Carrizo Plain Research Articles

Non-invasive baseline genetic monitoring of the endangered San Joaquin kit fox on a photovoltaic solar facility

Survival of endangered San Joaquin kit foxes Vulpes macrotis mutica is challenged by reduced and fragmented habitat resulting from anthropogenic uses. We monitored kit foxes on the 40 km2 proposed site for the Topaz Solar Farms (TSF) in San Luis Obispo County, California, which consisted of 76% agricultural fields and 24% grasslands. Prior to construction of the solar facility in December 2011, we used professionally trained dog-handler teams to conduct noninvasive genetic surveys annually from 2009 to 2011. We analyzed mtDNA to identify species, zinc finger genes for sex determination, and microsatellite loci to define individuals. We identified 45 individuals from 351 fresh scat samples (26 females, 18 males, and 1 individual of unknown sex), and recaptured 5 individuals between years. Kit foxes predominantly used the grasslands and rarely used agricultural fields. Samples from the TSF population had similar levels of genetic diversity to 2 areas less than 20 km away in the northern end of the Carrizo Plain National Monument. Capwire and LDNe estimates of population size using samples collected during annual November surveys indicated that ~33 individuals used the TSF over a 3 yr period. The relatively high population estimate, low recapture rates, and similar genetic diversity to 2 nearby locations suggest that individuals using the TSF site are part of a larger population using the surrounding landscape. Our study provided baseline data that, when coupled with future surveys, will help assess the effects on San Joaquin kit foxes of solar facility construction and habitat regeneration on agricultural lands removed from production.

Four New Species of California Legless Lizards (Anniella)

A previous genetic study of the California legless lizard (Anniella pulchra) revealed five deep genetic lineages and alluded to morphological differences among them. Here we show that three of these genetic lineages can be readily diagnosed from topotypic A. pulchra through a combination of coloration, scalation, and skeletal characters (trunk vertebra number). A fourth lineage is cryptic, but can be diagnosed from A. pulchra by its karyotype. We argue that these genetic clades of A. pulchra are strong candidates for species recognition because they exhibit properties that corroborate the DNA evidence for lineage separation. We therefore hypothesize that each of the five genetic clades of A. pulchra (“Anniella clades A–E”) are distinct species and so describe four new species (Anniella alexanderae, sp. nov., Anniella campi, sp. nov., Anniella grinnelli, sp. nov., and Anniella stebbinsi, sp. nov.). In naming these new species we have chosen to honor four natural historians whose contributions to the study of California's vertebrate biodiversity are an ongoing inspiration for students of natural history and natural history museum curators. Two of these new species have small and poorly characterized ranges in the San Joaquin Valley and Carrizo Plain (A. alexanderae and A. grinnelli). A third restricted-range species (A. campi) is known from just three sites in the eastern Sierra Nevada. The fourth new species (A. stebbinsi) is a wide-ranging cryptic lineage that occurs throughout Southern California and into Baja California, Mexico. The limited distribution and fragile habitats occupied by the new species of Anniella warrant additional scientific research and conservation attention.

An evaluation of monitoring methods for the endangered giant kangaroo rat

AbstractAccurate, reliable, and efficient monitoring methods for detecting changes in the distribution and abundance of wildlife populations are the cornerstone of effective management. Aerial surveys of active burrow sites and ground counts of open burrows have been used to estimate distribution and abundance, respectively, of a number of rodent species. We compared the efficacy of these and other methods for estimating distribution, abundance, and population growth of the endangered giant kangaroo rat (Dipodomys ingens) to determine the best practices for monitoring. Specifically, we compared aerial surveys, rapid expert assessments, and live‐trapping for estimating giant kangaroo rat range, and burrow counts and live‐trapping for estimating abundance and growth. We carried out the study in the Carrizo Plain National Monument, California, USA, from 2007 to 2011. Expert rapid assessment of sites performed nearly as well as trapping in determining range extent, while aerial surveys provided estimates of total range extent but with less precision. Active burrow counts were adequate to determine relative abundance averaged over multiple years, but were not reliable as an estimate of annual population size or growth. © 2012 The Wildlife Society.

