ‘dogtail’ taper. pic.twitter.com/S5CfsKd5AP

— Chris Milliner (@Geo_GIF) July 7, 2019

A complete image of the Mw 7.1 Ridgecrest #earthquake showing amount of surface displacement measured by @planetlabs satellite imagery. Rupture is ~40 km in length with up to ~5m of fault slip. Fault trace has remarkably similar rupture geometry to 1999 Mw 7.1 Hector Mine event. pic.twitter.com/ORBA5D0gKz

— Chris Milliner (@Geo_GIF) July 8, 2019

Came across this sandy vegetation mound out on the China Lake bed, which was cut in half by the fault rupture. Measured offset is approximately 8 feet. #earthquake #Ridgecrest pic.twitter.com/ok95QmfZQ8

— Brian Olson (@mrbrianolson) July 8, 2019

Estimated preliminary extent of the main rupture of Mw7.1 #earthquake #Ridgecrest CA, combining surface rupture traces from @CATnewsDE and @Geo_GIF (traced on @planetlabs imagery). Main rupture (red) extends at >45km. Black dots: reviewed epicenters USGS. Quaternary Faults: USGS. pic.twitter.com/Yq68sg86ub

— Sotiris Valkaniotis (@SotisValkan) July 8, 2019

Great day mapping. Even made a 2 second cameo on PBS News hour. ;)
@patton_cascadia@FaultyAndSalty#RidgecrestEarthquake https://t.co/kkDR4WP2ib

— Nick Graehl (@nickgraehl) July 9, 2019

As promised, here are pictures of formerly high-speed dirt and environs! Enjoy these annotated photos from our recon mapping with J. Dolan and S. Attia yesterday of the Searles Valley EQ seq. near Ridgecrest, CA. Please contact me for more photos and information-ahatem@usc.edu pic.twitter.com/jZSIEaJuZY

— Alex Hatem (@pride_of_lowell) July 9, 2019

A few more! pic.twitter.com/OckTe5LSx7

— Alex Hatem (@pride_of_lowell) July 9, 2019

OK, this really is the last one. The M6.4 earthquake strikes almost perpendicular to the track direction, and shows a deformation pattern that is more symmetric. We are mostly seeing the E-W movement of the fault in this case.

[Thanks to @JAXA_en for a great radar satellite!] pic.twitter.com/joFeJ5tURk

— Gareth Funning (@gfun) July 9, 2019

#RidgecrestQuake from Space

This colorful map shows surface changes from the two earthquakes that rattled California last week. More here: https://t.co/qnj4B8zJm8 pic.twitter.com/w44MXwd3xL

— NASA JPL (@NASAJPL) July 9, 2019

Some photos from today…#RidgecrestEarthquake pic.twitter.com/x5HrsdpJc6

— Nick Graehl (@nickgraehl) July 9, 2019

Surface rupture & displacement from the Mw 7.1 #Ridgecrest #earthquake CA as seen from #Sentinel2 images from @CopernicusEU. Animation using June 28 and July 8 images. Optical correlation map to follow later. pic.twitter.com/4cW0ovSIcM

— Sotiris Valkaniotis (@SotisValkan) July 9, 2019

Quake ripped right through the flattest parts of the basin with maybe a little compression ridge in the southern stepover pic.twitter.com/NnSmKa3kSv

— Bill Barnhart (@HawkeyeSeismo) July 9, 2019

It was a boots on the ground kind of day for CGS and USGS. Today we focused on measuring fault rupture offsets on the China Lake NAWS base #faultmapping #earthquake #Ridgecrest @CalConservation pic.twitter.com/L2PTZZF3ed

— Ellie Spangler (@EllieSpangler) July 9, 2019

Data available; high-resolution figures and raster files for subpixel co-seismic offsets for the Mw6.4 and Mw7.1 #Ridgecrest, California #earthquakes, using #Sentinel2 images. #MicMac and CosiCorr files. Files uploaded in Zenodo repository: https://t.co/l10csPV4n7 pic.twitter.com/1MQIeeEzFj

