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Sample records for san simeon earthquake

  1. Liquefaction at Oceano, California, during the 2003 San Simeon earthquake

    Science.gov (United States)

    Holzer, T.L.; Noce, T.E.; Bennett, M.J.; Tinsley, J. C.; Rosenberg, L.I.

    2005-01-01

    The 2003 M 6.5 San Simeon, California, earthquake caused liquefaction-induced lateral spreading at Oceano at an unexpectedly large distance from the seismogenic rupture. We conclude that the liquefaction was caused by ground motion that was enhanced by both rupture directivity in the mainshock and local site amplification by unconsolidated fine-grained deposits. Liquefaction occurred in sandy artificial fill and undisturbed eolian sand and fluvial deposits. The largest and most damaging lateral spread was caused by liquefaction of artificial fill; the head of this lateral spread coincided with the boundary between the artificial fill and undisturbed eolian sand deposits. Values of the liquefaction potential index, in general, were greater than 5 at liquefaction sites, the threshold value that has been proposed for liquefaction hazard mapping. Although the mainshock ground motion at Oceano was not recorded, peak ground acceleration was estimated to range from 0.25 and 0.28g on the basis of the liquefaction potential index and aftershock recordings. The estimates fall within the range of peak ground acceleration values associated with the modified Mercalli intensity = VII reported at the U.S. Geological Survey (USGS) "Did You Feel It?" web site.

  2. Liquefaction-induced lateral spreading in Oceano, California, during the 2003 San Simeon Earthquake

    Science.gov (United States)

    Holzer, Thomas L.; Noce, Thomas E.; Bennett, Michael J.; Di Alessandro, Carola; Boatwright, John; Tinsley, John C.; Sell, Russell W.; Rosenberg, Lewis I.

    2004-01-01

    The December 22, 2003, San Simeon, California, (M6.5) earthquake caused damage to houses, road surfaces, and underground utilities in Oceano, California. The community of Oceano is approximately 50 miles (80 km) from the earthquake epicenter. Damage at this distance from a M6.5 earthquake is unusual. To understand the causes of this damage, the U.S. Geological Survey conducted extensive subsurface exploration and monitoring of aftershocks in the months after the earthquake. The investigation included 37 seismic cone penetration tests, 5 soil borings, and aftershock monitoring from January 28 to March 7, 2004. The USGS investigation identified two earthquake hazards in Oceano that explain the San Simeon earthquake damage?site amplification and liquefaction. Site amplification is a phenomenon observed in many earthquakes where the strength of the shaking increases abnormally in areas where the seismic-wave velocity of shallow geologic layers is low. As a result, earthquake shaking is felt more strongly than in surrounding areas without similar geologic conditions. Site amplification in Oceano is indicated by the physical properties of the geologic layers beneath Oceano and was confirmed by monitoring aftershocks. Liquefaction, which is also commonly observed during earthquakes, is a phenomenon where saturated sands lose their strength during an earthquake and become fluid-like and mobile. As a result, the ground may undergo large permanent displacements that can damage underground utilities and well-built surface structures. The type of displacement of major concern associated with liquefaction is lateral spreading because it involves displacement of large blocks of ground down gentle slopes or towards stream channels. The USGS investigation indicates that the shallow geologic units beneath Oceano are very susceptible to liquefaction. They include young sand dunes and clean sandy artificial fill that was used to bury and convert marshes into developable lots. Most of

  3. Fluid‐driven seismicity response of the Rinconada fault near Paso Robles, California, to the 2003 M 6.5 San Simeon earthquake

    Science.gov (United States)

    Hardebeck, Jeanne L.

    2012-01-01

    The 2003 M 6.5 San Simeon, California, earthquake caused significant damage in the city of Paso Robles and a persistent cluster of aftershocks close to Paso Robles near the Rinconada fault. Given the importance of secondary aftershock triggering in sequences of large events, a concern is whether this cluster of events could trigger another damaging earthquake near Paso Robles. An epidemic‐type aftershock sequence (ETAS) model is fit to the Rinconada seismicity, and multiple realizations indicate a 0.36% probability of at least one M≥6.0 earthquake during the next 30 years. However, this probability estimate is only as good as the projection into the future of the ETAS model. There is evidence that the seismicity may be influenced by fluid pressure changes, which cannot be forecasted using ETAS. The strongest evidence for fluids is the delay between the San Simeon mainshock and a high rate of seismicity in mid to late 2004. This delay can be explained as having been caused by a pore pressure decrease due to an undrained response to the coseismic dilatation, followed by increased pore pressure during the return to equilibrium. Seismicity migration along the fault also suggests fluid involvement, although the migration is too slow to be consistent with pore pressure diffusion. All other evidence, including focal mechanisms and b‐value, is consistent with tectonic earthquakes. This suggests a model where the role of fluid pressure changes is limited to the first seven months, while the fluid pressure equilibrates. The ETAS modeling adequately fits the events after July 2004 when the pore pressure stabilizes. The ETAS models imply that while the probability of a damaging earthquake on the Rinconada fault has approximately doubled due to the San Simeon earthquake, the absolute probability remains low.

  4. Seismicity rate changes along the central California coast due to stress changes from the 2003 M 6.5 San Simeon and 2004 M 6.0 Parkfield earthquakes

    Science.gov (United States)

    Aron, A.; Hardebeck, J.L.

    2009-01-01

    We investigated the relationship between seismicity rate changes and modeled Coulomb static stress changes from the 2003 M 6.5 San Simeon and the 2004 M 6.0 Parkfield earthquakes in central California. Coulomb stress modeling indicates that the San Simeon mainshock loaded parts of the Rinconada, Hosgri, and San Andreas strike-slip faults, along with the reverse faults of the southern Los Osos domain. All of these loaded faults, except for the San Andreas, experienced a seismicity rate increase at the time of the San Simeon mainshock. The Parkfield earthquake occurred 9 months later on the loaded portion of the San Andreas fault. The Parkfield earthquake unloaded the Hosgri fault and the reverse faults of the southern Los Osos domain, which both experienced seismicity rate decreases at the time of the Parkfield event, although the decreases may be related to the decay of San Simeon-triggered seismicity. Coulomb stress unloading from the Parkfield earthquake appears to have altered the aftershock decay rate of the southern cluster of San Simeon after-shocks, which is deficient compared to the expected number of aftershocks from the Omori decay parameters based on the pre-Parkfield aftershocks. Dynamic stress changes cannot explain the deficiency of aftershocks, providing evidence that static stress changes affect earthquake occurrence. However, a burst of seismicity following the Parkfield earthquake at Ragged Point, where the static stress was decreased, provides evidence for dynamic stress triggering. It therefore appears that both Coulomb static stress changes and dynamic stress changes affect the seismicity rate.

  5. Effects of topographic position and geology on shaking damage to residential wood-framed structures during the 2003 San Simeon earthquake, western San Luis obispo county, California

    Science.gov (United States)

    McCrink, T.P.; Wills, C.J.; Real, C.R.; Manson, M.W.

    2010-01-01

    A statistical evaluation of shaking damage to wood-framed houses caused by the 2003 M6.5 San Simeon earthquake indicates that both the rate and severity of damage, independent of structure type, are significantly greater on hilltops compared to hill slopes when underlain by Cretaceous or Tertiary sedimentary rocks. This increase in damage is interpreted to be the result of topographic amplification. An increase in the damage rate is found for all structures built on Plio-Pleistocene rocks independent of topographic position, and this is interpreted to be the result of amplified shaking caused by geologic site response. Damage rate and severity to houses built on Tertiary rocks suggest that amplification due to both topographic position and geologic site response may be occurring in these rocks, but effects from other topographic parameters cannot be ruled out. For all geologic and topographic conditions, houses with raised foundations are more frequently damaged than those with slab foundations. However, the severity of damage to houses on raised foundations is only significantly greater for those on hill slopes underlain by Tertiary rocks. Structures with some damage-resistant characteristics experienced greater damage severity on hilltops, suggesting a spectral response to topographic amplification. ?? 2010, Earthquake Engineering Research Institute.

  6. A stochastic estimate of ground motion at Oceano, California, for the M 6.5 22 December 2003 San Simeon earthquake, derived from aftershock recordings

    Science.gov (United States)

    Di, Alessandro C.; Boatwright, J.

    2006-01-01

    The U.S. Geological Survey deployed a digital seismic station in Oceano, California, in February 2004, to investigate the cause of damage and liquefaction from the 22 December 2003 M 6.5 San Simeon earthquake. This station recorded 11 M > 2.8 aftershocks in almost 8 weeks. We analyze these recordings, together with recordings of the mainshock and the same aftershocks obtained from nearby stations in Park Hill and San Luis Obispo, to estimate the mainshock ground motion in Oceano. We estimate the Fourier amplitude spectrum using generalized spectral ratio analysis. We test a set of aftershocks as Green's functions by comparing simulated and recorded acceleration amplitude spectra for the mainshock at San Luis Obispo and Park Hill. We convolve the aftershock accelerograms with a stochastic operator to simulate the duration and phase of the mainshock accelerograms. This approximation allows us to extend the range of aftershocks that can be used as Green's functions to events nearly three magnitude units smaller than the mainshock. Our realizations for the mainshock accelerogram at Oceano yield peak ground accelerations distributed as 28% ?? 4%g. We interpret these realizations as upper bounds for the actual ground motion, because our analysis assumes a linear response, whereas the presence of liquefaction indicates that the ground behaved nonlinearly in Oceano.

  7. A Stochastic Estimate of Ground Motion at Oceano, California, for the M6.5 December 22, 2003, San Simeon Earthquake, Derived from Aftershock Recordings

    Science.gov (United States)

    di Alessandro, C.; Boatwright, J.

    2004-12-01

    The U.S. Geological Survey deployed a digital seismic station in Oceano, California, in February 2004, to investigate the cause of damage and liquefaction from the 22 December 2003 M6.5 San Simeon earthquake. This station recorded 11 M\\> 2.8 aftershocks in almost eight weeks. We use these recordings, together with recordings of the main shock and the same aftershocks obtained from nearby stations in Park Hill and San Luis Obispo, to estimate the mainshock ground motion in Oceano. We estimate the Fourier amplitude spectrum using a generalized spectral ratio analysis that averages the spectral ratios from both stations for all the co-recorded aftershocks. We test three aftershocks as Green's functions by comparing simulated and recorded acceleration amplitude spectra for the main shock at Park Hill and San Luis Obispo. Instead of deconvolving the aftershock recordings from the mainshock recordings to estimate a source-time function, we convolve the aftershock accelerograms with a stochastic operator to simulate the duration and phase of the mainshock accelerograms. These stochastic operators are determined as sets of delta functions whose delays are randomly generated from a gamma distribution with a shape parameter of 1. We choose the scale parameter by fitting Husid plots of the Park Hill and San Luis Obsipo mainshock accelerograms. This stochastic approach allows us to extend the range of aftershocks that can be used as Green's functions to events nearly three magnitude units smaller than the main shock. Our realizations for the mainshock accelerogram at Oceano yield PGAs distributed as 28±4% g. We interpret these realizations as upper bounds for the actual ground motion because our analysis assumes that the ground behaved linearly, while the liquefaction and lateral spreading indicates that the ground behaved non-linearly. Geotechnical analysis of the site indicates that a PGA of 25% g would have initiated the liquefaction.

  8. The Observation of Fault Finiteness and Rapid Velocity Variation in Pnl Waveforms for the Mw 6.5, San Simeon, California Earthquake

    Science.gov (United States)

    Konca, A. O.; Ji, C.; Helmberger, D. V.

    2004-12-01

    We observed the effect of the fault finiteness in the Pnl waveforms from regional distances (4° to 12° ) for the Mw6.5 San Simeon Earthquake on 22 December 2003. We aimed to include more of the high frequencies (2 seconds and longer periods) than the studies that use regional data for focal solutions (5 to 8 seconds and longer periods). We calculated 1-D synthetic seismograms for the Pn_l portion for both a point source, and a finite fault solution. The comparison of the point source and finite fault waveforms with data show that the first several seconds of the point source synthetics have considerably higher amplitude than the data, while finite fault does not have a similar problem. This can be explained by reversely polarized depth phases overlapping with the P waves from the later portion of the fault, and causing smaller amplitudes for the beginning portion of the seismogram. This is clearly a finite fault phenomenon; therefore, can not be explained by point source calculations. Moreover, the point source synthetics, which are calculated with a focal solution from a long period regional inversion, are overestimating the amplitude by three to four times relative to the data amplitude, while finite fault waveforms have the similar amplitudes to the data. Hence, a moment estimation based only on the point source solution of the regional data could have been wrong by half of magnitude. We have also calculated the shifts of synthetics relative to data to fit the seismograms. Our results reveal that the paths from Central California to the south are faster than to the paths to the east and north. The P wave arrival to the TUC station in Arizona is 4 seconds earlier than the predicted Southern California model, while most stations to the east are delayed around 1 second. The observed higher uppermost mantle velocities to the south are consistent with some recent tomographic models. Synthetics generated with these models significantly improves the fits and the

  9. Local Postseismic Relaxation Observed After the 1992 Landers (M=7.3), 1999 Hector Mine (M=7.1), 2002 Denali (M=7.9), and 2003 San Simeon (M=6.5) Earthquakes

    Science.gov (United States)

    Svarc, J. L.; Savage, J. C.

    2004-12-01

    The U. S. Geological Survey has observed the local postseismic deformation following the 1992 Landers (M=7.3), 1999 Hector Mine (M=7.1), 2002 Denali (M=7.9), and 2003 San Simeon (M=6.5) earthquakes. The observations consist of repeated campaign-style GPS surveys of geodetic arrays (aperture ˜ 50 km) in the epicentral area of each earthquake. The data span the intervals from 0.037 to 5.6, 0.0025 to 4.5, 0.022 to 1.6, and 0.005 to 0.55 yr postearthquake for the Landers, Hector Mine, Denali, and San Simeon earthquakes, respectively. We have reduced the observations to positions of the monuments measured relative to another monument within the array. The temporal dependence of the relative displacements for each monument can be approximated by a+bt+c(1-exp[-t/d]) where a, b, c, and d are constants particular to that monument and t is the time after the earthquake. The relaxation times d were found to be 0.367±0.062, 0.274±0.024, 0.145±0.017, and 0.032±0.002 yr for the Landers, Hector Mine, Denali, and San Simeon earthquakes, respectively. The observed increase in d with the duration of the time series fit suggests that the relaxation process involves more than a single relaxation time. An alternative function a'+b't+c'log(1+t/d') where a', b', c', and d' are constants particular to each monument furnishes a better fit to the data. This logarithmic form of the relaxation (Lomnitz creep function), identical to the calculated response of a simple spring-slider system subject to rate-state friction [Marone et al., 1991], contains a continuous spectrum of relaxation times. In fitting data the time constant d' is determined by observations within the first few days postseismic and consequently is poorly defined. Adequate fits to the data are found by simply setting d'=0.001 yr and determining a', b', and c' by linear least squares. That the temporal dependence is so readily fit by both exponential and logarithmic functions suggests that the temporal dependence by itself

  10. Complex faulting associated with the 22 December 2003 Mw 6.5 San Simeon California, earthquake, aftershocks and postseismic surface deformation

    Science.gov (United States)

    McLaren, M.K.; Hardebeck, J.L.; van der Elst, N.; Unruh, J.R.; Bawden, G.W.; Blair, J.L.

    2008-01-01

    We use data from two seismic networks and satellite interferometric synthetic aperture radar (InSAR) imagery to characterize the 22 December 2003 Mw 6.5 San Simeon earthquake sequence. Absolute locations for the mainshock and nearly 10,000 aftershocks were determined using a new three-dimensional (3D) seismic velocity model; relative locations were obtained using double difference. The mainshock location found using the 3D velocity model is 35.704?? N, 121.096?? W at a depth of 9.7 ?? 0.7 km. The aftershocks concentrate at the northwest and southeast parts of the aftershock zone, between the mapped traces of the Oceanic and Nacimiento fault zones. The northwest end of the mainshock rupture, as defined by the aftershocks, projects from the mainshock hypocenter to the surface a few kilometers west of the mapped trace of the Oceanic fault, near the Santa Lucia Range front and the > 5 mm postseismic InSAR imagery contour. The Oceanic fault in this area, as mapped by Hall (1991), is therefore probably a second-order synthetic thrust or reverse fault that splays upward from the main seismogenic fault at depth. The southeast end of the rupture projects closer to the mapped Oceanic fault trace, suggesting much of the slip was along this fault, or at a minimum is accommodating much of the postseismic deformation. InSAR imagery shows ???72 mm of postseismic uplift in the vicinity of maximum coseismic slip in the central section of the rupture, and ???48 and ???45 mm at the northwest and southeast end of the aftershock zone, respectively. From these observations, we model a ???30-km-long northwest-trending northeast-dipping mainshock rupture surface - called the mainthrust - which is likely the Oceanic fault at depth, a ???10-km-long southwest-dipping backthrust parallel to the mainthrust near the hypocenter, several smaller southwest-dipping structures in the southeast, and perhaps additional northeast-dipping or subvertical structures southeast of the mainshock plane

  11. 2013 Pacific Gas and Electric Diablo Canyon Power Plant (DCPP): San Simeon, CA Central Coast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Diablo Canyon Power Plant (DCPP) LiDAR and Imagery datasets are comprised of three separate LiDAR surveys: Diablo Canyon (2010), Los Osos (2011), and San Simeon...

  12. Thermal-maturity trends within Franciscan rocks near Big Sur, California: Implications for offset along the San Gregorio San Simeon Hosgri fault zone

    Science.gov (United States)

    Underwood, Michael B.; Laughland, Matthew M.; Shelton, Kevin L.; Sedlock, Richard L.

    1995-09-01

    Conventional neotectonic interpretations place the Lucia and Point Sur subterranes of the Franciscan subduction complex on opposite sides of the San Gregorio San Simeon Hosgri dextral fault system and connect that system through the Sur fault zone. Our reconstructed paleotemperature contours, however, are not offset across the San Simeon segment, so differential displacement between the subterranes after peak heating appears to have been negligible. One explanation is that dextral slip on the faults has totaled only 5 10 km. A second possibility is that a discrete Hosgri San Simeon segment extends offshore of the amalgamated Point Sur and Lucia subterranes and that an en echelon stepover transfers dextral slip eastward to the San Gregorio Palo Colorado segment. In either case, the Sur fault zone appears to play a relatively insignificant role in the late Cenozoic tectonic evolution of central California.

  13. Hydrogeology, water quality, water budgets, and simulated responses to hydrologic changes in Santa Rosa and San Simeon Creek ground-water basins, San Luis Obispo County, California

    Science.gov (United States)

    Yates, Eugene B.; Van Konyenburg, Kathryn M.

    1998-01-01

    Santa Rosa and San Simeon Creeks are underlain by thin, narrow ground-water basins that supply nearly all water used for local agricultural and municipal purposes. The creeks discharge to the Pacific Ocean near the northwestern corner of San Luis Obispo County, California. The basins contain heterogeneous, unconsolidated alluvial deposits and are underlain by relatively impermeable bedrock. Both creeks usually stop flowing during the summer dry season, and most of the pumpage during that time is derived from ground-water storage. Annual pumpage increased substantially during 1956?88 and is now a large fraction of basin storage capacity. Consequently, dry-season water levels are lower and the water supply is more vulnerable to drought. The creeks are the largest source of ground-water recharge, and complete basin recharge can occur within the first few weeks of winter streamflow. Agricultural and municipal pumpages are the largest outflows and cause dry-season water-level declines throughout the San Simeon Basin. Pumping effects are more localized in the Santa Rosa Basin because of subsurface flow obstructions. Even without pumpage, a large quantity of water naturally drains out of storage at the upper ends of the basins during the dry season. Ground water is more saline in areas close to the coast than in inland areas. Although seawater intrusion has occurred in the past, it probably was not the cause of high salinity in 1988?89. Ground water is very hard, and concentrations of dissolved solids, chloride, iron, and manganese exceed drinking-water standards in some locations. Probability distributions of streamflow were estimated indirectly from a 120-year rainfall record because the periods of record for local stream-gaging stations were wetter than average. Dry-season durations with recurrence intervals between 5 and 43 years are likely to dry up some wells but not cause seawater intrusion. A winter with no streamflow is likely to occur about every 32 years and to

  14. Earthquake Damage in San Francisco, CA, April 18, 1906

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1906 San Francisco earthquake was the largest event (magnitude 8.3) to occur in the conterminous United States in the 20th Century. Recent estimates indicate...

  15. Discovery Along the San Andreas Fault: Relocating Photographs From the 1906 Earthquake in San Francisco and San Mateo Counties

    Science.gov (United States)

    Grove, K.; Prentice, C.; Polly, J.; Yuen, C.; Wu, K.; Zhong, S.; Lopez, J.

    2005-12-01

    April of 2006 will mark the 100-year anniversary of the great 1906 San Francisco earthquake. This earthquake was important not only because of its human tragedy (thousands of dead or homeless people), but also because of its scientific significance. The 8.3 magnitude earthquake ruptured 430 km of the northern San Andreas fault (SAF) and lasted nearly one minute. Investigations after the earthquake led to discoveries that were the beginning of modern earthquake theories and measuring instruments. This was also one of the first large-scale natural disasters to be photographed. Our research group, which is part of the National Science Foundation funded SF-ROCKS program, acquired photographs that were taken shortly after the earthquake in downtown San Francisco and along the SAF in San Mateo County. The SAF photos are part of a Geographical Information System (GIS) database being published on a U.S. Geological Survey web site. The goal of our project was to improve estimates of photograph locations and to compare the landscape features that were visible after the earthquake with the landscape that we see today. We used the GIS database to find initial photo locations, and we then used a high-precision Global Positioning System (GPS) to measure the geographic coordinates of the locations once we matched our view to what we saw in a photo. Where possible, we used a digital camera to retake photos from the same position, to show the difference in the landscape 100 years later. The 1906 photos show fault zone features such as ground rupture, sag ponds, shutter ridges, and offset fences. Changes to the landscape since 1906 have included erosion and grading of the land, building of houses and other structures, and more tree cover compared to previous grassland vegetation. Our project is part of 1906 Earthquake Centennial activities; it is contributing to the photo archive that helps scientists and engineers who study earthquakes and their effects. It will also help the

  16. Large scale simulations of the great 1906 San Francisco earthquake

    Science.gov (United States)

    Nilsson, S.; Petersson, A.; Rodgers, A.; Sjogreen, B.; McCandless, K.

    2006-12-01

    As part of a multi-institutional simulation effort, we present large scale computations of the ground motion during the great 1906 San Francisco earthquake using a new finite difference code called WPP. The material data base for northern California provided by USGS together with the rupture model by Song et al. is demonstrated to lead to a reasonable match with historical data. In our simulations, the computational domain covered 550 km by 250 km of northern California down to 40 km depth, so a 125 m grid size corresponds to about 2.2 Billion grid points. To accommodate these large grids, the simulations were run on 512-1024 processors on one of the supercomputers at Lawrence Livermore National Lab. A wavelet compression algorithm enabled storage of time-dependent volumetric data. Nevertheless, the first 45 seconds of the earthquake still generated 1.2 TByte of disk space and the 3-D post processing was done in parallel.

  17. Earthquake outlook for the San Francisco Bay region 2014–2043

    Science.gov (United States)

    Aagaard, Brad T.; Blair, James Luke; Boatwright, John; Garcia, Susan H.; Harris, Ruth A.; Michael, Andrew J.; Schwartz, David P.; DiLeo, Jeanne S.; Jacques, Kate; Donlin, Carolyn

    2016-06-13

    Using information from recent earthquakes, improved mapping of active faults, and a new model for estimating earthquake probabilities, the 2014 Working Group on California Earthquake Probabilities updated the 30-year earthquake forecast for California. They concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking somewhere in the San Francisco Bay region before 2043. Earthquakes this large are capable of causing widespread damage; therefore, communities in the region should take simple steps to help reduce injuries, damage, and disruption, as well as accelerate recovery from these earthquakes.

  18. San Andreas fault zone, California: M≥5.5 earthquake history

    Science.gov (United States)

    Toppozada, Tousson R.; Branum, D.M.; Reichle, M.S.; Hallstrom, C.L.

    2002-01-01

    The San Andreas fault zone has been a very significant source of major California earthquakes. From 1812 to 1906 it generated four major earthquakes of M 7 or larger in two pairs on two major portions of the fault. A pair of major earthquakes occurred on the central to southern region, where the 1857 faulting overlapped the 1812 earthquake faulting. A pair of major earthquakes occurred on the northern region, where the 1906 faulting overlapped the 1838 earthquake faulting. Also, earthquakes of M 7 occurred in the San Francisco Bay area on the Hayward fault in 1868 and the Santa Cruz Mountains near Loma Prieta in 1989 and on the Imperial fault near the border with Mexico in 1940.

  19. San Andreas Fault, California, M 5.5 or greater Earthquakes 1800-2000

    Science.gov (United States)

    Toppozada, T.; Branum, D.; Reichle, M.; Hallstrom, C.

    2001-12-01

    The San Andreas fault has been the most significant source of major California earthquakes since 1800. From 1812 to 1906 it generated four major earthquakes of M 7.2 or greater in two pairs on two major regions of the fault. A pair of major earthquakes occurred on the Central to Southern region, where the 1857 faulting overlapped the 1812 earthquake faulting. And a pair of major earthquakes occurred on the Northern region, where the 1906 faulting overlapped the 1838 earthquake faulting. The 1812 earthquake resulted from a rupture of up to about 200 km, from the region of Cajon Pass to as far as about 50 km west of Fort Tejon (Sieh and others, 1989). This rupture is the probable source of both the destructive 1812.12.8 "San Juan Capistrano" and the 1812.12.21 "Santa Barbara Channel" earthquakes. The 1838 earthquake's damage effects throughout the Bay area, from San Francisco to Santa Clara Valley and Monterey, were unequalled by any Bay area earthquake other than the 1906 event. The mainshock's effects, and numerous strong probable aftershocks in the San Juan Bautista vicinity in the following three years, suggest 1838 faulting from San Francisco to San Juan Bautista, and M about 7.4. The 630 km length of the San Andreas fault between San Francisco and Cajon Pass ruptured in the 1838 and 1857 earthquakes, except for about 75 km between Bitterwater and San Juan Bautista. The 1840-1841 probable aftershocks of the 1838 event occurred near San Juan Bautista, and the foreshocks and aftershocks of the 1857 event occurred near Bitterwater. In the Bitterwater area, strong earthquakes continued to occur until the 1885 earthquake of M 6.5. Near Parkfield, 40 to 70 km southeast of Bitterwater, M 5.5 or greater earthquakes have occurred from the 1870s to the 1960s. In the total Bitterwater to Parkfield zone bracketing the northern end of the 1857 rupture, the seismicity and moment release has decreased steadily since 1857, and has tended to migrate southeastward with time. The

  20. Predicted liquefaction of East Bay fills during a repeat of the 1906 San Francisco earthquake

    Science.gov (United States)

    Holzer, T.L.; Blair, J.L.; Noce, T.E.; Bennett, M.J.

    2006-01-01

    Predicted conditional probabilities of surface manifestations of liquefaction during a repeat of the 1906 San Francisco (M7.8) earthquake range from 0.54 to 0.79 in the area underlain by the sandy artificial fills along the eastern shore of San Francisco Bay near Oakland, California. Despite widespread liquefaction in 1906 of sandy fills in San Francisco, most of the East Bay fills were emplaced after 1906 without soil improvement to increase their liquefaction resistance. They have yet to be shaken strongly. Probabilities are based on the liquefaction potential index computed from 82 CPT soundings using median (50th percentile) estimates of PGA based on a ground-motion prediction equation. Shaking estimates consider both distance from the San Andreas Fault and local site conditions. The high probabilities indicate extensive and damaging liquefaction will occur in East Bay fills during the next M ??? 7.8 earthquake on the northern San Andreas Fault. ?? 2006, Earthquake Engineering Research Institute.

  1. Long-period building response to earthquakes in the San Francisco Bay Area

    Science.gov (United States)

    Olsen, A.H.; Aagaard, B.T.; Heaton, T.H.

    2008-01-01

    This article reports a study of modeled, long-period building responses to ground-motion simulations of earthquakes in the San Francisco Bay Area. The earthquakes include the 1989 magnitude 6.9 Loma Prieta earthquake, a magnitude 7.8 simulation of the 1906 San Francisco earthquake, and two hypothetical magnitude 7.8 northern San Andreas fault earthquakes with hypocenters north and south of San Francisco. We use the simulated ground motions to excite nonlinear models of 20-story, steel, welded moment-resisting frame (MRF) buildings. We consider MRF buildings designed with two different strengths and modeled with either ductile or brittle welds. Using peak interstory drift ratio (IDR) as a performance measure, the stiffer, higher strength building models outperform the equivalent more flexible, lower strength designs. The hypothetical magnitude 7.8 earthquake with hypocenter north of San Francisco produces the most severe ground motions. In this simulation, the responses of the more flexible, lower strength building model with brittle welds exceed an IDR of 2.5% (that is, threaten life safety) on 54% of the urban area, compared to 4.6% of the urban area for the stiffer, higher strength building with ductile welds. We also use the simulated ground motions to predict the maximum isolator displacement of base-isolated buildings with linear, single-degree-of-freedom (SDOF) models. For two existing 3-sec isolator systems near San Francisco, the design maximum displacement is 0.5 m, and our simulations predict isolator displacements for this type of system in excess of 0.5 m in many urban areas. This article demonstrates that a large, 1906-like earthquake could cause significant damage to long-period buildings in the San Francisco Bay Area.

  2. Ground motion modeling of the 1906 San Francisco earthquake II: Ground motion estimates for the 1906 earthquake and scenario events

    Energy Technology Data Exchange (ETDEWEB)

    Aagaard, B; Brocher, T; Dreger, D; Frankel, A; Graves, R; Harmsen, S; Hartzell, S; Larsen, S; McCandless, K; Nilsson, S; Petersson, N A; Rodgers, A; Sjogreen, B; Tkalcic, H; Zoback, M L

    2007-02-09

    We estimate the ground motions produced by the 1906 San Francisco earthquake making use of the recently developed Song et al. (2008) source model that combines the available geodetic and seismic observations and recently constructed 3D geologic and seismic velocity models. Our estimates of the ground motions for the 1906 earthquake are consistent across five ground-motion modeling groups employing different wave propagation codes and simulation domains. The simulations successfully reproduce the main features of the Boatwright and Bundock (2005) ShakeMap, but tend to over predict the intensity of shaking by 0.1-0.5 modified Mercalli intensity (MMI) units. Velocity waveforms at sites throughout the San Francisco Bay Area exhibit characteristics consistent with rupture directivity, local geologic conditions (e.g., sedimentary basins), and the large size of the event (e.g., durations of strong shaking lasting tens of seconds). We also compute ground motions for seven hypothetical scenarios rupturing the same extent of the northern San Andreas fault, considering three additional hypocenters and an additional, random distribution of slip. Rupture directivity exerts the strongest influence on the variations in shaking, although sedimentary basins do consistently contribute to the response in some locations, such as Santa Rosa, Livermore, and San Jose. These scenarios suggest that future large earthquakes on the northern San Andreas fault may subject the current San Francisco Bay urban area to stronger shaking than a repeat of the 1906 earthquake. Ruptures propagating southward towards San Francisco appear to expose more of the urban area to a given intensity level than do ruptures propagating northward.

  3. San Fernando Valley California Earthquakes of 1971 and 1994

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This slide set compares two earthquakes that were separated by a distance of 10 miles and a time of 23 years. Disproving the notion that once an earthquake has...

  4. Broadband Ground Motion Estimates for Scenario Earthquakes in the San Francisco Bay Region

    Science.gov (United States)

    Graves, R. W.

    2006-12-01

    Using broadband (0-10 Hz) simulation procedures, we are assessing the ground motions that could be generated by different earthquake scenarios occurring on major strike-slip faults of the San Francisco Bay region. These simulations explicitly account for several important ground motion features, including rupture directivity, 3D basin response, and the depletion of high frequency ground motions that occurs for surface rupturing events. This work compliments ongoing USGS efforts to quantify the ground shaking hazards throughout the San Francisco Bay region. These efforts involve development and testing of a 3D velocity model for northern California (USGS Bay Area Velocity Model, version 05.1.0) using observations from the 1989 Loma Prieta earthquake, characterization of 1906 rupture scenarios and ground motions, and the development and analysis of rupture scenarios on other Bay Area faults. The adequacy of the simulation model has been tested using ground motion data recorded during the 1989 Loma Prieta earthquake and by comparison with the reported intensity data from the 1906 earthquake. Comparisons of the simulated broadband (0-10 Hz) ground motions with the recorded motions for the 1989 Loma Prieta earthquake demonstrate that the modeling procedure matches the observations without significant bias over a broad range of frequencies, site types, and propagation distances. The Loma Prieta rupture model is based on a wavenumber-squared refinement of the Wald et al (1991) slip distribution, with the rupture velocity set at 75 percent of the local shear wave velocity and a Kostrov-type slip function having a rise time of about 1.4 sec. Simulations of 1906 scenario ruptures indicate very strong directivity effects to the north and south of the assumed epicenter, adjacent to San Francisco. We are currently analyzing additional earthquake scenarios on the Hayward-Rodgers Creek and San Andreas faults in order to provide a more comprehensive framework for assessing

  5. Effects of the 1989 San Francisco earthquake on frequency and content of nightmares.

    Science.gov (United States)

    Wood, J M; Bootzin, R R; Rosenhan, D; Nolen-Hoeksema, S; Jourden, F

    1992-05-01

    In a systematic evaluation of the effects of a natural disaster on nightmares, nightmare frequency was found to be about twice as high among 92 San Francisco Bay area college students as among 97 control subjects in Tucson, Arizona, after the 1989 Loma Prieta earthquake. Subjects in California had not only more nightmares in general but substantially more nightmares about earthquakes. Over a 3-week period, about 40% of those in the San Francisco Bay area reported one or more nightmares about an earthquake, as compared with only 5% of those in Arizona. However, nightmares about earthquakes were not more emotionally intense than other nightmares. These findings support the long-held view that the experience of a potentially traumatic event can result in more frequent nightmares, particularly about the event itself, but contradict the common opinion that nightmares about such events are unusually intense.

  6. Dual-system Tectonics of the San Luis Range and Vicinity, Coastal Central California

    Science.gov (United States)

    Hamilton, D. H.

    2010-12-01

    The M 6.5 "San Simeon" earthquake of December 22, 2003, occurred beneath the Santa Lucia Range in coastal central California, and resulted in around $250,000,000 property damage and two deaths from collapse of an historic building in the town of Paso Robles, located 40 km from the epicenter. The earthquake and more than 10,000 aftershocks were well recorded by nearby seismographs, which permitted detailed analysis of the event (eg: McLaren et al., 2008). This analysis facilitated evaluation of the hazard of the occurrence of a similar event in the nearby San Luis Range, located along the coast west of the city of San Luis Obispo some 55 km south of the San Simeon epicenter. The future occurrence of earthquakes analogous to the 2003 event in this area had been proposed in the late 1960’s (eg: Benioff and Smith, 1967; Richter, 1969) but the apparent hazard of such occurrences came to be overshadowed by the discovery of the “Hosgri” strike slip fault passing close to the area in the offshore. However data accumulated since the early 1970’s clearly demonstrate the hazard as being partitioned between nearby earthquakes of strike slip origin, and underlying earthquakes of thrust origin analogous to that of the 2003 San Simeon earthquake. And for the onshore San Luis Range area, an underlying actively seismogenic thrust wedge appears to provide the maximum potential seismic ground motion; exceeding that potentially resulting from large events on nearby strike slip faults of the San Simeon-Hosgri system, for onshore sites. Understanding and documentation of the geology, geomorphology, tectonics and seismogenesis of the San Luis Range and vicinity has recently experienced a quantum improvement as both new and accumulated data have been analysed. An integrated interpretation of all available data now clearly shows that a dual “side by side” system of active tectonics exists in the region. Essentially the most obvious evidence for this is seen simply in the

  7. Tidal triggering of earthquakes suggests poroelastic behavior on the San Andreas Fault

    Science.gov (United States)

    Delorey, Andrew A.; van der Elst, Nicholas J.; Johnson, Paul A.