The San Joaquin Desert of California: Ecologically Misunderstood and Overlooked

The vegetation community of the San Joaquin Valley of California has been formally classified as a perennial grassland based largely on assumptions of past climax state. However, historical records suggest that the region might be more accurately classified as a desert. The distinction is important in determining the appropriate management strategies for this ecosystem, particularly for the many rare and endemic taxa that reside there. Abiotic and biotic factors—including low precipitation, arid soils, and desert-adapted plants and vertebrate—are consistent with conditions typical of desert areas. We examined the distributions of these factors to define the extent of the San Joaquin Desert. We conclude that the San Joaquin Desert historically encompassed 28,493 km2 including the western and southern two thirds of the San Joaquin Valley, and the Carrizo Plain and Cuyama Valley to the southwest. However, this ecosystem has been reduced by up to 59% from agricultural, industrial, and urban activities. The conservation of the unique biodiversity of this region is dependent upon this ecosystem being appropriately managed as a desert and not as a perennial or annual grassland.

Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California

Research Article| March 01, 2011 Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California Nathan A. Toké; Nathan A. Toké 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar J Ramón Arrowsmith; J Ramón Arrowsmith 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Michael J. Rymer; Michael J. Rymer 2U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025-3591, USA Search for other works by this author on: GSW Google Scholar Angela Landgraf; Angela Landgraf 3Institut für Erd- und Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany Search for other works by this author on: GSW Google Scholar David E. Haddad; David E. Haddad 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Melanie Busch; Melanie Busch 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Joshua Coyan; Joshua Coyan 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Alexander Hannah Alexander Hannah 4Department of Geological Sciences, California State University Northridge, Northridge, California 91330, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Nathan A. Toké 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA J Ramón Arrowsmith 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Michael J. Rymer 2U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025-3591, USA Angela Landgraf 3Institut für Erd- und Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany David E. Haddad 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Melanie Busch 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Joshua Coyan 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Alexander Hannah 4Department of Geological Sciences, California State University Northridge, Northridge, California 91330, USA Publisher: Geological Society of America Received: 19 Jun 2010 Revision Received: 05 Oct 2010 Accepted: 08 Oct 2010 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2011 Geological Society of America Geology (2011) 39 (3): 243–246. https://doi.org/10.1130/G31498.1 Article history Received: 19 Jun 2010 Revision Received: 05 Oct 2010 Accepted: 08 Oct 2010 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Nathan A. Toké, J Ramón Arrowsmith, Michael J. Rymer, Angela Landgraf, David E. Haddad, Melanie Busch, Joshua Coyan, Alexander Hannah; Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California. Geology 2011;; 39 (3): 243–246. doi: https://doi.org/10.1130/G31498.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Investigation of a right-laterally offset channel at the Miller's Field paleoseismic site yields a late Holocene slip rate of 26.2 +6.4/−4.3 mm/yr (1σ) for the main trace of the San Andreas fault at Parkfield, California. This is the first well-documented geologic slip rate between the Carrizo and creeping sections of the San Andreas fault. This rate is lower than Holocene measurements along the Carrizo Plain and rates implied by far-field geodetic measurements (∼35 mm/yr). However, the rate is consistent with historical slip rates, measured to the northwest, along the creeping section of the San Andreas fault (<30 mm/yr). The paleoseismic exposures at the Miller's Field site reveal a pervasive fabric of clay shear bands, oriented clockwise oblique to the San Andreas fault strike and extending into the uppermost stratigraphy. This fabric is consistent with dextral aseismic creep and observations of surface slip from the 28 September 2004 M6 Parkfield earthquake. Together, this slip rate and deformation fabric suggest that the historically observed San Andreas fault slip behavior along the Parkfield section has persisted for at least a millennium, and that significant slip is accommodated by structures in a zone beyond the main San Andreas fault trace. 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A New Species ofSchiniafrom Central California (Noctuidae: Heliothinae)

Schinia carrizoensis new species, is described from specimens collected on the Carrizo Plain National Monument, San Luis Obispo County and northeastern Santa Barbara County, California. This new Schinia is a member of the S. cupes (Grote) complex and is remarkable in the group for having subtle maculation with rusty coloration and a limited distribution.