— Sotiris Valkaniotis (@SotisValkan) July 9, 2019

More from our #RidgecrestEarthquake coverage: DOC Drone footage south of Ransberg Road captures surface rupture. Photo: Roadway surface displacement – right-lateral offset approx. 6.5 ft and 3' vertical. Offset bottom of pic 5' ~ Footage: Nathaniel Roth. Photo: @mrbrianolson pic.twitter.com/6kDX8Tcc1e

— DeptofConservation (@CalConservation) July 10, 2019

Surface fault ruptures from the July 4th Mw6.4 #Ridgecrest #earthquake visible using #Sentinel2 optical (normalized difference – Band4) and #Sentinel1 interferogram (made with SNAP at @esa_gep). Multiple traces, marked with orange arrows pic.twitter.com/70ePXUsiQD

— Sotiris Valkaniotis (@SotisValkan) July 10, 2019

The Ridgecrest earthquakes: Torn ground, nested foreshocks, Garlock shocks, and Temblor’s forecast | https://t.co/1twVj9F84q https://t.co/x6aHPj0Az0 via #NSFfunded @temblor #California #Earthquake

— temblor (@temblor) July 10, 2019

Azimuth phase gradient map, Range phase gradient map, Zoom in of range phase gradient map. It is filled with cracks!!!! #RidgecrestEarthquake pic.twitter.com/pJ5ydG5xR0

— Xiaohua Xu (@XiaohuaXu1) July 10, 2019

#Ridgecrest #Trona #earthquakes
M≥2.0 2019-07-04>2019-07-10-09h https://t.co/sRUqn89xEO relocations w/ station corrections, over ALOS-2/JAXA/@NASAJPL-ARIA interferogram https://t.co/NpRQTwvQn8
Events colored by origin time before & after M7 mainshock (left), & by depth (right) pic.twitter.com/GnOO4kYR0K

— Anthony Lomax 🌍🇪🇺 (@ALomaxNet) July 10, 2019

Track 64 interferogram from Sentinel-1 data acquired by @esa. Remind me of the Hector Mine interferogram. #RidgecrestEarthquake #ridgecrestearthquakes pic.twitter.com/oqDQa5qC6e

— Xiaohua Xu (@XiaohuaXu1) July 10, 2019

Following #Ridgecrest earthquake, @NASAJPL ARIA ALOS-2 interferogram, appears to show very small triggered slip on the Garlock fault. Bottom shows USGS Quaternary fault trace. pic.twitter.com/kppDaIkpsD

— Chris Milliner (@Geo_GIF) July 9, 2019

I saw some spectacular faulting while putting in extra seismometers around Ridgecrest. pic.twitter.com/aOXz9aaNnY

— Elizabeth Cochran (@escochran) July 10, 2019

Ken Hudnut (USGS), along w/partners Bob Fenton (FEMA Region IX Admin.) and Mark Ghilarducci (Director of CalOES) briefed @VP about the M7.1 earthquake that struck CA on July 5, 2019. Emphasis was placed upon coordination between CGS, USGS and @USNavy. https://t.co/suTpYkbe5z pic.twitter.com/lrSXC04T8W

— USGS (@USGS) July 11, 2019

A preliminary semi-realistic finite element model of M6.9 Ridgecrest EQ, with fault curvature following pixel-tracked trace, CVM-H tomography, topography. Vertical fault is set for this stage. Green's function library on its way. @SotisValkan @chandraphyctc @shirzaei @ratlab3 pic.twitter.com/WSd9520fiT

— Jay Tung (@jaytung_earth) July 11, 2019

Thanks to incoming InSAR images covering the complete rupture (below ALOS-2 interferogram from the @NASAJPL ARIA project), the information value provided by previous rapid slip inversions using strong motion data (SLIPNEAR) can be evaluated: pic.twitter.com/KDTC45kKuP

