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Index map showing the California Missions and the dates the missions were established. All missions were secularized in 1834 (modified from Toppozada et al., 2002).
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This paper presents an overview of the advancement in our knowledge of California's earthquake history since ~ 1800, and especially during the last 30 years. We first review the basic statewide research on earthquake occurrences that was published from 1928 through 2002, to show how the current catalogs and their levels of completeness have ev...
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We utilized relative polarity measurements and machine learning techniques to better resolve focal mechanisms and stress orientations considering a catalog of ∼29,000 relocated earthquakes that occurred during 1984–2021 in the southeastern San Francisco Bay Area. Earthquake focal mechanisms are commonly produced using P wave first motion polarities...
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... The largest part of the displacement is in the San Andreas fault and other faults parallel with this: the San Jacinto, Elsinore, and Imperial faults. The majority of earthquakes occur at depths from 1 to 30 km (Toppozada, 2004). Japan is probably the most known seismic hotspot, where many historical seismicity data is well documented and modern time data are recorded with great accuracy (Matsu'ura, 2017). ...
Universalities and intriguing analogies in the statistics of avalanches are revealed for three physical systems defined on largely different length and energy scales. Earthquakes induced by tectonic scale dynamics, micro-scale level quakes observed from slipping crystallographic planes in metals and a one-dimensional , room-scale spring-block type Burridge-Knopoff model is studied from similar statistical viewpoints. The validity of the Gutenberg-Richter law for the probability density of the energies dissipated in the avalanches is proven for all three systems. By analysing data for three different seismic zones and performing acoustic detection for different Zn samples under deformation, universality for the involved scaling exponent is revealed. With proper parameter choices the 1D Burridge-Knopoff model is able to reproduce the same scaling law. The recurrence times of earthquakes and micro-quakes with magnitudes above a given threshold present again similar distributions and striking quantitative similarities. However, the 1D Burridge-Knopoff model cannot account for the correlations observed in such statistics.
... Toppozada and Branum [5] listed 35 significant earthquakes in California for the 19th and 20th centuries. We mention the earthquakes of 9 January 1857 Fort Tejon (M 7.9), 21 October 1868 Hayward Fault (M 7.0), and 18 April 1906 San Francisco (M 7.8) [5]. ...
... Toppozada and Branum [5] listed 35 significant earthquakes in California for the 19th and 20th centuries. We mention the earthquakes of 9 January 1857 Fort Tejon (M 7.9), 21 October 1868 Hayward Fault (M 7.0), and 18 April 1906 San Francisco (M 7.8) [5]. The last event was one of California's most famous earthquakes, which caused directly or indirectly over 3000 deaths in San Francisco and USD 400,000,000 in 1906 dollars from the earthquake and earthquake-triggered fires [6,7]. ...
California has a high seismic hazard, as many historical and recent earthquakes remind us. To deal with potential future damaging earthquakes, a voluntary insurance system for residential properties is in force in the state. However, the insurance penetration rate is quite low. Bearing this in mind, the aim of this article is to ascertain whether Big Data can provide policymakers and stakeholders with useful information in view of future action plans on earthquake coverage. Therefore, we extracted and analyzed the online search interest in earthquake insurance over time (2004–2021) through Google Trends (GT), a website that explores the popularity of top search queries in Google Search across various regions and languages. We found that (1) the triggering of online searches stems primarily from the occurrence of earthquakes in California and neighboring areas as well as oversea regions, thus suggesting that the interest of users was guided by both direct and vicarious earthquake experiences. However, other natural hazards also come to people’s notice; (2) the length of the higher level of online attention spans from one day to one week, depending on the magnitude of the earthquakes, the place where they occur, the temporal proximity of other natural hazards, and so on; (3) users interested in earthquake insurance are also attentive to knowing the features of the policies, among which are first the price of coverage, and then their worth and practical benefits; (4) online interest in the time span analyzed fits fairly well with the real insurance policy underwritings recorded over the years. Based on the research outcomes, we can propose the establishment of an observatory to monitor the online behavior that is suitable for supporting well-timed and geographically targeted information and communication action plans.