Basking in the moonlight? Effect of illumination on capture success of the endangered giant kangaroo rat

Bright moonlight is thought to increase predation risk for nocturnal rodents and consequently reduce their activity levels and capture rates. We examined the effect of moonlight on the foraging activity and capture success of the federally endangered giant kangaroo rat (Dipodomys ingens) in the Carrizo Plain National Monument, California. D. ingens is adapted to open grasslands, a habitat type where moonlight should strongly influence its visibility to predators. Using a trapping data set of 11,353 captures from 2007 to 2009 and accounting for factors such as cloud cover, temperature, abundance of the San Joaquin kit fox (Vulpes macrotis mutica), plant biomass, trap acclimation, and trap effort, we found a consistently positive effect of moonlight on capture success. In foraging trials we detected no effect of moonlight on giving-up densities or time spent at seed piles. Our results suggest that giant kangaroo rats do not perceive a higher risk of predation in bright moonlight. Nocturnal rodents that rely on early visual detection of predators might benefit from moonlight as much as their predators do, thus resulting in no net change in predation risk.

Century-long average time intervals between earthquake ruptures of the San Andreas fault in the Carrizo Plain, California

Paleoseismological data constrain the age, location, and associated magnitude of past surface-rupturing earthquakes; these are critical parameters for developing and testing fault behavior models and characterizing seismic hazard. We present new earthquake evidence and radiocarbon analyses that refi ne the chronology of the six most recent earthquakes that ruptured the south-central San Andreas fault in the Carrizo Plain (California, United States) at the Bidart Fan site. Modeled 95 percentile ranges of the earthquakes prior to the A.D. 1857 earthquake are A.D. 1631‐1823, 1580‐1640, 1510‐1612, 1450‐1475, and 1360‐1452. The average time interval between the last six earthquakes that ruptured the San Andreas fault in the Carrizo Plain is 88 ± 41 yr. This is less than the time since the most recent A.D. 1857 earthquake, less than all reported average intervals of prehistoric earthquakes along the entire San Andreas fault, and signifi cantly shorter than the 235 yr average used in recent seismic hazard evaluations. The new chronological data combined with recent slip studies imply that the magnitudes of the earthquakes that ruptured the southern San Andreas fault in the Carrizo Plain since ca. A.D. 1360 were variable, and suggest that the widely held view of rare but great surface rupturing earthquakes along this portion of the southern San Andreas fault should be reevaluated. 118°

Slip in the 1857 and Earlier Large Earthquakes Along the Carrizo Plain, San Andreas Fault

The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a approximately 350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the approximately 60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes. New high-resolution topographic data show that the average slip along the Carrizo segment during the 1857 event was 5.3 +/- 1.4 meters, eliminating the core assumption for a linkage between Carrizo segment rupture and recurrence of major earthquakes along the south-central San Andreas Fault. Earthquake slip along the Carrizo segment may recur in earthquake clusters with cumulative slip of approximately 5 meters.

Revised dates of large earthquakes along the Carrizo section of the San Andreas Fault, California, since A.D. 1310 ± 30

Precise knowledge of the age and magnitude of past earthquakes is essential for characterizing models of earthquake recurrence and key to forecasting future earthquakes. We present 28 new radiocarbon analyses that refine the chronology of the last five earthquakes at the Bidart Fan site along the Carrizo section of the south central San Andreas Fault, which last ruptured during the Fort Tejon earthquake in A.D. 1857. The new data show that the penultimate earthquake in the Carrizo Plain occurred not earlier than A.D. 1640 and the modeled 95th percentile ranges of the three earlier earthquakes (and their mean) are A.D. 1540–1630 (1585), A.D. 1360–1425 (1393), and A.D. 1280–1340 (1310), indicating an average time interval of 137 ± 44 years between large earthquakes since A.D. 1310 ± 30. A robust earthquake recurrence model of the Carrizo section will require even more well‐dated earthquakes for thorough characterization. However, these new data imply that since A.D. 1310 ± 30, the Carrizo section has failed more regularly and more often than previously thought.

High genetic diversity among fossorial lizard populations (Anniella pulchra) in a rapidly developing landscape (Central California)

California is a biodiversity hotspot facing unbridled human population growth, especially in Central California. One of the poorly known, sensitive species in this area is the California legless lizard (Anniella pulchra), a fossorial worm-like reptile. We report mt and nuDNA sequences from 69 museum-vouchered samples of Anniella (A. pulchra and its sister species A. geronimensis) from 48 localities. Our genetic survey reveals substantially more genetic diversity within A. pulchra than previously reported. Our two independently evolving markers (mt and nuDNA) reveal five major lineages of A. pulchra. Two of the five major lineages of A. pulchra correspond to a north-south split found in other widespread California reptiles. These northern and southern clades also correspond to a previous study showing variation in chromosomal number. Unlike most other Californian reptiles, A. pulchra has major genetic lineages that are endemic to Central California including two that are endemic to the San Joaquin Valley and Carrizo Plain. Although A. pulchra is threatened throughout its range, the distinct San Joaquin lineages are seriously imperiled by urban sprawl. Some of the localities for the newly recognized genetic lineages have already been destroyed by development.