    2017-02-01

    Tidal triggering of earthquakes is hypothesized to provide quantitative information regarding the fault's stress state, poroelastic properties, and may be significant for our understanding of seismic hazard. To date, studies of regional or global earthquake catalogs have had only modest successes in identifying tidal triggering. We posit that the smallest events that may provide additional evidence of triggering go unidentified and thus we developed a technique to improve the identification of very small magnitude events. We identify events applying a method known as inter-station seismic coherence where we prioritize detection and discrimination over characterization. Here we show tidal triggering of earthquakes on the San Andreas Fault. We find the complex interaction of semi-diurnal and fortnightly tidal periods exposes both stress threshold and critical state behavior. Our findings reveal earthquake nucleation processes and pore pressure conditions - properties of faults that are difficult to measure, yet extremely important for characterizing earthquake physics and seismic hazards.

  8. What is a surprise earthquake? The example of the 2002, San Giuliano (Italy event

    Directory of Open Access Journals (Sweden)

    M. Mucciarelli

    2005-06-01

    Full Text Available Both in scientific literature and in the mass media, some earthquakes are defined as «surprise earthquakes». Based on his own judgment, probably any geologist, seismologist or engineer may have his own list of past «surprise earthquakes». This paper tries to quantify the underlying individual perception that may lead a scientist to apply such a definition to a seismic event. The meaning is different, depending on the disciplinary approach. For geologists, the Italian database of seismogenic sources is still too incomplete to allow for a quantitative estimate of the subjective degree of belief. For seismologists, quantification is possible defining the distance between an earthquake and its closest previous neighbor. Finally, for engineers, the San Giuliano quake could not be considered a surprise, since probabilistic site hazard estimates reveal that the change before and after the earthquake is just 4%.

  9. Earthquake probabilities in the San Francisco Bay Region: 2000 to 2030 - a summary of findings

    Science.gov (United States)

    ,

    1999-01-01

    The San Francisco Bay region sits astride a dangerous “earthquake machine,” the tectonic boundary between the Pacific and North American Plates. The region has experienced major and destructive earthquakes in 1838, 1868, 1906, and 1989, and future large earthquakes are a certainty. The ability to prepare for large earthquakes is critical to saving lives and reducing damage to property and infrastructure. An increased understanding of the timing, size, location, and effects of these likely earthquakes is a necessary component in any effective program of preparedness. This study reports on the probabilities of occurrence of major earthquakes in the San Francisco Bay region (SFBR) for the three decades 2000 to 2030. The SFBR extends from Healdsberg on the northwest to Salinas on the southeast and encloses the entire metropolitan area, including its most rapidly expanding urban and suburban areas. In this study a “major” earthquake is defined as one with M≥6.7 (where M is moment magnitude). As experience from the Northridge, California (M6.7, 1994) and Kobe, Japan (M6.9, 1995) earthquakes has shown us, earthquakes of this size can have a disastrous impact on the social and economic fabric of densely urbanized areas. To reevaluate the probability of large earthquakes striking the SFBR, the U.S. Geological Survey solicited data, interpretations, and analyses from dozens of scientists representing a wide crosssection of the Earth-science community (Appendix A). The primary approach of this new Working Group (WG99) was to develop a comprehensive, regional model for the long-term occurrence of earthquakes, founded on geologic and geophysical observations and constrained by plate tectonics. The model considers a broad range of observations and their possible interpretations. Using this model, we estimate the rates of occurrence of earthquakes and 30-year earthquake probabilities. Our study considers a range of magnitudes for earthquakes on the major faults in the

  10. Catalog of earthquakes along the San Andreas fault system in Central California, April-June 1972

    Science.gov (United States)

    Wesson, R.L.; Bennett, R.E.; Lester, F.W.

    1973-01-01

    Numerous small earthquakes occur each day in the coast ranges of Central California. The detailed study of these earthquakes provides a tool for gaining insight into the tectonic and physical processes responsible for the generation of damaging earthquakes. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated by the National Center for Earthquake Research (NCER), U.S. Geological Survey, during the period April - June, 1972. The motivation for these detailed studies has been described by Pakiser and others (1969) and by Eaton and others (1970). Similar catalogs of earthquakes for the years 1969, 1970 and 1971 have been prepared by Lee and others (1972 b, c, d). A catalog for the first quarter of 1972 has been prepared by Wesson and others (1972). The basic data contained in these catalogs provide a foundation for further studies. This catalog contains data on 910 earthquakes in Central California. A substantial portion of the earthquakes reported in this catalog represents a continuation of the sequence of earthquakes in the Bear Valley area which began in February, 1972 (Wesson and others, 1972). Arrival times at 126 seismograph stations were used to locate the earthquakes listed in this catalog. Of these, 101 are telemetered stations operated by NCER. Readings from the remaining 25 stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley (UCB); the Earthquake Mechanism Laboratory, National Oceanic and Atmospheric Administration, San Francisco (EML); and the California Department of Water Resources, Sacramento. The Seismographic Stations of the University of California, Berkeley, have for many years published a bulletin describing earthquakes in Northern California and the surrounding area, and readings at UCB Stations from more distant events. The purpose of the present catalog is not to replace the UCB Bulletin, but rather to supplement

  11. Catalog of earthquakes along the San Andreas fault system in Central California: January-March, 1972

    Science.gov (United States)

    Wesson, R.L.; Bennett, R.E.; Meagher, K.L.

    1973-01-01

    Numerous small earthquakes occur each day in the Coast Ranges of Central California. The detailed study of these earthquakes provides a tool for gaining insight into the tectonic and physical processes responsible for the generation of damaging earthquakes. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated by the National Center for Earthquake Research (NCER), U.S. Geological Survey, during the period January - March, 1972. The motivation for these detailed studies has been described by Pakiser and others (1969) and by Eaton and others (1970). Similar catalogs of earthquakes for the years 1969, 1970 and 1971 have been prepared by Lee and others (1972 b,c,d). The basic data contained in these catalogs provide a foundation for further studies. This catalog contains data on 1,718 earthquakes in Central California. Of particular interest is a sequence of earthquakes in the Bear Valley area which contained single shocks with local magnitudes of S.O and 4.6. Earthquakes from this sequence make up roughly 66% of the total and are currently the subject of an interpretative study. Arrival times at 118 seismograph stations were used to locate the earthquakes listed in this catalog. Of these, 94 are telemetered stations operated by NCER. Readings from the remaining 24 stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley (UCB); the Earthquake Mechanism Laboratory, National Oceanic and Atmospheric Administration, San Francisco (EML); and the California Department of Water Resources, Sacramento. The Seismographic Stations of the University of California, Berkeley,have for many years published a bulletin describing earthquakes in Northern California and the surrounding area, and readings at UCB Stations from more distant events. The purpose of the present catalog is not to replace the UCB Bulletin, but rather to supplement it, by describing the

  12. Estimates of aseismic slip associated with small earthquakes near San Juan Bautista, CA

    Science.gov (United States)

    Hawthorne, J. C.; Simons, M.; Ampuero, J.-P.

    2016-11-01

    Postseismic slip observed after large (M > 6) earthquakes typically has an equivalent moment of a few tens of percent of the coseismic moment. Some observations of the recurrence intervals of repeating earthquakes suggest that postseismic slip following small (M≲4) earthquakes could be much larger—up to 10 or 100 times the coseismic moment. We use borehole strain data from U.S. Geological Survey strainmeter SJT to analyze deformation in the days before and after 1000 1.9 < M < 5 earthquakes near San Juan Bautista, CA. We find that on average, postseismic strain is roughly equal in magnitude to coseismic strain for the magnitude range considered, suggesting that postseismic moment following these small earthquakes is roughly equal to coseismic moment. This postseismic to coseismic moment ratio is larger than typically observed in earthquakes that rupture through the seismogenic zone but is much smaller than was hypothesized from modeling repeating earthquakes. Our results are consistent with a simple, self-similar model of earthquakes.

  13. Postseismic Deformation and Stress Evolution Following the 1906 San Francisco Earthquake

    Science.gov (United States)

    Glasscoe, M. T.

    2007-12-01

    Large earthquakes, like the M 7.8 1906 San Francisco earthquake, can have both short- and long-term effects on the strain field. Numerical simulation using finite element models is a key method to study time-dependent tectonic deformation mechanisms. Geodetic data are essential for testing model results for accuracy and realism. Previous GeoFEST (Geophysical Finite Element Simulation Tool) viscoelastic finite element model results indicate about 2-5 mm/yr of residual velocities in the 100 years following the 1906 San Francisco earthquake. These models combined simple, single fault viscoelastic finite element models featuring variable relaxation times in the lower crust with various elastic backslip models in order to create velocity profiles to compare with currently observed geodetic rates. This study will include new results from more sophisticated 3D GeoFEST models that incorporate multiple faults and imposed plate velocity boundary conditions and compare these results with GPS velocities recorded by the Bay Area Regional Deformation (BARD) network. In addition, the study will include results examining the evolution of the Coulomb stress changes in the viscoelastic model over the 100 years following the San Francisco earthquake.

  14. Catalog of earthquakes along the San Andreas fault system in Central California, July-September 1972

    Science.gov (United States)

    Wesson, R.L.; Meagher, K.L.; Lester, F.W.

    1973-01-01

    Numerous small earthquakes occur each day in the coast ranges of Central California. The detailed study of these earthquakes provides a tool for gaining insight into the tectonic and physical processes responsible for the generation of damaging earthquakes. This catalog contains the fundamental parameters for earthquakes located within and adjacent to the seismograph network operated by the National Center for Earthquake Research (NCER), U.S. Geological Survey, during the period July - September, 1972. The motivation for these detailed studies has been described by Pakiser and others (1969) and by Eaton and others (1970). Similar catalogs of earthquakes for the years 1969, 1970 and 1971 have been prepared by Lee and others (1972 b, c, d). Catalogs for the first and second quarters of 1972 have been prepared by Wessan and others (1972 a & b). The basic data contained in these catalogs provide a foundation for further studies. This catalog contains data on 1254 earthquakes in Central California. Arrival times at 129 seismograph stations were used to locate the earthquakes listed in this catalog. Of these, 104 are telemetered stations operated by NCER. Readings from the remaining 25 stations were obtained through the courtesy of the Seismographic Stations, University of California, Berkeley (UCB), the Earthquake Mechanism Laboratory, National Oceanic and Atmospheric Administration, San Francisco (EML); and the California Department of Water Resources, Sacramento. The Seismographic Stations of the University of California, Berkeley, have for many years published a bulletin describing earthquakes in Northern California and the surrounding area, and readings at UCB Stations from more distant events. The purpose of the present catalog is not to replace the UCB Bulletin, but rather to supplement it, by describing the seismicity of a portion of central California in much greater detail.

  15. A Viscoelastic earthquake simulator with application to the San Francisco Bay region

    Science.gov (United States)

    Pollitz, F.F.

    2009-01-01

    Earthquake simulation on synthetic fault networks carries great potential for characterizing the statistical patterns of earthquake occurrence. I present an earthquake simulator based on elastic dislocation theory. It accounts for the effects of interseismic tectonic loading, static stress steps at the time of earthquakes, and postearthquake stress readjustment through viscoelastic relaxation of the lower crust and mantle. Earthquake rupture initiation and termination are determined with a Coulomb failure stress criterion and the static cascade model. The simulator is applied to interacting multifault systems: one, a synthetic two-fault network, and the other, a fault network representative of the San Francisco Bay region. The faults are discretized both along strike and along dip and can accommodate both strike slip and dip slip. Stress and seismicity functions are evaluated over 30,000 yr trial time periods, resulting in a detailed statistical characterization of the fault systems. Seismicity functions such as the coefficient of variation and a- and b-values exhibit systematic patterns with respect to simple model parameters. This suggests that reliable estimation of the controlling parameters of an earthquake simulator is a prerequisite to the interpretation of its output in terms of seismic hazard.

  16. Long-Term Earthquake Forecasts in the San Francisco Bay Area: A Contrarian Perspective

    Science.gov (United States)

    Lindh, A. G.

    2003-12-01

    In historic time the San Francisco Bay Area (SFBA) has been the site of four large earthquakes, including the M7.8 1906 San Francisco earthquake, and most recently, the M6.9 1989 Loma Prieta earthquake. Of the eight major fault segments considered here, two have not experienced large earthquakes in about 200 years, and the SF Peninsula segment of the 1906 rupture on the San Andreas appears from my calculations to be close to fully reloaded as well. I have used simple geophysical and statistical models (elastic rebound model and Weibull distribution) to estimate the probability of large earthquakes (M7 or larger) in the SFBA in the coming decades. I have used seismicity, geology, and geodesy to estimate segment boundaries, recurrence intervals, and the associated uncertainties. The results indicate that the SFBA has an approximately 80% chance of a large earthquake in the next 30 years, with four segments dominating the 30 yr probabilities; San Francisco Peninsula (32%), Southern Hayward (39%), Northern Hayward (28%) and Rodgers Cr (30%). Because of the proximity of these four segments to the urban portions of San Francisco and Oakland, the probability of these most vulnerable areas experiencing strong ground motion (an M7 within 25 km or less) one or more times within the next 30 years is about 70%. Because of the breadth and quality of our understanding of the earthquake machine in the SFBA, these probabilities depend in large part on the intrinsic variance in the earthquake recurrence process itself -- most conveniently expressed as the ratio of the standard deviation to the mean recurrence time, or intrinsic coefficient of variation (CVI). I have applied a new approach to estimating CVI, using the time since the last characteristic event (the "open-interval") on well characterized segments. Combined with an estimate of the mean recurrence time on each segment, an estimate of the likelihood of each open interval can be computed, and a simple maximum likelihood

  17. Rupture directivity of micro-earthquakes along the San Andreas fault

    Science.gov (United States)

    Wang, E.; Rubin, A. M.

    2009-12-01

    Theoretically, it is expected that earthquakes occurring on an interface separating materials with different elastic properties might have a preferential rupture propagation direction. To test for this, we searched for indications of directivity by examining spectral ratios of multiple pairs of nearby earthquakes at azimuthally distributed seismic stations. By taking the spectral ratios, this technique is capable of canceling path and station terms in seismic spectra. It differs from a typical empirical Green's Function approach in that it compares events with similar sizes as well as events with significant size differences. The spectral ratios are fitted with a simple forward model, in which a bidirectional earthquake source is composed of two point sources moving at constant velocities in opposite directions (assumed to be horizontal). Each bidirectional earthquake has four model parameters: the lengths of the two rupture halves running in opposite directions, and their propagation velocities. A priori information concerning the total rupture length of bidirectional events are computed from catalog magnitude using a moment-magnitude relation and a 3MPa stress drop on an equidimensional rupture. The a priori rupture velocity is peaked at 0.8Vs and constrained to be smaller than Vs. Since identical earthquakes would produce frequency-independent spectral ratios at all azimuths, determining the initiation points of earthquakes requires variability in event size and/or relative directivity. The relocated catalog of Rubin [2002] was used to define 78 clusters of repeating earthquakes along the central San Andreas fault. The spectral ratios of all combinations of earthquake pairs in each cluster were fitted with synthetic spectral ratios at stations with sufficient signal-to-noise ratio and coherence. The inversion results show that, as might have been expected, differences in rupture processes (duration and relative directivity) of the earthquakes within most

  18. Cradle of the Earthquake: Exploring the Underwater San Andreas Fault on the R/V Pacific Storm and the SRV Derek M. Baylis between 20100910 and 20101003

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Over one hundred years after the devastating Great 1906 Earthquake that nearly destroyed San Francisco, this expedition explored the Northern San Andreas Fault, the...

  19. Holocene slip rates along the San Andreas Fault System in the San Gorgonio Pass and implications for large earthquakes in southern California

    Science.gov (United States)

    Heermance, Richard V.; Yule, Doug

    2017-06-01

    The San Gorgonio Pass (SGP) in southern California contains a 40 km long region of structural complexity where the San Andreas Fault (SAF) bifurcates into a series of oblique-slip faults with unknown slip history. We combine new 10Be exposure ages (Qt4: 8600 (+2100, -2200) and Qt3: 5700 (+1400, -1900) years B.P.) and a radiocarbon age (1260 ± 60 years B.P.) from late Holocene terraces with scarp displacement of these surfaces to document a Holocene slip rate of 5.7 (+2.7, -1.5) mm/yr combined across two faults. Our preferred slip rate is 37-49% of the average slip rates along the SAF outside the SGP (i.e., Coachella Valley and San Bernardino sections) and implies that strain is transferred off the SAF in this area. Earthquakes here most likely occur in very large, throughgoing SAF events at a lower recurrence than elsewhere on the SAF, so that only approximately one third of SAF ruptures penetrate or originate in the pass.Plain Language SummaryHow large are earthquakes on the southern San Andreas Fault? The answer to this question depends on whether or not the earthquake is contained only along individual fault sections, such as the Coachella Valley section north of Palm Springs, or the rupture crosses multiple sections including the area through the San Gorgonio Pass. We have determined the age and offset of faulted stream deposits within the San Gorgonio Pass to document slip rates of these faults over the last 10,000 years. Our results indicate a long-term slip rate of 6 mm/yr, which is almost 1/2 of the rates east and west of this area. These new rates, combined with faulted geomorphic surfaces, imply that large magnitude earthquakes must occasionally rupture a 300 km length of the San Andreas Fault from the Salton Sea to the Mojave Desert. Although many ( 65%) earthquakes along the southern San Andreas Fault likely do not rupture through the pass, our new results suggest that large >Mw 7.5 earthquakes are possible on the southern San Andreas Fault and likely

  20. Along-strike variations in fault frictional properties along the San Andreas Fault near Cholame, California from joint earthquake and low-frequency earthquake relocations

    Science.gov (United States)

    Harrington, R.M; Cochran, Elizabeth S.; Griffiths, E.M.; Zeng, X.; Thurber, C.

    2016-01-01

    Recent observations of low‐frequency earthquakes (LFEs) and tectonic tremor along the Parkfield–Cholame segment of the San Andreas fault suggest slow‐slip earthquakes occur in a transition zone between the shallow fault, which accommodates slip by a combination of aseismic creep and earthquakes (35  km depth). However, the spatial relationship between shallow earthquakes and LFEs remains unclear. Here, we present precise relocations of 34 earthquakes and 34 LFEs recorded during a temporary deployment of 13 broadband seismic stations from May 2010 to July 2011. We use the temporary array waveform data, along with data from permanent seismic stations and a new high‐resolution 3D velocity model, to illuminate the fine‐scale details of the seismicity distribution near Cholame and the relation to the distribution of LFEs. The depth of the boundary between earthquakes and LFE hypocenters changes along strike and roughly follows the 350°C isotherm, suggesting frictional behavior may be, in part, thermally controlled. We observe no overlap in the depth of earthquakes and LFEs, with an ∼5  km separation between the deepest earthquakes and shallowest LFEs. In addition, clustering in the relocated seismicity near the 2004 Mw 6.0 Parkfield earthquake hypocenter and near the northern boundary of the 1857 Mw 7.8 Fort Tejon rupture may highlight areas of frictional heterogeneities on the fault where earthquakes tend to nucleate.

  1. Along-strike variations in fault frictional properties along the San Andreas Fault near Cholame, California from joint earthquake and low-frequency earthquake relocations

    Science.gov (United States)

    Harrington, Rebecca M.; Cochran, Elizabeth S.; Griffiths, Emily M.; Zeng, Xiangfang; Thurber, Clifford H.

    2016-01-01

    Recent observations of low‐frequency earthquakes (LFEs) and tectonic tremor along the Parkfield–Cholame segment of the San Andreas fault suggest slow‐slip earthquakes occur in a transition zone between the shallow fault, which accommodates slip by a combination of aseismic creep and earthquakes (fault, which accommodates slip by stable sliding (>35  km depth). However, the spatial relationship between shallow earthquakes and LFEs remains unclear. Here, we present precise relocations of 34 earthquakes and 34 LFEs recorded during a temporary deployment of 13 broadband seismic stations from May 2010 to July 2011. We use the temporary array waveform data, along with data from permanent seismic stations and a new high‐resolution 3D velocity model, to illuminate the fine‐scale details of the seismicity distribution near Cholame and the relation to the distribution of LFEs. The depth of the boundary between earthquakes and LFE hypocenters changes along strike and roughly follows the 350°C isotherm, suggesting frictional behavior may be, in part, thermally controlled. We observe no overlap in the depth of earthquakes and LFEs, with an ∼5  km separation between the deepest earthquakes and shallowest LFEs. In addition, clustering in the relocated seismicity near the 2004 Mw 6.0 Parkfield earthquake hypocenter and near the northern boundary of the 1857 Mw 7.8 Fort Tejon rupture may highlight areas of frictional heterogeneities on the fault where earthquakes tend to nucleate.

  2. Ultra-low frequency electromagnetic measurements associated with the 1998 Mw 5.1 San Juan Bautista, California earthquake and implications for mechanisms of electromagnetic earthquake precursors

    Science.gov (United States)

    Karakelian, D.; Klemperer, S. L.; Fraser-Smith, A. C.; Thompson, G. A.

    2002-11-01

    Ultra-low frequency (ULF: 0.01-10 Hz) magnetic field anomalies prior to M≥6.0 earthquakes have been reported in various regions of the world. Here, we test whether smaller magnitude earthquakes have associated ULF anomalies by using continuous measurements made ˜9 km above and ˜2 km NE of the epicenter of the Mw 5.1 8/12/98 San Juan Bautista, CA earthquake. Half-hour spectral averages of the magnetic field data in nine different ULF frequency bands show no long-term (days to weeks) magnetic field anomaly prior to the earthquake. In addition, magnetic and electric field polarization shows no anomalous behavior clearly associated with seismic activity. An ˜0.02 nT increase in activity for 2 h prior to the earthquake is close to the background noise levels precluding identification of a precursor. We present scaling calculations to show if precursory ULF anomalies are related to the size of the earthquake. The observed ˜0.02 nT increase is the approximately expected magnetic anomaly prior to the San Juan Bautista (SBJ) earthquake, based on the anomaly observed prior to the 1989 Loma Prieta (LP) earthquake. Our reexamination of previously proposed dilatant-conductive and piezomagnetic mechanisms for ULF precursors shows that these effects are consistent with the observations prior to the SJB earthquake based on the observations (i.e., lack of a strong precursor). In contrast, previously proposed electrokinetic and magnetohydrodynamic (MHD) mechanisms do not appear to be appropriate for this particular earthquake. This analysis further supports the hypothesis that precursory ULF signals are related to the size of the earthquake.

  3. Ground-motion modeling of the 1906 San Francisco Earthquake, part II: Ground-motion estimates for the 1906 earthquake and scenario events

    Science.gov (United States)

    Aagaard, B.T.; Brocher, T.M.; Dolenc, D.; Dreger, D.; Graves, R.W.; Harmsen, S.; Hartzell, S.; Larsen, S.; McCandless, K.; Nilsson, S.; Petersson, N.A.; Rodgers, A.; Sjogreen, B.; Zoback, M.L.

    2008-01-01

    We estimate the ground motions produce by the 1906 San Francisco earthquake making use of the recently developed Song et al. (2008) source model that combines the available geodetic and seismic observations and recently constructed 3D geologic and seismic velocity models. Our estimates of the ground motions for the 1906 earthquake are consistent across five ground-motion modeling groups employing different wave propagation codes and simulation domains. The simulations successfully reproduce the main features of the Boatwright and Bundock (2005) ShakeMap, but tend to over predict the intensity of shaking by 0.1-0.5 modified Mercalli intensity (MMI) units. Velocity waveforms at sites throughout the San Francisco Bay Area exhibit characteristics consistent with rupture directivity, local geologic conditions (e.g., sedimentary basins), and the large size of the event (e.g., durations of strong shaking lasting tens of seconds). We also compute ground motions for seven hypothetical scenarios rupturing the same extent of the northern San Andreas fault, considering three additional hypocenters and an additional, random distribution of slip. Rupture directivity exerts the strongest influence on the variations in shaking, although sedimentary basins do consistently contribute to the response in some locations, such as Santa Rosa, Livermore, and San Jose. These scenarios suggest that future large earthquakes on the northern San Andreas fault may subject the current San Francisco Bay urban area to stronger shaking than a repeat of the 1906 earthquake. Ruptures propagating southward towards San Francisco appear to expose more of the urban area to a given intensity level than do ruptures propagating northward.

  4. GPS Seismology and Earthquake Early Warning along the Southern San Andreas Fault System

    Science.gov (United States)

    Bock, Y.; Jackson, M. E.

    2007-05-01

    We are in the process of upgrading CGPS stations in southern California to high-rate (1-10 Hz) real-time (latency Cerro Prieto faults, the region of highest strain rate in southern California and the narrowest part of the North America-Pacific plate boundary. South of the Big Bend, the zero velocity contour (the "boundary") between the North America and Pacific plates does not follow the SAF segment, but rather is located just east of the San Jacinto Fault (SJF) segment and then follows the Imperial and Cerro Prieto faults. The primary purpose of the real-time network is to serve as an early warning system for a large earthquake along the southern San Andreas Fault System by quickly measuring coseismic displacements, and also for GPS seismology to rapidly measure the associated dynamic displacements. The network, called the California Real Time Network (CRTN), also supplies data for real GPS surveys within the region and will provide rapid displacement waveforms to the SCEC data archive at Caltech in the event of a medium to large earthquake. Although the real-time data flow is currently at 1 Hz, the PBO stations have an internal buffer that records GPS data at a 10 Hz rate.

  5. Strong earthquake motion estimates for three sites on the U.C. San Diego campus

    Energy Technology Data Exchange (ETDEWEB)

    Day, S; Doroudian, M; Elgamal, A; Gonzales, S; Heuze, F; Lai, T; Minster, B; Oglesby, D; Riemer, M; Vernon, F; Vucetic, M; Wagoner, J; Yang, Z

    2002-05-07

    The approach of the Campus Earthquake Program (CEP) is to combine the substantial expertise that exists within the UC system in geology, seismology, and geotechnical engineering, to estimate the earthquake strong motion exposure of UC facilities. These estimates draw upon recent advances in hazard assessment, seismic wave propagation modeling in rocks and soils, and dynamic soil testing. The UC campuses currently chosen for application of our integrated methodology are Riverside, San Diego, and Santa Barbara. The procedure starts with the identification of possible earthquake sources in the region and the determination of the most critical fault(s) related to earthquake exposure of the campus. Combined geological, geophysical, and geotechnical studies are then conducted to characterize each campus with specific focus on the location of particular target buildings of special interest to the campus administrators. We drill, sample, and geophysically log deep boreholes next to the target structure, to provide direct in-situ measurements of subsurface material properties, and to install uphole and downhole 3-component seismic sensors capable of recording both weak and strong motions. The boreholes provide access below the soil layers, to deeper materials that have relatively high seismic shear-wave velocities. Analyses of conjugate downhole and uphole records provide a basis for optimizing the representation of the low-strain response of the sites. Earthquake rupture scenarios of identified causative faults are combined with the earthquake records and with nonlinear soil models to provide site-specific estimates of strong motions at the selected target locations. The predicted ground motions are shared with the UC consultants, so that they can be used as input to the dynamic analysis of the buildings. Thus, for each campus targeted by the CEP project, the strong motion studies consist of two phases, Phase 1--initial source and site characterization, drilling

  6. Space Geodetic Imaging of Earthquake Potential in the San Francisco Bay Area

    Science.gov (United States)

    Bürgmann, R.; Funning, G. J.; Ferretti, A.; Novali, F.

    2008-12-01

    Active crustal deformation in the San Francisco Bay Area includes contributions from elastic strain buildup across major faults and aseismic fault creep relieving a small portion of the plate tectonic fault slip budget. Increasingly precise and dense measurements of surface motions using GPS and InSAR satellite data provide valuable information on the distribution and rates of surface deformation. In the Eastern Bay Area, the Hayward, Calaveras and Concord faults are known to be source areas of moderate to large earthquakes, but also exhibit significant aseismic fault creep. Modeling of space geodetic data collected along the Hayward fault over > 10-year period allows for the determination of the distribution of currently locked asperities and creeping portions of the fault zone. Inversions of these data reveal a locked zone at depth which has built up a slip deficit since the 1868 Hayward fault rupture that is large enough to produce a M > 6.7 earthquake. The inferred slip rates along the creeping portions of the Hayward fault are significantly less than the long-term slip rate, and thus a substantial slip deficit is accumulating there as well. However, it is possible that the creeping portions of the East Bay faults will catch up most of their slip deficit by accelerated postseismic creep following large ruptures of the currently locked asperities. The kinematic locking models help inform dynamic rupture scenarios and ground motion simulations of major earthquakes along the Hayward fault (Aagaard et al., 2008 Fall AGU).

  7. A new method to identify earthquake swarms applied to seismicity near the San Jacinto Fault, California

    Science.gov (United States)

    Zhang, Qiong; Shearer, Peter M.

    2016-05-01

    Understanding earthquake clustering in space and time is important but also challenging because of complexities in earthquake patterns and the large and diverse nature of earthquake catalogues. Swarms are of particular interest because they likely result from physical changes in the crust, such as slow slip or fluid flow. Both swarms and clusters resulting from aftershock sequences can span a wide range of spatial and temporal scales. Here we test and implement a new method to identify seismicity clusters of varying sizes and discriminate them from randomly occurring background seismicity. Our method searches for the closest neighbouring earthquakes in space and time and compares the number of neighbours to the background events in larger space/time windows. Applying our method to California's San Jacinto Fault Zone (SJFZ), we find a total of 89 swarm-like groups. These groups range in size from 0.14 to 7.23 km and last from 15 min to 22 d. The most striking spatial pattern is the larger fraction of swarms at the northern and southern ends of the SJFZ than its central segment, which may be related to more normal-faulting events at the two ends. In order to explore possible driving mechanisms, we study the spatial migration of events in swarms containing at least 20 events by fitting with both linear and diffusion migration models. Our results suggest that SJFZ swarms are better explained by fluid flow because their estimated linear migration velocities are far smaller than those of typical creep events while large values of best-fitting hydraulic diffusivity are found.

  8. Earthquake stress drops and inferred fault strength on the Hayward Fault, east San Francisco Bay, California

    Science.gov (United States)

    Hardebeck, J.L.; Aron, A.

    2009-01-01

    We study variations in earthquake stress drop with respect to depth, faulting regime, creeping versus locked fault behavior, and wall-rock geology. We use the P-wave displacement spectra from borehole seismic recordings of M 1.0-4.2 earthquakes in the east San Francisco Bay to estimate stress drop using a stack-and-invert empirical Green's function method. The median stress drop is 8.7 MPa, and most stress drops are in the range between 0.4 and 130 MPa. An apparent correlation between stress drop and magnitude is entirely an artifact of the limited frequency band of 4-55 Hz. There is a trend of increasing stress drop with depth, with a median stress drop of ~5 MPa for 1-7 km depth, ~10 MPa for 7-13 km depth, and ~50 MPa deeper than 13 km. We use S=P amplitude ratios measured from the borehole records to better constrain the first-motion focal mechanisms. High stress drops are observed for a deep cluster of thrust-faulting earthquakes. The correlation of stress drops with depth and faulting regime implies that stress drop is related to the applied shear stress. We compare the spatial distribution of stress drops on the Hayward fault to a model of creeping versus locked behavior of the fault and find that high stress drops are concentrated around the major locked patch near Oakland. This also suggests a connection between stress drop and applied shear stress, as the locked patch may experience higher applied shear stress as a result of the difference in cumulative slip or the presence of higher-strength material. The stress drops do not directly correlate with the strength of the proposed wall-rock geology at depth, suggesting that the relationship between fault strength and the strength of the wall rock is complex.

  9. Locating Very-Low-Frequency Earthquakes in the San Andreas Fault.

    Science.gov (United States)

    Peña-Castro, A. F.; Harrington, R. M.; Cochran, E. S.

    2016-12-01

    The portion of tectonic fault where rheological properties transtition from brittle to ductile hosts a variety of seismic signals suggesting a range of slip velocities. In subduction zones, the two dominantly observed seismic signals include very-low frequency earthquakes ( VLFEs), and low-frequency earthquakes (LFEs) or tectonic tremor. Tremor and LFE are also commonly observed in transform faults, however, VLFEs have been reported dominantly in subduction zone environments. Here we show some of the first known observations of VLFEs occurring on a plate boundary transform fault, the San Andreas Fault (SAF) between the Cholame-Parkfield segment in California. We detect VLFEs using both permanent and temporary stations in 2010-2011 within approximately 70 km of Cholame, California. We search continous waveforms filtered from 0.02-0.05 Hz, and remove time windows containing teleseismic events and local earthquakes, as identified in the global Centroid Moment Tensor (CMT) and the Northern California Seismic Network (NCSN) catalog. We estimate the VLFE locations by converting the signal into envelopes, and cross-correlating them for phase-picking, similar to procedures used for locating tectonic tremor. We first perform epicentral location using a grid search method and estimate a hypocenter location using Hypoinverse and a shear-wave velocity model when the epicenter is located close to the SAF trace. We account for the velocity contrast across the fault using separate 1D velocity models for stations on each side. Estimated hypocentral VLFE depths are similar to tremor catalog depths ( 15-30 km). Only a few VLFEs produced robust hypocentral locations, presumably due to the difficulty in picking accurate phase arrivals with such a low-frequency signal. However, for events for which no location could be obtained, the moveout of phase arrivals across the stations were similar in character, suggesting that other observed VLFEs occurred in close proximity.

  10. A comparative study of bridge damage due to the Wenchuan,Northridge, Loma Prieta and San Fernando earthquakes

    Institute of Scientific and Technical Information of China (English)

    Wang Zhiqiang; George C. Lee

    2009-01-01

    A comparative study of selected bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes is described in this paper. Typical ground motion effects considered include large ground fault displacement, liquefaction, landslide, and strong ground shaking. Issues related to falling spans, inadequate detailing for structural ductility and complex bridge configurations are discussed within the context of the recent seismic design codes of China and the US. A significant lesson learned from the Great Wenchuan earthquake, far beyond the opportunities to improve the seismic design provisions for bridges, is articulated.

  11. A comparative study of bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes

    Science.gov (United States)

    Wang, Zhiqiang; Lee, George C.

    2009-06-01

    A comparative study of selected bridge damage due to the Wenchuan, Northridge, Loma Prieta and San Fernando earthquakes is described in this paper. Typical ground motion effects considered include large ground fault displacement, liquefaction, landslide, and strong ground shaking. Issues related to falling spans, inadequate detailing for structural ductility and complex bridge configurations are discussed within the context of the recent seismic design codes of China and the US. A significant lesson learned from the Great Wenchuan earthquake, far beyond the opportunities to improve the seismic design provisions for bridges, is articulated.

  12. Liquefaction during the 1977 San Juan Province, Argentina earthquake (Ms = 7.4)

    Science.gov (United States)

    Youd, T.L.; Keefer, D.K.

    1994-01-01

    Liquefaction effects generated by the 1977 San Juan Province, Argentina, earthquake (Ms = 7.4) are described. The larger and more abundant effects were concentrated in the 60-km long band of the lowlands in the Valle del Bermejo and in an equally long band along the Rio San Juan in the Valle de Tulum. Fissures in the Valle del Bermejo were up to several hundred meters long and up to several meters wide. Sand deposits, from boils that erupted through the fissures, covered areas up to tens of square meters. Fissures generally parallelled nearby stream channels. Because the Valle del Bermejo is undeveloped, these large features caused no damage. Liquefaction in the Valle del Tulum caused important or unusual damage at several localities, including the following five sites: (1) At the Barrio Justo P. Castro, a subdivision of Caucete, liquefaction of subsurface sediments decoupled overlying, unliquefied stiff sediments, producing a form of ground failure called "ground oscillation". The associated differential ground movements pulled apart houses and pavements in extension, while shearing curbs and buckling canal linings in compression at the same locality. (2) At the Escuela Normal, in Caucete, the roof of a 30-m long single-story classroom building shifted westward relative to the foundation. That displacement fractured and tilted columns supporting the roof. The foundation was fractured at several places, leaving open cracks, as wide as 15 mm. The cumulative width of the open cracks was 48 mm, an amount roughly equivalent to the 63 mm of offset between the roof and foundation at the east end of the building. The ground and foundation beneath the building extended (or spread) laterally opening cracks and lengthening the foundation while the roof remained in place. (3) The most spectacular damage to structures at the community of San Martin was the tilting of a 6-m high water tower and the toppling of a nearby pump house into a 1-m deep crater. Similarly, a small

  13. San Andreas fault geometry at Desert Hot Springs, California, and its effects on earthquake hazards and groundwater

    Science.gov (United States)

    Catchings, R.D.; Rymer, M.J.; Goldman, M.R.; Gandhok, G.