... The seismicity along the Ventura Basin and the Santa Barbara Channel is moderate, both in terms of earthquake frequency and magnitude and mainly shallow, between 3 and 15 km (Hutton et al., 1991). Large earthquakes with magnitudes above 6.0 have occurred in the area since the XVIII century as the December 21, 1812 (M7.1), the May 31, 1854 (M6.0) and the June 26, 1925 (M6.8) (Toppozada et al., 2002;Hutton et al., 2010) (Figure 1); however it has been discussed that the 1812 event may have been related to a rupture along the San Andreas fault and probably triggered by the December 8, 1812 earthquake that ruptured approximately between Pallett Creek and Cajon Pass (Toppozada et al., 2002;Toppozada and Branum, 2004). The distribution of the instrumental seismicity (colored circles in Figure 1) shows an area with a high density of earthquakes within the Santa Barbara Channel, south of Santa Barbara, although most of them occurred in 1941 and 1968 and, thus, probably corresponding to the aftershock sequence of the July 1, 1941 (M 5.5) and the July 5, 1968 (M5.1) events ( Figure 1). ...
... Dolan and Rockwell (2001) identified the last earthquake occurred in the eastern part of the San Cayetano fault, which produced 4.3 m of surface slip. The event occurred after 1660 CE and these autohrs proposed that could correspond to the December 21, 1812 event; however, as mentioned before, the 1812 earthquake could have been produced by the San Andreas fault (Toppozada et al., 2002;Toppozada and Branum, 2004). A study carried out in the Punta Gorda marine terrace revealed that the terrace was vertically separated 34 m across the Red Mountain fault system and that the slip may have occurred in the last 45 ka (Lindvall et al., 2002). ...
Identifying the offshore thrust faults of the Western Transverse Ranges that could produce large earthquakes and seafloor uplift is essential to assess potential geohazards for the region. The Western Transverse Ranges in southern California are an E-W trending fold-and-thrust system that extends offshore west of Ventura. Using a high-resolution seismic CHIRP dataset, we have identified the Last Glacial Transgressive Surface (LGTS) and two Holocene seismostratigraphic units. Deformation of the LGTS, together with onlapping packages that exhibit divergence and rotation across the active structures, provide evidence for three to four deformational events with vertical uplifts ranging from 1 to 10 m. Based on the depth of the LGTS and the Holocene sediment thickness, age estimates for the deformational events reveal a good correlation with the onshore paleoseismological results for the Ventura-Pitas Point fault and the Ventura-Avenue anticline. The observed deformation along the offshore segments of the Ventura-Pitas Point fault and Ventura-Avenue anticline trend diminishes toward the west. Farther north, the deformation along the offshore Red Mountain anticline also diminishes to the west with the shortening stepping north onto the Mesa-Rincon Creek fault system. These observations suggest that offshore deformation along the fault-fold structures moving westward is systematically stepping to the north toward the hinterland. The decrease in the amount of deformation along the frontal structures towards the west corresponds to an increase in deformation along the hinterland fold systems, which could result from a connection of the fault strands at depth. A connection at depth of the northward dipping thrusts to a regional master detachment may explain the apparent jump of the deformation moving west, from the Ventura-Pitas Point fault and the Ventura-Avenue anticline to the Red Mountain anticline, and then, from the Red Mountain anticline to the Mesa-Rincon Creek fold system. Finally, considering the maximum vertical uplift estimated for events on these structures (max ∼10 m), along with the potential of a common master detachment that may rupture in concert, this system could generate a large magnitude earthquake (>Mw 7.0) and a consequent tsunami.
... We can also quantify the seismic moment budget over a longer time period. Toppozada & Branum (2004) presented a history of M > 5.5 earthquakes in the Parkfield and the Creeping section from 1800 to 2001. They calculated the cumulative seismic moment released from 1857 to 2001 from the Parkfield to the Bitterwater region to be approximately 3.25 × 10 19 Nm. ...
... Assuming the moment accumulation rate we derived in this study represents a long-term average, we estimate that the accumulated seismic moment over the same area (from Parkfield to Bitterwater) and the same time period to be 3.9 × 10 19 Nm, which is 120 per cent of the moment release. After removing the contribution of seismic moment from historical earthquakes from 1857 to 2001 (Toppozada et al. 2002;Toppozada & Branum 2004), the moment deficit is reduced to 6.5 × 10 18 Nm (∼M w 6.5). When considering the 2004 Parkfield earthquake and its post-seismic afterslip (Johanson et al. 2006), the moment gap reduces to even a smaller value of 3.44 × 10 18 Nm (∼M w 6.3). ...