Geodetic strain across the San Andreas fault reflects elastic plate thickness variations (rather than fault slip rate)

The interseismic velocity field provided by geodetic methods is generally interpreted in the framework of a thick elastic lithosphere with a slipping fault at depth. Because lateral variations of lithospheric rheology play a key role in determining the geological strain distribution, I examine the idea that interseismic strain rate variations also occur in response to lateral variations in the elastic thickness of the lithosphere. Using a stress balance principle and some simplifying assumptions, I show using a 1D model that elastic thickness is inversely proportional to strain rate for the simple case of pure strike-slip faulting. Elastic thickness computed on three profiles crossing the San Andreas fault system (SAFS) suggests that the distribution of interseismic strain rate is compatible with a thick elastic lithosphere in the Great Basin-Sierra Nevada province and on the Pacific plate. Conversely, a thin plate with a shallow asthenosphere is needed on the SAFS to explain its high strain rate. A 2.5D Finite Element model of interseismic strain in the Carrizo Plain region in Central California shows how known vertical and horizontal variations of elastic properties refine 1D model predictions. In a case of a multiple fault system, I point out that the interseismic velocity is not causally tied to faults slip rate. Therefore, analysing the velocity field across the SAFS cannot reliably provide faults slip rate distribution as previously claimed. Rather, the apparent correlation between geologic slip rate and interseismic strain may only indicate that the elastic thickness plays a dominant role in controlling fault strength. Finally, I suggest that interseismic geodetic strain could be a new way to infer effective elastic plate thickness on the continents.

Geomorphic response to uplift along the Dragon's Back pressure ridge, Carrizo Plain, California

We used high-resolution topography, geomorphic mapping of active surface processes, and geologic mapping to study the topographic and erosional response of small drainage basins to rock uplift along the Dragon's Back pressure ridge along the San Andreas fault in the Carrizo Plain, California. We infer the history of deformation experienced by ~40 small drainage basins formed in poorly consolidated sedimentary rocks. A space-for-time substitution directly images the erosional and topographic responses to deformation. Progressive deformation and rock uplift are accompanied by increases in channel steepness and basin relief. As uplift ceases, channel concavity rapidly increases, causing channels to undercut hillslopes—this undercutting promotes the consumption of hillslopes by landsliding. This undercutting also causes basin relief to be greatest after uplift has stopped. This analysis indicates that channels of the Dragon's Back pressure ridge respond to changes in rock uplift rates over thousands of years, whereas hillslope processes may take more than an order of magnitude longer to adjust to changes in rock uplift rates. Our study directly measures changes in erosional processes due to the initiation and cessation of rock uplift, which can typically only be inferred using numerical models, by direct field observations.

Serial ruptures of the San Andreas fault, Carrizo Plain, California, revealed by three‐dimensional excavations

It is poorly known if fault slip repeats regularly through many earthquake cycles. Well‐documented measurements of successive slips rarely span more than three earthquake cycles. In this paper, we present evidence of six sequential offsets across the San Andreas fault at a site in the Carrizo Plain, using stream channels as piercing lines. We opened a latticework of trenches across the offset channels on both sides of the fault to expose their subsurface stratigraphy. We can correlate the channels across the fault on the basis of their elevations, shapes, stratigraphy, and ages. The three‐dimensional excavations allow us to locate accurately the offset channel pairs and to determine the amounts of motion for each pair. We find that the dextral slips associated with the six events in the last millennium are, from oldest to youngest, ≥5.4 ± 0.6, 8.0 ± 0.5, 1.4 ± 0.5, 5.2 ± 0.6, 7.6 ± 0.4 and 7.9 ± 0.1 m. In this series, three and possibly four of the six offset values are between 7 and 8 m. The common occurrence of 7–8 m offsets suggests remarkably regular, but not strictly uniform, slip behavior. Age constraints for these events at our site, combined with previous paleoseismic investigations within a few kilometers, allow a construction of offset history and a preliminary evaluation of slip‐ and time‐predictable models. The average slip rate over the span of the past five events (between A.D. 1210 and A.D. 1857.) has been 34 mm/yr, not resolvably different from the previously determined late Holocene slip rate and the modern geodetic strain accumulation rate. We find that the slip‐predictable model is a better fit than the time‐predictable model. In general, earthquake slip is positively correlated with the time interval preceding the event. Smaller offsets coincide with shorter prior intervals and larger offset with longer prior intervals.