    2009-01-01

    The Mission Creek and Banning faults are two of the principal strands of the San Andreas fault zone in the northern Coachella Valley of southern California. Structural characteristics of the faults affect both regional earthquake hazards and local groundwater resources. We use seismic, gravity, and geological data to characterize the San Andreas fault zone in the vicinity of Desert Hot Springs. Seismic images of the upper 500 m of the Mission Creek fault at Desert Hot Springs show multiple fault strands distributed over a 500 m wide zone, with concentrated faulting within a central 200 m wide area of the fault zone. High-velocity (up to 5000 m=sec) rocks on the northeast side of the fault are juxtaposed against a low-velocity (6.0) earthquakes in the area (in 1948 and 1986) occurred at or near the depths (~10 to 12 km) of the merged (San Andreas) fault. Large-magnitude earthquakes that nucleate at or below the merged fault will likely generate strong shaking from guided waves along both fault zones and from amplified seismic waves in the low-velocity basin between the two fault zones. The Mission Creek fault zone is a groundwater barrier with the top of the water table varying by 60 m in depth and the aquifer varying by about 50 m in thickness across a 200 m wide zone of concentrated faulting.

  14. Retardations in fault creep rates before local moderate earthquakes along the San Andreas fault system, central California

    Science.gov (United States)

    Burford, R.O.

    1988-01-01

    Records of shallow aseismic slip (fault creep) obtained along parts of the San Andreas and Calaveras faults in central California demonstrate that significant changes in creep rates often have been associated with local moderate earthquakes. An immediate postearthquake increase followed by gradual, long-term decay back to a previous background rate is generally the most obvious earthquake effect on fault creep. This phenomenon, identified as aseismic afterslip, usually is characterized by above-average creep rates for several months to a few years. In several cases, minor step-like movements, called coseismic slip events, have occurred at or near the times of mainshocks. One extreme case of coseismic slip, recorded at Cienega Winery on the San Andreas fault 17.5 km southeast of San Juan Bautista, consisted of 11 mm of sudden displacement coincident with earthquakes of ML=5.3 and ML=5.2 that occurred 2.5 minutes apart on 9 April 1961. At least one of these shocks originated on the main fault beneath the winery. Creep activity subsequently stopped at the winery for 19 months, then gradually returned to a nearly steady rate slightly below the previous long-term average. The phenomena mentioned above can be explained in terms of simple models consisting of relatively weak material along shallow reaches of the fault responding to changes in load imposed by sudden slip within the underlying seismogenic zone. In addition to coseismic slip and afterslip phenomena, however, pre-earthquake retardations in creep rates also have been observed. Onsets of significant, persistent decreases in creep rates have occurred at several sites 12 months or more before the times of moderate earthquakes. A 44-month retardation before the 1979 ML=5.9 Coyote Lake earthquake on the Calaveras fault was recorded at the Shore Road creepmeter site 10 km northwest of Hollister. Creep retardation on the San Andreas fault near San Juan Bautista has been evident in records from one creepmeter site for

  15. Heterogeneous slip and rupture models of the San Andreas fault zone based upon three-dimensional earthquake tomography

    Energy Technology Data Exchange (ETDEWEB)

    Foxall, William [Univ. of California, Berkeley, CA (United States)

    1992-11-01

    Crystal fault zones exhibit spatially heterogeneous slip behavior at all scales, slip being partitioned between stable frictional sliding, or fault creep, and unstable earthquake rupture. An understanding the mechanisms underlying slip segmentation is fundamental to research into fault dynamics and the physics of earthquake generation. This thesis investigates the influence that large-scale along-strike heterogeneity in fault zone lithology has on slip segmentation. Large-scale transitions from the stable block sliding of the Central 4D Creeping Section of the San Andreas, fault to the locked 1906 and 1857 earthquake segments takes place along the Loma Prieta and Parkfield sections of the fault, respectively, the transitions being accomplished in part by the generation of earthquakes in the magnitude range 6 (Parkfield) to 7 (Loma Prieta). Information on sub-surface lithology interpreted from the Loma Prieta and Parkfield three-dimensional crustal velocity models computed by Michelini (1991) is integrated with information on slip behavior provided by the distributions of earthquakes located using, the three-dimensional models and by surface creep data to study the relationships between large-scale lithological heterogeneity and slip segmentation along these two sections of the fault zone.

  16. Mafic and ultramafic inclusions along the San Andreas Fault System: their geophysical character and effect on earthquake behavior, California, USA

    Science.gov (United States)

    Ponce, D. A.; Langenheim, V. E.; Jachens, R. C.; Hildenbrand, T. G.

    2003-04-01

    Mafic and ultramafic rocks along the San Andreas Fault System (SAFS) influence earthquake processes where their geologic setting often provides information on the tectonic evolution of these large-scale strike-slip faults. In the northern part of the SAFS, along the Hayward Fault (HF), inversion of gravity and magnetic data indicate that seismicity avoids the interior of a large gabbro body and mechanical models may be able to explain how this massive mafic block influences the distribution of stress. Aftershocks of the M6.7 1989 Loma Prieta earthquake are also spatially related to the distribution of a gabbro body, clustering along the SAF and terminating at the NW end of the gabbro body where it abuts the fault surface. Based on geophysical modeling and a three-dimensional view of the subsurface geology and seismicity, aftershocks do not occur in the interior of the buried gabbro body. In the southern part of the SAFS, aftershocks and ruptures of the M7.1 1999 Hector Mine and M7.3 1992 Landers earthquakes avoid the interior of a Jurassic diorite that extends to depths of approximately 15 km and was probably an important influence on the rupture geometry of the these earthquakes. Seismicity prior to the Landers earthquake also tend to avoid the diorite, suggesting that it affects strain distribution. The San Jacinto Fault (SJF), a discontinuity within the Peninsular Ranges batholith (PRB), separates mafic, dense, and magnetic rocks of the western PRB from more felsic, less dense, and weakly magnetic rocks of the eastern PRB. The geophysical gradients do not cross the SJF zone, but instead bend to the northwest and coincide with the fault zone. Because emplacement of the PRB presumably welded across this older crustal boundary, the SJF zone probably developed along the favorably oriented margin of the dense, stronger western PRB. Two historical M6.7 earthquakes may have nucleated along the PRB discontinuity suggesting that the PRB may continue to affect how strain

  17. Observed and simulated ground motions in the San Bernardino basin region for the Hector Mine, California, earthquake

    Science.gov (United States)

    Graves, R.W.; Wald, D.J.

    2004-01-01

    During the MW 7.1 Hector Mine earthquake, peak ground velocities recorded at sites in the central San Bernardino basin region were up to 2 times larger and had significantly longer durations of strong shaking than sites just outside the basin. To better understand the effects of 3D structure on the long-period ground-motion response in this region, we have performed finite-difference simulations for this earthquake. The simulations are numerically accurate for periods of 2 sec and longer and incorporate the detailed spatial and temporal heterogeneity of source rupture, as well as complex 3D basin structure. Here, we analyze three models of the San Bernardino basin: model A (with structural constraints from gravity and seismic reflection data), model F (water well and seismic refraction data), and the Southern California Earthquake Center version 3 model (hydrologic and seismic refraction data). Models A and F are characterized by a gradual increase in sediment thickness toward the south with an abrupt step-up in the basement surface across the San Jacinto fault. The basin structure in the SCEC version 3 model has a nearly uniform sediment thickness of 1 km with little basement topography along the San Jacinto fault. In models A and F, we impose a layered velocity structure within the sediments based on the seismic refraction data and an assumed depth-dependent Vp/Vs ratio. Sediment velocities within the SCEC version 3 model are given by a smoothly varying rule-based function that is calibrated to the seismic refraction measurements. Due to computational limitations, the minimum shear-wave velocity is fixed at 600 m/sec in all of the models. Ground-motion simulations for both models A and F provide a reasonably good match to the amplitude and waveform characteristics of the recorded motions. In these models, surface waves are generated as energy enters the basin through the gradually sloping northern margin. Due to the basement step along the San Jacinto fault, the

  18. Inferring fault rheology from low-frequency earthquakes on the San Andreas

    Science.gov (United States)

    Beeler, Nicholas M.; Thomas, Amanda; Bürgmann, Roland; Shelly, David R.

    2013-01-01

    Families of recurring low-frequency earthquakes (LFEs) within nonvolcanic tremor (NVT) on the San Andreas fault in central California show strong sensitivity to shear stress induced by the daily tidal cycle. LFEs occur at all levels of the tidal shear stress and are in phase with the very small, ~400 Pa, stress amplitude. To quantitatively explain the correlation, we use a model from the existing literature that assumes the LFE sources are small, persistent regions that repeatedly fail during shear of a much larger scale, otherwise aseismically creeping fault zone. The LFE source patches see tectonic loading, creep of the surrounding fault which may be modulated by the tidal stress, and direct tidal loading. If the patches are small relative to the surrounding creeping fault then the stressing is dominated by fault creep, and if patch failure occurs at a threshold stress, then the resulting seismicity rate is proportional to the fault creep rate or fault zone strain rate. Using the seismicity rate as a proxy for strain rate and the tidal shear stress, we fit the data with possible fault rheologies that produce creep in laboratory experiments at temperatures of 400 to 600°C appropriate for the LFE source depth. The rheological properties of rock-forming minerals for dislocation creep and dislocation glide are not consistent with the observed fault creep because strong correlation between small stress perturbations and strain rate requires perturbation on the order of the ambient stress. The observed tidal modulation restricts ambient stress to be at most a few kilopascal, much lower than rock strength. A purely rate dependent friction is consistent with the observations only if the product of the friction rate dependence and effective normal stress is ~ 0.5 kPa. Extrapolating the friction rate strengthening dependence of phyllosilicates (talc) to depth would require the effective normal stress to be ~50 kPa, implying pore pressure is lithostatic. If the LFE

  19. A reevaluation of the Pallett Creek earthquake chronology based on new AMS radiocarbon dates, San Andreas fault, California

    Science.gov (United States)

    Scharer, K.M.; Biasi, G.P.; Weldon, R.J.

    2011-01-01

    The Pallett Creek paleoseismic record occupies a keystone position in most attempts to develop rupture histories for the southern San Andreas fault. Previous estimates of earthquake ages at Pallett Creek were determined by decay counting radiocarbon methods. That method requires large samples which can lead to unaccounted sources of uncertainty in radiocarbon ages because of the heterogeneous composition of organic layers. In contrast, accelerator mass spectrometry (AMS) radiocarbon dates may be obtained from small samples that have known carbon sources and also allow for a more complete sampling of the section. We present 65 new AMS radiocarbon dates that span nine ground-rupturing earthquakes at Pallett Creek. Overall, the AMS dates are similar to and reveal no dramatic bias in the conventional dates. For many layers, however, individual charcoal samples were younger than the conventional dates, leading to earthquake ages that are overall slightly younger than previously reported. New earthquake ages are determined by Bayesian refinement of the layer ages based on stratigraphic ordering and sedimentological constraints. The new chronology is more regular than previously published records in large part due to new samples constraining the age of event R. The closed interval from event C to 1857 has a mean recurrence of 135years (?? = 83.2 years) and a quasiperiodic coefficient of variation (COV) of 0.61. We show that the new dates and resultant earthquake chronology have a stronger effect on COV than the specific membership of this long series and dating precision improvements from sedimentation rates. Copyright 2011 by the American Geophysical Union.

  20. Testing for Changes in Crustal Velocity at the Tocopilla Earthquake, Northern Chile

    Science.gov (United States)

    Richter, T.; Asch, G.; Kind, R.

    2011-12-01

    We use two different techniques to investigate the region between Antofagasta and Arica in northern Chile for crustal velocity changes. Data are taken from the 19 broadband stations of the IPOC project (Integrated Plate Boundary Observatory Chile) operating partly since 2006 by GFZ and Institut de Physique du Globe de Paris (IPGP). In the neighborhood of the seismic stations an M7.0 earthquake occurred near Tocopilla on 14 November 2007. Other studies have shown that in the course of such earthquakes seismic velocities may be changing (e.g. Brenguier et al. 2008). The first method is testing for phase shifts in receiver functions. To avoid varying travel paths of different events we compare events located in small source regions. Although temporal variations have been found in receiver functions for the Parkfield M6.0 and San Simeon M6.5 earthquakes (Audet 2006) we cannot find any variations exceeding the noise level of our dataset at the time of the M7.0 earthquake near Tocopilla. Therefore the data is analyzed with the help of cross-correlation technique of ambient seismic noise (Bensen et al. 2007). Compared to the first method it has the advantage of regularly available correlation functions (e.g. 1 per day). We report on first results.

  1. Characterization of a Strain Rate Transient Along the San Andreas and San Jacinto Faults Following the October 1999 Hector Mine Earthquake.

    Science.gov (United States)

    Hernandez, D.; Holt, W. E.; Bennett, R. A.; Dimitrova, L.; Haines, A. J.

    2006-12-01

    We are continuing work on developing and refining a tool for recognizing strain rate transients as well as for quantifying the magnitude and style of their temporal and spatial variations. We determined time-averaged velocity values in 0.05 year epochs using time-varying velocity estimates for continuous GPS station data from the Southern California Integrated GPS Network (SCIGN) for the time period between October 1999 and February 2004 [Li et al., 2005]. A self-consistent model velocity gradient tensor field solution is determined for each epoch by fitting bi-cubic Bessel interpolation to the GPS velocity vectors and we determine model dilatation strain rates, shear strain rates, and the rotation rates. Departures of the time dependent model strain rate and velocity fields from a master solution, obtained from a time-averaged solution for the period 1999-2004, with imposed plate motion constraints and Quaternary fault data, are evaluated in order to best characterize the time dependent strain rate field. A particular problem in determining the transient strain rate fields is the level of smoothing or damping that is applied. Our current approach is to choose a damping that both maximizes the departure of the transient strain rate field from the long-term master solution and achieves a reduced chi-squared value between model and observed GPS velocities of around 1.0 for all time epochs. We observe several noteworthy time-dependent changes. First, in the Eastern California Shear Zone (ECSZ) region, immediately following the October 1999 Hector Mine earthquake, there occurs a significant spatial increase of relatively high shear strain rate, which encompasses a significant portion of the ECSZ. Second, also following the Hector Mine event, there is a strain rate corridor that extends through the Pinto Mt. fault connecting the ECSZ to the San Andreas fault segment in the Salton Trough region. As this signal slowly decays, shear strain rates on segments of the San

  2. Validation of the Earthquake Archaeological Effects methodology by studying the San Clemente cemetery damages generated during the Lorca earthquake of 2011

    Science.gov (United States)

    Martín-González, Fidel; Martín-Velazquez, Silvia; Rodrigez-Pascua, Miguel Angel; Pérez-López, Raul; Silva, Pablo

    2014-05-01

    The intensity scales determined the damage caused by an earthquake. However, a new methodology takes into account not only the damage but the type of damage "Earthquake Archaeological Effects", EAE's, and its orientation (e.g. displaced masonry blocks, conjugated fractures, fallen and oriented columns, impact marks, dipping broken corners, etc.) (Rodriguez-Pascua et al., 2011; Giner-Robles et al., 2012). Its main contribution is that it focuses not only on the amount of damage but also in its orientation, giving information about the ground motion during the earthquake. Therefore, this orientations and instrumental data can be correlated with historical earthquakes. In 2011 an earthquake of magnitude Mw 5.2 took place in Lorca (SE Spain) (9 casualties and 460 million Euros in reparations). The study of the EAE's was carried out through the whole city (Giner-Robles et al., 2012). The present study aimed to a.- validate the EAE's methodology using it only in a small place, specifically the cemetery of San Clemente in Lorca, and b.- constraining the range of orientation for each EAE's. This cemetery has been selected because these damage orientation data can be correlated with instrumental information available, and also because this place has: a.- wide variety of architectural styles (neogothic, neobaroque, neoarabian), b.- its Cultural Interest (BIC), and c.- different building materials (brick, limestone, marble). The procedure involved two main phases: a.- inventory and identification of damage (EAE's) by pictures, and b.- analysis of the damage orientations. The orientation was calculated for each EAE's and plotted in maps. Results are NW-SE damage orientation. This orientation is consistent with that recorded in the accelerometer of Lorca (N160°E) and with that obtained from the analysis of EAE's for the whole town of Lorca (N130°E) (Giner-Robles et al., 2012). Due to the existence of an accelerometer, we know the orientation of the peak ground acceleration

  3. Deep-water turbidites as Holocene earthquake proxies: the Cascadia subduction zone and Northern San Andreas Fault systems

    Directory of Open Access Journals (Sweden)

    J. E. Johnson

    2003-06-01

    Full Text Available New stratigraphic evidence from the Cascadia margin demonstrates that 13 earthquakes ruptured the margin from Vancouver Island to at least the California border following the catastrophic eruption of Mount Mazama. These 13 events have occurred with an average repeat time of ?? 600 years since the first post-Mazama event ?? 7500 years ago. The youngest event ?? 300 years ago probably coincides with widespread evidence of coastal subsidence and tsunami inundation in buried marshes along the Cascadia coast. We can extend the Holocene record to at least 9850 years, during which 18 events correlate along the same region. The pattern of repeat times is consistent with the pattern observed at most (but not all localities onshore, strengthening the contention that both were produced by plate-wide earthquakes. We also observe that the sequence of Holocene events in Cascadia may contain a repeating pattern, a tantalizing look at what may be the long-term behavior of a major fault system. Over the last ?? 7500 years, the pattern appears to have repeated at least three times, with the most recent A.D. 1700 event being the third of three events following a long interval of 845 years between events T4 and T5. This long interval is one that is also recognized in many of the coastal records, and may serve as an anchor point between the offshore and onshore records. Similar stratigraphic records are found in two piston cores and one box core from Noyo Channel, adjacent to the Northern San Andreas Fault, which show a cyclic record of turbidite beds, with thirty- one turbidite beds above a Holocene/.Pleistocene faunal «datum». Thus far, we have determined ages for 20 events including the uppermost 5 events from these cores. The uppermost event returns a «modern» age, which we interpret is likely the 1906 San Andreas earthquake. The penultimate event returns an intercept age of A.D. 1664 (2 ?? range 1505- 1822. The third event and fourth event

  4. The influence of critical Moho Reflections on strong ground motions recorded in San Francisco and Oakland during the 1989 Loma Prieta Earthquake

    Science.gov (United States)

    Somerville, Paul; Yoshimura, Joanne

    1990-07-01

    The amplitudes of strong ground motions from the Loma Prieta earthquake recorded in the San Francisco and Oakland areas exceeded the levels predicted by standard empirical attenuation relations. Preliminary analysis of accelerograms having known trigger times strongly suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust. These reflections, which are identified on the basis of their arrival times and phase velocity, and by comparison with simulated accelerograms, were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust. These motions were further amplified, presumably by impedance contrast effects, at soft soil sites in San Francisco and Oakland. The effect of the critical reflections in amplifying peak accelerations of the Loma Prieta earthquake in the San Francisco and Oakland regions was as large as the effect of soft soil site conditions. Focal depth has an important influence on strong motion attenuation at distances beyond about 40 km, and empirical attenuation relations derived from shallow crustal earthquakes may underpredict the ground motions of deeper crustal events in this distance range. Further analyses using an expanded data base that includes recordings of aftershocks are required to rigorously test the proposed explanation of the ground motions recorded in San Francisco and Oakland, and the conclusions drawn from that explanation.

  5. Landslide Probability in the San Francisco Bay Region. The Haywired Earthquake Scenario

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map shows the potential of widespread slope failures, in terms of landslide probability, triggered by a M7.0 scenario earthquake on the Hayward Fault in the...

  6. Landslide Displacement in the San Francisco Bay Region. The HayWired Earthquake Scenario

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This map shows the potential of widespread slope failures, in terms of Newmark displacement (measured in centimeters), triggered by a M7.0 scenario earthquake on the...

  7. Nucleation process of magnitude 2 repeating earthquakes on the San Andreas Fault predicted by rate-and-state fault models with SAFOD drill core data

    Science.gov (United States)

    Kaneko, Yoshihiro; Carpenter, Brett M.; Nielsen, Stefan B.

    2017-01-01

    Recent laboratory shear-slip experiments conducted on a nominally flat frictional interface reported the intriguing details of a two-phase nucleation of stick-slip motion that precedes the dynamic rupture propagation. This behavior was subsequently reproduced by a physics-based model incorporating laboratory-derived rate-and-state friction laws. However, applying the laboratory and theoretical results to the nucleation of crustal earthquakes remains challenging due to poorly constrained physical and friction properties of fault zone rocks at seismogenic depths. Here we apply the same physics-based model to simulate the nucleation process of crustal earthquakes using unique data acquired during the San Andreas Fault Observatory at Depth (SAFOD) experiment and new and existing measurements of friction properties of SAFOD drill core samples. Using this well-constrained model, we predict what the nucleation phase will look like for magnitude ˜2 repeating earthquakes on segments of the San Andreas Fault at a 2.8 km depth. We find that despite up to 3 orders of magnitude difference in the physical and friction parameters and stress conditions, the behavior of the modeled nucleation is qualitatively similar to that of laboratory earthquakes, with the nucleation consisting of two distinct phases. Our results further suggest that precursory slow slip associated with the earthquake nucleation phase may be observable in the hours before the occurrence of the magnitude ˜2 earthquakes by strain measurements close (a few hundred meters) to the hypocenter, in a position reached by the existing borehole.

  8. Timing of large earthquakes during the past 500 years along the Santa Cruz Mountains segment of the San Andreas fault at Mill Canyon, near Watsonville, California

    Science.gov (United States)

    Fumal, Thomas E.

    2012-01-01

    A paleoseismic investigation across the Santa Cruz Mountains section of the San Andreas fault at Mill Canyon indicates that four surface‐rupturing earthquakes have occurred there during the past ~500  years. At this site, right‐lateral fault slip has moved a low shutter ridge across the mouth of the canyon, ponding latest Holocene sediments. These alluvial deposits are deformed along a narrow zone of faulting. There is excellent evidence for a 1906 (M 7.8) and three earlier earthquakes consisting of well‐developed fissures, scarps, and colluvial wedges. Deformation resulting from the earlier earthquakes is comparable to that from 1906, suggesting they also were large‐magnitude events. The earthquake prior to 1906 occurred either about A.D. 1750 (1711–1770) or A.D. 1855 (1789–1904), depending on assumptions incorporated into two alternative OxCal models. If the later age range is correct, then the earthquake may have been a historical early‐to‐mid‐nineteenth‐century earthquake, possibly the A.D. 1838 earthquake. Both models are viable, and there is no way to select one over the other with the available data. Two earlier earthquakes occurred about A.D. 1690 (1660–1720) and A.D. 1522 (1454–1605). Using OxCal, recalculation of the age of the reported penultimate earthquake reported from the Grizzly Flat site, located about 10 km northwest of Mill Canyon, indicates it occurred about A.D. 1105–1545, earlier than any of the past three earthquakes, and possibly correlates to the fourth earthquake at Mill Canyon.

  9. Slip rate on the San Diego trough fault zone, inner California Borderland, and the 1986 Oceanside earthquake swarm revisited

    Science.gov (United States)

    Ryan, Holly F.; Conrad, James E.; Paull, C.K.; McGann, Mary

    2012-01-01

    The San Diego trough fault zone (SDTFZ) is part of a 90-km-wide zone of faults within the inner California Borderland that accommodates motion between the Pacific and North American plates. Along with most faults offshore southern California, the slip rate and paleoseismic history of the SDTFZ are unknown. We present new seismic reflection data that show that the fault zone steps across a 5-km-wide stepover to continue for an additional 60 km north of its previously mapped extent. The 1986 Oceanside earthquake swarm is located within the 20-km-long restraining stepover. Farther north, at the latitude of Santa Catalina Island, the SDTFZ bends 20° to the west and may be linked via a complex zone of folds with the San Pedro basin fault zone (SPBFZ). In a cooperative program between the U.S. Geological Survey (USGS) and the Monterey Bay Aquarium Research Institute (MBARI), we measure and date the coseismic offset of a submarine channel that intersects the fault zone near the SDTFZ–SPBFZ junction. We estimate a horizontal slip rate of about 1:5 0:3 mm=yr over the past 12,270 yr.

  10. Paleoseismic investigations in the Santa Cruz mountains, California: Implications for recurrence of large-magnitude earthquakes on the San Andreas Fault

    Science.gov (United States)

    Schwartz, D. P.; Pantosti, D.; Okumura, K.; Powers, T. J.; Hamilton, J. C.

    1998-08-01

    Trenching, microgeomorphic mapping, and tree ring analysis provide information on timing of paleoearthquakes and behavior of the San Andreas fault in the Santa Cruz mountains. At the Grizzly Flat site alluvial units dated at 1640-1659 A.D., 1679-1894 A.D., 1668-1893 A.D., and the present ground surface are displaced by a single event. This was the 1906 surface rupture. Combined trench dates and tree ring analysis suggest that the penultimate event occurred in the mid-1600 s, possibly in an interval as narrow as 1632-1659 A.D. There is no direct evidence in the trenches for the 1838 or 1865 earthquakes, which have been proposed as occurring on this part of the fault zone. In a minimum time of about 340 years only one large surface faulting event (1906) occurred at Grizzly Flat, in contrast to previous recurrence estimates of 95-110 years for the Santa Cruz mountains segment. Comparison with dates of the penultimate San Andreas earthquake at sites north of San Francisco suggests that the San Andreas fault between Point Arena and the Santa Cruz mountains may have failed either as a sequence of closely timed earthquakes on adjacent segments or as a single long rupture similar in length to the 1906 rupture around the mid-1600 s. The 1906 coseismic geodetic slip and the late Holocene geologic slip rate on the San Francisco peninsula and southward are about 50-70% and 70% of their values north of San Francisco, respectively. The slip gradient along the 1906 rupture section of the San Andreas reflects partitioning of plate boundary slip onto the San Gregorio, Sargent, and other faults south of the Golden Gate. If a mid-1600 s event ruptured the same section of the fault that failed in 1906, it supports the concept that long strike-slip faults can contain master rupture segments that repeat in both length and slip distribution. Recognition of a persistent slip rate gradient along the northern San Andreas fault and the concept of a master segment remove the requirement that

  11. Earthquake

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    正A serious earthquake happened in Wenchuan, Sichuan. Over 60,000 people died in the earhtquake, millins of people lost their homes. After the earthquake, people showed their love in different ways. Some gave food, medicine and everything necessary, some gave money,

  12. Characterizing the recent behavior and earthquake potential of the blind western San Cayetano and Ventura fault systems

    Science.gov (United States)

    McAuliffe, L. J.; Dolan, J. F.; Hubbard, J.; Shaw, J. H.

    2011-12-01

    The recent occurrence of several destructive thrust fault earthquakes highlights the risks posed by such events to major urban centers around the world. In order to determine the earthquake potential of such faults in the western Transverse Ranges of southern California, we are studying the activity and paleoearthquake history of the blind Ventura and western San Cayetano faults through a multidisciplinary analysis of strata that have been folded above the fault tiplines. These two thrust faults form the middle section of a >200-km-long, east-west belt of large, interconnected reverse faults that extends across southern California. Although each of these faults represents a major seismic source in its own right, we are exploring the possibility of even larger-magnitude, multi-segment ruptures that may link these faults to other major faults to the east and west in the Transverse Ranges system. The proximity of this large reverse-fault system to several major population centers, including the metropolitan Los Angeles region, and the potential for tsunami generation during offshore ruptures of the western parts of the system, emphasizes the importance of understanding the behavior of these faults for seismic hazard assessment. During the summer of 2010 we used a mini-vibrator source to acquire four, one- to three-km-long, high-resolution seismic reflection profiles. The profiles were collected along the locus of active folding above the blind, western San Cayetano and Ventura faults - specifically, across prominent fold scarps that have developed in response to recent slip on the underlying thrust ramps. These high-resolution data overlap with the uppermost parts of petroleum-industry seismic reflection data, and provide a near-continuous image of recent folding from several km depth to within 50-100 m of the surface. Our initial efforts to document the earthquake history and slip-rate of this large, multi-fault reverse fault system focus on a site above the blind

  13. Seismic Documentation for Rock Damage and Heal on the San Andreas Fault Involved in the 2004 M6 Parkfield Earthquake

    Science.gov (United States)

    Malin, P. M.; Li, Y.; Chen, P.; Cochran, E. M.; Vidale, J. E.

    2007-12-01

    After the M6 Parkfield earthquake that occurred on 28 September 2004, we deployed a dense seismic array at the same sites as used in our experiment in the fall of 2002. The measurements using moving-window cross- correlation of waveforms for the repeated explosions and microearthquakes recorded in 2002 and 2004 show a decrease in shear velocity of at least ~2.5% within a ~200-m-wide zone across the San Andreas main fault trace most likely owing to co-seismic damage of fault rocks caused by dynamic rupture in this M6 earthquake. The width of the damage zone characterized by larger velocity changes is consistent with the low-velocity waveguide model on the SAF near Parkfield derived from fault-zone trapped waves [Li et al., 2004]. The estimated ratio between the P and S wave traveltime changes is 0.57 within the rupture zone and ~0.65 in the surrounding rocks, indicating wetter cracks within the damaged fault zone, probably due to the ground water percolating into the cracks opened in the mainshock. The measurements of traveltime changes for repeated aftershocks in 21 clusters, with a total of ~130 events, located at different depths along the rupture in 2004 show that the maximum shear velocity increased by ~1.2% within the damage zone in 3.5 months starting a week after the mainshock, indicating that the fault heals in the post-seismic stage due to the closure of cracks in the damaged rock. The data recorded at a seismograph installed in the SAFOD mainhole passing the San Andreas fault zone at ~3-km depths for repeated aftershocks in December of 2004 and later show that seismic velocities within the damage zone were changed by ~0.3% in a month, but no changes were registered at seismographs installed in the vertical pilot borehole drilled ~1.8 km away from the main fault trace for the same repeated events. We find that the healing rate is logarithmically decreasing through time with greater healing rate in the earlier stage after the mainshock. The magnitude of

  14. Paleoseismic event dating and the conditional probability of large earthquakes on the southern San Andreas fault, California

    Science.gov (United States)

    Biasi, G.P.; Weldon, R.J.; Fumal, T.E.; Seitz, G.G.

    2002-01-01

    We introduce a quantitative approach to paleoearthquake dating and apply it to paleoseismic data from the Wrightwood and Pallett Creek sites on the southern San Andreas fault. We illustrate how stratigraphic ordering, sedimentological, and historical data can be used quantitatively in the process of estimating earthquake ages. Calibrated radiocarbon age distributions are used directly from layer dating through recurrence intervals and recurrence probability estimation. The method does not eliminate subjective judgements in event dating, but it does provide a means of systematically and objectively approaching the dating process. Date distributions for the most recent 14 events at Wrightwood are based on sample and contextual evidence in Fumal et al. (2002) and site context and slip history in Weldon et al. (2002). Pallett Creek event and dating descriptions are from published sources. For the five most recent events at Wrightwood, our results are consistent with previously published estimates, with generally comparable or narrower uncertainties. For Pallett Creek, our earthquake date estimates generally overlap with previous results but typically have broader uncertainties. Some event date estimates are very sensitive to details of data interpretation. The historical earthquake in 1857 ruptured the ground at both sites but is not constrained by radiocarbon data. Radiocarbon ages, peat accumulation rates, and historical constraints at Pallett Creek for event X yield a date estimate in the earliest 1800s and preclude a date in the late 1600s. This event is almost certainly the historical 1812 earthquake, as previously concluded by Sieh et al. (1989). This earthquake also produced ground deformation at Wrightwood. All events at Pallett Creek, except for event T, about A.D. 1360, and possibly event I, about A.D. 960, have corresponding events at Wrightwood with some overlap in age ranges. Event T falls during a period of low sedimentation at Wrightwood when conditions

  15. Active Crustal Deformation in the Area of San Carlos, Baja California Sur, Mexico as Shown by Data of Local Earthquake Sequences

    Science.gov (United States)

    Munguía, Luis; González-Escobar, Mario; Navarro, Miguel; Valdez, Tito; Mayer, Sergio; Aguirre, Alfredo; Wong, Victor; Luna, Manuel

    2016-10-01

    We analyzed earthquakes of sequences that occurred at different times near San Carlos, a town of approximately 5000 inhabitants. The seismic sequences happened during March-April 1989, October 2000-June 2001, and 5-15 February 2004 at about 200 km west of the Pacific-North America plate boundary. The strong shaking from initial earthquakes of the first two sequences prompted the installation of temporary seismic stations in the area. With data recorded by these stations, we found an earthquake distribution that is consistent with the northwest segment of the Santa Margarita fault. Both the focal depth, that seemed to increase in E-NE direction, and a composite fault-plane solution, obtained from polarity data of the small earthquakes, were also consistent with the main characteristics of that fault. We also found that our normal-faulting mechanism (east side down) was quite similar to centroid moment tensor solutions for earthquakes with M w 5.4 and 5.3 that occurred in the area in February 2004. It is likely, then, that these larger earthquakes also occurred along the Santa Margarita Fault. To get some insight into the regional stress pattern, we compared the above mechanisms with mechanisms reported for other earthquakes of the Pacific margin of Baja California Sur and the Gulf of California regions. We observed that focal mechanisms of the two regions have T axes of stress that plunge sub horizontally in E-NE average direction. The corresponding P axes have N-NW average trend, but for the Pacific earthquakes these axes plunge at angles that are ~35° larger than those for the Gulf earthquakes. These more vertically inclined P axes of compressive stress mean substantial oblique fault motions. The mixture of oblique and strike-slip components of fault motions, as the focal mechanisms show, confirms a transtensional stress regime for the region. Before this research, we knew little about the seismicity and styles of faulting in the area. Now we know that

  16. Using SW4 for 3D Simulations of Earthquake Strong Ground Motions: Application to Near-Field Strong Motion, Building Response, Basin Edge Generated Waves and Earthquakes in the San Francisco Bay Are

    Science.gov (United States)

    Rodgers, A. J.; Pitarka, A.; Petersson, N. A.; Sjogreen, B.; McCallen, D.; Miah, M.

    2016-12-01

    Simulation of earthquake ground motions is becoming more widely used due to improvements of numerical methods, development of ever more efficient computer programs (codes), and growth in and access to High-Performance Computing (HPC). We report on how SW4 can be used for accurate and efficient simulations of earthquake strong motions. SW4 is an anelastic finite difference code based on a fourth order summation-by-parts displacement formulation. It is parallelized and can run on one or many processors. SW4 has many desirable features for seismic strong motion simulation: incorporation of surface topography; automatic mesh generation; mesh refinement; attenuation and supergrid boundary conditions. It also has several ways to introduce 3D models and sources (including Standard Rupture Format for extended sources). We are using SW4 to simulate strong ground motions for several applications. We are performing parametric studies of near-fault motions from moderate earthquakes to investigate basin edge generated waves and large earthquakes to provide motions to engineers study building response. We show that 3D propagation near basin edges can generate significant amplifications relative to 1D analysis. SW4 is also being used to model earthquakes in the San Francisco Bay Area. This includes modeling moderate (M3.5-5) events to evaluate the United States Geologic Survey's 3D model of regional structure as well as strong motions from the 2014 South Napa earthquake and possible large scenario events. Recently SW4 was built on a Commodity Technology Systems-1 (CTS-1) at LLNL, new systems for capacity computing at the DOE National Labs. We find SW4 scales well and runs faster on these systems compared to the previous generation of LINUX clusters.

  17. Increasing lengths of aftershock zones with depths of moderate-size earthquakes on the San Jacinto Fault suggests triggering of deep creep in the middle crust

    Science.gov (United States)

    Meng, Xiaofeng; Peng, Zhigang

    2016-01-01

    Recent geodetic studies along the San Jacinto Fault (SJF) in southern California revealed a shallower locking depth than the seismogenic depth outlined by microseismicity. This disagreement leads to speculations that creeping episodes drive seismicity in the lower part of the seismogenic zone. Whether deep creep occurs along the SJF holds key information on how fault slips during earthquake cycle and potential seismic hazard imposed to southern California. Here we apply a matched filter technique to 10 M > 4 earthquake sequences along the SJF since 2000 and obtain more complete earthquake catalogues. We then systematic investigate spatio-temporal evolutions of these aftershock sequences. We find anomalously large aftershock zones for earthquakes occurred below the geodetically inferred locking depth (i.e. 11-12 km), while aftershock zones of shallower main shocks are close to expectations from standard scaling relationships. Although we do not observe clear migration of aftershocks, most aftershock zones do expand systematically with logarithmic time since the main shock. All the evidences suggest that aftershocks near or below the locking depth are likely driven by deep creep following the main shock. The presence of a creeping zone below 11-12 km may have significant implications on the maximum sizes of events in this region.