— Bertrand Delouis (@BertrandDelouis) July 10, 2019

Map of permanent ground displacement due to M6.4 and M7.1 earthquakes near Ridgecrest California from NASA Caltech-JPL ARIA processing of JAXA ALOS-2 (unwrapped interferogram, path 65). This InSAR sensitive to west and up motion of ground. @zross_ relocated main and aftershocks pic.twitter.com/CuGtOv78nB

— Eric Fielding (@EricFielding) July 10, 2019

Our Automatic Sentinel1 processing of co-seismic interferogram for the California Earthquakes with Mw. 7.1 and Mw 6.4 (Interferogram and LOS Displacement map) using #Sentinel1 @ESA_EO @CopernicusEU Track 64 (20190704-20190710) #IREA #CNR @FraxInSAR @claudiodeluca @VDN75 pic.twitter.com/ruGHFoQ0pv

— Fernando Monterroso (@maferp_13) July 10, 2019

Left lateral faulting #SoCalEarthquake #drone #Ridgecrest #California pic.twitter.com/7QHGGXGm7G

— Forrest Lanning (@rabidmarmot) July 11, 2019

#Sentinel2 mapped co-seismic #fault traces from the #Ridgecrest CA #earthquakes. While Sentinel-2 (Band 4 normalized difference) offers extravagant detail at certain parts, is missing traces in other areas. Interesting when in comparison with other sensors/methods & field. pic.twitter.com/VCb8ghN8WM

— Sotiris Valkaniotis (@SotisValkan) July 11, 2019

My first look at #RidgecrestEarthquake rupture on Tues and first tweet ever!! pic.twitter.com/QFOpokctQR

— Stephen Angster (@faultjumper) July 11, 2019

Found our BIGGEST offset yet for the fault that caused the M7.1 earthquake. This channel is offset about 13 feet! #ridgecrestearthquake #earthquake #ridgecrest pic.twitter.com/EQCh3Z9DBj

— Brian Olson (@mrbrianolson) July 12, 2019

An amazing week working with colleagues from @CalConservation California Geological Survey and the @usgs mapping ruptures from the earthquakes in Ridgecrest. Thanks to the residents who have been welcoming and the @USNavy for incredible logistical support. #ridgecrestearthquakes pic.twitter.com/Yqs8yAZtLY

— Tim Dawson (@timblor) July 12, 2019

This animation shows preliminary results from precise relocation of the Ridgecrest foreshock sequence, up to the the time of occurrence of the M 7.1 mainshock. Full details at: https://t.co/Gm3GuSPt0s pic.twitter.com/RfIijTiHfu

— USGS (@USGS) July 12, 2019

A very preliminary fault slip model for #RidgecrestEarthquake, using data from GPS, @esa Sentinel-1, @ALOS2_JAXA, optical imagery from @planetlabs by @Geo_GIF. Model, surface displacement and Coulomb stress available at https://t.co/SSyQaHdJYh. pic.twitter.com/TZ8PQop7cZ

— Xiaohua Xu (@XiaohuaXu1) July 12, 2019

CGS and USGS teams mapped fault offsets that were an order of magnitude less than yesterday’s, but in someways much cleaner to measure. Here is a shrub dune left-laterally offset 30 cm by the July 4 M 6.4 pic.twitter.com/F7UH6f82An

— Tim Dawson (@timblor) July 13, 2019

Updated rupture map of #Ridgecrest earthquake. Faults mapped from @Planetlabs offsets, and Sentinel-1 wrapped and phase gradient. Juncture of Mw 6.4 and 7.1 is highly complex.