Stream Channel Offset and Late Holocene Slip Rate of the San Andreas Fault at the Van Matre Ranch Site, Carrizo Plain, California

Sets of well-preserved channels offset across the San Andreas fault (SAF) at the Van Matre Ranch (VMR) site in the northwestern Elkhorn Hills area of the Carrizo Plain offer the opportunity to measure slip rate and examine geomorphic development of the channels. The fault zone and offset channels were exposed by excavation in one fault-perpendicular and five fault-parallel trenches. The geomor- phology and stratigraphy in the channels reveal a record of filling by fluvial sedi- mentation, lateral colluviation, and pedogenesis. The buried thalweg of the currently active channel is offset 24.8 1 m, while the geomorphic channel is offset approx- imately 27.6 1 m. Seventeen samples were collected from channel margin deposits for 14 C dating. An OxCal model of the radiocarbon dates with stratigraphic control suggests that the oldest date for channel incision was A.D. 1160. Minimum and maximum slip rates ranging from 29.3 to 35.6 mm/yr are derived from different assumptions about the timing of channel incision and offset. The resulting slip rates at VMR agree well with the late-Holocene slip rate of 33.9 2.9 mm/yr at Wallace Creek, approximately 18 km to the northwest, and imply that within measurement uncertainty the 30-37 mm/yr velocity gradient across the SAF from decadal time- scale geodetic measurements is accommodated across the several-meter-wide SAF zone at VMR over the last millennium.

Post-Breeding Dispersal of Burrowing Owls in an Extensive California Grassland

Understanding patterns of dispersal is key to developing effective conservation plans, yet dispersal is poorly known for most species. We radio-tracked 15 adult burrowing owls (Athene cunicularia) from 13 nests within the Carrizo Plain National Monument in southern California. Our goal was to describe post-breeding movements in this extensive grassland system. Of nests that failed (n = 9 nests), 8 radio-tagged individuals from 7 nests dispersed, whereas none of the owls from successful nests (n = 4 nests) dispersed. Dispersal distances ranged from 0.2 km to 53 km (median = 3.1 km). The large dispersal distances we observed within the breeding season were greater than previously published estimates of between-year breeding dispersal based on mark-recapture methods and provide insight into the lack of genetic differentiation observed among burrowing owl populations.

Development of offset channels across the San Andreas fault

The San Andreas fault offsets some small gullies incising the relatively flat surfaces in the Carrizo Plain, California. Among these gullies, those with larger drainage basins have larger offsets, probably because gullies that have larger floods can keep the channels entrenched and subjected to the fault displacement longer. On the other hand, older offset channels in the area, which have much larger offsets, indicate that the gradual shift to straighter courses seems probable only for offset channels able to keep and accumulate the offset for a long time. The strike-slip fault displacement offsets a channel as much as the channel can follow with some modification by fluvial processes until overbank floods at the upper bend induce channel avulsion to a straighter course, or until the channel is captured by the beheaded and abandoned downstream reach of the adjacent channel moved with the fault displacement. The offset channel promotes aggradation upstream from the upper bend, and this makes the channel increasingly susceptible to overbank floods. The older offset channels are confined in valleys, and this condition is apparently preventive of channel avulsion or capture. The strike-slip fault displacement also deforms longitudinal profiles of channels. Assuming that the elimination of discontinuities in the longitudinal profile is the main response of fluvial processes to the deformation by fault displacement, nearly continuous longitudinal profiles of some old offset channels seem to indicate the full adjustment, the condition in which no more changes will occur as a response to fault displacement until the next fault slip deforms them. The irregularities in longitudinal profiles of other offset channels indicate that the channel adjustment by fluvial processes may be occurring but not enough to eliminate the irregularities. An offset river can attain a continuous longitudinal profile if it has enough time to adjust its longitudinal profile after the fault displacement. Otherwise, the discontinuity reflecting a various degree of adjustment would remain in the longitudinal profile until channel avulsion or capture occurs. The degree of adjustment and the probability of channel avulsion or capture depend highly on the fluvial ability and condition of each river as well as the time after the deformation.