  18. Depicting ‘Natural’ Disasters in U.S.-American History and Culture: San Francisco’s City Hall as an Icon of the 1906 Earthquake and Fire

    Directory of Open Access Journals (Sweden)

    Leikam, Susanne

    2009-01-01

    Full Text Available The article examines the role that visual representations of San Francisco’s first City Hall played in the aftermath of the 1906 Earthquake and Fire. Not only did they offer a projection screen for the collective trauma but they also provided a starting point for recollection and re-enactment. With the City Hall vicinity as an example, it is further shown that what was perceived at the time as nature’s obliteration of the metropolis was rather a man-made disaster.

  19. A Large Scale Automatic Earthquake Location Catalog in the San Jacinto Fault Zone Area Using An Improved Shear-Wave Detection Algorithm

    Science.gov (United States)

    White, M. C. A.; Ross, Z.; Vernon, F.; Ben-Zion, Y.

    2015-12-01

    UC San Diego's ANZA network began archiving event-triggered data in 1982. As a result of improved recording technology, continuous waveform data archives are available starting in 1998. This continuous dataset, from 1998-present, represents a wealth of potential insight into spatio-temporal seismicity patterns, earthquake physics and mechanics of the San Jacinto Fault Zone. However, the volume of data renders manual analysis costly. In order to investigate the characteristics of the data in space and time, an automatic earthquake location catalog is needed. To this end, we apply standard earthquake signal processing techniques to the continuous data to detect first-arriving P-waves in combination with a recently developed S-wave detection algorithm. The resulting dataset of arrival time observations are processed using a grid association algorithm to produce initial absolute locations which are refined using a location inversion method that accounts for 3-D velocity heterogeneities. Precise relative locations are then derived from the refined absolute locations using the HypoDD double-difference algorithm. Moment magnitudes for the events are estimated from multi-taper spectral analysis. A >650% increase in the S:P pick ratio is achieved using the updated S-wave detection algorithm, when compared to the currently available catalog for the ANZA network. The increased number of S-wave observations leads to improved earthquake location accuracy and reliability (ie. less false event detections). Various aspects of spatio-temporal seismicity patterns and size distributions are investigated. Updated results will be presented at the meeting.

  20. Three-dimensional compressional wavespeed model, earthquake relocations, and focal mechanisms for the Parkfield, California, region

    Science.gov (United States)

    Thurber, C.; Zhang, H.; Waldhauser, F.; Hardebeck, J.; Michael, A.; Eberhart-Phillips, D.

    2006-01-01

    We present a new three-dimensional (3D) compressional vvavespeed (V p) model for the Parkfield region, taking advantage of the recent seismicity associated with the 2003 San Simeon and 2004 Parkfield earthquake sequences to provide increased model resolution compared to the work of Eberhart-Phillips and Michael (1993) (EPM93). Taking the EPM93 3D model as our starting model, we invert the arrival-time data from about 2100 earthquakes and 250 shots recorded on both permanent network and temporary stations in a region 130 km northeast-southwest by 120 km northwest-southeast. We include catalog picks and cross-correlation and catalog differential times in the inversion, using the double-difference tomography method of Zhang and Thurber (2003). The principal Vp features reported by EPM93 and Michelini and McEvilly (1991) are recovered, but with locally improved resolution along the San Andreas Fault (SAF) and near the active-source profiles. We image the previously identified strong wavespeed contrast (faster on the southwest side) across most of the length of the SAF, and we also improve the image of a high Vp body on the northeast side of the fault reported by EPM93. This narrow body is at about 5- to 12-km depth and extends approximately from the locked section of the SAP to the town of Parkfield. The footwall of the thrust fault responsible for the 1983 Coalinga earthquake is imaged as a northeast-dipping high wavespeed body. In between, relatively low wavespeeds (model to derive absolute locations for about 16,000 earthquakes from 1966 to 2005 and high-precision double-difference locations for 9,000 earthquakes from 1984 to 2005, and also to determine focal mechanisms for 446 earthquakes. These earthquake locations and mechanisms show that the seismogenic fault is a simple planar structure. The aftershock sequence of the 2004 mainshock concentrates into the same structures defined by the pre-2004 seismicity, confirming earlier observations (Waldhauser et al., 2004

  1. Seismic evidence for rock damage and healing on the San Andreas fault associated with the 2004 M 6.0 Parkfield earthquake

    Science.gov (United States)

    Li, Y.-G.; Chen, P.; Cochran, E.S.; Vidale, J.E.; Burdette, T.

    2006-01-01

    We deployed a dense linear array of 45 seismometers across and along the San Andreas fault near Parkfield a week after the M 6.0 Parkfield earthquake on 28 September 2004 to record fault-zone seismic waves generated by aftershocks and explosions. Seismic stations and explosions were co-sited with our previous experiment conducted in 2002. The data from repeated shots detonated in the fall of 2002 and 3 months after the 2004 M 6.0 mainshock show ???1.0%-1.5% decreases in seismic-wave velocity within an ???200-m-wide zone along the fault strike and smaller changes (0.2%-0.5%) beyond this zone, most likely due to the coseismic damage of rocks during dynamic rupture in the 2004 M 6.0 earthquake. The width of the damage zone characterized by larger velocity changes is consistent with the low-velocity waveguide model on the San Andreas fault, near Parkfield, that we derived from fault-zone trapped waves (Li et al., 2004). The damage zone is not symmetric but extends farther on the southwest side of the main fault trace. Waveform cross-correlations for repeated aftershocks in 21 clusters, with a total of ???130 events, located at different depths and distances from the array site show ???0.7%-1.1% increases in S-wave velocity within the fault zone in 3 months starting a week after the earthquake. The velocity recovery indicates that the damaged rock has been healing and regaining the strength through rigidity recovery with time, most likely . due to the closure of cracks opened during the mainshock. We estimate that the net decrease in seismic velocities within the fault zone was at least ???2.5%, caused by the 2004 M 6.0 Parkfield earthquake. The healing rate was largest in the earlier stage of the postmainshock healing process. The magnitude of fault healing varies along the rupture zone, being slightly larger for the healing beneath Middle Mountain, correlating well with an area of large mapped slip. The fault healing is most prominent at depths above ???7 km.

  2. Arias intensity assessment of liquefaction test sites on the east side of San Francisco Bay affected by the Loma Prieta, California, earthquake of 17 October 1989

    Science.gov (United States)

    Kayen, R.E.

    1997-01-01

    Abstract. Uncompacted artificial-fill deposits on the east side of San Francisco Bay suffered severe levels of soil liquefaction during the Loma Prieta earthquake of 17 October 1989. Damaged areas included maritime-port facilities, office buildings, and shoreline transportation arteries, ranging from 65 to 85 km from the north end of the Loma Prieta rupture zone. Typical of all these sites, which represent occurrences of liquefaction-induced damage farthest from the rupture zone, are low cone penetration test and Standard Penetration Test resistances in zones of cohesionless silty and sandy hydraulic fill, and underlying soft cohesive Holocene and Pleistocene sediment that strongly amplified ground motions. Postearthquake investigations at five study sites using standard penetration tests and cone penetration tests provide a basis for evaluation of the Arias intensity-based methodology for assessment of liquefaction susceptibility. ?? 1997 Kluwer Academic Publishers.

  3. Distributed Plate Boundary Deformation Across the San Andreas Fault System, Central California

    Science.gov (United States)

    Dyson, M.; Titus, S. J.; Demets, C.; Tikoff, B.

    2007-12-01

    Plate boundaries are now recognized as broad zones of complex deformation as opposed to narrow zones with discrete offsets. When assessing how plate boundary deformation is accommodated, both spatially and temporally, it is therefore crucial to understand the relative contribution of the discrete and distributed components of deformation. The creeping segment of the San Andreas fault is an ideal location to study the distribution of plate boundary deformation for several reasons. First, the geometry of the fault system in central California is relatively simple. Plate motion is dominated by slip along the relatively linear strike-slip San Andreas fault, but also includes lesser slip along the adjacent and parallel Hosgri-San Gregorio and Rinconada faults, as well as within the borderlands between the three fault strands. Second, the aseismic character of the San Andreas fault in this region allows for the application of modern geodetic techniques to assess creep rates along the fault and across the region. Third, geologic structures within the borderlands are relatively well-preserved allowing comparison between modern and ancient rates and styles of deformation. Continuous GPS stations, alignment arrays surveys, and other geodetic methods demonstrate that approximately 5 mm/yr of distributed slip is accumulated (on top of the fault slip rate) across a 70-100 km wide region centered on the San Andreas fault. New campaign GPS data also suggest 2-5 mm/yr of deformation in the borderlands. These rates depend on the magnitude of the coseismic and postseismic corrections that must be made to our GPS time series to compensate for the 2003 San Simeon and 2004 Parkfield earthquakes, which rupture faults outside, but near the edges of our GPS network. The off-fault deformation pattern can be compared to the style of permanent deformation recorded in the geologic record. Fold and thrust belts in the borderlands are better developed in the Tertiary sedimentary rocks west of

  4. A 15 year catalog of more than 1 million low-frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault

    Science.gov (United States)

    Shelly, David R.

    2017-05-01

    Low-frequency earthquakes (LFEs) are small, rapidly recurring slip events that occur on the deep extensions of some major faults. Their collective activation is often observed as a semicontinuous signal known as tectonic (or nonvolcanic) tremor. This manuscript presents a catalog of more than 1 million LFEs detected along the central San Andreas Fault from 2001 to 2016. These events have been detected via a multichannel matched-filter search, cross-correlating waveform templates representing 88 different LFE families with continuous seismic data. Together, these source locations span nearly 150 km along the central San Andreas Fault, ranging in depth from 16 to 30 km. This accumulating catalog has been the source for numerous studies examining the behavior of these LFE sources and the inferred slip behavior of the deep fault. The relatively high temporal and spatial resolutions of the catalog have provided new insights into properties such as tremor migration, recurrence, and triggering by static and dynamic stress perturbations. Collectively, these characteristics are inferred to reflect a very weak fault likely under near-lithostatic fluid pressure, yet the physical processes controlling the stuttering rupture observed as tremor and LFE signals remain poorly understood. This paper aims to document the LFE catalog assembly process and associated caveats, while also updating earlier observations and inferred physical constraints. The catalog itself accompanies this manuscript as part of the electronic supplement, with the goal of providing a useful resource for continued future investigations.

  5. Stress-based aftershock forecasts made within 24h post mainshock: Expected north San Francisco Bay area seismicity changes after the 2014M=6.0 West Napa earthquake

    Science.gov (United States)

    Parsons, Thomas E.; Segou, Margaret; Sevilgen, Volkan; Milner, Kevin; Field, Ned; Toda, Shinji; Stein, Ross S.

    2014-01-01

    We calculate stress changes resulting from the M= 6.0 West Napa earthquake on north San Francisco Bay area faults. The earthquake ruptured within a series of long faults that pose significant hazard to the Bay area, and we are thus concerned with potential increases in the probability of a large earthquake through stress transfer. We conduct this exercise as a prospective test because the skill of stress-based aftershock forecasting methodology is inconclusive. We apply three methods: (1) generalized mapping of regional Coulomb stress change, (2) stress changes resolved on Uniform California Earthquake Rupture Forecast faults, and (3) a mapped rate/state aftershock forecast. All calculations were completed within 24 h after the main shock and were made without benefit of known aftershocks, which will be used to evaluative the prospective forecast. All methods suggest that we should expect heightened seismicity on parts of the southern Rodgers Creek, northern Hayward, and Green Valley faults.

  6. Stress-based aftershock forecasts made within 24 h postmain shock: Expected north San Francisco Bay area seismicity changes after the 2014 M = 6.0 West Napa earthquake

    Science.gov (United States)

    Parsons, Tom; Segou, Margaret; Sevilgen, Volkan; Milner, Kevin; Field, Edward; Toda, Shinji; Stein, Ross S.

    2014-12-01

    We calculate stress changes resulting from the M = 6.0 West Napa earthquake on north San Francisco Bay area faults. The earthquake ruptured within a series of long faults that pose significant hazard to the Bay area, and we are thus concerned with potential increases in the probability of a large earthquake through stress transfer. We conduct this exercise as a prospective test because the skill of stress-based aftershock forecasting methodology is inconclusive. We apply three methods: (1) generalized mapping of regional Coulomb stress change, (2) stress changes resolved on Uniform California Earthquake Rupture Forecast faults, and (3) a mapped rate/state aftershock forecast. All calculations were completed within 24 h after the main shock and were made without benefit of known aftershocks, which will be used to evaluative the prospective forecast. All methods suggest that we should expect heightened seismicity on parts of the southern Rodgers Creek, northern Hayward, and Green Valley faults.

  7. Dealing with Disaster through Compassionate Giving: San Francisco Earthquake Survivors Write to President Theodore Roosevelt, January 3, 1909

    Science.gov (United States)

    Hussey, Michael

    2011-01-01

    On January 3, 1909, Emily Hamilton and Louis Overstreet wrote to President Theodore Roosevelt begging his "leave to work under your Committee for the relief of the sufferers of Italy." The two were engaged and were willing to rush their marriage plans if the president needed them. Their letter was prompted by the powerful earthquake that…

  8. Liquefaction Hazard Maps for Three Earthquake Scenarios for the Communities of San Jose, Campbell, Cupertino, Los Altos, Los Gatos, Milpitas, Mountain View, Palo Alto, Santa Clara, Saratoga, and Sunnyvale, Northern Santa Clara County, California

    Science.gov (United States)

    Holzer, Thomas L.; Noce, Thomas E.; Bennett, Michael J.

    2008-01-01

    Maps showing the probability of surface manifestations of liquefaction in the northern Santa Clara Valley were prepared with liquefaction probability curves. The area includes the communities of San Jose, Campbell, Cupertino, Los Altos, Los Gatos Milpitas, Mountain View, Palo Alto, Santa Clara, Saratoga, and Sunnyvale. The probability curves were based on complementary cumulative frequency distributions of the liquefaction potential index (LPI) for surficial geologic units in the study area. LPI values were computed with extensive cone penetration test soundings. Maps were developed for three earthquake scenarios, an M7.8 on the San Andreas Fault comparable to the 1906 event, an M6.7 on the Hayward Fault comparable to the 1868 event, and an M6.9 on the Calaveras Fault. Ground motions were estimated with the Boore and Atkinson (2008) attenuation relation. Liquefaction is predicted for all three events in young Holocene levee deposits along the major creeks. Liquefaction probabilities are highest for the M7.8 earthquake, ranging from 0.33 to 0.37 if a 1.5-m deep water table is assumed, and 0.10 to 0.14 if a 5-m deep water table is assumed. Liquefaction probabilities of the other surficial geologic units are less than 0.05. Probabilities for the scenario earthquakes are generally consistent with observations during historical earthquakes.

  9. 1906 San Francisco, USA Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1906 San Francisco earthquake was the largest event (magnitude 8.3) to occur in the conterminous United States in the 20th Century. Recent estimates indicate...

  10. Liquefaction potential as a result of HayWired earthquake scenario mainshock (April 18, 2018) shaking in Alameda and Santa Clara Counties, San Francisco Bay area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — These data are a geospatial representation of liquefaction potential for the HayWired earthquake scenario, a magnitude 7.0 earthquake occurring on the Hayward Fault...

  11. Brief communication "Ground failure and liquefaction phenomena triggered by the 20 May 2012 Emilia-Romagna (Northern Italy earthquake: case study of Sant'Agostino–San Carlo–Mirabello zone"

    Directory of Open Access Journals (Sweden)

    R. Caputo

    2012-10-01

    Full Text Available The basic aim of this study was to observe and report the earthquake-induced ground deformation of the MW = 6.1 Emilia-Romagna (Northern Italy event that occurred on the 20 May 2012. The event caused widespread structural damages in a large area of the Po Plain, while the most characteristic geological effects were ground failure, lateral spreading and liquefaction. This post-earthquake reconnaissance report focuses on secondary effects within the area between the villages of Sant'Agostino, San Carlo and Mirabello located along a former reach of the Reno River. Our field observations started just few hours after the main shock until the 28 May 2012.

  12. Effects of the earthquake of 11 May 2011 upon the historic family vaults in the San Clemente cemetery, the church of Santa Maria, the church of San Pedro and the Golden Fountain at Lorca in Murcia (SE Spain); Afecciones ocasionadas por el terremoto en el conjunto de panteones historicos del cementerio de San Clemente, iglesia de Santa Maria, iglesia de San Pedro y la Fuente del Oro de Lorca, Murcia

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Ballesteros, J. A.; Gallardo Carrillo, J.; Lopez Aguilera, V.

    2012-11-01

    This study forms a contribution to the record of deformations caused by the earthquake that occurred on 11 May 2011 in and around the city of Lorca, affecting a wide variety of its historic buildings. Our work has focused on the San Clemente cemetery, the churches of the Barrios Altos (the higher districts) and on the Fuente del Oro (the Golden Fountain). Our aim was to quantify the deformations and the numerous other effects using archaeological and architectural methods and retrieve as much of this information as possible before the works of structural consolidation and cleaning of the debris could begin. At the same time we tried to analyse the impact of the seismic shocks upon other historic buildings in the city. (Author) 9 refs.

  13. S-wave triggering of tremor beneath the Parkfield, California, section of the San Andreas fault by the 2011 Tohoku, Japan earthquake: observations and theory

    Science.gov (United States)

    Hill, David P.; Peng, Zhigang; Shelly, David R.; Aiken, Chastity

    2013-01-01

    The dynamic stresses that are associated with the energetic seismic waves generated by the Mw 9.0 Tohoku earthquake off the northeast coast of Japan triggered bursts of tectonic tremor beneath the Parkfield section of the San Andreas fault (SAF) at an epicentral distance of ∼8200  km. The onset of tremor begins midway through the ∼100‐s‐period S‐wave arrival, with a minor burst coinciding with the SHSH arrival, as recorded on the nearby broadband seismic station PKD. A more pronounced burst coincides with the Love arrival, followed by a series of impulsive tremor bursts apparently modulated by the 20‐ to 30‐s‐period Rayleigh wave. The triggered tremor was located at depths between 20 and 30 km beneath the surface trace of the fault, with the burst coincident with the S wave centered beneath the fault 30 km northwest of Parkfield. Most of the subsequent activity, including the tremor coincident with the SHSH arrival, was concentrated beneath a stretch of the fault extending from 10 to 40 km southeast of Parkfield. The seismic waves from the Tohoku epicenter form a horizontal incidence angle of ∼14°, with respect to the local strike of the SAF. Computed peak dynamic Coulomb stresses on the fault at tremor depths are in the 0.7–10 kPa range. The apparent modulation of tremor bursts by the small, strike‐parallel Rayleigh‐wave stresses (∼0.7  kPa) is likely enabled by pore pressure variations driven by the Rayleigh‐wave dilatational stress. These results are consistent with the strike‐parallel dynamic stresses (δτs) associated with the S, SHSH, and surface‐wave phases triggering small increments of dextral slip on the fault with a low friction (μ∼0.2). The vertical dynamic stresses δτd do not trigger tremor with vertical or oblique slip under this simple Coulomb failure model.

  14. Habitat information in the region on the underwater San Andreas Fault - Topic: Exploring the Undersea San Andreas Fault: Revealing the Past, Present, and Future at the Centennial of the Great 1906 Earthquake

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — During this exploration, the first comprehensive high-resolution multi-beam sonar and seismic reflection survey of the Northern San Andreas Fault (NSAF) was...

  15. The HayWired earthquake scenario—Earthquake hazards

    Science.gov (United States)

    Detweiler, Shane T.; Wein, Anne M.

    2017-01-01

    The HayWired scenario is a hypothetical earthquake sequence that is being used to better understand hazards for the San Francisco Bay region during and after an earthquake of magnitude 7 on the Hayward Fault. The 2014 Working Group on California Earthquake Probabilities calculated that there is a 33-percent likelihood of a large (magnitude 6.7 or greater) earthquake occurring on the Hayward Fault within three decades. A large Hayward Fault earthquake will produce strong ground shaking, permanent displacement of the Earth’s surface, landslides, liquefaction (soils becoming liquid-like during shaking), and subsequent fault slip, known as afterslip, and earthquakes, known as aftershocks. The most recent large earthquake on the Hayward Fault occurred on October 21, 1868, and it ruptured the southern part of the fault. The 1868 magnitude-6.8 earthquake occurred when the San Francisco Bay region had far fewer people, buildings, and infrastructure (roads, communication lines, and utilities) than it does today, yet the strong ground shaking from the earthquake still caused significant building damage and loss of life. The next large Hayward Fault earthquake is anticipated to affect thousands of structures and disrupt the lives of millions of people. Earthquake risk in the San Francisco Bay region has been greatly reduced as a result of previous concerted efforts; for example, tens of billions of dollars of investment in strengthening infrastructure was motivated in large part by the 1989 magnitude 6.9 Loma Prieta earthquake. To build on efforts to reduce earthquake risk in the San Francisco Bay region, the HayWired earthquake scenario comprehensively examines the earthquake hazards to help provide the crucial scientific information that the San Francisco Bay region can use to prepare for the next large earthquake, The HayWired Earthquake Scenario—Earthquake Hazards volume describes the strong ground shaking modeled in the scenario and the hazardous movements of

  16. 3D VIRTUAL ANASTYLOSIS AND RECONSTRUCTION OF SOME BUILDINGS IN THE SITE OF SAINT-SIMEON, SYRIA

    Directory of Open Access Journals (Sweden)

    M. Kurdy

    2012-09-01

    Full Text Available The site of Qal'at Sem'an, located in the north of Syria, was built in the honor of Saint Simeon around the column on the top of which he lived many years and died in 459. Since 2003, this site has been the object of digital surveys which covered the major part of the area. The sanctuary (Qal'at Sem'an and the village (Deir Sem'an are composed of different types of edifices; this variety gives us a large field of studies. Several surveying methods were applied on these sectors according to the morphology of the analyzed parts and to the analysis needs. This article presents a case study based on a combination of different digital measurement and modeling techniques for the virtual reconstruction of various parts of this complex site. As this work is conducted over several years, different acquisition tools have been experimented for image-based and range-based 3D modeling. In particular, we focus on the "Residence", a civil building of the 6th century which probably was an oil mill. We will describe the anastylosis process founded firstly on the digital surveying, secondly on the 3D model structuring and finally on the information interfacing by using NUBES, an integrated platform for describing, analyzing, documenting and sharing digital representations of heritage buildings. The final goal of our work is to evaluate the relevance of the survey / modeling / semantic structuring workflow for an effective analysis of a complex site.

  17. Loma Prieta Earthquake, October 18, 1989, Part 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — On October 17, 1989, a 7.1 magnitude earthquake occurred near Loma Prieta in the Santa Cruz Mountains. This earthquake is also known as the "San Francisco World...

  18. LiDAR-derived measurements of slip in the most recent ground-rupturing earthquakes along elements of the San Andreas fault system

    Science.gov (United States)

    Haddad, D. E.; Madden, C.; Salisbury, J. B.; Arrowsmith, R.; Weldon, R. J.

    2011-12-01

    Tectonically displaced geomorphic markers record the surface manifestation of earthquake-induced ground ruptures. Of particular interest to earthquake forecast models is the slip produced during the most recent ground-rupturing earthquake. High-resolution digital topography from light detection and ranging (LiDAR) is a powerful tool for measuring the most recent meter-scale slip along fault zones. We present surface slip measurements of recent ground-rupturing earthquakes along the Garlock, Owens Valley, Elsinore, and Blackwater-Calico fault zones. Fault scarp traces were mapped using LiDAR-derived digital elevation models (DEMs), local topographic gradient and relief maps, and aerial photography. An individual slip measurement was made for each offset feature by iteratively reconstructing the topography on either side of the fault and finding the best-matching vertically backslipped value. A goodness-of-fit approach was then used to calculate the best laterally backslipped displacement using a combination of vertical backslip, horizontal backslip, and topographic scaling. Along-strike, reach-averaged surface displacement distributions of the most recent earthquakes were then generated from the LiDAR-derived offsets and compared to published field-derived offset measurements. For the eastern section of the Garlock fault, our LiDAR-derived offsets compared well with those measured in the field and attained an R2 value of 0.88 with reach-averaged slip in the last event of 4.19 m ±0.69 m for the Searles Valley area (2.67 km reach), 4.65 m +0.76/-0.92 m for the Pilot Knob Valley area (24.68 km reach), and 3.45 m +0.82/-0.87 m for the Leach Lake and Avawatz Mountains areas (12.65 km reach), computed from a total of 129 offsets. Our results show that LiDAR-derived offset measurements compare well with field measurements in the comprehensive documentation of along-strike surface slip distributions of the most recent earthquake. Furthermore, our results demonstrate the

  19. 1906 Letter to the San Francisco Health Department

    Science.gov (United States)

    Schmachtenberg, Kristin

    2006-01-01

    On Wednesday, April 18, 1906, an earthquake, measuring 7.8 on the Richter magnitude scale and lasting 48 seconds, erupted along the San Andreas fault with a flash point originating in the San Francisco Bay area. The force of the earthquake tore apart buildings and roads, causing water and gas mains to twist and break. The resulting effects of the…

  20. Estimation of Future Earthquake Losses in California

    Science.gov (United States)

    Rowshandel, B.; Wills, C. J.; Cao, T.; Reichle, M.; Branum, D.

    2003-12-01

    Recent developments in earthquake hazards and damage modeling, computing, and data management and processing, have made it possible to develop estimates of the levels of damage from earthquakes that may be expected in the future in California. These developments have been mostly published in the open literature, and provide an opportunity to estimate the levels of earthquake damage Californians can expect to suffer during the next several decades. Within the past 30 years, earthquake losses have increased dramatically, mostly because our exposure to earthquake hazards has increased. All but four of the recent damaging earthquakes have occurred distant from California's major population centers. Two, the Loma Prieta earthquake and the San Fernando earthquake, occurred on the edges of major populated areas. Loma Prieta caused significant damage in the nearby Santa Cruz and in the more distant, heavily populated, San Francisco Bay area. The 1971 San Fernando earthquake had an epicenter in the lightly populated San Gabriel Mountains, but caused slightly over 2 billion dollars in damage in the Los Angeles area. As urban areas continue to expand, the population and infrastructure at risk increases. When earthquakes occur closer to populated areas, damage is more significant. The relatively minor Whittier Narrows earthquake of 1987 caused over 500 million dollars in damage because it occurred in the Los Angeles metropolitan area, not at its fringes. The Northridge earthquake had fault rupture directly beneath the San Fernando Valley, and caused about 46 billion dollars in damage. This vast increase in damage from the San Fernando earthquake reflected both the location of the earthquake directly beneath the populated area and the 23 years of continued development and resulting greater exposure to potential damage. We have calculated losses from potential future earthquake, both as scenarios of potential earthquakes and as annualized losses considering all the potential

  1. Detecting Significant Stress Drop Variations in Large Micro-Earthquake Datasets: A Comparison Between a Convergent Step-Over in the San Andreas Fault and the Ventura Thrust Fault System, Southern California

    Science.gov (United States)

    Goebel, T. H. W.; Hauksson, E.; Plesch, A.; Shaw, J. H.

    2016-06-01

    A key parameter in engineering seismology and earthquake physics is seismic stress drop, which describes the relative amount of high-frequency energy radiation at the source. To identify regions with potentially significant stress drop variations, we perform a comparative analysis of source parameters in the greater San Gorgonio Pass (SGP) and Ventura basin (VB) in southern California. The identification of physical stress drop variations is complicated by large data scatter as a result of attenuation, limited recording bandwidth and imprecise modeling assumptions. In light of the inherently high uncertainties in single stress drop measurements, we follow the strategy of stacking large numbers of source spectra thereby enhancing the resolution of our method. We analyze more than 6000 high-quality waveforms between 2000 and 2014, and compute seismic moments, corner frequencies and stress drops. Significant variations in stress drop estimates exist within the SGP area. Moreover, the SGP also exhibits systematically higher stress drops than VB and shows more scatter. We demonstrate that the higher scatter in SGP is not a generic artifact of our method but an expression of differences in underlying source processes. Our results suggest that higher differential stresses, which can be deduced from larger focal depth and more thrust faulting, may only be of secondary importance for stress drop variations. Instead, the general degree of stress field heterogeneity and strain localization may influence stress drops more strongly, so that more localized faulting and homogeneous stress fields favor lower stress drops. In addition, higher loading rates, for example, across the VB potentially result in stress drop reduction whereas slow loading rates on local fault segments within the SGP region result in anomalously high stress drop estimates. Our results show that crustal and fault properties systematically influence earthquake stress drops of small and large events and should

  2. Detecting Significant Stress Drop Variations in Large Micro-Earthquake Datasets: A Comparison Between a Convergent Step-Over in the San Andreas Fault and the Ventura Thrust Fault System, Southern California

    Science.gov (United States)

    Goebel, T. H. W.; Hauksson, E.; Plesch, A.; Shaw, J. H.

    2017-06-01

    A key parameter in engineering seismology and earthquake physics is seismic stress drop, which describes the relative amount of high-frequency energy radiation at the source. To identify regions with potentially significant stress drop variations, we perform a comparative analysis of source parameters in the greater San Gorgonio Pass (SGP) and Ventura basin (VB) in southern California. The identification of physical stress drop variations is complicated by large data scatter as a result of attenuation, limited recording bandwidth and imprecise modeling assumptions. In light of the inherently high uncertainties in single stress drop measurements, we follow the strategy of stacking large numbers of source spectra thereby enhancing the resolution of our method. We analyze more than 6000 high-quality waveforms between 2000 and 2014, and compute seismic moments, corner frequencies and stress drops. Significant variations in stress drop estimates exist within the SGP area. Moreover, the SGP also exhibits systematically higher stress drops than VB and shows more scatter. We demonstrate that the higher scatter in SGP is not a generic artifact of our method but an expression of differences in underlying source processes. Our results suggest that higher differential stresses, which can be deduced from larger focal depth and more thrust faulting, may only be of secondary importance for stress drop variations. Instead, the general degree of stress field heterogeneity and strain localization may influence stress drops more strongly, so that more localized faulting and homogeneous stress fields favor lower stress drops. In addition, higher loading rates, for example, across the VB potentially result in stress drop reduction whereas slow loading rates on local fault segments within the SGP region result in anomalously high stress drop estimates. Our results show that crustal and fault properties systematically influence earthquake stress drops of small and large events and should

  3. Abrupt along-strike change in tectonic style: San Andreas Fault zone, San Francisco Peninsula

    Science.gov (United States)

    Zoback, Mary Lou; Jachens, Robert C.; Olson, Jean A.

    1999-05-01

    Seismicity and high-resolution aeromagnetic data are used to define an abrupt change from compressional to extensional tectonism within a 10- to 15-km-wide zone along the San Andreas fault on the San Francisco Peninsula and offshore from the Golden Gate. This 100-km-long section of the San Andreas fault includes the hypocenter of the Mw = 7.8 1906 San Francisco earthquake as well as the highest level of persistent microseismicity along that ˜470-km-long rupture. We define two distinct zones of deformation along this stretch of the fault using well-constrained relocations of all post-1969 earthquakes based a joint one-dimensional velocity/hypocenter inversion and a redetermination of focal mechanisms. The southern zone is characterized by thrust- and reverse-faulting focal mechanisms with NE trending P axes that indicate "fault-normal" compression in 7- to 10-km-wide zones of deformation on both sides of the San Andreas fault. A 1- to 2-km-wide vertical zone beneath the surface trace of the San Andreas is characterized by its almost complete lack of seismicity. The compressional deformation is consistent with the young, high topography of the Santa Cruz Mountains/Coast Ranges as the San Andreas fault makes a broad restraining left bend (˜10°) through the southernmost peninsula. A zone of seismic quiescence ˜15 km long separates this compressional zone to the south from a zone of combined normal-faulting and strike-slip-faulting focal mechanisms (including a ML = 5.3 earthquake in 1957) on the northernmost peninsula and offshore on the Golden Gate platform. Both linear pseudogravity gradients, calculated from the aeromagnetic data, and seismic reflection data indicate that the San Andreas fault makes an abrupt ˜3-km right step less than 5 km offshore in this northern zone. A similar right-stepping (dilatational) geometry is also observed for the subparallel San Gregorio fault offshore. Persistent seismicity and extensional tectonism occur within the San Andreas

  4. San Francisco District Laboratory (SAN)

    Data.gov (United States)

    Federal Laboratory Consortium — Program Capabilities Food Analysis SAN-DO Laboratory has an expert in elemental analysis who frequently performs field inspections of materials. A recently acquired...

  5. Study on the Stability of San'guanmiao Landslides under Earthquake Based on GTS%基于GTS的地震作用下三官庙滑坡稳定性研究

    Institute of Scientific and Technical Information of China (English)

    王海龙; 张伟; 秦丽杰

    2016-01-01

    The landslide of San'guanmiao in Gongchangling District of Liaoyang city lies in the zone ofⅦ degree earth-quake intensity,and slides on both sides. Although the slope of the landslide is gentle,with the lubricating effect of the polluted water within the sewage canal,the landslide is currently in the creep deformation stage. The finite element simulation model was established by Midas-GTS to calculate and stability of Sanguanmiao landslide under the condition of natural condition and seis-mic condition. Considering the seismic probability exceeding by 10% in 50 years,the grid topology is made by adopting the quadrilateral circular grid method with the peak of time history load 0. 1g to make the strength reduction on the physical param-eters of rock mass. Through analyzing the slope shear strain and equivalent analysis of plastic zone,the potential sliding zone is determined. Compared with the result by limit equilibrium method,it is found that both fit very well. The calculating results show that the slope basically keeps stable in the natural state,with the safety coefficient varying from 1. 2 to 1. 3. But with the participation of the acceleration of 0. 1g for dynamic peak of earthquake,the slope become in an unstable state with the safety coefficient of 1 or lower.%辽阳市弓长岭区三官庙滑坡体处在Ⅶ度地震烈度区,滑坡体呈对滑状,滑坡体整体坡度较缓,受渠内污水的润滑作用,该滑坡目前处于蠕动变形阶段.采用Midas-GTS建立有限元仿真动态模拟分析模型,对三官庙滑坡在天然工况和地震工况下的稳定性进行了分析.考虑未来50 a地震超越概率10%工况,采用峰值为0.1g的时程荷载,运用四边形循环化网格法进行网格拓扑,对岩土体物理参数进行强度折减,分析坡体剪切应变区及等效塑性区,确定潜在滑动带,并将其与极限平衡法所得结果进行对比分析,两者拟合度很好,计算结果显示斜坡在天然状态下基本稳

  6. Nowcasting Earthquakes

    Science.gov (United States)

    Rundle, J. B.; Donnellan, A.; Grant Ludwig, L.; Turcotte, D. L.; Luginbuhl, M.; Gail, G.

    2016-12-01

    Nowcasting is a term originating from economics and finance. It refers to the process of determining the uncertain state of the economy or markets at the current time by indirect means. We apply this idea to seismically active regions, where the goal is to determine the current state of the fault system, and its current level of progress through the earthquake cycle. In our implementation of this idea, we use the global catalog of earthquakes, using "small" earthquakes to determine the level of hazard from "large" earthquakes in the region. Our method does not involve any model other than the idea of an earthquake cycle. Rather, we define a specific region and a specific large earthquake magnitude of interest, ensuring that we have enough data to span at least 20 or more large earthquake cycles in the region. We then compute the earthquake potential score (EPS) which is defined as the cumulative probability distribution P(nearthquakes in the region. From the count of small earthquakes since the last large earthquake, we determine the value of EPS = P(nearthquake cycle in the defined region at the current time.

  7. Earthquake Facts

    Science.gov (United States)

    Jump to Navigation Earthquake Facts The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, ... we know, there is no such thing as "earthquake weather" . Statistically, there is an equal distribution of ...

  8. Nowcasting earthquakes

    Science.gov (United States)

    Rundle, J. B.; Turcotte, D. L.; Donnellan, A.; Grant Ludwig, L.; Luginbuhl, M.; Gong, G.