Green = primary fault rupture
Red = secondary faults
Blue dots = aftershocks (SCSN) pic.twitter.com/N3TSO02GYA

— Chris Milliner (@Geo_GIF) July 12, 2019


This one woke me up:

Today's M4.9 aftershock was recorded by a temporary seismometer at ~2 km epicentral distance. It recorded a peak acceleration of 14%g. Intensities in Ridgecrest imply accelerations in the same range, or maybe even higher locally. This illustrates an important point. pic.twitter.com/ruefagOhdT

— Susan Hough (@SeismoSue) July 13, 2019

Headed home after a week working on response to #RidgecrestEarthquake. Impressive effort by all involved from #USGS #CGS #UNR #EERI and many more. A few of my favorite photos: ~4 m offset dirt road, 108F temps, central part of M7.1 rupture with @timblor and @chrisduross for scale pic.twitter.com/B8fIfaNxti

— Ryan Gold (@runr447) July 13, 2019

'NASA's ARIA Team Maps California Quake Damage' news article from the #NASA_App ⁦@NASAJPL⁩ https://t.co/Kyk34SmN6q

— Eric Fielding (@EricFielding) July 13, 2019

Growing evidence for Garlock fault having very small triggered slip. Both ALOS-2 wrapped phase and Sentinel 1 aziumuthal gradient map show small slip for ~35 km alongfault. @XiaohuaXu1 pic.twitter.com/bKSbGmWO9U

— Chris Milliner (@Geo_GIF) July 10, 2019

This @UNVACO map shows how GPS stations moved from just before to just after the #RidgecrestEarthquake. The arrows show the direction & size of motion. This represents how much the ground moved at each site. The scale arrow in the lower left represents 100 mm, or 10 cm (~4 in). pic.twitter.com/tQzvNGugms

— IRIS Earthquake Sci (@IRIS_EPO) July 8, 2019

The possible fault sources of the #ridgecrestearthquake by analytical solution combining #sentinel1 #sentinel2 @UNAVCO gps and @USGS faultlines data.
The path has just begun.@SimoneAtzori73 @maferp_13 @FraxInSAR @EugenioSansosti pic.twitter.com/F34nIjfZKL

— Vincenzo De Novellis (@VDN75) July 13, 2019

Ground deformation after #Ridgecrest earthquake using #Sentinel1 ascending dataset. #RidgecrestEarthquake #RIKEN #RIKEN_AIP #Earthquake #Deformation pic.twitter.com/EFQadAoaZ7

— Sadra Karimzadeh (@Sadra_Krmz) July 13, 2019

Why historical seismology? Some years ago @Kate6HTN and I wrote a paper on the 1872 Owens Valley earthquake, presenting evidence that the rupture continued south of Lone Pine, to Haiwee. pic.twitter.com/VNND3HfniX

— Susan Hough (@SeismoSue) July 14, 2019

"Scientists from the USGS and other organizations continue field work and analyses". Here is a release of the surface rupture map:https://t.co/cC53bdzEQZ pic.twitter.com/tS3p5t9c6z

— Stéphane Baize (@stef92320) July 13, 2019

More results using @ALOS2_JAXA data available on https://t.co/SSyQaHdJYh . What really needed is the other look direction. Waiting for 16th Sentinel-1. Also check out the north west corner. That's central valley going down. pic.twitter.com/419xh9uJQi

— Xiaohua Xu (@XiaohuaXu1) July 14, 2019

Here it is. With @YorgosBz and @ESM_db we've been looking at the (possibly) impulsive features of ground motions from the #californiaearthquake, as identified by Baker's 2007 algorithm. Polygon is source projection, E is epicenter. (Note: just preliminary, no conclusions yet.) pic.twitter.com/4vucfl8nuV

— iunio iervolino (@iuniervo) July 14, 2019

Last 12 days on a seismogram ~15km S of #Ridgecrest showing:#Ridgecrest #Trona #earthquake
M6.4 2019-07-04 (green)
M7 2019-07-06 (black)
…and many, many aftershocks#Australia
M6.6 2019-07-14 (blue, lower left, 06h)#Indonesia
M7.3 2019-07-14 (blue, lower right) pic.twitter.com/vxnqPB8zd6

— Anthony Lomax 🌍🇪🇺 (@ALomaxNet) July 15, 2019

Many are asking *why* Ridgecrest didn't suffer more damage from the M7.1 earthquake. I noticed the peak ground accelerations measured IN Ridgecrest were actually LESS for the M7.1 despite it releasing 11x more energy. pic.twitter.com/UyUGVYyNh0