Block models of crustal motion in southern California constrained by GPS measurements

We estimate slip rates on major active faults in southern California using a block model constrained by Global Positioning System measurements of interseismic deformation. The block model includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle. Our estimates of the right‐lateral strike‐slip rate on the San Andreas fault vary by at least a factor of 5, from a high of 35.9 ± 0.5 mm/yr in the Carrizo Plain to a low of 5.1 ± 1.5 mm/yr through the San Bernadino segment. Shortening across the Puente Hills Thrust and left‐lateral slip on the Raymond Hill fault are consistent with both thickening and escape tectonics in the Los Angeles Basin. Discrepancies between geodetic and geologic slip rate estimates along the San Andreas and San Jacinto faults, as well as in the Eastern California Shear Zone, may be explained by a temporal change in fault system behavior. We find no substantial evidence for long‐term postseismic relaxation and infer that the viscosity of the lower crust/upper mantle may be relatively high (η &gt; 1019 Pa s).

Viscoelastic earthquake cycle models with deep stress‐driven creep along the San Andreas fault system

We develop a two‐dimensional boundary element earthquake cycle model including deep interseismic creep on vertical strike‐slip faults in an elastic lithosphere coupled to a viscoelastic asthenosphere. Uniform slip on the upper part of the fault is prescribed periodically to represent great strike‐slip earthquakes. Below the coseismic rupture the fault creeps in response to lithospheric shear stresses within a narrow linear viscous fault zone. The model is applied to the GPS contemporary velocity field across the Carrizo Plain and northern San Francisco Bay segments of the San Andreas fault, as well as triangulation measurements of postseismic strain following the 1906 San Francisco earthquake. Previous analysis of these data, using conventional viscoelastic coupling models without stress‐driven creep [Segall, 2002], shows that it is necessary to invoke different lithosphere‐asthenosphere rheology in northern and southern California in order to explain the data. We show that with deep stress‐driven interseismic creep on the San Andreas fault, the data can be explained with the same rheology for northern and southern California. We estimate elastic thickness in the range 44–100 km (95% confidence level), fault zone viscosity per unit width of 0.5–8.2 × 1017Pa s/m, and asthenosphere relaxation time of 24–622 years (0.1–2.9 × 1020Pa s) for northern and southern California. We estimate a slip rate of 21–27 mm/yr and recurrence time of 188–315 years for the northern San Francisco Bay San Andreas fault and slip rate of 32–42 mm/yr with recurrence time of 247–536 years for the Carrizo Plain.

Six similar sequential ruptures of the San Andreas fault, Carrizo Plain, California

Research Article| August 01, 2004 Six similar sequential ruptures of the San Andreas fault, Carrizo Plain, California Jing Liu; Jing Liu 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA, and Laboratoire de Tectonique, Institut de Physique du Globe de Paris, 4 place Jussieu, 75252 Paris cedex 05, France Search for other works by this author on: GSW Google Scholar Yann Klinger; Yann Klinger 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA, and Laboratoire de Tectonique, Institut de Physique du Globe de Paris, 4 place Jussieu, 75252 Paris cedex 05, France Search for other works by this author on: GSW Google Scholar Kerry Sieh; Kerry Sieh 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA Search for other works by this author on: GSW Google Scholar Charles Rubin Charles Rubin 3Department of Geological Sciences, Central Washington University, Ellensburg, Washington 98926, USA Search for other works by this author on: GSW Google Scholar Geology (2004) 32 (8): 649–652. https://doi.org/10.1130/G20478.1 Article history received: 12 Jan 2004 rev-recd: 27 Apr 2004 accepted: 30 Apr 2004 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jing Liu, Yann Klinger, Kerry Sieh, Charles Rubin; Six similar sequential ruptures of the San Andreas fault, Carrizo Plain, California. Geology 2004;; 32 (8): 649–652. doi: https://doi.org/10.1130/G20478.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We document the precise sizes, but not the dates, of the six latest offsets across the San Andreas fault at Wallace Creek, California. Three and perhaps four of these, including the latest in 1857, show dextral offset of 7.5–8 m. The third and fourth offsets, however, are just 1.4 and 5.2 m. The predominance of similar offsets for the latest six events suggests that the fundamental properties of the fault system that control slip size do not vary greatly from event to event. The large offsets imply that ruptures involving this site are typically more than 200 km long. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.