    2016-11-01

    Nowcasting is a term originating from economics and finance. It refers to the process of determining the uncertain state of the economy or markets at the current time by indirect means. We apply this idea to seismically active regions, where the goal is to determine the current state of the fault system and its current level of progress through the earthquake cycle. In our implementation of this idea, we use the global catalog of earthquakes, using "small" earthquakes to determine the level of hazard from "large" earthquakes in the region. Our method does not involve any model other than the idea of an earthquake cycle. Rather, we define a specific region and a specific large earthquake magnitude of interest, ensuring that we have enough data to span at least 20 or more large earthquake cycles in the region. We then compute the earthquake potential score (EPS) which is defined as the cumulative probability distribution P(n < n(t)) for the current count n(t) for the small earthquakes in the region. From the count of small earthquakes since the last large earthquake, we determine the value of EPS = P(n < n(t)). EPS is therefore the current level of hazard and assigns a number between 0% and 100% to every region so defined, thus providing a unique measure. Physically, the EPS corresponds to an estimate of the level of progress through the earthquake cycle in the defined region at the current time.

  9. Loma Prieta Earthquake, October 18, 1989, Part 1

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — On October 17, 1989, a 7.1 magnitude earthquake occurred near Loma Prieta in the Santa Cruz Mountains. Movement occurred along a 40-km segment of the San Andreas...

  10. San Francisco District Laboratory (SAN)

    Data.gov (United States)

    Federal Laboratory Consortium — Program CapabilitiesFood Analysis SAN-DO Laboratory has an expert in elemental analysis who frequently performs field inspections of materials. A recently acquired...

  11. Earthquake Surface Fault Rupture Interaction with Building Foundations

    OpenAIRE

    Oettle, Nicolas Karl

    2013-01-01

    Recent earthquakes have provided numerous examples of the devastating effects of earthquake surface fault rupture on structures. Several major cities are built in areas containing active faults that can break the ground surface (e.g., Los Angeles, Salt Lake City, San Diego, San Francisco, and Seattle). Along with the often spectacular observations of damage, examples of satisfactory performance of structures were also observed. These examples of satisfactory performance indicate that similar ...

  12. A Case for Historic Joint Rupture of the San Andreas and San Jacinto Faults

    Science.gov (United States)

    Lozos, J.

    2015-12-01

    The ~M7.5 southern California earthquake of 8 December 1812 ruptured the San Andreas Fault from Cajon Pass to at least as far north as Pallet Creek (Biasi et al., 2002). The 1812 rupture has also been identified in trenches at Burro Flats to the south (Yule and Howland, 2001). However, the lack of a record of 1812 at Plunge Creek, between Cajon Pass and Burro Flats (McGill et al., 2002), complicates the interpretation of this event as a straightforward San Andreas rupture. Paleoseismic records of a large early 19th century rupture on the northern San Jacinto Fault (Onderdonk et al., 2013; Kendrick and Fumal, 2005) allow for alternate interpretations of the 1812 earthquake. I use dynamic rupture modeling on the San Andreas-San Jacinto junction to determine which rupture behaviors produce slip patterns consistent with observations of the 1812 event. My models implement realistic fault geometry, a realistic velocity structure, and stress orientations based on seismicity literature. Under these simple assumptions, joint rupture of the two faults is the most common behavior. My modeling rules out a San Andreas-only rupture that is consistent with the data from the 1812 earthquake, and also shows that single fault events are unable to match the average slip per event for either fault. The choice of nucleation point affects the details of rupture directivity and slip distribution, but not the first order result that multi-fault rupture is the preferred behavior. While it cannot be definitively said that joint San Andreas-San Jacinto rupture occurred in 1812, these results are consistent with paleoseismic and historic data. This has implications for the possibility of future multi-fault rupture within the San Andreas system, as well as for interpretation of other paleoseismic events in regions of complex fault interactions.

  13. San Marino.

    Science.gov (United States)

    1985-02-01

    San Marino, an independent republic located in north central Italy, in 1983 had a population of 22,206 growing at an annual rate of .9%. The literacy rate is 97% and the infant mortality rate is 9.6/1000. The terrain is mountainous and the climate is moderate. According to local tradition, San Marino was founded by a Christian stonecutter in the 4th century A.D. as a refuge against religious persecution. Its recorded history began in the 9th century, and it has survived assaults on its independence by the papacy, the Malatesta lords of Rimini, Cesare Borgia, Napoleon, and Mussolini. An 1862 treaty with the newly formed Kingdom of Italy has been periodically renewed and amended. The present government is an alliance between the socialists and communists. San Marino has had its own statutes and governmental institutions since the 11th century. Legislative authority at present is vested in a 60-member unicameral parliament. Executive authority is exercised by the 11-member Congress of State, the members of which head the various administrative departments of the goverment. The posts are divided among the parties which form the coalition government. Judicial authority is partly exercised by Italian magistrates in civil and criminal cases. San Marino's policies are tied to Italy's and political organizations and labor unions active in Italy are also active in San Marino. Since World War II, there has been intense rivalry between 2 political coalitions, the Popular Alliance composed of the Christian Democratic Party and the Independent Social Democratic Party, and the Liberty Committee, coalition of the Communist Party and the Socialist Party. San Marino's gross domestic product was $137 million and its per capita income was $6290 in 1980. The principal economic activities are farming and livestock raising, along with some light manufacturing. Foreign transactions are dominated by tourism. The government derives most of its revenue from the sale of postage stamps to

  14. Modeling earthquake indexes derived from the earthquake warning system upon the planet earth

    Science.gov (United States)

    Li, Yong

    2010-12-01

    By studying the correlation between historical earthquake data and the distributional characteristics of parameters of solid earth tides in the earthquake epicenter, we are able to design a forecasting function of earthquake probability. We put forward a design method for the Earthquake Warning System. The model could theoretically simulate and be used to predict the probability of strong earthquakes that could occur anywhere at any time. In addition, the system could also conveniently obtain global or partial Modeling Earthquake Indexes to finally combine the precise pointing prediction and forecast of partial indexes. The literature quotes global data values, provided by NEIC, of 1544 M ⩾ 6.5 earthquakes. It also gives examples of instantaneous earthquake indexes of the whole world and Taiwan Area on 1st January 2010, UT=0:00 and the average earthquake index near the Taiwan Area. According to the 10-year pointing prediction of strong earthquakes in San Francisco, the literature provides the average earthquake index on 24th June 2015 (± 15 days), in its neighborhood.

  15. Modeling earthquake indexes derived from the earthquake warning system upon the planet earth

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    By studying the correlation between historical earthquake data and the distributional characteristics of parameters of solid earth tides in the earthquake epicenter, we are able to design a forecasting function of earthquake probability. We put forward a design method for the Earthquake Warning System. The model could theoretically simulate and be used to predict the probability of strong earthquakes that could occur anywhere at any time. In addition, the system could also conveniently obtain global or partial Modeling Earthquake Indexes to finally combine the precise pointing prediction and forecast of partial indexes. The literature quotes global data values, provided by NEIC, of 1544 M ≥ 6.5 earthquakes. It also gives examples of instantaneous earthquake indexes of the whole world and Taiwan Area on 1st January 2010, UT=0:00 and the average earthquake index near the Taiwan Area. According to the 10-year pointing prediction of strong earthquakes in San Francisco, the literature provides the average earthquake index on 24th June 2015 (± 15 days), in its neighborhood.

  16. Analog earthquakes

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, R.B. [Center for Nuclear Waste Regulatory Analyses, San Antonio, TX (United States)

    1995-09-01

    Analogs are used to understand complex or poorly understood phenomena for which little data may be available at the actual repository site. Earthquakes are complex phenomena, and they can have a large number of effects on the natural system, as well as on engineered structures. Instrumental data close to the source of large earthquakes are rarely obtained. The rare events for which measurements are available may be used, with modfications, as analogs for potential large earthquakes at sites where no earthquake data are available. In the following, several examples of nuclear reactor and liquified natural gas facility siting are discussed. A potential use of analog earthquakes is proposed for a high-level nuclear waste (HLW) repository.

  17. Vertical tectonic deformation associated with the San Andreas fault zone offshore of San Francisco, California

    Science.gov (United States)

    Ryan, H. F.; Parsons, T.; Sliter, R. W.

    2008-10-01

    A new fault map of the shelf offshore of San Francisco, California shows that faulting occurs as a distributed shear zone that involves many fault strands with the principal displacement taken up by the San Andreas fault and the eastern strand of the San Gregorio fault zone. Structures associated with the offshore faulting show compressive deformation near where the San Andreas fault goes offshore, but deformation becomes extensional several km to the north off of the Golden Gate. Our new fault map serves as the basis for a 3-D finite element model that shows that the block between the San Andreas and San Gregorio fault zone is subsiding at a long-term rate of about 0.2-0.3 mm/yr, with the maximum subsidence occurring northwest of the Golden Gate in the area of a mapped transtensional basin. Although the long-term rates of vertical displacement primarily show subsidence, the model of coseismic deformation associated with the 1906 San Francisco earthquake indicates that uplift on the order of 10-15 cm occurred in the block northeast of the San Andreas fault. Since 1906, 5-6 cm of regional subsidence has occurred in that block. One implication of our model is that the transfer of slip from the San Andreas fault to a fault 5 km to the east, the Golden Gate fault, is not required for the area offshore of San Francisco to be in extension. This has implications for both the deposition of thick Pliocene-Pleistocene sediments (the Merced Formation) observed east of the San Andreas fault, and the age of the Peninsula segment of the San Andreas fault.

  18. Synthetic seismicity for the San Andreas fault

    Directory of Open Access Journals (Sweden)

    S. N. Ward

    1994-06-01

    Full Text Available Because historical catalogs generally span only a few repetition intervals of major earthquakes, they do not provide much constraint on how regularly earthquakes recur. In order to obtain better recurrence statistics and long-term probability estimates for events M ? 6 on the San Andreas fault, we apply a seismicity model to this fault. The model is based on the concept of fault segmentation and the physics of static dislocations which allow for stress transfer between segments. Constraints are provided by geological and seismological observations of segment lengths, characteristic magnitudes and long-term slip rates. Segment parameters slightly modified from the Working Group on California Earthquake Probabilities allow us to reproduce observed seismicity over four orders of magnitude. The model yields quite irregular earthquake recurrence patterns. Only the largest events (M ? 7.5 are quasi-periodic; small events cluster. Both the average recurrence time and the aperiodicity are also a function of position along the fault. The model results are consistent with paleoseismic data for the San Andreas fault as well as a global set of historical and paleoseismic recurrence data. Thus irregular earthquake recurrence resulting from segment interaction is consistent with a large range of observations.

  19. Deep Borehole Instrumentation Along San Francisco Bay Bridges - 2001

    Energy Technology Data Exchange (ETDEWEB)

    Hutchings, L.; Kasameyer, P.; Long, L.; McEvilly, T.; Clymer, R.; Urhhammer, R.; Baise, L.

    2001-05-01

    This is a progress report on the Bay Bridges downhole network. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges in San Francisco Bay, California. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty-one sensor packages at fifteen sites. The downhole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 731 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes. This report list earthquakes and stations where recordings were obtained during the period February 29, 2000 to November 11, 2000. Also, preliminary results on noise analysis for up and down hole recordings at Yerba Buena Island is presented.

  20. The Parkfield experiment; capturing what happens in an earthquake

    Science.gov (United States)

    Hickman, Steve; Langbein, John; Stauffer, Peter H.

    2004-01-01

    To better understand what happens on and near a fault before, during, and after an earthquake, the U.S. Geological Survey (USGS) and the California Geological Survey began the Parkfield Earthquake Experiment in the 1980's. Researchers from the USGS and collaborating institutions have created a dense network of instruments on the San Andreas Fault at Parkfield, California, where moderate earthquakes have occurred at fairly regular intervals. Data from these instruments are revealing the earthquake process in unprecedented detail and will aid in predicting the time and severity of future shocks. The USGS and the National Science Foundation plan to expand the Parkfield Experiment by drilling a deep borehole and installing instruments at the actual depths where earthquakes initiate, creating a San Andreas Fault Observatory at Depth.

  1. Napa Earthquake impact on water systems

    Science.gov (United States)

    Wang, J.

    2014-12-01

    South Napa earthquake occurred in Napa, California on August 24 at 3am, local time, and the magnitude is 6.0. The earthquake was the largest in SF Bay Area since the 1989 Loma Prieta earthquake. Economic loss topped $ 1 billion. Wine makers cleaning up and estimated the damage on tourism. Around 15,000 cases of lovely cabernet were pouring into the garden at the Hess Collection. Earthquake potentially raise water pollution risks, could cause water crisis. CA suffered water shortage recent years, and it could be helpful on how to prevent underground/surface water pollution from earthquake. This research gives a clear view on drinking water system in CA, pollution on river systems, as well as estimation on earthquake impact on water supply. The Sacramento-San Joaquin River delta (close to Napa), is the center of the state's water distribution system, delivering fresh water to more than 25 million residents and 3 million acres of farmland. Delta water conveyed through a network of levees is crucial to Southern California. The drought has significantly curtailed water export, and salt water intrusion reduced fresh water outflows. Strong shaking from a nearby earthquake can cause saturated, loose, sandy soils liquefaction, and could potentially damage major delta levee systems near Napa. Napa earthquake is a wake-up call for Southern California. It could potentially damage freshwater supply system.

  2. Earthquake Hazards Program: Earthquake Scenarios

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — A scenario represents one realization of a potential future earthquake by assuming a particular magnitude, location, and fault-rupture geometry and estimating...

  3. Coulomb static stress interactions between simulated M>7 earthquakes and major faults in Southern California

    Science.gov (United States)

    Rollins, J. C.; Ely, G. P.; Jordan, T. H.

    2010-12-01

    We calculate the Coulomb stress changes imparted to major Southern California faults by thirteen simulated worst-case-scenario earthquakes for the region, including the “Big Ten” scenarios (Ely et al, in progress). The source models for the earthquakes are variable-slip simulations from the SCEC CyberShake project (Graves et al, 2010). We find strong stress interactions between the San Andreas and subparallel right-lateral faults, thrust faults under the Los Angeles basin, and the left-lateral Garlock Fault. M>7 earthquakes rupturing sections of the southern San Andreas generally decrease Coulomb stress on the San Jacinto and Elsinore faults and impart localized stress increases and decreases to the Garlock, San Cayetano, Puente Hills and Sierra Madre faults. A M=7.55 quake rupturing the San Andreas between Lake Hughes and San Gorgonio Pass increases Coulomb stress on the eastern San Cayetano fault, consistent with Deng and Sykes (1996). M>7 earthquakes rupturing the San Jacinto, Elsinore, Newport-Inglewood and Palos Verdes faults decrease stress on parallel right-lateral faults. A M=7.35 quake on the San Cayetano Fault decreases stress on the Garlock and imparts localized stress increases and decreases to the San Andreas. A M=7.15 quake on the Puente Hills Fault increases stress on the San Andreas and San Jacinto faults, decreases stress on the Sierra Madre Fault and imparts localized stress increases and decreases to the Newport-Inglewood and Palos Verdes faults. A M=7.25 shock on the Sierra Madre Fault increases stress on the San Andreas and decreases stress on the Puente Hills Fault. These findings may be useful for hazard assessment, paleoseismology, and comparison with dynamic stress interactions featuring the same set of earthquakes.

  4. Strong ground motion prediction using virtual earthquakes.

    Science.gov (United States)

    Denolle, M A; Dunham, E M; Prieto, G A; Beroza, G C

    2014-01-24

    Sedimentary basins increase the damaging effects of earthquakes by trapping and amplifying seismic waves. Simulations of seismic wave propagation in sedimentary basins capture this effect; however, there exists no method to validate these results for earthquakes that have not yet occurred. We present a new approach for ground motion prediction that uses the ambient seismic field. We apply our method to a suite of magnitude 7 scenario earthquakes on the southern San Andreas fault and compare our ground motion predictions with simulations. Both methods find strong amplification and coupling of source and structure effects, but they predict substantially different shaking patterns across the Los Angeles Basin. The virtual earthquake approach provides a new approach for predicting long-period strong ground motion.

  5. Earthquake fault superhighways

    Science.gov (United States)

    Robinson, D. P.; Das, S.; Searle, M. P.

    2010-10-01

    Motivated by the observation that the rare earthquakes which propagated for significant distances at supershear speeds occurred on very long straight segments of faults, we examine every known major active strike-slip fault system on land worldwide and identify those with long (> 100 km) straight portions capable not only of sustained supershear rupture speeds but having the potential to reach compressional wave speeds over significant distances, and call them "fault superhighways". The criteria used for identifying these are discussed. These superhighways include portions of the 1000 km long Red River fault in China and Vietnam passing through Hanoi, the 1050 km long San Andreas fault in California passing close to Los Angeles, Santa Barbara and San Francisco, the 1100 km long Chaman fault system in Pakistan north of Karachi, the 700 km long Sagaing fault connecting the first and second cities of Burma, Rangoon and Mandalay, the 1600 km Great Sumatra fault, and the 1000 km Dead Sea fault. Of the 11 faults so classified, nine are in Asia and two in North America, with seven located near areas of very dense populations. Based on the current population distribution within 50 km of each fault superhighway, we find that more than 60 million people today have increased seismic hazards due to them.

  6. Effects of a major earthquake on calls to regional poison control centers.

    OpenAIRE

    Nathan, A. R.; Olson, K.R.; Everson, G. W.; Kearney, T E; Blanc, P. D.

    1992-01-01

    We retrospectively evaluated the effect of the Loma Prieta earthquake on calls to 2 designated regional poison control centers (San Francisco and Santa Clara) in the area. In the immediate 12 hours after the earthquake, there was an initial drop (31%) in call volume, related to telephone system overload and other technical problems. Calls from Bay Area counties outside of San Francisco and Santa Clara decreased more dramatically than those from within the host counties where the poison contro...

  7. Earthquake engineering research: 1982

    Science.gov (United States)

    The Committee on Earthquake Engineering Research addressed two questions: What progress has research produced in earthquake engineering and which elements of the problem should future earthquake engineering pursue. It examined and reported in separate chapters of the report: Applications of Past Research, Assessment of Earthquake Hazard, Earthquake Ground Motion, Soil Mechanics and Earth Structures, Analytical and Experimental Structural Dynamics, Earthquake Design of Structures, Seismic Interaction of Structures and Fluids, Social and Economic Aspects, Earthquake Engineering Education, Research in Japan.

  8. Variability of fault slip behavior along the San Andreas Fault in the San Juan Bautista Region

    Science.gov (United States)

    Taira, Taka'aki; Bürgmann, Roland; Nadeau, Robert M.; Dreger, Douglas S.

    2014-12-01

    An improved understanding of the time history of fault slip at depth is an essential step toward understanding the underlying mechanics of the faulting process. Using a waveform cross-correlation approach, we document spatially and temporally varying fault slip along the northernmost creeping section of the San Andreas Fault near San Juan Bautista (SJB), California, by systematically examining spatiotemporal behaviors of characteristically repeating earthquakes (CREs). The spatial distribution of pre-1998 SJB earthquake (1984-1998) fault slip rate inferred from the CREs reveals a ~15 km long low creep or partially locked section located near the 1998 Mw 5.1 SJB earthquake rupture. A finite-fault slip inversion reveals that the rupture of the 1998 SJB earthquake is characterized by the failure of a compact ~4 km2 asperity with a maximum slip of about 90 cm and corresponding peak stress drop of up to 50 MPa, whereas the mean stress drop is about 15 MPa. Following the 1998 earthquake, the CRE activity was significantly increased in a 5-10 km deep zone extending 2-7 km northwest of the main shock, which indicates triggering of substantial aseismic slip. The postseismic slip inferred from the CRE activity primarily propagated to the northwest and released a maximum slip of 9 cm. In this 5-10 km depth range, the estimated postseismic moment release is 8.6 × 1016 N m, which is equivalent to Mw 5.22. The aseismic slip distribution following the 1998 earthquake is not consistent with coseismic stress-driven afterslip but represents a triggered, long-lasting slow earthquake.

  9. The Bay Area Earthquake Cycle:A Paleoseismic Perspective

    Science.gov (United States)

    Schwartz, D. P.; Seitz, G.; Lienkaemper, J. J.; Dawson, T. E.; Hecker, S.; William, L.; Kelson, K.

    2001-12-01

    Stress changes produced by the 1906 San Francisco earthquake had a profound effect on Bay Area seismicity, dramatically reducing it in the 20th century. Whether the San Francisco Bay Region (SFBR) is still within, is just emerging from it, or is out of the 1906 stress shadow is an issue of strong debate with important implications for earthquake mechanics and seismic hazards. Historically the SFBR has not experienced one complete earthquake cycle--the interval immediately following, then leading up to and repeating, a 1906-type (multi-segment rupture, M7.9) San Andreas event. The historical record of earthquake occurrence in the SFBR appears to be complete at about M5.5 back to 1850 (Bakun, 1999), which is less than half a cycle. For large events (qualitatively placed at M*7) Toppozada and Borchardt (1998) suggest the record is complete back to 1776, which may represent about half a cycle. During this period only the southern Hayward fault (1868) and the San Andreas fault (1838?, 1906) have produced their expected large events. New paleoseismic data now provide, for the first time, a more complete view of the most recent pre-1906 SFBR earthquake cycle. Focused paleoseismic efforts under the Bay Area Paleoearthquake Experiment (BAPEX) have developed a chronology of the most recent large earthquakes (MRE) on major SFBR faults. The San Andreas (SA), northern Hayward (NH), southern Hayward (SH), Rodgers Creek (RC), and northern Calaveras (NC) faults provide clear paleoseismic evidence for large events post-1600 AD. The San Gregorio (SG) may have also produced a large earthquake after this date. The timing of the MREs, in years AD, follows. The age ranges are 2-sigma radiocarbon intervals; the dates in parentheses are 1-sigma. MRE ages are: a) SA 1600-1670 (1630-1660), NH 1640-1776 (1635-1776); SH 1635-1776 (1685-1676); RC 1670-1776 (1730-1776); NC 1670-1830?; and San Gregorio 1270-1776 but possibly 1640-1776 (1685-1776). Based on present radiocarbon dating, the NH

  10. Crowd-Sourced Global Earthquake Early Warning

    Science.gov (United States)

    Minson, S. E.; Brooks, B. A.; Glennie, C. L.; Murray, J. R.; Langbein, J. O.; Owen, S. E.; Iannucci, B. A.; Hauser, D. L.

    2014-12-01

    Although earthquake early warning (EEW) has shown great promise for reducing loss of life and property, it has only been implemented in a few regions due, in part, to the prohibitive cost of building the required dense seismic and geodetic networks. However, many cars and consumer smartphones, tablets, laptops, and similar devices contain low-cost versions of the same sensors used for earthquake monitoring. If a workable EEW system could be implemented based on either crowd-sourced observations from consumer devices or very inexpensive networks of instruments built from consumer-quality sensors, EEW coverage could potentially be expanded worldwide. Controlled tests of several accelerometers and global navigation satellite system (GNSS) receivers typically found in consumer devices show that, while they are significantly noisier than scientific-grade instruments, they are still accurate enough to capture displacements from moderate and large magnitude earthquakes. The accuracy of these sensors varies greatly depending on the type of data collected. Raw coarse acquisition (C/A) code GPS data are relatively noisy. These observations have a surface displacement detection threshold approaching ~1 m and would thus only be useful in large Mw 8+ earthquakes. However, incorporating either satellite-based differential corrections or using a Kalman filter to combine the raw GNSS data with low-cost acceleration data (such as from a smartphone) decreases the noise dramatically. These approaches allow detection thresholds as low as 5 cm, potentially enabling accurate warnings for earthquakes as small as Mw 6.5. Simulated performance tests show that, with data contributed from only a very small fraction of the population, a crowd-sourced EEW system would be capable of warning San Francisco and San Jose of a Mw 7 rupture on California's Hayward fault and could have accurately issued both earthquake and tsunami warnings for the 2011 Mw 9 Tohoku-oki, Japan earthquake.

  11. Earthquake Education in Prime Time

    Science.gov (United States)

    de Groot, R.; Abbott, P.; Benthien, M.

    2004-12-01

    Since 2001, the Southern California Earthquake Center (SCEC) has collaborated on several video production projects that feature important topics related to earthquake science, engineering, and preparedness. These projects have also fostered many fruitful and sustained partnerships with a variety of organizations that have a stake in hazard education and preparedness. The Seismic Sleuths educational video first appeared in the spring season 2001 on Discovery Channel's Assignment Discovery. Seismic Sleuths is based on a highly successful curriculum package developed jointly by the American Geophysical Union and The Department of Homeland Security Federal Emergency Management Agency. The California Earthquake Authority (CEA) and the Institute for Business and Home Safety supported the video project. Summer Productions, a company with a reputation for quality science programming, produced the Seismic Sleuths program in close partnership with scientists, engineers, and preparedness experts. The program has aired on the National Geographic Channel as recently as Fall 2004. Currently, SCEC is collaborating with Pat Abbott, a geology professor at San Diego State University (SDSU) on the video project Written In Stone: Earthquake Country - Los Angeles. Partners on this project include the California Seismic Safety Commission, SDSU, SCEC, CEA, and the Insurance Information Network of California. This video incorporates live-action demonstrations, vivid animations, and a compelling host (Abbott) to tell the story about earthquakes in the Los Angeles region. The Written in Stone team has also developed a comprehensive educator package that includes the video, maps, lesson plans, and other supporting materials. We will present the process that facilitates the creation of visually effective, factually accurate, and entertaining video programs. We acknowledge the need to have a broad understanding of the literature related to communication, media studies, science education, and

  12. Deep bore hole instrumentation along San Francisco Bay Bridges

    Energy Technology Data Exchange (ETDEWEB)

    Bakun, W.; Bowman, J.; Clymer, R.; Foxall, W.; Hipley, P.; Hollfelder, J.; Hutchings, L.; Jarpe, S.; Kasameyer, P.; McEvilly, T.; Mualchin, L.; Palmer, M.

    1998-10-01

    The Bay Bridges down hole network consists of sensors in bore holes that are drilled 100 ft. into bedrock around and in the San Francisco Bay. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty- one sensor packages at fifteen sites. Extensive financial support is being contributed by Caltrans, UCB, LBL, LLNL-LDRD, U.C. Campus/Laboratory Collaboration (CLC) program, and USGS. The down hole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 73 1 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes.

  13. The San Andreas Fault in the San Francisco Bay area, California: a geology fieldtrip guidebook to selected stops on public lands

    Science.gov (United States)

    Stoffer, Philip W.

    2005-01-01

    This guidebook contains a series of geology fieldtrips with selected destinations along the San Andreas Fault in part of the region that experienced surface rupture during the Great San Francisco Earthquake of 1906. Introductory materials present general information about the San Andreas Fault System, landscape features, and ecological factors associated with faults in the South Bay, Santa Cruz Mountains, the San Francisco Peninsula, and the Point Reyes National Seashore regions. Trip stops include roadside areas and recommended hikes along regional faults and to nearby geologic and landscape features that provide opportunities to make casual observations about the geologic history and landscape evolution. Destinations include the sites along the San Andreas and Calaveras faults in the San Juan Bautista and Hollister region. Stops on public land along the San Andreas Fault in the Santa Cruz Mountains in Santa Clara and Santa Cruz counties include in the Loma Prieta summit area, Forest of Nicene Marks State Park, Lexington County Park, Sanborn County Park, Castle Rock State Park, and the Mid Peninsula Open Space Preserve. Destinations on the San Francisco Peninsula and along the coast in San Mateo County include the Crystal Springs Reservoir area, Mussel Rock Park, and parts of Golden Gate National Recreation Area, with additional stops associated with the San Gregorio Fault system at Montara State Beach, the James F. Fitzgerald Preserve, and at Half Moon Bay. Field trip destinations in the Point Reyes National Seashore and vicinity provide information about geology and character of the San Andreas Fault system north of San Francisco.

  14. Connecting slow earthquakes to huge earthquakes.

    Science.gov (United States)

    Obara, Kazushige; Kato, Aitaro

    2016-07-15

    Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of their high sensitivity to stress changes in the seismogenic zone. Episodic stress transfer to megathrust source faults leads to an increased probability of triggering huge earthquakes if the adjacent locked region is critically loaded. Careful and precise monitoring of slow earthquakes may provide new information on the likelihood of impending huge earthquakes.

  15. Connecting slow earthquakes to huge earthquakes

    Science.gov (United States)

    Obara, Kazushige; Kato, Aitaro

    2016-07-01

    Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of their high sensitivity to stress changes in the seismogenic zone. Episodic stress transfer to megathrust source faults leads to an increased probability of triggering huge earthquakes if the adjacent locked region is critically loaded. Careful and precise monitoring of slow earthquakes may provide new information on the likelihood of impending huge earthquakes.

  16. A Study of the San Andreas Slip Rate on the San Francisco Peninsula, California

    Science.gov (United States)

    Feigelson, L. M.; Prentice, C.; Grove, K.; Caskey, J.; Ritz, J. F.; Leslie, S.

    2008-12-01

    The most recent large earthquake on the San Andreas Fault (SAF) along the San Francisco Peninsula was the great San Francisco earthquake of April 18, 1906, when a Mw= 7.8 event ruptured 435-470 km of the northern SAF. The slip rate for this segment of the SAF is incompletely known but is important for clarifying seismic hazard in this highly urbanized region. A previous study south of our site has found an average slip rate of 17±4 mm/yr for the late Holocene on the San Francisco Peninsula segment of the SAF. North of the Golden Gate, the SAF joins the San Gregorio Fault with an estimated slip rate of 6 mm/yr. A trench study north of where the two faults join has produced an average late Holocene slip rate of 24±3 mm/yr. To refine slip-rate estimates for the peninsula segment of the SAF, we excavated a trench across the fault where we located an abandoned channel between the San Andreas and Lower Crystal Springs reservoirs. This abandoned channel marks the time when a new channel cut across the SAF; the new channel has since been offset in a right-lateral sense about 20 m. The measured amount of offset and the age of the youngest fluvial sediments in the abandoned channel will yield a slip rate for the San Francisco Peninsula segment of the SAF. We excavated a trench across the abandoned channel and logged the exposed sediments. Our investigation revealed channel-fill alluvium incised and filled by probable debris flow sediments, and a wide fault zone in bedrock, west of the channel deposits. The most prominent fault is probably the strand that moved in 1906. We completed a total-station survey to more precisely measure the offset stream, and to confirm that the fault exposed in the trench aligns with a fence that is known to have been offset 2.8m during the 1906 earthquake. We interpret the debris flow sediments to represent the last phase of deposition prior to abandonment of the old channel. We collected samples for radiocarbon dating, optically stimulated

  17. The Elmore Ranch and Superstition Hills earthquakes of 24 November 1987: Introduction to the special issue

    OpenAIRE

    Hanks, Thomas C.; Allen, Clarence R.

    1989-01-01

    On 24 November 1987, two significant earthquakes occurred along the southern San Jacinto fault zone and related structural elements in southern California, not far from the International Border. These two events, the Elmore Ranch earthquake (M = 6.2 at 0154 GMT) and the Superstition Hills earthquake (M = 6.6 at 1315 GMT, both moment magnitudes from Sipkin, 1989), and their aftershocks have yielded a rich harvest of geological, seismological, and engineering data pertinent to the cause and ...

  18. Is Earthquake Triggering Driven by Small Earthquakes?

    CERN Document Server

    Helmstetter, A

    2002-01-01

    Using a catalog of seismicity for Southern California, we measure how the number of triggered earthquakes increases with the earthquake magnitude. The trade-off between this scaling and the distribution of earthquake magnitudes controls the relative role of small compared to large earthquakes. We show that seismicity triggering is driven by the smallest earthquakes, which trigger fewer aftershocks than larger earthquakes, but which are much more numerous. We propose that the non-trivial scaling of the number of aftershocks emerges from the fractal spatial distribution of aftershocks.

  19. Predictable earthquakes?

    Science.gov (United States)

    Martini, D.

    2002-12-01

    acceleration) and global number of earthquake for this period from published literature which give us a great picture about the dynamical geophysical phenomena. Methodology: The computing of linear correlation coefficients gives us a chance to quantitatively characterise the relation among the data series, if we suppose a linear dependence in the first step. The correlation coefficients among the Earth's rotational acceleration and Z-orbit acceleration (perpendicular to the ecliptic plane) and the global number of the earthquakes were compared. The results clearly demonstrate the common feature of both the Earth's rotation and Earth's Z-acceleration around the Sun and also between the Earth's rotational acceleration and the earthquake number. This fact might means a strong relation among these phenomena. The mentioned rather strong correlation (r = 0.75) and the 29 year period (Saturn's synodic period) was clearly shown in the counted cross correlation function, which gives the dynamical characteristic of correlation, of Earth's orbital- (Z-direction) and rotational acceleration. This basic period (29 year) was also obvious in the earthquake number data sets with clear common features in time. Conclusion: The Core, which involves the secular variation of the Earth's magnetic field, is the only sufficiently mobile part of the Earth with a sufficient mass to modify the rotation which probably effects on the global time distribution of the earthquakes. Therefore it might means that the secular variation of the earthquakes is inseparable from the changes in Earth's magnetic field, i.e. the interior process of the Earth's core belongs to the dynamical state of the solar system. Therefore if the described idea is real the global distribution of the earthquakes in time is predictable.

  20. Defeating Earthquakes

    Science.gov (United States)

    Stein, R. S.

    2012-12-01

    The 2004 M=9.2 Sumatra earthquake claimed what seemed an unfathomable 228,000 lives, although because of its size, we could at least assure ourselves that it was an extremely rare event. But in the short space of 8 years, the Sumatra quake no longer looks like an anomaly, and it is no longer even the worst disaster of the Century: 80,000 deaths in the 2005 M=7.6 Pakistan quake; 88,000 deaths in the 2008 M=7.9 Wenchuan, China quake; 316,000 deaths in the M=7.0 Haiti, quake. In each case, poor design and construction were unable to withstand the ferocity of the shaken earth. And this was compounded by inadequate rescue, medical care, and shelter. How could the toll continue to mount despite the advances in our understanding of quake risk? The world's population is flowing into megacities, and many of these migration magnets lie astride the plate boundaries. Caught between these opposing demographic and seismic forces are 50 cities of at least 3 million people threatened by large earthquakes, the targets of chance. What we know for certain is that no one will take protective measures unless they are convinced they are at risk. Furnishing that knowledge is the animating principle of the Global Earthquake Model, launched in 2009. At the very least, everyone should be able to learn what his or her risk is. At the very least, our community owes the world an estimate of that risk. So, first and foremost, GEM seeks to raise quake risk awareness. We have no illusions that maps or models raise awareness; instead, earthquakes do. But when a quake strikes, people need a credible place to go to answer the question, how vulnerable am I, and what can I do about it? The Global Earthquake Model is being built with GEM's new open source engine, OpenQuake. GEM is also assembling the global data sets without which we will never improve our understanding of where, how large, and how frequently earthquakes will strike, what impacts they will have, and how those impacts can be lessened by

  1. Earthquake and bay: Response of Monterey Bay to the Loma Prieta Earthquake

    Science.gov (United States)

    Schwing, Franklin B.; Norton, Jerrold G.; Pilskaln, Cynthia H.

    The magnitude-7.1 Loma Prieta earthquake, which ruptured a segment of the San Andreas fault on October 17, 1989, and caused extensive damage over a large area of central California, also produced substantial motions in nearby Monterey Bay (Figure 1). Earthquake effects included a tsunami, or seismic sea wave, and subsequent surface water oscillations that were detected for about 24 hours following the main shock and widespread, substantial slumping of sediments on the Monterey Bay continental shelf and along the walls of Monterey Submarine Canyon.

  2. 77 FR 54811 - Safety Zone; TriRock San Diego, San Diego Bay, San Diego, CA

    Science.gov (United States)

    2012-09-06

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; TriRock San Diego, San Diego Bay, San Diego... safety zone upon the navigable waters of the San Diego Bay, San Diego, CA, in support of a bay swim in San Diego Harbor. This safety zone is necessary to provide for the safety of the participants, crew...

  3. 78 FR 58878 - Safety Zone; San Diego Shark Fest Swim; San Diego Bay, San Diego, CA

    Science.gov (United States)

    2013-09-25

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Shark Fest Swim; San Diego Bay, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone upon the navigable waters of the San Diego Bay, San Diego, CA, in support of San...