— Brian Olson (@mrbrianolson) July 15, 2019

Wanted to say I was honored to join the team collecting location & offset data from recent Ridgecrest earthquakes. From huddling under tables w/ @kwhudnut & @earthquakemom during the M7.1 to sweating profusely on the dry lake bed, I valued all of it. #TeamCGS #TeamUSGS pic.twitter.com/Yxzf8yrQ15

— Brian Olson (@mrbrianolson) July 14, 2019

Another preliminary fault slip model for #RidgecrestEarthquake, using data from @esa #Sentinel1 and @UNAVCO GPS. @USGS faultlines (black) & @IRIS_EPO earthquakes distribution (red) are also shown; the darkest blue corresponds to ~5.5 m slip value.@SimoneAtzori73 @EricFielding pic.twitter.com/gSTzlTDD4X

— Vincenzo De Novellis (@VDN75) July 15, 2019

Well, at AGU it is going to be called:
"S041 – The 2019 M6.4 Searles Valley and M7.1 Ridgecrest Earthquakes"
Some improvement…https://t.co/adGovA3GyP

— Anthony Lomax 🌍🇪🇺 (@ALomaxNet) July 16, 2019

Another phase gradient image from the M7.1 Hector Mine Earthquake. Not as many conjugate fractures as the M7.1 in Ridgecrest. pic.twitter.com/pwTr8vEIlI

— David Sandwell (@sandwell_david) July 14, 2019

And it's official, or very close to it: the earthquake sequence formerly known as Searles Valley will henceforth be known, in official circles as well as the media, as the 2019 Ridgecrest sequence. pic.twitter.com/cWICiSZ8Ry

— Susan Hough (@SeismoSue) July 16, 2019

Earthquake now officially renamed! pic.twitter.com/vNwjzQob3z

— Susan Hough (@SeismoSue) July 16, 2019

Post-seismic slip (~2-6cm) along the fault rupture of both Mw6.4 & Mw 7.1 #Ridgecrest #earthquakes, as hinted by #Sentinel1 #InSAR for the time interval June 10 – June 16. pic.twitter.com/71oFb0Z4A4

— Sotiris Valkaniotis (@SotisValkan) July 16, 2019

Descending interferogram #InSAR from #Sentinel1 data, #Ridgecrest #earthquake sequence. Rupture trace from previous InSAR & optical data. July 4 – July 16. Processed with DIAPASON at @esa_gep pic.twitter.com/VThrEHNqj9

— Sotiris Valkaniotis (@SotisValkan) July 16, 2019

Unwrapped (LOS displacement) descending interferogram #InSAR from #Sentinel1 data, #Ridgecrest #earthquake sequence. Rupture trace from previous InSAR & optical data. July 4 – July 16. Processed with DIAPASON at @esa_gep pic.twitter.com/Qs8DOuUjix

— Sotiris Valkaniotis (@SotisValkan) July 16, 2019

A new phase gradient map from @Sentinel1a descending track 71 for #ridgecrestquake. Data quality is just better. And a screen shot that shows sharp creep on the Garlock. Soon these will be available on https://t.co/sUnZG76gzM. pic.twitter.com/ovIzBTgS9p

— Xiaohua Xu (@XiaohuaXu1) July 17, 2019

Garlock Fault @AmauryVallage pic.twitter.com/6MlmdcWouK

— Sotiris Valkaniotis (@SotisValkan) July 16, 2019

Just released: 2019 Ridgecrest Earthquake Sequence: July 4, 2019–July 16, 2019. Download or view a text version at https://t.co/C864c132ol pic.twitter.com/jHRm0e0fLp

— USGS (@USGS) July 17, 2019

And the ascending pair from #Sentinel1, #Ridgecrestearthquake. Gradient render from unwrapped LOS displacement map (higher quality 20m from SNAP). Processing in @esa_gep. pic.twitter.com/IzaHeceXUU