Moment accumulation rate (also referred to as moment deficit rate) is a fundamental quantity for evaluating seismic hazard. The conventional approach for evaluating moment accumulation rate of creeping faults is to invert for the slip distribution from geodetic measurements, although even with perfect data these slip-rate inversions are non-unique. In this study, we show that the slip-rate versus depth inversion is not needed because moment accumulation rate can be estimated directly from surface geodetic data. We propose an integral approach that uses dense geodetic observations from Interferometric Synthetic Aperture Radar (InSAR) and the Global Positioning System (GPS) to constrain the moment accumulation rate. The moment accumulation rate is related to the integral of the product of the along-strike velocity and the distance from the fault. We demonstrate our methods by studying the Creeping Section of the San Andreas fault observed by GPS and radar interferometry onboard the ERS and ALOS satellites. Along-strike variation of the moment accumulation rate is derived in order to investigate the degree of partial locking of the Creeping Section. The central Creeping Segment has a moment accumulation rate of 0.25–3.1 × 1015 Nm yr−1 km−1. The upper and lower bounds of the moment accumulation rates are derived based on the statistics of the noise. Our best-fitting model indicates that the central portion of the Creeping Section is accumulating seismic moment at rates that are about 5 per cent to 23 per cent of the fully locked Carrizo segment that will eventually be released seismically. A cumulative moment budget calculation with the historical earthquake catalogue ( M > 5.5) since 1857 shows that the net moment deficit at present is equivalent to a M w 6.3 earthquake.
... The Hayward fault lies in the center of the SFBA fault system accommodating $20% of the total slip budget [e.g., Graymer et al., 2002;Schmidt et al., 2005;d'Alessio et al., 2005], and has been interpreted as the SFBA fault most likely to rupture in a M W = 6.7 or larger earthquake in the next 20 years [2007Working Group for California Earthquake Probabilities, 2008 based on paleoseismic estimates of earthquake recurrence intervals and geologic and geodetic fault slip rate estimates. The last major (M W = 7) Hayward fault earthquake occurred in 1868, with a reported surface rupture from Fremont in the south to San Leandro in the north ( Figure 1) [Lawson, 1908;Yu and Segall, 1996;Bakun, 1999;Toppozada and Branum, 2004]. ...
The Hayward fault in the San Francisco Bay Area (SFBA) is sometimes
considered unusual among continental faults for exhibiting significant
aseismic creep during the interseismic phase of the seismic cycle while
also generating sufficient elastic strain to produce major earthquakes.
Imaging the spatial variation in interseismic fault creep on the Hayward
fault is complicated because of the interseismic strain accumulation
associated with nearby faults in the SFBA, where the relative motion
between the Pacific plate and the Sierra block is partitioned across
closely spaced subparallel faults. To estimate spatially variable creep
on the Hayward fault, we interpret geodetic observations with a
three-dimensional kinematically consistent block model of the SFBA fault
system. Resolution tests reveal that creep rate variations with a length
scale of <15 km are poorly resolved below 7 km depth. In addition,
creep at depth may be sensitive to assumptions about the kinematic
consistency of fault slip rate models. Differential microplate motions
result in a slip rate of 6.7 ± 0.8 mm/yr on the Hayward fault,
and we image along-strike variations in slip deficit rate at ˜15
km length scales shallower than 7 km depth. Similar to previous studies,
we identify a strongly coupled asperity with a slip deficit rate of up
to 4 mm/yr on the central Hayward fault that is spatially correlated
with the mapped surface trace of the 1868 MW = 6.9-7.0
Hayward earthquake and adjacent to gabbroic fault surfaces.
... [3] The Santa Barbara Basin is bounded by the Channel Islands to the south and the Santa Ynez mountains to the north ( Figure 1). Significant earthquakes have affected the region in 1812 (M7.1), 1925 (M6.8), 1927 (M7.1) [Toppozada and Branum, 2004], and a damaging M5.1 event in 1978 [Miller, 1979]. ...
Seafloor slope instability in the Santa Barbara Basin, California, poses
risk to the region. Two prominent landslides, the Goleta and Gaviota
slides, occupy the northern flank, with a scarp-like crack extending
east from the headwall of the Gaviota slide towards the Goleta complex.
Downslope creep across the crack might indicate an imminent risk of
failure. Sub-bottom CHIRP profiles with <1 m accuracy across the
crack exhibit no evidence of internal deformation. Daily seafloor
acoustic range measurements spanning the crack detected no significant
motion above a 99% confidence level of ±7 mm/yr over two years of
monitoring. These disparate data over different timescales suggest no
active creep and that the crack is likely a relict feature that formed
concomitantly with the Gaviota slide.
... In this case, time-intervals could not be assessed in terms of magnitude, but of peak intensity values at a significant inhabited area. Some attempts at considering this problem from a historical perspective are present also in some other papers in this same volume, and especially in the contributions by Toppozada and Branum (2004) on California, by Tatevossian (2004) on Russia and by Downes (2004) on New Zealand. ...