  4. 78 FR 53243 - Safety Zone; TriRock San Diego, San Diego Bay, San Diego, CA

    Science.gov (United States)

    2013-08-29

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; TriRock San Diego, San Diego Bay, San Diego... temporary safety zone upon the navigable waters of the San Diego Bay, San Diego, CA, in support of a... Bryan Gollogly, Waterways Management, U.S. Coast Guard Sector San Diego; telephone (619) 278-7656, email...

  5. Hurricane Sandy and earthquakes

    OpenAIRE

    MAVASHEV BORIS; MAVASHEV IGOR

    2013-01-01

    Submit for consideration the connection between formation of a hurricane Sandy and earthquakes. As a rule, weather anomalies precede and accompany earthquakes. The hurricane Sandy emerged 2 days prior to strong earthquakes that occurred in the area. And the trajectory of the hurricane Sandy matched the epicenter of the earthquakes. Possibility of early prediction of natural disasters will minimize the moral and material damage.

  6. Protecting Your Family From Earthquakes-The Seven Steps to Earthquake Safety (in Spanish and English)

    Science.gov (United States)

    Developed by American Red Cross, Asian Pacific Fund

    2007-01-01

    This book is provided here to share an important message on emergency preparedness. Historically, we have suffered earthquakes here in the San Francisco Bay Area that have caused severe hardship for residents and incredible damage to our cities. It is likely we will experience a severe earthquake within the next 30 years. Many of us come from other countries where we have experienced earth- quakes, so we believe that we understand them. However, the way we prepare for earthquakes in our home country may be different from the way it is necessary to prepare for earthquakes here. Very f w people die from collapsing buildings in the Bay Area because most structures are built to stand up to the shaking. But it is quite possible that your family will be without medical care or grocery stores and separated from one another for several days to weeks. It will ultimately be up to you to keep your family safe until help arrives, so we are asking you to join us in learning to take care of your family before, during, and after an earthquake. The first step is to read this book. Everyone in your family, children and adults, can learn how to prepare for an earthquake. Then take advantage of the American Red Cross Earthquake Preparedness training courses offered in your community. These preparedness courses are free, and also offered in Spanish and available to everyone in the community regardless of family history, leg al status, gender, or age. We encourage you to take one of these free training workshops. Look on the back cover for more information. Remember that an earthquake can occur without warning, and the only way that we can reduce the harm caused by earthquakes is to be prepared. Get Prepared!

  7. Are Earthquake Clusters/Supercycles Real or Random?

    Science.gov (United States)

    Salditch, L.; Brooks, E. M.; Stein, S.; Spencer, B. D.

    2016-12-01

    Long records of earthquakes at plate boundaries such as the San Andreas or Cascadia often show that large earthquakes occur in temporal clusters, also termed supercycles, separated by less active intervals. These are intriguing because the boundary is presumably being loaded by steady plate motion. If so, earthquakes resulting from seismic cycles - in which their probability is small shortly after the past one, and then increases with time - should occur quasi-periodically rather than be more frequent in some intervals than others. We are exploring this issue with two approaches. One is to assess whether the clusters result purely by chance from a time-independent process that has no "memory." Thus a future earthquake is equally likely immediately after the past one and much later, so earthquakes can cluster in time. We analyze the agreement between such a model and inter-event times for Parkfield, Pallet Creek, and other records. A useful tool is transformation by the inverse cumulative distribution function, so the inter-event times have a uniform distribution when the memorylessness property holds. The second is via a time-variable model in which earthquake probability increases with time between earthquakes and decreases after an earthquake. The probability of an event increases with time until one happens, after which it decreases, but not to zero. Hence after a long period of quiescence, the probability of an earthquake can remain higher than the long-term average for several cycles. Thus the probability of another earthquake is path dependent, i.e. depends on the prior earthquake history over multiple cycles. Time histories resulting from simulations give clusters with properties similar to those observed. The sequences of earthquakes result from both the model parameters and chance, so two runs with the same parameters look different. The model parameters control the average time between events and the variation of the actual times around this average, so

  8. Loading of the San Andreas fault by flood-induced rupture of faults beneath the Salton Sea

    Science.gov (United States)

    Brothers, Daniel; Kilb, Debi; Luttrell, Karen; Driscoll, Neal W.; Kent, Graham

    2011-01-01

    The southern San Andreas fault has not experienced a large earthquake for approximately 300 years, yet the previous five earthquakes occurred at ~180-year intervals. Large strike-slip faults are often segmented by lateral stepover zones. Movement on smaller faults within a stepover zone could perturb the main fault segments and potentially trigger a large earthquake. The southern San Andreas fault terminates in an extensional stepover zone beneath the Salton Sea—a lake that has experienced periodic flooding and desiccation since the late Holocene. Here we reconstruct the magnitude and timing of fault activity beneath the Salton Sea over several earthquake cycles. We observe coincident timing between flooding events, stepover fault displacement and ruptures on the San Andreas fault. Using Coulomb stress models, we show that the combined effect of lake loading, stepover fault movement and increased pore pressure could increase stress on the southern San Andreas fault to levels sufficient to induce failure. We conclude that rupture of the stepover faults, caused by periodic flooding of the palaeo-Salton Sea and by tectonic forcing, had the potential to trigger earthquake rupture on the southern San Andreas fault. Extensional stepover zones are highly susceptible to rapid stress loading and thus the Salton Sea may be a nucleation point for large ruptures on the southern San Andreas fault.

  9. Southern San Andreas Fault seismicity is consistent with the Gutenberg-Richter magnitude-frequency distribution

    Science.gov (United States)

    Page, Morgan T.; Felzer, Karen

    2015-01-01

    The magnitudes of any collection of earthquakes nucleating in a region are generally observed to follow the Gutenberg-Richter (G-R) distribution. On some major faults, however, paleoseismic rates are higher than a G-R extrapolation from the modern rate of small earthquakes would predict. This, along with other observations, led to formulation of the characteristic earthquake hypothesis, which holds that the rate of small to moderate earthquakes is permanently low on large faults relative to the large-earthquake rate (Wesnousky et al., 1983; Schwartz and Coppersmith, 1984). We examine the rate difference between recent small to moderate earthquakes on the southern San Andreas fault (SSAF) and the paleoseismic record, hypothesizing that the discrepancy can be explained as a rate change in time rather than a deviation from G-R statistics. We find that with reasonable assumptions, the rate changes necessary to bring the small and large earthquake rates into alignment agree with the size of rate changes seen in epidemic-type aftershock sequence (ETAS) modeling, where aftershock triggering of large earthquakes drives strong fluctuations in the seismicity rates for earthquakes of all magnitudes. The necessary rate changes are also comparable to rate changes observed for other faults worldwide. These results are consistent with paleoseismic observations of temporally clustered bursts of large earthquakes on the SSAF and the absence of M greater than or equal to 7 earthquakes on the SSAF since 1857.

  10. Uniform California earthquake rupture forecast, version 2 (UCERF 2)

    Science.gov (United States)

    Field, E.H.; Dawson, T.E.; Felzer, K.R.; Frankel, A.D.; Gupta, V.; Jordan, T.H.; Parsons, T.; Petersen, M.D.; Stein, R.S.; Weldon, R.J.; Wills, C.J.

    2009-01-01

    The 2007 Working Group on California Earthquake Probabilities (WGCEP, 2007) presents the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2). This model comprises a time-independent (Poisson-process) earthquake rate model, developed jointly with the National Seismic Hazard Mapping Program and a time-dependent earthquake-probability model, based on recent earthquake rates and stress-renewal statistics conditioned on the date of last event. The models were developed from updated statewide earthquake catalogs and fault deformation databases using a uniform methodology across all regions and implemented in the modular, extensible Open Seismic Hazard Analysis framework. The rate model satisfies integrating measures of deformation across the plate-boundary zone and is consistent with historical seismicity data. An overprediction of earthquake rates found at intermediate magnitudes (6.5 ??? M ???7.0) in previous models has been reduced to within the 95% confidence bounds of the historical earthquake catalog. A logic tree with 480 branches represents the epistemic uncertainties of the full time-dependent model. The mean UCERF 2 time-dependent probability of one or more M ???6.7 earthquakes in the California region during the next 30 yr is 99.7%; this probability decreases to 46% for M ???7.5 and to 4.5% for M ???8.0. These probabilities do not include the Cascadia subduction zone, largely north of California, for which the estimated 30 yr, M ???8.0 time-dependent probability is 10%. The M ???6.7 probabilities on major strike-slip faults are consistent with the WGCEP (2003) study in the San Francisco Bay Area and the WGCEP (1995) study in southern California, except for significantly lower estimates along the San Jacinto and Elsinore faults, owing to provisions for larger multisegment ruptures. Important model limitations are discussed.

  11. Hotspots, Lifelines, and the Safrr Haywired Earthquake Sequence

    Science.gov (United States)

    Ratliff, J. L.; Porter, K.

    2014-12-01

    Though California has experienced many large earthquakes (San Francisco, 1906; Loma Prieta, 1989; Northridge, 1994), the San Francisco Bay Area has not had a damaging earthquake for 25 years. Earthquake risk and surging reliance on smartphones and the Internet to handle everyday tasks raise the question: is an increasingly technology-reliant Bay Area prepared for potential infrastructure impacts caused by a major earthquake? How will a major earthquake on the Hayward Fault affect lifelines (roads, power, water, communication, etc.)? The U.S. Geological Survey Science Application for Risk Reduction (SAFRR) program's Haywired disaster scenario, a hypothetical two-year earthquake sequence triggered by a M7.05 mainshock on the Hayward Fault, addresses these and other questions. We explore four geographic aspects of lifeline damage from earthquakes: (1) geographic lifeline concentrations, (2) areas where lifelines pass through high shaking or potential ground-failure zones, (3) areas with diminished lifeline service demand due to severe building damage, and (4) areas with increased lifeline service demand due to displaced residents and businesses. Potential mainshock lifeline vulnerability and spatial demand changes will be discerned by superimposing earthquake shaking, liquefaction probability, and landslide probability damage thresholds with lifeline concentrations and with large-capacity shelters. Intersecting high hazard levels and lifeline clusters represent potential lifeline susceptibility hotspots. We will also analyze possible temporal vulnerability and demand changes using an aftershock shaking threshold. The results of this analysis will inform regional lifeline resilience initiatives and response and recovery planning, as well as reveal potential redundancies and weaknesses for Bay Area lifelines. Identified spatial and temporal hotspots can provide stakeholders with a reference for possible systemic vulnerability resulting from an earthquake sequence.

  12. Tohoku earthquake: a surprise?

    CERN Document Server

    Kagan, Yan Y

    2011-01-01

    We consider three issues related to the 2011 Tohoku mega-earthquake: (1) how to evaluate the earthquake maximum size in subduction zones, (2) what is the repeat time for the largest earthquakes in Tohoku area, and (3) what are the possibilities of short-term forecasts during the 2011 sequence. There are two quantitative methods which can be applied to estimate the maximum earthquake size: a statistical analysis of the available earthquake record and the moment conservation principle. The latter technique studies how much of the tectonic deformation rate is released by earthquakes. For the subduction zones, the seismic or historical record is not sufficient to provide a reliable statistical measure of the maximum earthquake. The moment conservation principle yields consistent estimates of maximum earthquake size: for all the subduction zones the magnitude is of the order 9.0--9.7, and for major subduction zones the maximum earthquake size is statistically indistinguishable. Starting in 1999 we have carried out...

  13. Paleothermal structure of the Point San Luis slab of central California: Effects of Late Cretaceous underplating, out-of-sequence thrusting, and late Cenozoic dextral offset

    Science.gov (United States)

    Underwood, Michael B.; Laughland, Matthew M.

    2001-02-01

    Late Cretaceous shale and sandstone turbidites of the Point San Luis "slab" are isoclinally folded, locally sheared, and faulted, but their severity of stratal disruption is relatively mild when compared to adjacent polymictic mélange of the Franciscan Complex. We tested the interpretation of a trench-slope basin origin for these strata by documenting their paleothermal structure, including contacts between turbidites and mélange. Values of mean random vitrinite reflectance (Rm) from turbidites are 0.9-1.7% estimates of maximum paleotemperature are 135°-200°C. Mélange matrix samples yield Rm values of 1.1-2.5%, with an average of 1.5%, and peak temperatures between 160° and 240°C. The turbidite-over-mélange contact is locally "cooler over warmer" and was folded after peak heating. The relatively high paleotemperatures cast doubt on a shallow slope basin model (i.e., 1-2 km burial depth). We suggest, instead, that thermal maturation of the Point San Luis slab occurred much deeper in an accretionary prism (10-15 km), where offscraped trench wedge deposits were faulted against underplated mélange. The paleothermal structure was offset and tilted after peak heating by two out-of-sequence faults. Late Oligocene to Pliocene strata rest unconformably above the Franciscan, and there is a significant gap in thermal maturity across this unconformity, with no evidence to show that Franciscan rocks were reset thermally following the main episode of uplift and erosion. Three-dimensional orientations of isoreflectance surfaces on opposite sides of the San Gregorio-San Simeon-Hosgri fault system also can be used to test interpretations of strike-slip neotectonics. The failure to match these geometries among suspected piercing points at Point San Luis, Cambria, and Point Sur favors a suggestion that differential, post thermal peak, dextral offset of Franciscan basement has not exceeded 10-15 km.

  14. Protecting Your Family From Earthquakes-The Seven Steps to Earthquake Safety (in English, Chinese, Vietnamese, and Korean)

    Science.gov (United States)

    Developed by American Red Cross, Asian Pacific Fund

    2007-01-01

    This book is provided here because of the importance of preparing for earthquakes before they happen. Experts say it is very likely there will be a damaging San Francisco Bay Area earthquake in the next 30 years and that it will strike without warning. It may be hard to find the supplies and services we need after this earthquake. For example, hospitals may have more patients than they can treat, and grocery stores may be closed for weeks. You will need to provide for your family until help arrives. To keep our loved ones and our community safe, we must prepare now. Some of us come from places where earthquakes are also common. However, the dangers of earthquakes in our homelands may be very different than in the Bay Area. For example, many people in Asian countries die in major earthquakes when buildings collapse or from big sea waves called tsunami. In the Bay Area, the main danger is from objects inside buildings falling on people. Take action now to make sure your family will be safe in an earthquake. The first step is to read this book carefully and follow its advice. By making your home safer, you help make our community safer. Preparing for earthquakes is important, and together we can make sure our families and community are ready. English version p. 3-13 Chinese version p. 14-24 Vietnamese version p. 25-36 Korean version p. 37-48

  15. Mechanism of 2003, 2007 and 2009 earthquakes (S. Vicente Cape) and implications for the 1755 Lisbon earthquake.

    Science.gov (United States)

    Buforn, E.; Pro, C.; Bezzeghoud, M.; Udias, A.

    2012-04-01

    The San Vicente Cape region (SW Iberia) is of great seismological interest due to its tectonic complexity and for the occurrence of the 1755 Lisbon mega-earthquake. A structure capable of generating such large earthquake has not been convincingly found but authors agree with the possible occurrence in the future of a similar earthquake offshore of San Vicente Cape. We have studied the mechanism of three earthquakes in this area: 29 July 2003 (Mw = 5.3), 12 February 2007 (Mw = 6.1) and 17 December 2009 (Mw = 5.5) which throw light on the dynamics of the region. These earthquakes are the largest occurred in the last 40 years at the western of San Vicente Cape. From inversion of body waves and kinematic slip distribution, we have obtained that the three shocks have similar characteristics (dimensions, maximum slip, stress drop, source time function, focal depth and rupture velocity), but we can observe differences on geometry of the rupture that reflect the great seismotectonics complexity of the zone. The 2003 and 2007 focal mechanisms are similar, corresponding to thrusting motion but the 2009 earthquake has dip-slip motion on a vertical plane. The ruptures planes for the three shocks, deduced from the slip distribution, show ruptures on NE-SW planes, with the released energy propagating to NE direction, compatible with the regional horizontal compression in the NW-SE direction produced by the convergence between the Eurasian and African plates. This direction of faulting may be applied to the generation of the 1755 Lisbon earthquake, in terms of a complex rupture along NE-SW trending thrust faults at the Gorringe Bank, the Horseshoe Scarp and the Marques de Pombal Fault, with rupture propagating in NE direction toward the coast of Portugal and which may explain the large damage at Lisbon city.

  16. Geologic Map of the San Luis Quadrangle, Costilla County, Colorado

    Science.gov (United States)

    Machette, Michael N.; Thompson, Ren A.; Drenth, Benjamin J.

    2008-01-01

    The map area includes San Luis and the primarily rural surrounding area. San Luis, the county seat of Costilla County, is the oldest surviving settlement in Colorado (1851). West of the town are San Pedro and San Luis mesas (basalt-covered tablelands), which are horsts with the San Luis fault zone to the east and the southern Sangre de Cristo fault zone to the west. The map also includes the Sanchez graben (part of the larger Culebra graben), a deep structural basin that lies between the San Luis fault zone (on the west) and the central Sangre de Cristo fault zone (on the east). The oldest rocks exposed in the map area are the Pliocene to upper Oligocene basin-fill sediments of the Santa Fe Group, and Pliocene Servilleta Basalt, a regional series of 3.7?4.8 Ma old flood basalts. Landslide deposits and colluvium that rest on sediments of the Santa Fe Group cover the steep margins of the mesas. Rare exposures of the sediment are comprised of siltstones, sandstones, and minor fluvial conglomerates. Most of the low ground surrounding the mesas and in the graben is covered by surficial deposits of Quaternary age. The alluvial deposits are subdivided into three Pleistocene-age units and three Holocene-age units. The oldest Pleistocene gravel (unit Qao) forms extensive coalesced alluvial fan and piedmont surfaces, the largest of which is known as the Costilla Plain. This surface extends west from San Pedro Mesa to the Rio Grande. The primary geologic hazards in the map area are from earthquakes, landslides, and localized flooding. There are three major fault zones in the area (as discussed above), and they all show evidence for late Pleistocene to possible Holocene movement. The landslides may have seismogenic origins; that is, they may be stimulated by strong ground shaking during large earthquakes. Machette and Thompson based this geologic map entirely on new mapping, whereas Drenth supplied geophysical data and interpretations.

  17. The Loma Prieta earthquake of October 17, 1989 : a brief geologic view of what caused the Loma Prieta earthquake and implications for future California earthquakes: What happened ... what is expected ... what can be done.

    Science.gov (United States)

    Ward, Peter L.; Page, Robert A.

    1990-01-01

    The San Andreas fault, in California, is the primary boundary between the North American plate and the Pacific plate. Land west of the fault has been moving northwestward relative to land on the east at an average rate of 2 inches per year for millions of years. This motion is not constant but occurs typically in sudden jumps during large earthquakes. This motion is relentless; therefore earthquakes in California are inevitable.

  18. Simulating Earthquakes for Science and Society: New Earthquake Visualizations Ideal for Use in Science Communication

    Science.gov (United States)

    de Groot, R. M.; Benthien, M. L.

    2006-12-01

    The Southern California Earthquake Center (SCEC) has been developing groundbreaking computer modeling capabilities for studying earthquakes. These visualizations were initially shared within the scientific community but have recently have gained visibility via television news coverage in Southern California. These types of visualizations are becoming pervasive in the teaching and learning of concepts related to earth science. Computers have opened up a whole new world for scientists working with large data sets, and students can benefit from the same opportunities (Libarkin &Brick, 2002). Earthquakes are ideal candidates for visualization products: they cannot be predicted, are completed in a matter of seconds, occur deep in the earth, and the time between events can be on a geologic time scale. For example, the southern part of the San Andreas fault has not seen a major earthquake since about 1690, setting the stage for an earthquake as large as magnitude 7.7 -- the "big one." Since no one has experienced such an earthquake, visualizations can help people understand the scale of such an event. Accordingly, SCEC has developed a revolutionary simulation of this earthquake, with breathtaking visualizations that are now being distributed. According to Gordin and Pea (1995), theoretically visualization should make science accessible, provide means for authentic inquiry, and lay the groundwork to understand and critique scientific issues. This presentation will discuss how the new SCEC visualizations and other earthquake imagery achieve these results, how they fit within the context of major themes and study areas in science communication, and how the efficacy of these tools can be improved.

  19. SAN CARLOS APACHE PAPERS.

    Science.gov (United States)

    ROESSEL, ROBERT A., JR.

    THE FIRST SECTION OF THIS BOOK COVERS THE HISTORICAL AND CULTURAL BACKGROUND OF THE SAN CARLOS APACHE INDIANS, AS WELL AS AN HISTORICAL SKETCH OF THE DEVELOPMENT OF THEIR FORMAL EDUCATIONAL SYSTEM. THE SECOND SECTION IS DEVOTED TO THE PROBLEMS OF TEACHERS OF THE INDIAN CHILDREN IN GLOBE AND SAN CARLOS, ARIZONA. IT IS DIVIDED INTO THREE PARTS--(1)…

  20. San Carlo Operaen

    DEFF Research Database (Denmark)

    Holm, Bent

    2005-01-01

    En indplacering af operahuset San Carlo i en kulturhistorisk repræsentationskontekst med særligt henblik på begrebet napolalità.......En indplacering af operahuset San Carlo i en kulturhistorisk repræsentationskontekst med særligt henblik på begrebet napolalità....

  1. A Virtual Tour of the 1868 Hayward Earthquake in Google EarthTM

    Science.gov (United States)

    Lackey, H. G.; Blair, J. L.; Boatwright, J.; Brocher, T.

    2007-12-01

    The 1868 Hayward earthquake has been overshadowed by the subsequent 1906 San Francisco earthquake that destroyed much of San Francisco. Nonetheless, a modern recurrence of the 1868 earthquake would cause widespread damage to the densely populated Bay Area, particularly in the east Bay communities that have grown up virtually on top of the Hayward fault. Our concern is heightened by paleoseismic studies suggesting that the recurrence interval for the past five earthquakes on the southern Hayward fault is 140 to 170 years. Our objective is to build an educational web site that illustrates the cause and effect of the 1868 earthquake drawing on scientific and historic information. We will use Google EarthTM software to visually illustrate complex scientific concepts in a way that is understandable to a non-scientific audience. This web site will lead the viewer from a regional summary of the plate tectonics and faulting system of western North America, to more specific information about the 1868 Hayward earthquake itself. Text and Google EarthTM layers will include modeled shaking of the earthquake, relocations of historic photographs, reconstruction of damaged buildings as 3-D models, and additional scientific data that may come from the many scientific studies conducted for the 140th anniversary of the event. Earthquake engineering concerns will be stressed, including population density, vulnerable infrastructure, and lifelines. We will also present detailed maps of the Hayward fault, measurements of fault creep, and geologic evidence of its recurrence. Understanding the science behind earthquake hazards is an important step in preparing for the next significant earthquake. We hope to communicate to the public and students of all ages, through visualizations, not only the cause and effect of the 1868 earthquake, but also modern seismic hazards of the San Francisco Bay region.

  2. Overview of the Southern San Andreas Fault Model

    Science.gov (United States)

    Weldon, Ray J.; Biasi, Glenn P.; Wills, Chris J.; Dawson, Timothy E.

    2008-01-01

    This appendix summarizes the data and methodology used to generate the source model for the southern San Andreas fault. It is organized into three sections, 1) a section by section review of the geological data in the format of past Working Groups, 2) an overview of the rupture model, and 3) a manuscript by Biasi and Weldon (in review Bulletin of the Seismological Society of America) that describes the correlation methodology that was used to help develop the ?geologic insight? model. The goal of the Biasi and Weldon methodology is to quantify the insight that went into developing all A faults; as such it is in concept consistent with all other A faults but applied in a more quantitative way. The most rapidly slipping fault and the only known source of M~8 earthquakes in southern California is the San Andreas fault. As such it plays a special role in the seismic hazard of California, and has received special attention in the current Working Group. The underlying philosophy of the current Working Group is to model the recurrence behavior of large, rapidly slipping faults like the San Andreas from observed data on the size, distribution and timing of past earthquakes with as few assumptions about underlying recurrence behavior as possible. In addition, we wish to carry the uncertainties in the data and the range of reasonable extrapolations from the data to the final model. To accomplish this for the Southern San Andreas fault we have developed an objective method to combine all of the observations of size, timing, and distribution of past earthquakes into a comprehensive set of earthquake scenarios that each represent a possible history of earthquakes for the past ~1400 years. The scenarios are then ranked according to their overall consistency with the data and then the frequencies of all of the ruptures permitted by the current Working Group?s segmentation model are calculated. We also present 30-yr conditional probabilities by segment and compare to previous

  3. Estimating surface faulting impacts from the shakeout scenario earthquake

    Science.gov (United States)

    Treiman, J.A.; Pontib, D.J.

    2011-01-01

    An earthquake scenario, based on a kinematic rupture model, has been prepared for a Mw 7.8 earthquake on the southern San Andreas Fault. The rupture distribution, in the context of other historic large earthquakes, is judged reasonable for the purposes of this scenario. This model is used as the basis for generating a surface rupture map and for assessing potential direct impacts on lifelines and other infrastructure. Modeling the surface rupture involves identifying fault traces on which to place the rupture, assigning slip values to the fault traces, and characterizing the specific displacements that would occur to each lifeline impacted by the rupture. Different approaches were required to address variable slip distribution in response to a variety of fault patterns. Our results, involving judgment and experience, represent one plausible outcome and are not predictive because of the variable nature of surface rupture. ?? 2011, Earthquake Engineering Research Institute.

  4. Earthquake Damage - General

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — An earthquake is the motion or trembling of the ground produced by sudden displacement of rock in the Earth's crust. Earthquakes result from crustal strain,...

  5. Earthquake Notification Service

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The Earthquake Notification Service (ENS) is a free service that sends you automated notifications to your email or cell phone when earthquakes happen.

  6. Earthquakes: hydrogeochemical precursors

    Science.gov (United States)

    Ingebritsen, Steven E.; Manga, Michael

    2014-01-01

    Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

  7. Earthquakes in Southern California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — There have been many earthquake occurrences in Southern California. This set of slides shows earthquake damage from the following events: Imperial Valley, 1979,...

  8. EARTHQUAKE SCALING PARADOX

    Institute of Scientific and Technical Information of China (English)

    WU ZHONG-LIANG

    2001-01-01

    Two measures of earthquakes, the seismic moment and the broadband radiated energy, show completely different scaling relations. For shallow earthquakes worldwide from January 1987 to December 1998, the frequency distribution of the seismic moment shows a clear kink between moderate and large earthquakes, as revealed by previous works. But the frequency distribution of the broadband radiated energy shows a single power law, a classical Gutenberg-Richter relation. This inconsistency raises a paradox in the self-organized criticality model of earthquakes.

  9. Children's Ideas about Earthquakes

    Science.gov (United States)

    Simsek, Canan Lacin

    2007-01-01

    Earthquake, a natural disaster, is among the fundamental problems of many countries. If people know how to protect themselves from earthquake and arrange their life styles in compliance with this, damage they will suffer will reduce to that extent. In particular, a good training regarding earthquake to be received in primary schools is considered…

  10. Earthquake and Schools. [Videotape].

    Science.gov (United States)

    Federal Emergency Management Agency, Washington, DC.

    Designing schools to make them more earthquake resistant and protect children from the catastrophic collapse of the school building is discussed in this videotape. It reveals that 44 of the 50 U.S. states are vulnerable to earthquake, but most schools are structurally unprepared to take on the stresses that earthquakes exert. The cost to the…

  11. School Safety and Earthquakes.

    Science.gov (United States)

    Dwelley, Laura; Tucker, Brian; Fernandez, Jeanette

    1997-01-01

    A recent assessment of earthquake risk to Quito, Ecuador, concluded that many of its public schools are vulnerable to collapse during major earthquakes. A subsequent examination of 60 buildings identified 15 high-risk buildings. These schools were retrofitted to meet standards that would prevent injury even during Quito's largest earthquakes. US…

  12. Redefining Earthquakes and the Earthquake Machine

    Science.gov (United States)

    Hubenthal, Michael; Braile, Larry; Taber, John

    2008-01-01

    The Earthquake Machine (EML), a mechanical model of stick-slip fault systems, can increase student engagement and facilitate opportunities to participate in the scientific process. This article introduces the EML model and an activity that challenges ninth-grade students' misconceptions about earthquakes. The activity emphasizes the role of models…

  13. Redefining Earthquakes and the Earthquake Machine

    Science.gov (United States)

    Hubenthal, Michael; Braile, Larry; Taber, John

    2008-01-01

    The Earthquake Machine (EML), a mechanical model of stick-slip fault systems, can increase student engagement and facilitate opportunities to participate in the scientific process. This article introduces the EML model and an activity that challenges ninth-grade students' misconceptions about earthquakes. The activity emphasizes the role of models…

  14. Operational earthquake forecasting can enhance earthquake preparedness

    Science.gov (United States)

    Jordan, T.H.; Marzocchi, W.; Michael, A.J.; Gerstenberger, M.C.

    2014-01-01

    We cannot yet predict large earthquakes in the short term with much reliability and skill, but the strong clustering exhibited in seismic sequences tells us that earthquake probabilities are not constant in time; they generally rise and fall over periods of days to years in correlation with nearby seismic activity. Operational earthquake forecasting (OEF) is the dissemination of authoritative information about these time‐dependent probabilities to help communities prepare for potentially destructive earthquakes. The goal of OEF is to inform the decisions that people and organizations must continually make to mitigate seismic risk and prepare for potentially destructive earthquakes on time scales from days to decades. To fulfill this role, OEF must provide a complete description of the seismic hazard—ground‐motion exceedance probabilities as well as short‐term rupture probabilities—in concert with the long‐term forecasts of probabilistic seismic‐hazard analysis (PSHA).

  15. Assessment of earthquake-induced landslides hazard in El Salvador after the 2001 earthquakes using macroseismic analysis

    Science.gov (United States)

    Esposito, Eliana; Violante, Crescenzo; Giunta, Giuseppe; Ángel Hernández, Miguel

    2016-04-01

    Two strong earthquakes and a number of smaller aftershocks struck El Salvador in the year 2001. The January 13 2001 earthquake, Mw 7.7, occurred along the Cocos plate, 40 km off El Salvador southern coast. It resulted in about 1300 deaths and widespread damage, mainly due to massive landsliding. Two of the largest earthquake-induced landslides, Las Barioleras and Las Colinas (about 2x105 m3) produced major damage to buildings and infrastructures and 500 fatalities. A neighborhood in Santa Tecla, west of San Salvador, was destroyed. The February 13 2001 earthquake, Mw 6.5, occurred 40 km east-southeast of San Salvador. This earthquake caused over 300 fatalities and triggered several landslides over an area of 2,500 km2 mostly in poorly consolidated volcaniclastic deposits. The La Leona landslide (5-7x105 m3) caused 12 fatalities and extensive damage to the Panamerican Highway. Two very large landslides of 1.5 km3 and 12 km3 produced hazardous barrier lakes at Rio El Desague and Rio Jiboa, respectively. More than 16.000 landslides occurred throughout the country after both quakes; most of them occurred in pyroclastic deposits, with a volume less than 1x103m3. The present work aims to define the relationship between the above described earthquake intensity, size and areal distribution of induced landslides, as well as to refine the earthquake intensity in sparsely populated zones by using landslide effects. Landslides triggered by the 2001 seismic sequences provided useful indication for a realistic seismic hazard assessment, providing a basis for understanding, evaluating, and mapping the hazard and risk associated with earthquake-induced landslides.

  16. Deep Borehole Instrumentation Along San Francisco Bay Bridges - 2000

    Energy Technology Data Exchange (ETDEWEB)

    Hutchings, L.; Kasameyer, P.; Turpin, C.; Long, L.; Hollfelder, J.; McEvilly, T.; Clymer, R.; Uhrhammer, R.

    2000-03-01

    This is a progress report on the Bay Bridges downhole network. Between 2 and 8 instruments have been spaced along the Dumbarton, San Mateo, Bay, and San Rafael bridges in San Francisco Bay, California. The instruments will provide multiple use data that is important to geotechnical, structural engineering, and seismological studies. The holes are between 100 and 1000 ft deep and were drilled by Caltrans. There are twenty-one sensor packages at fifteen sites. The downhole instrument package contains a three component HS-1 seismometer and three orthogonal Wilcox 731 accelerometers, and is capable of recording a micro g from local M = 1.0 earthquakes to 0.5 g strong ground motion form large Bay Area earthquakes. Preliminary results on phasing across the Bay Bridge, up and down hole wave amplification at Yerba Buena Island, and sensor orientation analysis are presented. Events recorded and located during 1999 are presented. Also, a senior thesis on the deep structure of the San Francisco Bay beneath the Bay Bridge is presented as an addendum.

  17. Tsunami Hazards From Strike-Slip Earthquakes

    Science.gov (United States)

    Legg, M. R.; Borrero, J. C.; Synolakis, C. E.

    2003-12-01

    Strike-slip faulting is often considered unfavorable for tsunami generation during large earthquakes. Although large strike-slip earthquakes triggering landslides and then generating substantial tsunamis are now recognized hazards, many continue to ignore the threat from submarine tectonic displacement during strike-slip earthquakes. Historical data record the occurrence of tsunamis from strike-slip earthquakes, for example, 1906 San Francisco, California, 1994 Mindoro, Philippines, and 1999 Izmit, Turkey. Recognizing that strike-slip fault zones are often curved and comprise numerous en echelon step-overs, we model tsunami generation from realistic strike-slip faulting scenarios. We find that tectonic seafloor uplift, at a restraining bend or"pop-up" structure, provides an efficient mechanism to generate destructive local tsunamis; likewise for subsidence at divergent pull-apart basin structures. Large earthquakes on complex strike-slip fault systems may involve both types of structures. The California Continental Borderland is a high-relief submarine part of the active Pacific-North America transform plate boundary. Natural harbors and bays created by long term vertical motion associated with strike-slip structural irregularities are now sites of burgeoning population and major coastal infrastructure. Significant local tsunamis generated by large strike-slip earthquakes pose a serious, and previously unrecognized threat. We model several restraining bend pop-up structures offshore southern California to quantify the local tsunami hazard. Maximum runup derived in our scenarios ranges from one to several meters, similar to runup observed from the 1994 Mindoro, Philippines, (M=7.1) earthquake. The runup pattern is highly variable, with local extremes along the coast. We only model the static displacement field for the strike-slip earthquake source; dynamic effects of moving large island or submerged banks laterally during strike-slip events remains to be examined

  18. A Look Inside the San Andreas fault at Parkfield Through Vertical Seismic Profiling

    Science.gov (United States)

    Chavarria, J.A.; Malin, P.; Catchings, R.D.; Shalev, E.

    2003-01-01

    The San Andreas Fault Observatory at Depth pilot hole is located on the southwestern side of the Parkfield San Andreas fault. This observatory includes a vertical seismic profiling (VSP) array. VSP seismograms from nearby micro-earthquakes contain signals between the P and S waves. These signals may be P and S waves scattered by the local geologic structure. The collected scattering points form planar surfaces that we interpret as the San Andreas fault and four other secondary faults. The scattering process includes conversions between P and S waves, the strengths of which suggest large contrasts in material properties, possibly indicating the presence of cracks or fluids.

  19. Upper-Plate Earthquake Swarms Remotely Triggered by the 2012 Mw-7.6 Nicoya Earthquake, Costa Rica

    Science.gov (United States)

    Linkimer, L.; Arroyo, I. G.; Montero Pohly, W. K.; Lücke, O. H.