— Sotiris Valkaniotis (@SotisValkan) July 17, 2019

Some more animations from #Sentinel2 imagery, sgowing possible liquefaction/lateral-spreading or surface distrurbance in #Searles Lake from the Mw 7.1 #RidgecrestEarthquake 2/2 pic.twitter.com/1MXynzpvQR

— Sotiris Valkaniotis (@SotisValkan) July 17, 2019

Building on our previous InSAR result across the #californiaearthquake #Ridgecrest we've been able to determine the East-West and Vertical components of movement using two opposing @CopernicusEU Sentinel-1 lines-of-sight. Over 90 cm of westward movement is detected! pic.twitter.com/LcIMMk9HkI

— NPA SatelliteMapping (@CGGNPA) July 17, 2019

Instrumental ground motion observations of the #ridgecrestearthquake sequence. Portable real-time stations get us good close in strong-motion measurements of the Mw 4.9 and other aftershocks. @usgs_seismic @usgs @GeoGinger pic.twitter.com/o1Eka8K1lD

— Daniel McNamara (@DanielEMcNamara) July 17, 2019

Came across an elongate cobble that was FLIPPED over by the earthquake shaking. This is fairly flat ground, no slope for gravity assistance. Suggests some pretty strong shaking in this area south of Hwy 178. #RidgecrestEarthquake #ridgecrest #earthquake pic.twitter.com/l1rDnFogYQ

— Brian Olson (@mrbrianolson) July 18, 2019

Complex and detailed pattern of co-seismic ruptures for the #RidgecrestEarthquake sequence. Red lines are primary & secondary surface ruptures, together with small triggered ruptures away from main faults. Previously mapped Quaternary Faults with yellow, for comparison. pic.twitter.com/wZi8H9i78O

— Sotiris Valkaniotis (@SotisValkan) July 18, 2019

Shaken, not stirred! We observed this strong ground motion indicator of a toppled tufa pile along the SW strand of the Mw 7.1 Ridgecrest rupture. These tufa piles are least 14,000 years old and have been thru many regional EQs, but one decided to fall now! James Dolan for scale. pic.twitter.com/KcyE4OAnKs

— Alex Hatem (@pride_of_lowell) July 18, 2019

These before & after #Landsat panchromatic band images show a surface rupture near the epicenter of the #Ridgecrest 7.1 #earthquake.
Visit https://t.co/umhIv4gJkU for more information about the earthquake pic.twitter.com/vxCY9663om

— USGS Landsat Program (@USGSLandsat) July 18, 2019

Preliminary fault slip distribution for 7.1 #Ridgecrest earthquake measured from pixel tracking of Sentinel-2 optical images. Rupture shows compact slip asperity near epicenter, with max. being ~4 m, consistent with field observations. pic.twitter.com/yGQ1usV2DQ

— Chris Milliner (@Geo_GIF) July 18, 2019

Preliminary rupture models for M6.4 and M7.1 by joint inversions of strong-motion, GPS, and teleseismic. Seems possible that it could have slipped twice. #RidgecrestEarthquake pic.twitter.com/jUYE8hUwsE

— Chengli Liu (@chengli_liu) July 15, 2019


Quite possibly the best animations on this sequence.

How Two Big Earthquakes Triggered 16,000 More in Southern California – The New York Times. Love the animations! ⁦@nytimes⁩ https://t.co/qL4A5cPUb7

— Susan Hough (@SeismoSue) July 19, 2019

The Geotechnical Extreme Events Reconnaissance (GEER) Association report for the Ridgecrest Earthquake Sequence is now online. #RidgecrestEarthquake @USGSBigQuakes @CalConservation #CAgeologicalSurvey and @UCLAengineering collaboration w/@USNavy https://t.co/OQwenwYM2x pic.twitter.com/zBlkAaksMR

— Jason "Jay" R. Patton (@patton_cascadia) July 20, 2019

References:

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