The assessment of the completeness of historical earthquake data (such as, for instance, parametric earthquake catalogues) has usually been approached in seismology - and mainly in Probabilistic Seismic Hazard Assessment(PSHA) - by means of statistical procedures. Such procedures look «inside» the data set under investigation and compare it to seismicity models, which often require more or less explicitly that seismicity is stationary. They usually end up determining times (Ti), from which on the data set is considered as complete above a given magnitude (Mi); the part of the data set before Ti is considered as incomplete and, for that reason, not suitable for statistical analysis. As a consequence, significant portions of historical data sets are not used for PSHA. Dealing with historical data sets - which are incomplete by nature, although this does not mean that they are of low value - it seems more appropriate to estimate «how much incomplete» the data sets can be and to use them together with such estimates. In other words, it seems more appropriate to assess the completeness looking «outside » the data sets; that is, investigating the way historical records have been produced, preserved and retrieved. This paper presents the results of investigation carried out in Italy, according to historical methods. First, the completeness of eighteen site seismic histories has been investigated; then, from those results, the completeness of areal portions of the catalogue has been assessed and compared with similar results obtained by statistical methods. Finally, the impact of these results on PSHA is described. published
The Parkfield segment of the San Andreas Fault (SAF) sits at the transition between the locked Cholame segment to the South and the SAF creeping segment to the North. The Parkfield segment hosts regular ∼Mw $\sim {\boldsymbol{M}}_{\boldsymbol{w}}$6 earthquakes followed by postseismic deformation. Recent studies based on geodetic data have highlighted spatial and temporal variations of aseismic slip rate in addition to postseismic slip along this section of the fault. We combine Global Navigation Satellite Systems (GNSS) and seismicity data over the 2006–2018 period to detail a comprehensive picture of transient slip events. We produce a catalog of relocated seismicity and repeating earthquakes. We use a variational Bayesian independent component analysis decomposition on GNSS data to separate geodetic deformation due to non‐tectonic sources from signals of potential tectonic origin. We then reconstruct the temporal evolution of fault slip and detect potential slip transients. Those events, determined as mostly aseismic with the exception of one related to a Mw ${\boldsymbol{M}}_{\boldsymbol{w}}$4.8 earthquake, occur more frequently during the 2004 Mw ${\boldsymbol{M}}_{\boldsymbol{w}}$6 post‐seismic period than during the subsequent inter‐seismic phase. Our study illustrates the rich dynamics of seismic and aseismic slip during both post‐ and inter‐seismic periods along active faults.
In the American West, wildfires and earthquakes are increasingly threatening the archaeological, historical, and tribal resources that define the collective identity and connection with the past for millions of Americans. The loss of said resources diminishes societal understanding of the role cultural heritage plays in shaping our present and future. This paper examines the viability of employing stationary and SLAM-based terrestrial laser scanning, close-range photogrammetry, automated surface change detection, GIS, and WebGL visualization techniques to enhance the preservation of cultural resources in California. Our datafication approach combines multi-temporal remote sensing monitoring of historic features with legacy data and collaborative visualization to document and evaluate how environmental threats affect built heritage. We tested our methodology in response to recent environmental threats from wildfire and earthquakes at Bodie, an iconic Gold Rush-era boom town located on the California and Nevada border. Our multi-scale results show that the proposed approach effectively integrates highly accurate 3D snapshots of Bodie’s historic buildings before/after disturbance, or post-restoration, with surface change detection and online collaborative visualization of 3D geospatial data to monitor and preserve important cultural resources at the site. This study concludes that the proposed workflow enhances the monitoring of at-risk California’s cultural heritage and makes a call to action to employ remote sensing as a pathway to advanced planning.
Historical seismic intensity data are useful for myriad reasons, including assessment of the performance of probabilistic seismic hazard assessment (PSHA) models and corresponding hazard maps by comparing their predictions to a dataset of historically observed intensities in the region. To assess PSHA models for California, a long and consistently interpreted intensity record is needed. For this purpose, the California Historical Intensity Mapping Project (CHIMP) has compiled a dataset that combines and reinterprets intensity information that has been stored in disparate and sometimes hard-to-access locations. The CHIMP dataset also includes new observations of intensity from archival research and oral history collection. Version 1 of the dataset includes 46,502 intensity observations for 62 earthquakes with estimated magnitudes ranging from 4.7 to 7.9. The 162 yr of shaking data show observed shaking lower than expected from seismic hazard models. This discrepancy is reduced, but persists, if historical intensity data for the largest earthquakes are smoothed to reduce the effects of spatial undersampling. Possible reasons for this discrepancy include other limitations of the CHIMP dataset, the hazard models, and the possibility that California seismicity throughout the historical period has been lower than the long-term average. Some of these issues may also explain similar discrepancies observed for Italy and Japan.