    2013-12-01

    Remotely triggered seismicity that takes place at distances greater than 1-2 fault lengths appears to be a frequent phenomenon after large earthquakes, including damaging upper-plate 5.0-to-6.0 magnitude earthquakes in Costa Rica after the large (Mw greater than 7.0) inter-plate earthquakes in 1941, 1950, 1983, 1990, and 1991. On 5 of September 2012, an inter-plate 7.6-Mw earthquake struck the Nicoya Peninsula, triggering upper-plate seismicity in the interior of Costa Rica again. The number of upper plate-earthquakes outside the Nicoya source region that were recorded by the National Seismological Network (RSN: UCR-ICE) for the six-month period after the Nicoya event was two times higher than that number of upper plate-earthquakes during the six months before it happened. We analyze the three largest upper-plate earthquake swarms that took place during the first six months after the Nicoya event. We relocate the epicenters using a double difference algorithm with a 1D velocity model (HypoDD) and using a probabilistic method with a 3D velocity model (NonLinLoc). Additionally we compute first motion focal mechanisms for the largest events. The three swarms analyzed occurred at distances of 170 to 350 km from the Nicoya source region in three different tectonic settings: the Cartago area in the central part of Costa Rica near the active volcanic arc (approximately 170 km from the source region), the Calero Island near the Costa Rica-Nicaragua border in the backarc Caribbean region (approximately 220 km), and the San Vito area in the Costa Rica-Panama border region, at the southern flank of the Talamanca Cordillera, an inactive portion of the magmatic arc (approximately 300 km). The Cartago swarm with 95 1.8-to-4.1 Mw earthquakes occurred from September 5 to October 31, 2012. The location and left-lateral solution of the largest event suggest that the Aguacaliente fault, which caused the deadliest earthquake in Costa Rican history on May 4, 1910 (Ms 6.4), is the

  20. Strong-motion earthquake accelerograms digitization and analysis records from Lima, Peru, 1951 to 1974

    Science.gov (United States)

    Brady, A. Gerald; Perez, Virgilio

    1977-01-01

    This is the second of a series of reports planned to include the results of digitization and routine analyses of strong-motion earthquake accelerograms published by the U.S. Geological Survey. Serving as a model for this effort is the collection of data reports published by the Earthquake Engineering Research Laboratory of the California Institute of Technology during the years 1969 - 1975 and covering the significant records of the period from 1933 up to the San Fernando earthquake of February 9, 1971. The first of the present series of reports, Open File Report No. 76-609, covered the significant records of 1971 subsequent to the San Fernando earthquake. The present report includes the results of some ongoing work on Peru records.

  1. The M7 October 21, 1868 Hayward Earthquake, Northern California-140 Years Later

    Science.gov (United States)

    Brocher, T. M.; Boatwright, J.; Lienkaemper, J. J.; Schwartz, D. P.; Garcia, S.

    2007-12-01

    October 21, 2008 marks the 140th anniversary of the M7 1868 Hayward earthquake. This large earthquake, which occurred slightly before 8 AM, caused extensive damage to San Francisco Bay Area and remains the nation's 12th most lethal earthquake. Property loss was extensive and about 30 people were killed. This earthquake culminated a decade-long series of earthquakes in the Bay Area which started with an M~6 earthquake in the southern Peninsula in 1856, followed by a series of four M5.8 to M6.1 sized earthquakes along the northern Calaveras fault, and ended with a M~6.5 earthquake in the Santa Cruz Mountains in 1865. Despite this flurry of quakes, the shaking from the 1868 earthquake was the strongest that the new towns and growing cities of the Bay Area had ever experienced. The effect on the brick buildings of the time was devastating: walls collapsed in San Francisco, Oakland, and San Jose, and buildings cracked as far away as Napa, Santa Rosa, and Hollister. The area that was strongly shaken (at Modified Mercalli Intensity VII or higher) encompassed about 2,300 km2. Aftershocks continued into November 1868. Surface cracking of the ground along the southern end of the Hayward Fault was traced from Warm Springs in Fremont northward 32 km to San Leandro. As Lawson (1908) reports, "the evidence to the northward of San Leandro is not very satisfactory. The country was then unsettled, and the information consisted of reports of cow- boys riding on the range". Analysis of historical triangulation data suggest that the fault moved as far north as Berkeley, and from these data the average slip along the fault is inferred to be about 1.9 ± 0.4 meters. The paleoseismic record from the southern end of the Hayward Fault provides evidence for 10 earthquakes before 1868. The average interval between these earthquakes is 170 ± 80 years, but the last five earthquakes have had an average interval of only 140 ± 50 years. The 1868 Hayward earthquake and more recent analogs such

  2. Earthquake Education and Public Information Centers: A Collaboration Between the Earthquake Country Alliance and Free-Choice Learning Institutions in California

    Science.gov (United States)

    Degroot, R. M.; Springer, K.; Brooks, C. J.; Schuman, L.; Dalton, D.; Benthien, M. L.

    2009-12-01

    In 1999 the Southern California Earthquake Center initiated an effort to expand its reach to multiple target audiences through the development of an interpretive trail on the San Andreas fault at Wallace Creek and an earthquake exhibit at Fingerprints Youth Museum in Hemet. These projects and involvement with the San Bernardino County Museum in Redlands beginning in 2007 led to the creation of Earthquake Education and Public Information Centers (EPIcenters) in 2008. The impetus for the development of the network was to broaden participation in The Great Southern California ShakeOut. In 2009 it has grown to be more comprehensive in its scope including its evolution into a statewide network. EPIcenters constitute a variety of free-choice learning institutions, representing museums, science centers, libraries, universities, parks, and other places visited by a variety of audiences including families, seniors, and school groups. They share a commitment to demonstrating and encouraging earthquake preparedness. EPIcenters coordinate Earthquake Country Alliance activities in their county or region, lead presentations or organize events in their communities, or in other ways demonstrate leadership in earthquake education and risk reduction. The San Bernardino County Museum (Southern California) and The Tech Museum of Innovation (Northern California) serve as EPIcenter regional coordinating institutions. They interact with over thirty institutional partners who have implemented a variety of activities from displays and talks to earthquake exhibitions. While many activities are focused on the time leading up to and just after the ShakeOut, most EPIcenter members conduct activities year round. Network members at Kidspace Museum in Pasadena and San Diego Natural History Museum have formed EPIcenter focus groups on early childhood education and safety and security. This presentation highlights the development of the EPIcenter network, synergistic activities resulting from this

  3. Marked increase in substance use among young people after L?Aquila earthquake

    OpenAIRE

    Pollice, Rocco; Bianchini, Valeria; Roncone, Rita; Casacchia, Massimo

    2011-01-01

    Marked increase in substance use among young people after L?Aquila earthquake (Pollice, Rocco) Department of Health Sciences, Psychiatric Unit, `San Salvatore? Hospital, University of L?Aquila - L?Aquila - ITALY (Pollice, Rocco) Department of Health Sciences, Psychiatric Unit, University of L?Aquila - Via Vetoio, Loc. Coppito - 67100 - L?Aquila - ITALY (Pollice, Rocco) Department of Health Sciences, Psychiatric Unit, `San Salvatore? Hospital, Universi...

  4. Earthquake Science: a New Start

    Institute of Scientific and Technical Information of China (English)

    Chen Yun-tai

    2009-01-01

    @@ Understanding the mechanisms which cause earthquakes and thus earthquake prediction, is inher-ently difficult in comparison to other physical phenom-ena. This is due to the inaccessibility of the Earth's inte-rior, the infrequency of large earthquakes, and the com-plexities of the physical processes involved. Conse-quently, in its broadest sense, earthquake science--the science of studying earthquake phenomena, is a com-prehensive and inter-disciplinary field. The disciplines involved in earthquake science include: traditional seismology, earthquake geodesy, earthquake geology, rock mechanics, complex system theory, and informa-tion and communication technologies related to earth-quake studies.

  5. The San Andreas fault in the San Francisco Bay region, California: Structure and kinematics of a Young plate boundary

    Science.gov (United States)

    Jachens, R.C.; Zoback, M.L.

    1999-01-01

    with continued strike-slip movement) may explain the progressive narrowing of the basin to the southeast and the puzzling recent uplift of the Merced Formation in a predominantly extensional (pull-apart basin) setting. The 1906 San Francisco earthquake may have nucleated within the step-over region, and the step-over places a strand of the San Andreas fault 3 km closer to downtown San Francisco than previously thought.

  6. Quantifying Earthquake Collapse Risk of Tall Steel Braced Frame Buildings Using Rupture-to-Rafters Simulations

    Science.gov (United States)

    Mourhatch, Ramses

    This thesis examines collapse risk of tall steel braced frame buildings using rupture-to-rafters simulations due to suite of San Andreas earthquakes. Two key advancements in this work are the development of (i) a rational methodology for assigning scenario earthquake probabilities and (ii) an artificial correction-free approach to broadband ground motion simulation. The work can be divided into the following sections: earthquake source modeling, earthquake probability calculations, ground motion simulations, building response, and performance analysis. As a first step the kinematic source inversions of past earthquakes in the magnitude range of 6-8 are used to simulate 60 scenario earthquakes on the San Andreas fault. For each scenario earthquake a 30-year occurrence probability is calculated and we present a rational method to redistribute the forecast earthquake probabilities from UCERF to the simulated scenario earthquake. We illustrate the inner workings of the method through an example involving earthquakes on the San Andreas fault in southern California. Next, three-component broadband ground motion histories are computed at 636 sites in the greater Los Angeles metropolitan area by superposing short-period (0.2s-2.0s) empirical Green's function synthetics on top of long-period (> 2.0s) spectral element synthetics. We superimpose these seismograms on low-frequency seismograms, computed from kinematic source models using the spectral element method, to produce broadband seismograms. Using the ground motions at 636 sites for the 60 scenario earthquakes, 3-D nonlinear analysis of several variants of an 18-story steel braced frame building, designed for three soil types using the 1994 and 1997 Uniform Building Code provisions and subjected to these ground motions, are conducted. Model performance is classified into one of five performance levels: Immediate Occupancy, Life Safety, Collapse Prevention, Red-Tagged, and Model Collapse. The results are combined with

  7. Fine-scale delineation of the location of and relative ground shaking within the San Andreas Fault zone at San Andreas Lake, San Mateo County, California

    Science.gov (United States)

    Catchings, R.D.; Rymer, M.J.; Goldman, M.R.; Prentice, C.S.; Sickler, R.R.

    2013-01-01

    The San Francisco Public Utilities Commission is seismically retrofitting the water delivery system at San Andreas Lake, San Mateo County, California, where the reservoir intake system crosses the San Andreas Fault (SAF). The near-surface fault location and geometry are important considerations in the retrofit effort. Because the SAF trends through highly distorted Franciscan mélange and beneath much of the reservoir, the exact trace of the 1906 surface rupture is difficult to determine from surface mapping at San Andreas Lake. Based on surface mapping, it also is unclear if there are additional fault splays that extend northeast or southwest of the main surface rupture. To better understand the fault structure at San Andreas Lake, the U.S. Geological Survey acquired a series of seismic imaging profiles across the SAF at San Andreas Lake in 2008, 2009, and 2011, when the lake level was near historical lows and the surface traces of the SAF were exposed for the first time in decades. We used multiple seismic methods to locate the main 1906 rupture zone and fault splays within about 100 meters northeast of the main rupture zone. Our seismic observations are internally consistent, and our seismic indicators of faulting generally correlate with fault locations inferred from surface mapping. We also tested the accuracy of our seismic methods by comparing our seismically located faults with surface ruptures mapped by Schussler (1906) immediately after the April 18, 1906 San Francisco earthquake of approximate magnitude 7.9; our seismically determined fault locations were highly accurate. Near the reservoir intake facility at San Andreas Lake, our seismic data indicate the main 1906 surface rupture zone consists of at least three near-surface fault traces. Movement on multiple fault traces can have appreciable engineering significance because, unlike movement on a single strike-slip fault trace, differential movement on multiple fault traces may exert compressive and

  8. Recurrence of seismic migrations along the central California segment of the San Andreas fault system

    Science.gov (United States)

    Wood, M.D.; Allen, S.S.

    1973-01-01

    VERIFICATIONS of tectonic concepts1 concerning seafloor spreading are emerging in a manner that has direct bearing on earthquake prediction. Although the gross pattern of worldwide seismicity contributed to the formulation of the plate tectonic hypothesis, it is the space-time characteristics of this seismicity that may contribute more toward understanding the kinematics and dynamics of the driving mechanism long speculated to originate in the mantle. If the lithosphere is composed of plates that move essentially as rigid bodies, then there should be seismic edge effects associated with this movement. It is these interplate effects, especially seismic migration patterns, that we discuss here. The unidirectional propagation at constant velocity (80 km yr-1 east to west) for earthquakes (M???7.2) on the Antblian fault for the period 1939 to 1956 (ref. 2) is one of the earliest observations of such a phenomenon. Similar studies3,4 of the Alaska Aleutian seismic zone and certain regions of the west coast of South America suggest unidirectional and recurring migrations of earthquakes (M???7.7) occur in these areas. Between these two regions along the great transform faults of the west coast of North America, there is some evidence 5 for unidirectional, constant velocity and recurrent migration of great earthquakes. The small population of earthquakes (M>7.2) in Savage's investigation5 indicates a large spatial gap along the San Andreas system in central California from 1830 to 1970. Previous work on the seismicity of this gap in central California indicates that the recurrence curves remain relatively constant, independent of large earthquakes, for periods up to a century6. Recurrence intervals for earthquakes along the San Andreas Fault have been calculated empirically by Wallace7 on the basis of geological evidence, surface measurements and assumptions restricted to the surficial seismic layer. Here we examine the evidence for recurrence of seismic migrations along

  9. Connecting Aseismic Slip and Microseismicity on the Central San Andreas Fault

    Science.gov (United States)

    Johanson, I. A.; Bürgmann, R.

    2003-12-01

    High precision micro-earthquake relocations have revealed seismicity structures that may be an indicator of the fault's slip characteristics. Characteristically repeating micro-earthquakes and aligned streaks of micro-seismicity suggest that these structures are associated with areas of active aseismic fault slip. A general inverse correspondence between zones of abundant micro-seismicity and the coseismic slip area of large earthquakes also implies a relationship between creep and micro-earthquakes. We test this relationship using geodetic measurements of near-fault deformation. Modeling of such measurements allow for determination of locked and creeping sections of the fault. We focus on the central San Andreas fault near San Juan Bautista; a segment which experiences both aseismic and seismic fault slip and where there is a long history of geodetic measurements. Aseismic slip on the central San Andreas is time dependent and has varied in response to regional earthquakes and in the form of slow earthquakes. Dislocations in an elastic half space are used to evaluate a range of scenario fault slip models whose geometry is guided by the locations of micro-seismic streaks. The inversions for distributed sub-surface slip are constrained by range-change data from InSAR and GPS site velocities. The InSAR data (ERS1&2 track 299 frame 2861) spans from 1996-2000 and were processed using ROI_Pac with the SNAPHU unwrapper and combined in a patchwork stack to reduce atmospheric errors. Campaign and continuous GPS data were processed using GAMIT/GLOBK and form part of the regional BA¯VU¯ dataset. To minimize the effect on our analysis of transient slip induced by the 1989 Loma Prieta earthquake, we limit our dataset to GPS observations from 1994 to 2003. Preliminary results confirm that the presence of seismicity streaks and characteristically repeating micro-earthquakes are indicative of aseismic slip. However, the absence of such seismicity patterns does not necessarily

  10. San Francisco Bay Area Fault Observations Displayed in Google Earth

    Science.gov (United States)

    Lackey, H.; Hernandez, M.; Nayak, P.; Zapata, I.; Schumaker, D.

    2006-12-01

    According to the United States Geological Survey (USGS), the San Francisco Bay Area has a 62% probability of experiencing a major earthquake in the next 30 years. The Hayward fault and the San Andreas fault are the two main faults in the Bay Area that are capable of producing earthquakes of magnitude 6.7 or larger - a size that could profoundly affect many of the 7 million people who live in the Bay Area. The Hayward fault has a 27% probability of producing a major earthquake in next 30 years, and the San Andreas fault has a 21% probability. Our research group, which is part of the SF-ROCKS high school outreach program, studied the Hayward and San Andreas faults. The goal of our project was to observe these faults at various locations, measure the effects of creep, and to present the data in Google Earth, a freeware tool for the public to easily view and interact with these and other seismic-hazard data. We examined the Hayward and San Andreas faults (as mapped by USGS scientists) in Google Earth to identify various sites where we could possibly find evidence of fault creep. We next visited these sites in the field where we mapped the location using a hand- held Global Positioning System, identified and photographed fault evidence, and measured offset features with a ruler or tape measure. Fault evidence included en echelon shears in pavement, warped buildings, and offset features such as sidewalks. Fault creep offset measurements range from 1.5 19 cm. We also identified possible evidence of fault creep along the San Andreas fault in South San Francisco where it had not been previously described. In Google Earth, we plotted our field sites, linked photographs showing evidence of faulting, and included detailed captions to explain the photographs. We will design a webpage containing the data in a Keyhole Markup Language (KML) file format for display in Google Earth. Any interested person needs only to download the free version of Google Earth software and visit our

  11. The HayWired earthquake scenario

    Science.gov (United States)

    Detweiler, Shane T.; Wein, Anne M.

    2017-04-24

    ForewordThe 1906 Great San Francisco earthquake (magnitude 7.8) and the 1989 Loma Prieta earthquake (magnitude 6.9) each motivated residents of the San Francisco Bay region to build countermeasures to earthquakes into the fabric of the region. Since Loma Prieta, bay-region communities, governments, and utilities have invested tens of billions of dollars in seismic upgrades and retrofits and replacements of older buildings and infrastructure. Innovation and state-of-the-art engineering, informed by science, including novel seismic-hazard assessments, have been applied to the challenge of increasing seismic resilience throughout the bay region. However, as long as people live and work in seismically vulnerable buildings or rely on seismically vulnerable transportation and utilities, more work remains to be done.With that in mind, the U.S. Geological Survey (USGS) and its partners developed the HayWired scenario as a tool to enable further actions that can change the outcome when the next major earthquake strikes. By illuminating the likely impacts to the present-day built environment, well-constructed scenarios can and have spurred officials and citizens to take steps that change the outcomes the scenario describes, whether used to guide more realistic response and recovery exercises or to launch mitigation measures that will reduce future risk.The HayWired scenario is the latest in a series of like-minded efforts to bring a special focus onto the impacts that could occur when the Hayward Fault again ruptures through the east side of the San Francisco Bay region as it last did in 1868. Cities in the east bay along the Richmond, Oakland, and Fremont corridor would be hit hardest by earthquake ground shaking, surface fault rupture, aftershocks, and fault afterslip, but the impacts would reach throughout the bay region and far beyond. The HayWired scenario name reflects our increased reliance on the Internet and telecommunications and also alludes to the

  12. Encyclopedia of earthquake engineering

    CERN Document Server

    Kougioumtzoglou, Ioannis; Patelli, Edoardo; Au, Siu-Kui

    2015-01-01

    The Encyclopedia of Earthquake Engineering is designed to be the authoritative and comprehensive reference covering all major aspects of the science of earthquake engineering, specifically focusing on the interaction between earthquakes and infrastructure. The encyclopedia comprises approximately 265 contributions. Since earthquake engineering deals with the interaction between earthquake disturbances and the built infrastructure, the emphasis is on basic design processes important to both non-specialists and engineers so that readers become suitably well-informed without needing to deal with the details of specialist understanding. The content of this encyclopedia provides technically inclined and informed readers about the ways in which earthquakes can affect our infrastructure and how engineers would go about designing against, mitigating and remediating these effects. The coverage ranges from buildings, foundations, underground construction, lifelines and bridges, roads, embankments and slopes. The encycl...

  13. Reduction of earthquake disasters

    Institute of Scientific and Technical Information of China (English)

    陈顒; 陈祺福; 黄静; 徐文立

    2003-01-01

    The article summarizes the researches on mitigating earthquake disasters of the past four years in China. The studyof earthquake disasters′ quantification shows that the losses increase remarkably when population concentrates inurban area and social wealth increase. The article also summarizes some new trends of studying earthquake disas-ters′ mitigation, which are from seismic hazard to seismic risk, from engineering disaster to social disaster andintroduces the community-centered approach.

  14. Probabilistic fault displacement hazards for the southern san andreas fault using scenarios and empirical slips

    Science.gov (United States)

    Chen, R.; Petersen, M.D.

    2011-01-01

    We apply a probabilistic method to develop fault displacement hazard maps and profiles for the southern San Andreas Fault. Two slip models are applied: (1) scenario slip, defined by the ShakeOut rupture model, and (2) empirical slip, calculated using regression equations relating global slip to earthquake magnitude and distance along the fault. The hazard is assessed using a range of magnitudes defined by the Uniform California Earthquake Rupture Forecast and the ShakeOut. For hazard mapping we develop a methodology to partition displacement among multiple fault branches basedon geological observations. Estimated displacement hazard extends a few kilometers wide in areas of multiple mapped fault branches and poor mapping accuracy. Scenario and empirical displacement hazard differs by a factor of two or three, particularly along the southernmost section of the San Andreas Fault. We recommend the empirical slip model with site-specific geological data to constrain uncertainties for engineering applications. ?? 2011, Earthquake Engineering Research Institute.

  15. Global survey of earthquakes and non-volcanic tremor triggered by the 2008 Mw7.9 Wenchuan earthquake

    Science.gov (United States)

    Jiang, T.; Peng, Z.; Wang, W.; Chen, Q.

    2008-12-01

    We perform a global survey of triggered earthquakes and non-volcanic tremor by the 2008 Mw7.9 Wenchuan earthquake. The analyzed data is obtained from the Global Seismic Network and various local and regional seismic networks around the world. We identify triggered earthquakes as impulsive seismic energies with clear P and S arrivals on 5 Hz high-pass-filtered three-component velocity seismograms, and triggered tremor as bursts of high-frequency, non-impulsive seismic energies that are coherent among many stations and during the passage of teleseismic body and surface waves. We find wide-spread triggering of regular earthquakes within mainland China and elsewhere in the world. The triggered earthquakes mostly occur in tectonically active regions in northwest and northeast China. However, we also find clear evidence of triggered earthquakes in southeast China that is not tectonically active. Our observations are consistent with previous studies of earthquake triggering (e.g., Gomberg et al., 2004; Velasco et al., 2008), indicating that dynamic triggering of earthquakes is ubiquitous and independent of the tectonic environments. In comparison, clear triggered tremor associated with the Wenchuan earthquake is found in the Taiwan Island (Chao and Peng, 2008), southwest Japan, Cascadia (Vidale et al., 2008), and around the Parkfield section of the San Andreas fault (Peng et al., 2008), where regular and/or triggered tremor has been found before. So far we have not found clear evidence of triggered tremor within mainland China. At least part of the reason could be due to severe clippings of the broadband waveforms during large-amplitude surface waves for many stations within 2000 km of the epicenter. Updated results will be presented at the meeting.

  16. Deep crustal heterogeneity along and around the San Andreas fault system in central California and its relation to the segmentation

    Science.gov (United States)

    Nishigami, Kin'ya

    2000-04-01

    The three-dimensional distribution of scatterers in the crust along and around the San Andreas fault system in central California is estimated using an inversion analysis of coda envelopes from local earthquakes. I analyzed 3801 wave traces from 157 events recorded at 140 stations of the Northern California Seismic Network. The resulting scatterer distribution shows a correlation with the San Gregorio, San Andreas, Hayward, and Calaveras faults. These faults seem to be almost vertical from the surface to ˜15 km depth. Some of the other scatterers are estimated to be at shallow depths, 0-5 km, below the Diablo Range, and these may be interpreted as being generated by topographic roughness. The depth distribution of scatterers shows relatively stronger scattering in the lower crust, at ˜15-25 km depth, especially between the San Andreas fault and the Hayward-Calaveras faults. This suggests a subhorizontal detachment structure connecting these two faults in the lower crust. Several clusters of scatterers are located along the San Andreas fault at intervals of ˜20-30 km from south of San Francisco to the intersection with the Calaveras fault. This part of the San Andreas fault appears to consist of partially locked segments, also ˜20-30 km long, which rupture during M6-7 events, and segment boundaries characterized by stronger scattering and stationary microseismicity. The segment boundaries delineated by the present analysis correspond with those estimated from the slip distribution of the great 1906 San Francisco earthquake, and from the fault geometry as reported by the Working Group on California Earthquake Probabilities [1990], although the segment boundaries along the San Andreas fault in and around the San Francisco Bay area are still uncertain.

  17. A physically-based earthquake recurrence model for estimation of long-term earthquake probabilities

    Science.gov (United States)

    Ellsworth, William L.; Matthews, Mark V.; Nadeau, Robert M.; Nishenko, Stuart P.; Reasenberg, Paul A.; Simpson, Robert W.

    1999-01-01

    A physically-motivated model for earthquake recurrence based on the Brownian relaxation oscillator is introduced. The renewal process defining this point process model can be described by the steady rise of a state variable from the ground state to failure threshold as modulated by Brownian motion. Failure times in this model follow the Brownian passage time (BPT) distribution, which is specified by the mean time to failure, μ, and the aperiodicity of the mean, α (equivalent to the familiar coefficient of variation). Analysis of 37 series of recurrent earthquakes, M -0.7 to 9.2, suggests a provisional generic value of α = 0.5. For this value of α, the hazard function (instantaneous failure rate of survivors) exceeds the mean rate for times > μ⁄2, and is ~ ~ 2 ⁄ μ for all times > μ. Application of this model to the next M 6 earthquake on the San Andreas fault at Parkfield, California suggests that the annual probability of the earthquake is between 1:10 and 1:13.

  18. Liquefaction and soil failure during 1994 northridge earthquake

    Science.gov (United States)

    Holzer, T.L.

    1999-01-01

    The 1994 Northridge, Calif., earthquake caused widespread permanent ground deformation on the gently sloping alluvial fan surface of the San Fernando Valley. The ground cracks and distributed deformation damaged both pipelines and surface structures. To evaluate the mechanism of soil failure, detailed subsurface investigations were conducted at four sites. Three sites are underlain by saturated sandy silts with low standard penetration test and cone penetration test values. These soils are similar to those that liquefied during the 1971 San Fernando earthquake, and are shown by widely used empirical relationships to be susceptible to liquefaction. The remaining site is underlain by saturated clay whose undrained shear strength is approximately half the value of the earthquake-induced shear stress at this location. This study demonstrates that the heterogeneous nature of alluvial fan sediments in combination with variations in the ground-water table can be responsible for complex patterns of permanent ground deformation. It may also help to explain some of the spatial variability of strong ground motion observed during the 1994 earthquake. ?? ASCE,.

  19. San Pascual (1989) n. 272

    OpenAIRE

    Pérez, María Dolores, O.S.C. (Directora)

    1989-01-01

    Editorial. Entrevista madre abadesa. Ofrenda. San Pascual tercer centenario de la canonizacion y cuarto de su muerte. San Pascual, un Santo universal. Pascual Baylón, poeta. grupo Scout Sant Pasqual. Aportaciones, donativos, limosnas, benefactores. Boletin informativo del templo de San Pascual de villareal.

  20. Earthquakes and Schools

    Science.gov (United States)

    National Clearinghouse for Educational Facilities, 2008

    2008-01-01

    Earthquakes are low-probability, high-consequence events. Though they may occur only once in the life of a school, they can have devastating, irreversible consequences. Moderate earthquakes can cause serious damage to building contents and non-structural building systems, serious injury to students and staff, and disruption of building operations.…

  1. More Earthquake Misery

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Less than four months after the devastation of the Wenchuan earthquake on May 12, another quake brings further death and destruction to southwest China on August 30, a 6.1-magnitude earthquake hit southwest China, the border of Sichuan Province and Yunnan Province. Panzhihua City, Huili County in Sichuan and Yuanmou County and Yongren County in Yunnan were worst hit.

  2. Bam Earthquake in Iran

    CERN Multimedia

    2004-01-01

    Following their request for help from members of international organisations, the permanent Mission of the Islamic Republic of Iran has given the following bank account number, where you can donate money to help the victims of the Bam earthquake. Re: Bam earthquake 235 - UBS 311264.35L Bubenberg Platz 3001 BERN

  3. Demand surge following earthquakes

    Science.gov (United States)

    Olsen, Anna H.

    2012-01-01

    Demand surge is understood to be a socio-economic phenomenon where repair costs for the same damage are higher after large- versus small-scale natural disasters. It has reportedly increased monetary losses by 20 to 50%. In previous work, a model for the increased costs of reconstruction labor and materials was developed for hurricanes in the Southeast United States. The model showed that labor cost increases, rather than the material component, drove the total repair cost increases, and this finding could be extended to earthquakes. A study of past large-scale disasters suggested that there may be additional explanations for demand surge. Two such explanations specific to earthquakes are the exclusion of insurance coverage for earthquake damage and possible concurrent causation of damage from an earthquake followed by fire or tsunami. Additional research into these aspects might provide a better explanation for increased monetary losses after large- vs. small-scale earthquakes.

  4. Modeling earthquake dynamics

    Science.gov (United States)

    Charpentier, Arthur; Durand, Marilou

    2015-07-01

    In this paper, we investigate questions arising in Parsons and Geist (Bull Seismol Soc Am 102:1-11, 2012). Pseudo causal models connecting magnitudes and waiting times are considered, through generalized regression. We do use conditional model (magnitude given previous waiting time, and conversely) as an extension to joint distribution model described in Nikoloulopoulos and Karlis (Environmetrics 19: 251-269, 2008). On the one hand, we fit a Pareto distribution for earthquake magnitudes, where the tail index is a function of waiting time following previous earthquake; on the other hand, waiting times are modeled using a Gamma or a Weibull distribution, where parameters are functions of the magnitude of the previous earthquake. We use those two models, alternatively, to generate the dynamics of earthquake occurrence, and to estimate the probability of occurrence of several earthquakes within a year or a decade.

  5. Future Earth: Reducing Loss By Automating Response to Earthquake Shaking

    Science.gov (United States)

    Allen, R. M.

    2014-12-01

    Earthquakes pose a significant threat to society in the U.S. and around the world. The risk is easily forgotten given the infrequent recurrence of major damaging events, yet the likelihood of a major earthquake in California in the next 30 years is greater than 99%. As our societal infrastructure becomes ever more interconnected, the potential impacts of these future events are difficult to predict. Yet, the same inter-connected infrastructure also allows us to rapidly detect earthquakes as they begin, and provide seconds, tens or seconds, or a few minutes warning. A demonstration earthquake early warning system is now operating in California and is being expanded to the west coast (www.ShakeAlert.org). In recent earthquakes in the Los Angeles region, alerts were generated that could have provided warning to the vast majority of Los Angelinos who experienced the shaking. Efforts are underway to build a public system. Smartphone technology will be used not only to issue that alerts, but could also be used to collect data, and improve the warnings. The MyShake project at UC Berkeley is currently testing an app that attempts to turn millions of smartphones into earthquake-detectors. As our development of the technology continues, we can anticipate ever-more automated response to earthquake alerts. Already, the BART system in the San Francisco Bay Area automatically stops trains based on the alerts. In the future, elevators will stop, machinery will pause, hazardous materials will be isolated, and self-driving cars will pull-over to the side of the road. In this presentation we will review the current status of the earthquake early warning system in the US. We will illustrate how smartphones can contribute to the system. Finally, we will review applications of the information to reduce future losses.

  6. Potential earthquake faults offshore Southern California, from the eastern Santa Barbara Channel south to Dana Point

    Science.gov (United States)

    Fisher, M.A.; Sorlien, C.C.; Sliter, R.W.

    2009-01-01

    Urban areas in Southern California are at risk from major earthquakes, not only quakes generated by long-recognized onshore faults but also ones that occur along poorly understood offshore faults. We summarize recent research findings concerning these lesser known faults. Research by the U.S. Geological Survey during the past five years indicates that these faults from the eastern Santa Barbara Channel south to Dana Point pose a potential earthquake threat. Historical seismicity in this area indicates that, in general, offshore faults can unleash earthquakes having at least moderate (M 5-6) magnitude. Estimating the earthquake hazard in Southern California is complicated by strain partitioning and by inheritance of structures from early tectonic episodes. The three main episodes are Mesozoic through early Miocene subduction, early Miocene crustal extension coeval with rotation of the Western Transverse Ranges, and Pliocene and younger transpression related to plate-boundary motion along the San Andreas Fault. Additional complication in the analysis of earthquake hazards derives from the partitioning of tectonic strain into strike-slip and thrust components along separate but kinematically related faults. The eastern Santa Barbara Basin is deformed by large active reverse and thrust faults, and this area appears to be underlain regionally by the north-dipping Channel Islands thrust fault. These faults could produce moderate to strong earthquakes and destructive tsunamis. On the Malibu coast, earthquakes along offshore faults could have left-lateral-oblique focal mechanisms, and the Santa Monica Mountains thrust fault, which underlies the oblique faults, could give rise to large (M ??7) earthquakes. Offshore faults near Santa Monica Bay and the San Pedro shelf are likely to produce both strike-slip and thrust earthquakes along northwest-striking faults. In all areas, transverse structures, such as lateral ramps and tear faults, which crosscut the main faults, could

  7. Evidence for external forcing temporal clustering of great earthquakes

    Science.gov (United States)

    Khachikyan, Galina; Zhumabayev, Beibit; Toyshiev, Nursultan; Kairatkyzy, Dina; Kaldybayev, Azamat; Nurakynov, Serik

    2016-04-01

    It is shown by Bufe and Perkins [2005, BSSA, doi:10.1785/0120040110] and Shearera and Stark [2012, PNAS, doi: 10.1073/pnas.1118525109] that clustering of great earthquakes in 1950-1965 and 2004-2011 years is highly significant, with a 0.5% probability of random occurrence. Lutikov and Rogozhin [2014, Physics of the Solid Earth] reported on a similar clustering in the end of 19th - beginning of 20ty centuries as well, when strongest earthquakes occurred in Tien Shan (1889, M=8.3; and 1911, M=8.2); Alaska (1899, M=8.0); Kashgaria (1902, M=8.2); Mongolia (1905, M=8.2); San Francisco (1906, M=8.3), China(1906, M=8.3); Columbia (1906, M=8.6). Shearera and Stark [2012] have found that clustering of great earthquakes is analogous to seismic swarms that occur for a limited time. Simultaneously, they mentioned that at present no physical mechanism has been proposed to explain possible global seismicity swarms. Our results suggest that a mechanism responsible for temporal clustering of great earthquakes could be an external one related to the processes in the whole solar system including the Sun. We pay attention that the three marked periods of great earthquake clustering are related closely to the extreme phases of the recent Solar Centennial Gleissberg Cycle, which minimums occurred around of 1913 and 2008 years, and maximum - around of 1960 year. In particular, the great earthquake clustering in 1950-1965 coincides closely with the extremely high 19th eleven year solar cycle lasting from February 1954 to October 1964, while a great earthquake clustering after 2004 year coincides closely with the recent prolonged solar minimum developing after 2000 year. Also, we demonstrate that depending on the structure and composition of the lithosphere, strongest earthquakes may prefer to occur either in high or low solar activity. In particular, data analysis for 32 strongest (M=>7.0) earthquakes occurred in 1973-2014 years in the orogeny region of Eurasia, restricted by coordinates

  8. Modeling earthquake ground motion with an earthquake simulation program (EMPSYN) that utilizes empirical Green's functions

    Energy Technology Data Exchange (ETDEWEB)

    Hutchings, L.

    1992-01-01

    This report outlines a method of using empirical Green's functions in an earthquake simulation program EMPSYN that provides realistic seismograms from potential earthquakes. The theory for using empirical Green's functions is developed, implementation of the theory in EMPSYN is outlined, and an example is presented where EMPSYN is used to synthesize observed records from the 1971 San Fernando earthquake. To provide useful synthetic ground motion data from potential earthquakes, synthetic seismograms should model frequencies from 0.5 to 15.0 Hz, the full wave-train energy distribution, and absolute amplitudes. However, high-frequency arrivals are stochastically dependent upon the inhomogeneous geologic structure and irregular fault rupture. The fault rupture can be modeled, but the stochastic nature of faulting is largely an unknown factor in the earthquake process. The effect of inhomogeneous geology can readily be incorporated into synthetic seismograms by using small earthquakes to obtain empirical Green's functions. Small earthquakes with source corner frequencies higher than the site recording limit f{sub max}, or much higher than the frequency of interest, effectively have impulsive point-fault dislocation sources, and their recordings are used as empirical Green's functions. Since empirical Green's functions are actual recordings at a site, they include the effects on seismic waves from all geologic inhomogeneities and include all recordable frequencies, absolute amplitudes, and all phases. They scale only in amplitude with differences in seismic moment. They can provide nearly the exact integrand to the representation relation. Furthermore, since their source events have spatial extent, they can be summed to simulate fault rupture without loss of information, thereby potentially computing the exact representation relation for an extended source earthquake.

  9. A Threshold-Based Earthquake Early-Warning System for Offshore Events in Southern Iberia

    Science.gov (United States)

    Picozzi, M.; Colombelli, S.; Zollo, A.; Carranza, M.; Buforn, E.

    2015-09-01

    The south of the Iberian Peninsula is situated at the convergence of the Eurasian and African plates. This region experiences large earthquakes with long separation in time, the best known of which was the great 1755 Lisbon Earthquake, which occurred SW of San Vicente Cape (SW Iberian Peninsula). The high risk of damaging earthquakes has recently led Carranza et al. (Geophys. Res. Lett. 40, 2013) to investigate the feasibility of an EEWS in this region. Analysis of the geometry for the Iberian seismic networks and the San Vicente Cape area led the authors to conclude that a threshold-based approach, which would not require real-time location of the earthquake, might be the best option for an EEWS in SW Iberia. In this work we investigate this hypothesis and propose a new EEW approach that extends standard P-wave threshold-based single-station analysis to the whole network. The proposed method enables real-time estimation of the potential damage at stations that are triggered by P-waves and those which are not triggered, with the advantage of greater lead-times for release of alerts. Results of tests made with synthetic data mimicking the scenario of the great 1755 Lisbon Earthquake, and those conducted by applying the new approach to available recordings, indicate that an EEW estimation of the potential damage associated with an event in the San Vicente Cape area can be obtained for a very large part of the Iberian Peninsula.

  10. Earthquake forecast enrichment scores

    Directory of Open Access Journals (Sweden)

    Christine Smyth

    2012-03-01

    Full Text Available The Collaboratory for the Study of Earthquake Predictability (CSEP is a global project aimed at testing earthquake forecast models in a fair environment. Various metrics are currently used to evaluate the submitted forecasts. However, the CSEP still lacks easily understandable metrics with which to rank the universal performance of the forecast models. In this research, we modify a well-known and respected metric from another statistical field, bioinformatics, to make it suitable for evaluating earthquake forecasts, such as those submitted to the CSEP initiative. The metric, originally called a gene-set enrichment score, is based on a Kolmogorov-Smirnov statistic. Our modified metric assesses if, over a certain time period, the forecast values at locations where earthquakes have occurred are significantly increased compared to the values for all locations where earthquakes did not occur. Permutation testing allows for a significance value to be placed upon the score. Unlike the metrics currently employed by the CSEP, the score places no assumption on the distribution of earthquake occurrence nor requires an arbitrary reference forecast. In this research, we apply the modified metric to simulated data and real forecast data to show it is a powerful and robust technique, capable of ranking competing earthquake forecasts.

  11. Phase Transformations and Earthquakes

    Science.gov (United States)

    Green, H. W.

    2011-12-01

    Phase transformations have been cited as responsible for, or at least involved in, "deep" earthquakes for many decades (although the concept of "deep" has varied). In 1945, PW Bridgman laid out in detail the string of events/conditions that would have to be achieved for a solid/solid transformation to lead to a faulting instability, although he expressed pessimism that the full set of requirements would be simultaneously achieved in nature. Raleigh and Paterson (1965) demonstrated faulting during dehydration of serpentine under stress and suggested dehydration embrittlement as the cause of intermediate depth earthquakes. Griggs and Baker (1969) produced a thermal runaway model of a shear zone under constant stress, culminating in melting, and proposed such a runaway as the origin of deep earthquakes. The discovery of Plate Tectonics in the late 1960s established the conditions (subduction) under which Bridgman's requirements for earthquake runaway in a polymorphic transformation could be possible in nature and Green and Burnley (1989) found that instability during the transformation of metastable olivine to spinel. Recent seismic correlation of intermediate-depth-earthquake hypocenters with predicted conditions of dehydration of antigorite serpentine and discovery of metastable olivine in 4 subduction zones, suggests strongly that dehydration embrittlement and transformation-induced faulting are the underlying mechanisms of intermediate and deep earthquakes, respectively. The results of recent high-speed friction experiments and analysis of natural fault zones suggest that it is likely that similar processes occur commonly during many shallow earthquakes after initiation by frictional failure.

  12. An information infrastructure for earthquake science

    Science.gov (United States)

    Jordan, T. H.; Scec/Itr Collaboration

    2003-04-01

    The Southern California Earthquake Center (SCEC), in collaboration with the San Diego Supercomputer Center, the USC Information Sciences Institute,IRIS, and the USGS, has received a large five-year grant from the NSF's ITR Program and its Geosciences Directorate to build a new information infrastructure for earthquake science. In many respects, the SCEC/ITR Project presents a microcosm of the IT efforts now being organized across the geoscience community, including the EarthScope initiative. The purpose of this presentation is to discuss the experience gained by the project thus far and lay out the challenges that lie ahead; our hope is to encourage cross-discipline collaboration in future IT advancements. Project goals have been formulated in terms of four "computational pathways" related to seismic hazard analysis (SHA). For example, Pathway 1 involves the construction of an open-source, object-oriented, and web-enabled framework for SHA computations that can incorporate a variety of earthquake forecast models, intensity-measure relationships, and site-response models, while Pathway 2 aims to utilize the predictive power of wavefield simulation in modeling time-dependent ground motion for scenario earthquakes and constructing intensity-measure relationships. The overall goal is to create a SCEC "community modeling environment" or collaboratory that will comprise the curated (on-line, documented, maintained) resources needed by researchers to develop and use these four computational pathways. Current activities include (1) the development and verification of the computational modules, (2) the standardization of data structures and interfaces needed for syntactic interoperability, (3) the development of knowledge representation and management tools, (4) the construction SCEC computational and data grid testbeds, and (5) the creation of user interfaces for knowledge-acquisition, code execution, and visualization. I will emphasize the increasing role of standardized

  13. Development of Final A-Fault Rupture Models for WGCEP/ NSHMP Earthquake Rate Model 2

    Science.gov (United States)

    Field, Edward H.; Weldon, Ray J.; Parsons, Thomas; Wills, Chris J.; Dawson, Timothy E.; Stein, Ross S.; Petersen, Mark D.

    2008-01-01

    This appendix discusses how we compute the magnitude and rate of earthquake ruptures for the seven Type-A faults (Elsinore, Garlock, San Jacinto, S. San Andreas, N. San Andreas, Hayward-Rodgers Creek, and Calaveras) in the WGCEP/NSHMP Earthquake Rate Model 2 (referred to as ERM 2. hereafter). By definition, Type-A faults are those that have relatively abundant paleoseismic information (e.g., mean recurrence-interval estimates). The first section below discusses segmentation-based models, where ruptures are assumed be confined to one or more identifiable segments. The second section discusses an un-segmented-model option, the third section discusses results and implications, and we end with a discussion of possible future improvements. General background information can be found in the main report.

  14. Earthquake Disaster Management and Insurance

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    As one of the most powerful tools to reduce the earthquake loss, the Earthquake Disaster Management [EDM] and Insurance [EI] have been highlighted and have had a great progress in many countries in recent years. Earthquake disaster management includes a series of contents, such as earthquake hazard and risk analysis, vulnerability analysis of building and infrastructure, earthquake aware training, and building the emergency response system. EI, which has been included in EDM after this practice has been...

  15. Earthquakes and emergence

    Science.gov (United States)

    Earthquakes and emerging infections may not have a direct cause and effect relationship like tax evasion and jail, but new evidence suggests that there may be a link between the two human health hazards. Various media accounts have cited a massive 1993 earthquake in Maharashtra as a potential catalyst of the recent outbreak of plague in India that has claimed more than 50 lives and alarmed the world. The hypothesis is that the earthquake may have uprooted underground rat populations that carry the fleas infected with the bacterium that causes bubonic plague and can lead to the pneumonic form of the disease that is spread through the air.

  16. Earthquake engineering in Peru

    Science.gov (United States)

    Vargas, N.J

    1983-01-01

    During the last decade, earthquake engineering research in Peru has been carried out at the Catholic University of Peru and at the Universidad Nacional de Ingeniera (UNI). The Geophysical Institute (IGP) under the auspices of the Organization of American States (OAS) has initiated in Peru other efforts in regional seismic hazard assessment programs with direct impact to the earthquake engineering program. Further details on these programs have been reported by L. Ocola in the Earthquake Information Bulletin, January-February 1982, vol. 14, no. 1, pp. 33-38. 

  17. Structure of the San Fernando Valley region, California: implications for seismic hazard and tectonic history

    Science.gov (United States)

    Langenheim, V.E.; Wright, T.L.; Okaya, D.A.; Yeats, R.S.; Fuis, G.S.; Thygesen, K.; Thybo, H.

    2011-01-01

    Industry seismic reflection data, oil test well data, interpretation of gravity and magnetic data, and seismic refraction deep-crustal profiles provide new perspectives on the subsurface geology of San Fernando Valley, home of two of the most recent damaging earthquakes in southern California. Seismic reflection data provide depths to Miocene–Quaternary horizons; beneath the base of the Late Miocene Modelo Formation are largely nonreflective rocks of the Middle Miocene Topanga and older formations. Gravity and seismic reflection data reveal the North Leadwell fault zone, a set of down-to-the-north faults that does not offset the top of the Modelo Formation; the zone strikes northwest across the valley, and may be part of the Oak Ridge fault system to the west. In the southeast part of the valley, the fault zone bounds a concealed basement high that influenced deposition of the Late Miocene Tarzana fan and may have localized damage from the 1994 Northridge earthquake. Gravity and seismic refraction data indicate that the basin underlying San Fernando Valley is asymmetric, the north part of the basin (Sylmar subbasin) reaching depths of 5–8 km. Magnetic data suggest a major boundary at or near the Verdugo fault, which likely started as a Miocene transtensional fault, and show a change in the dip sense of the fault along strike. The northwest projection of the Verdugo fault separates the Sylmar subbasin from the main San Fernando Valley and coincides with the abrupt change in structural style from the Santa Susana fault to the Sierra Madre fault. The Simi Hills bound the basin on the west and, as defined by gravity data, the boundary is linear and strikes ~N45°E. That northeast-trending gravity gradient follows both the part of the 1971 San Fernando aftershock distribution called the Chatsworth trend and the aftershock trends of the 1994 Northridge earthquake. These data suggest that the 1971 San Fernando and 1994 Northridge earthquakes reactivated portions of

  18. Distant, delayed and ancient earthquake-induced landslides

    Science.gov (United States)

    Havenith, Hans-Balder; Torgoev, Almaz; Braun, Anika; Schlögel, Romy; Micu, Mihai

    2016-04-01

    On the basis of a new classification of seismically induced landslides we outline particular effects related to the delayed and distant triggering of landslides. Those cannot be predicted by state-of-the-art methods. First, for about a dozen events the 'predicted' extension of the affected area is clearly underestimated. The most problematic cases are those for which far-distant triggering of landslides had been reported, such as for the 1988 Saguenay earthquake. In Central Asia reports for such cases are known for areas marked by a thick cover of loess. One possible contributing effect could be a low-frequency resonance of the thick soils induced by distant earthquakes, especially those in the Pamir - Hindu Kush seismic region. Such deep focal and high magnitude (>>7) earthquakes are also found in Europe, first of all in the Vrancea region (Romania). For this area and others in Central Asia we computed landslide event sizes related to scenario earthquakes with M>7.5. The second particular and challenging type of triggering is the one delayed with respect to the main earthquake event: case histories have been reported for the Racha earthquake in 1991 when several larger landslides only started moving 2 or 3 days after the main shock. Similar observations were also made after other earthquake events in the U.S., such as after the 1906 San Francisco, the 1949 Tacoma, the 1959 Hebgen Lake and the 1983 Bora Peak earthquakes. Here, we will present a series of detailed examples of (partly monitored) mass movements in Central Asia that mainly developed after earthquakes, some even several weeks after the main shock: e.g. the Tektonik and Kainama landslides triggered in 1992 and 2004, respectively. We believe that the development of the massive failures is a consequence of the opening of tension cracks during the seismic shaking and their filling up with water during precipitations that followed the earthquakes. The third particular aspect analysed here is the use of large

  19. Mapping the rupture process of moderate earthquakes by inverting accelerograms

    Science.gov (United States)

    Hellweg, M.; Boatwright, J.

    1999-01-01

    We present a waveform inversion method that uses recordings of small events as Green's functions to map the rupture growth of moderate earthquakes. The method fits P and S waveforms from many stations simultaneously in an iterative procedure to estimate the subevent rupture time and amplitude relative to the Green's function event. We invert the accelerograms written by two moderate Parkfield earthquakes using smaller events as Green's functions. The first earthquake (M = 4.6) occurred on November 14, 1993, at a depth of 11 km under Middle Mountain, in the assumed preparation zone for the next Parkfield main shock. The second earthquake (M = 4.7) occurred on December 20, 1994, some 6 km to the southeast, at a depth of 9 km on a section of the San Andreas fault with no previous microseismicity and little inferred coseismic slip in the 1966 Parkfield earthquake. The inversion results are strikingly different for the two events. The average stress release in the 1993 event was 50 bars, distributed over a geometrically complex area of 0.9 km2. The average stress release in the 1994 event was only 6 bars, distributed over a roughly elliptical area of 20 km2. The ruptures of both events appear to grow spasmodically into relatively complex shapes: the inversion only constrains the ruptures to grow more slowly than the S wave velocity but does not use smoothness constraints. Copyright 1999 by the American Geophysical Union.

  20. 75 FR 55975 - Safety Zone; San Diego Harbor Shark Fest Swim; San Diego Bay, San Diego, CA

    Science.gov (United States)

    2010-09-15

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Harbor Shark Fest Swim; San Diego Bay, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone upon the navigable waters of the San Diego Bay, San Diego, CA, in support...

  1. Tweet Earthquake Dispatch (TED)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The USGS is offering earthquake alerts via two twitter accounts: @USGSted and @USGSBigQuakes. On average, @USGSted and @USGSBigQuakes will produce about one tweet...

  2. 1988 Spitak Earthquake Database

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1988 Spitak Earthquake database is an extensive collection of geophysical and geological data, maps, charts, images and descriptive text pertaining to the...

  3. Earthquake Damage to Schools

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This set of slides graphically illustrates the potential danger that major earthquakes pose to school structures and to the children and adults who happen to be...

  4. Chapter D. The Loma Prieta, California, Earthquake of October 17, 1989 - Aftershocks and Postseismic Effects

    Science.gov (United States)

    Reasenberg, Paul A.

    1997-01-01

    While the damaging effects of the earthquake represent a significant social setback and economic loss, the geophysical effects have produced a wealth of data that have provided important insights into the structure and mechanics of the San Andreas Fault system. Generally, the period after a large earthquake is vitally important to monitor. During this part of the seismic cycle, the primary fault and the surrounding faults, rock bodies, and crustal fluids rapidly readjust in response to the earthquake's sudden movement. Geophysical measurements made at this time can provide unique information about fundamental properties of the fault zone, including its state of stress and the geometry and frictional/rheological properties of the faults within it. Because postseismic readjustments are rapid compared with corresponding changes occurring in the preseismic period, the amount and rate of information that is available during the postseismic period is relatively high. From a geophysical viewpoint, the occurrence of the Loma Prieta earthquake in a section of the San Andreas fault zone that is surrounded by multiple and extensive geophysical monitoring networks has produced nothing less than a scientific bonanza. The reports assembled in this chapter collectively examine available geophysical observations made before and after the earthquake and model the earthquake's principal postseismic effects. The chapter covers four broad categories of postseismic effect: (1) aftershocks; (2) postseismic fault movements; (3) postseismic surface deformation; and (4) changes in electrical conductivity and crustal fluids.

  5. Timing of Surface-Rupturing Earthquakes on the Philippine Fault Zone in Central Luzon Island, Philippines

    Science.gov (United States)

    Tsutsumi, H.; Daligdig, J. A.; Goto, H.; Tungol, N. M.; Kondo, H.; Nakata, T.; Okuno, M.; Sugito, N.

    2006-12-01

    The Philippine fault zone is an arc-parallel left-lateral strike-slip fault zone related to oblique subduction of the Philippine Sea plate beneath the Philippine island arc. The fault zone extends for about 1300 km from the Luzon Island southward to the Mindanao Island. This fault zone has been seismically active with more than 10 earthquakes greater than M7 in the last century. The July 16, 1990, Luzon earthquake was the largest event that produced 120-km-long surface rupture along the Digdig fault. The coseismic displacement was predominantly left-lateral strike-slip with maximum slip of about 6 m. The Philippine fault zone in the Luzon Island consists of four left-stepping en echelon faults: the San Manuel, San Jose, Digdig, and Gabaldon faults from north to south. Historical documents and geomorphic data suggest that the San Manuel and Gabaldon faults ruptured most recently during historical earthquakes in 1796 and 1645, respectively. However, paleoseismic activities and slip rates for these faults were poorly constrained. In order to reconstruct chronology of surface-rupturing earthquakes, we excavated multiple trenches across these faults in the past three years. We have excavated two sites, San Gregorio and Puncan sites, across the Digdig fault. At the both sites, we identified near vertical fault zones that contain evidence for four surface-rupturing earthquakes during the past 2000 years, including the 1990 rupture. The timing of the penultimate earthquake is constrained to prior to 1400 AD, suggesting that the Digdig fault did not rupture during the 1645 earthquake. The average recurrence interval of the Digdig fault is about 600 years. A left-lateral slip rate of 8-13 mm/yr was obtained for the Digdig fault based on stream offsets and age of alluvial fan at San Juan in the central portion of the fault. For the San Jose fault, we excavated two trenches north of downtown San Jose. The sediments exposed on the trench walls were warped into a monocline by

  6. ElarmS Earthquake Early Warning System Updates and Performance

    Science.gov (United States)

    Chung, A. I.; Allen, R. M.; Hellweg, M.; Henson, I. H.; Neuhauser, D. S.

    2015-12-01

    The ElarmS earthquake early warning algorithm has been detecting earthquakes throughout California since 2007. It is one of the algorithms that contributes to CISN's ShakeAlert, a prototype earthquake early warning system being developed for California. Overall, ElarmS performance has been excellent. Over the past year (July 1, 2014 - July 1, 2015), ElarmS successfully detected all but three of the significant earthquakes (M4+) that occurred within California. Of the 24 events that were detected, the most notable was the M6.0 South Napa earthquake that occurred on August 24, 2014. The first alert for this event was sent in 5.1 seconds with an initial magnitude estimate of M5.7. This alert provided approximately 8 seconds of warning of the impending S-wave arrival to the city of San Francisco. The magnitude estimate increased to the final value of M6.0 within 15 seconds of the initial alert. One of the two events that were not detected by ElarmS occurred within 30 seconds of the M6.0 Napa mainshock. The two other missed events occurred offshore in a region with sparse station coverage in the Eureka area. Since its inception, ElarmS has evolved and adapted to meet new challenges. On May 30, 2015, an extraordinarily deep (678km) M7.8 teleseism in Japan generated 5 false event detections for earthquakes greater than M4 within a minute due to the simultaneous arrival of the P-waves at stations throughout California. In order to improve the speed and accuracy of the ElarmS detections, we are currently exploring new methodologies to quickly evaluate incoming triggers from individual stations. Rapidly determining whether or not a trigger at a given station is due to a local earthquake or some other source (such as a distant teleseism) could dramatically increase the confidence in individual triggers and reduce false alerts.

  7. Injection-induced earthquakes.

    Science.gov (United States)

    Ellsworth, William L

    2013-07-12

    Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard.

  8. Injection-induced earthquakes

    Science.gov (United States)

    Ellsworth, William L.

    2013-01-01

    Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard.

  9. Structure and mechanics of the San Andreas-San Gregorio fault junction, San Francisco, California

    Science.gov (United States)

    Parsons, Tom; Bruns, Terry R.; Sliter, Ray

    2005-01-01

    The right-lateral San Gregorio and San Andreas faults meet west of the Golden Gate near San Francisco. Coincident seismic reflection and refraction profiling across the San Gregorio and San Andreas faults south of their junction shows the crust between them to have formed shallow extensional basins that are dissected by parallel strike-slip faults. We employ a regional finite element model to investigate the long-term consequences of the fault geometry. Over the course of 2-3 m.y. of slip on the San Andreas-San Gregorio fault system, elongated extensional basins are predicted to form between the two faults. An additional consequence of the fault geometry is that the San Andreas fault is expected to have migrated eastward relative to the San Gregorio fault. We thus propose a model of eastward stepping right-lateral fault formation to explain the observed multiple fault strands and depositional basins. The current manifestation of this process might be the observed transfer of slip from the San Andreas fault east to the Golden Gate fault.

  10. The Loma Prieta, California, Earthquake of October 17, 1989: Performance of the Built Environment

    Science.gov (United States)

    Coordinated by Holzer, Thomas L.

    1998-01-01

    Professional Paper 1552 focuses on the response of buildings, lifelines, highway systems, and earth structures to the earthquake. Losses to these systems totaled approximated $5.9 billion. The earthquake displaced many residents from their homes and severely disrupted transportation systems. Some significant findings were: * Approximately 16,000 housing units were uninhabitable after the earthquake including 13,000 in the San Francisco Bay region. Another 30,000-35,000 units were moderately damaged in the earthquake. Renters and low-income residents were particularly hard hit. * Failure of highway systems was the single largest cause of loss of life during the earthquake. Forty-two of the 63 earthquake fatalities died when the Cypress Viaduct in Oakland collapsed. The cost to repair and replace highways damaged by the earthquake was $2 billion, about half of which was to replace the Cypress Viaduct. * Major bridge failures were the result of antiquated designs and inadequate anticipation of seismic loading. * Twenty one kilometers (13 mi) of gas-distribution lines had to be replaced in several communities and more than 1,200 leaks and breaks in water mains and service connections had to be excavated and repaired. At least 5 electrical substations were badly damaged, overwhelming the designed redundancy of the electrical system. * Instruments in 28 buildings recorded their response to earthquake shaking that provided opportunities to understand how different types of buildings responded, the importance of site amplification, and how buildings interact with their foundation when shaken (soil structure interaction).

  11. Charles Darwin's earthquake reports

    Science.gov (United States)

    Galiev, Shamil

    2010-05-01

    As it is the 200th anniversary of Darwin's birth, 2009 has also been marked as 170 years since the publication of his book Journal of Researches. During the voyage Darwin landed at Valdivia and Concepcion, Chile, just before, during, and after a great earthquake, which demolished hundreds of buildings, killing and injuring many people. Land was waved, lifted, and cracked, volcanoes awoke and giant ocean waves attacked the coast. Darwin was the first geologist to observe and describe the effects of the great earthquake during and immediately after. These effects sometimes repeated during severe earthquakes; but great earthquakes, like Chile 1835, and giant earthquakes, like Chile 1960, are rare and remain completely unpredictable. This is one of the few areas of science, where experts remain largely in the dark. Darwin suggested that the effects were a result of ‘ …the rending of strata, at a point not very deep below the surface of the earth…' and ‘…when the crust yields to the tension, caused by its gradual elevation, there is a jar at the moment of rupture, and a greater movement...'. Darwin formulated big ideas about the earth evolution and its dynamics. These ideas set the tone for the tectonic plate theory to come. However, the plate tectonics does not completely explain why earthquakes occur within plates. Darwin emphasised that there are different kinds of earthquakes ‘...I confine the foregoing observations to the earthquakes on the coast of South America, or to similar ones, which seem generally to have been accompanied by elevation of the land. But, as we know that subsidence has gone on in other quarters of the world, fissures must there have been formed, and therefore earthquakes...' (we cite the Darwin's sentences following researchspace. auckland. ac. nz/handle/2292/4474). These thoughts agree with results of the last publications (see Nature 461, 870-872; 636-639 and 462, 42-43; 87-89). About 200 years ago Darwin gave oneself airs by the

  12. Chapter F. The Loma Prieta, California, Earthquake of October 17, 1989 - Marina District

    Science.gov (United States)

    O'Rourke, Thomas D.

    1992-01-01

    During the earthquake, a total land area of about 4,300 km2 was shaken with seismic intensities that can cause significant damage to structures. The area of the Marina District of San Francisco is only 4.0 km2--less than 0.1 percent of the area most strongly affected by the earthquake--but its significance with respect to engineering, seismology, and planning far outstrips its proportion of shaken terrain and makes it a centerpiece for lessons learned from the earthquake. The Marina District provides perhaps the most comprehensive case history of seismic effects at a specific site developed for any earthquake. The reports assembled in this chapter, which provide an account of these seismic effects, constitute a unique collection of studies on site, as well as infrastructure and societal, response that cover virtually all aspects of the earthquake, ranging from incoming ground waves to the outgoing airwaves used for emergency communication. The Marina District encompasses the area bounded by San Francisco Bay on the north, the Presidio on the west, and Lombard Street and Van Ness Avenue on the south and east, respectively. Nearly all of the earthquake damage in the Marina District, however, occurred within a considerably smaller area of about 0.75 km2, bounded by San Francisco Bay and Baker, Chestnut, and Buchanan Streets. At least five major aspects of earthquake response in the Marina District are covered by the reports in this chapter: (1) dynamic site response, (2) soil liquefaction, (3) lifeline performance, (4) building performance, and (5) emergency services.

  13. Tokyo Metropolitan Earthquake Preparedness Project - A Progress Report

    Science.gov (United States)

    Hayashi, H.

    2010-12-01

    Munich Re once ranked that Tokyo metropolitan region, the capital of Japan, is the most vulnerable area for earthquake disasters, followed by San Francisco Bay Area, US and Osaka, Japan. Seismologists also predict that Tokyo metropolitan region may have at least one near-field earthquake with a probability of 70% for the next 30 years. Given this prediction, Japanese Government took it seriously to conduct damage estimations and revealed that, as the worst case scenario, if a7.3 magnitude earthquake under heavy winds as shown in the fig. 1, it would kill a total of 11,000 people and a total of direct and indirect losses would amount to 112,000,000,000,000 yen(1,300,000,000,000, 1=85yen) . In addition to mortality and financial losses, a total of 25 million people would be severely impacted by this earthquake in four prefectures. If this earthquake occurs, 300,000 elevators will be stopped suddenly, and 12,500 persons would be confined in them for a long time. Seven million people will come to use over 20,000 public shelters spread over the impacted area. Over one millions temporary housing units should be built to accommodate 4.6 million people who lost their dwellings. 2.5 million people will relocate to outside of the damaged area. In short, an unprecedented scale of earthquake disaster is expected and we must prepare for it. Even though disaster mitigation is undoubtedly the best solution, it is more realistic that the expected earthquake would hit before we complete this business. In other words, we must take into account another solution to make the people and the assets in this region more resilient for the Tokyo metropolitan earthquake. This is the question we have been tackling with for the last four years. To increase societal resilience for Tokyo metropolitan earthquake, we adopted a holistic approach to integrate both emergency response and long-term recovery. There are three goals for long-term recovery, which consists of Physical recovery, Economic

  14. San Cástulo

    OpenAIRE

    Jaramillo, Tania

    2014-01-01

    Porque no te acercas y nos entendemos, nos vamos cayendo por el lucro de la colonia, nos perdemos en la esquina de san Cástulo y nos vamos volando a Eleuterio, en una noche, que la luna nos vigile, que nos aguarde, que retrase el día, y la gente permanezca dormida o despierta pero temerosa de la noche, de los policías y los delincuentes, de los violadores y de nosotros, de la vida nocturna, de ese lugar oscuro en alguna parte, donde nos convertimos y aullamos.

  15. San Cástulo

    OpenAIRE

    Jaramillo, Tania

    2014-01-01

    Porque no te acercas y nos entendemos, nos vamos cayendo por el lucro de la colonia, nos perdemos en la esquina de san Cástulo y nos vamos volando a Eleuterio, en una noche, que la luna nos vigile, que nos aguarde, que retrase el día, y la gente permanezca dormida o despierta pero temerosa de la noche, de los policías y los delincuentes, de los violadores y de nosotros, de la vida nocturna, de ese lugar oscuro en alguna parte, donde nos convertimos y aullamos.

  16. Coma blisters sans coma.

    Science.gov (United States)

    Heinisch, Silke; Loosemore, Michael; Cusack, Carrie A; Allen, Herbert B

    2012-09-01

    Coma blisters (CBs) are self-limited lesions that occur in regions of pressure during unconscious states classically induced by barbiturates. We report a case of CBs sans coma that were histologically confirmed in a 41-year-old woman who developed multiple tense abdominal bullae with surrounding erythema following a transatlantic flight. Interestingly, the patient was fully conscious and denied medication use or history of medical conditions. A clinical diagnosis of CBs was confirmed by histopathologic findings of eccrine gland necrosis, a hallmark of these bulIous lesions.

  17. The Loma Prieta, California, Earthquake of October 17, 1989: Strong Ground Motion and Ground Failure

    Science.gov (United States)

    Coordinated by Holzer, Thomas L.

    1992-01-01

    Professional Paper 1551 describes the effects at the land surface caused by the Loma Prieta earthquake. These effects: include the pattern and characteristics of strong ground shaking, liquefaction of both floodplain deposits along the Pajaro and Salinas Rivers in the Monterey Bay region and sandy artificial fills along the margins of San Francisco Bay, landslides in the epicentral region, and increased stream flow. Some significant findings and their impacts were: * Strong shaking that was amplified by a factor of about two by soft soils caused damage at up to 100 kilometers (60 miles) from the epicenter. * Instrumental recordings of the ground shaking have been used to improve how building codes consider site amplification effects from soft soils. * Liquefaction at 134 locations caused $99.2 million of the total earthquake loss of $5.9 billion. Liquefaction of floodplain deposits and sandy artificial fills was similar in nature to that which occurred in the 1906 San Francisco earthquake and indicated that many areas remain susceptible to liquefaction damage in the San Francisco and Monterey Bay regions. * Landslides caused $30 million in earthquake losses, damaging at least 200 residences. Many landslides showed evidence of movement in previous earthquakes. * Recognition of the similarities between liquefaction and landslides in 1906 and 1989 and research in intervening years that established methodologies to map liquefaction and landslide hazards prompted the California legislature to pass in 1990 the Seismic Hazards Mapping Act that required the California Geological Survey to delineate regulatory zones of areas potentially susceptible to these hazards. * The earthquake caused the flow of many streams in the epicentral region to increase. Effects were noted up to 88 km from the epicenter. * Post-earthquake studies of the Marina District of San Francisco provide perhaps the most comprehensive case history of earthquake effects at a specific site developed for

  18. Earthquake number forecasts testing

    Science.gov (United States)

    Kagan, Yan Y.

    2017-10-01

    We study the distributions of earthquake numbers in two global earthquake catalogues: Global Centroid-Moment Tensor and Preliminary Determinations of Epicenters. The properties of these distributions are especially required to develop the number test for our forecasts of future seismic activity rate, tested by the Collaboratory for Study of Earthquake Predictability (CSEP). A common assumption, as used in the CSEP tests, is that the numbers are described by the Poisson distribution. It is clear, however, that the Poisson assumption for the earthquake number distribution is incorrect, especially for the catalogues with a lower magnitude threshold. In contrast to the one-parameter Poisson distribution so widely used to describe earthquake occurrences, the negative-binomial distribution (NBD) has two parameters. The second parameter can be used to characterize the clustering or overdispersion of a process. We also introduce and study a more complex three-parameter beta negative-binomial distribution. We investigate the dependence of parameters for both Poisson and NBD distributions on the catalogue magnitude threshold and on temporal subdivision of catalogue duration. First, we study whether the Poisson law can be statistically rejected for various catalogue subdivisions. We find that for most cases of interest, the Poisson distribution can be shown to be rejected statistically at a high significance level in favour of the NBD. Thereafter, we investigate whether these distributions fit the observed distributions of seismicity. For this purpose, we study upper statistical moments of earthquake numbers (skewness and kurtosis) and compare them to the theoretical values for both distributions. Empirical values for the skewness and the kurtosis increase for the smaller magnitude threshold and increase with even greater intensity for small temporal subdivision of catalogues. The Poisson distribution for large rate values approaches the Gaussian law, therefore its skewness

  19. Earthquake impact scale

    Science.gov (United States)

    Wald, D.J.; Jaiswal, K.S.; Marano, K.D.; Bausch, D.

    2011-01-01

    With the advent of the USGS prompt assessment of global earthquakes for response (PAGER) system, which rapidly assesses earthquake impacts, U.S. and international earthquake responders are reconsidering their automatic alert and activation levels and response procedures. To help facilitate rapid and appropriate earthquake response, an Earthquake Impact Scale (EIS) is proposed on the basis of two complementary criteria. On the basis of the estimated cost of damage, one is most suitable for domestic events; the other, on the basis of estimated ranges of fatalities, is generally more appropriate for global events, particularly in developing countries. Simple thresholds, derived from the systematic analysis of past earthquake impact and associated response levels, are quite effective in communicating predicted impact and response needed after an event through alerts of green (little or no impact), yellow (regional impact and response), orange (national-scale impact and response), and red (international response). Corresponding fatality thresholds for yellow, orange, and red alert levels are 1, 100, and 1,000, respectively. For damage impact, yellow, orange, and red thresholds are triggered by estimated losses reaching $1M, $100M, and $1B, respectively. The rationale for a dual approach to earthquake alerting stems from the recognition that relatively high fatalities, injuries, and homelessness predominate in countries in which local building practices typically lend themselves to high collapse and casualty rates, and these impacts lend to prioritization for international response. In contrast, financial and overall societal impacts often trigger the level of response in regions or countries in which prevalent earthquake resistant construction practices greatly reduce building collapse and resulting fatalities. Any newly devised alert, whether economic- or casualty-based, should be intuitive and consistent with established lexicons and procedures. Useful alerts should

  20. Earthquake and Geothermal Energy

    CERN Document Server

    Kapoor, Surya Prakash

    2013-01-01

    The origin of earthquake has long been recognized as resulting from strike-slip instability of plate tectonics along the fault lines. Several events of earthquake around the globe have happened which cannot be explained by this theory. In this work we investigated the earthquake data along with other observed facts like heat flow profiles etc... of the Indian subcontinent. In our studies we found a high-quality correlation between the earthquake events, seismic prone zones, heat flow regions and the geothermal hot springs. As a consequence, we proposed a hypothesis which can adequately explain all the earthquake events around the globe as well as the overall geo-dynamics. It is basically the geothermal power, which makes the plates to stand still, strike and slip over. The plates are merely a working solid while the driving force is the geothermal energy. The violent flow and enormous pressure of this power shake the earth along the plate boundaries and also triggers the intra-plate seismicity. In the light o...

  1. Rupture, waves and earthquakes

    Science.gov (United States)

    UENISHI, Koji

    2017-01-01

    Normally, an earthquake is considered as a phenomenon of wave energy radiation by rupture (fracture) of solid Earth. However, the physics of dynamic process around seismic sources, which may play a crucial role in the occurrence of earthquakes and generation of strong waves, has not been fully understood yet. Instead, much of former investigation in seismology evaluated earthquake characteristics in terms of kinematics that does not directly treat such dynamic aspects and usually excludes the influence of high-frequency wave components over 1 Hz. There are countless valuable research outcomes obtained through this kinematics-based approach, but “extraordinary” phenomena that are difficult to be explained by this conventional description have been found, for instance, on the occasion of the 1995 Hyogo-ken Nanbu, Japan, earthquake, and more detailed study on rupture and wave dynamics, namely, possible mechanical characteristics of (1) rupture development around seismic sources, (2) earthquake-induced structural failures and (3) wave interaction that connects rupture (1) and failures (2), would be indispensable. PMID:28077808

  2. Earthquake engineering in China

    Institute of Scientific and Technical Information of China (English)

    胡聿贤

    2002-01-01

    The development of earthquake engineering in China is described into three stages.The initial stage in 1950's -1960's was marked with the initiation of this branch of science from its creation in the first national 12-year plan of science andtechnology by specifying earthquake engineering as a branch item and IEM was one participant. The first earthquake zonationmap and the first seismic design code were soon completed and used in engineering design. Site effect on structural design andsite selection were seriously studied. The second stage marked with the occurrence of quite a few strong earthquakes in China,from which many lessons were learned and corresponding considerations were specified in our design codes and followed inconstruction practice. The third stage is a stage of disaster management, which is marked by a series of governmentdocumentations, leading by a national law of the People's Republic of China on the protecting against and mitigating earthquakedisasters adopted at the meeting of the Standing Committee of the National People's Congress of the People's Republic of Chinain 1997, and then followed by some provincial and municipal laws to force the actions outlined in the national law. It may beexpected that our society will be much more safer to resist the attack of future strong earthquakes with less losses. Lastly,possible future developments are also discussed.

  3. Rupture, waves and earthquakes.

    Science.gov (United States)

    Uenishi, Koji

    2017-01-01

    Normally, an earthquake is considered as a phenomenon of wave energy radiation by rupture (fracture) of solid Earth. However, the physics of dynamic process around seismic sources, which may play a crucial role in the occurrence of earthquakes and generation of strong waves, has not been fully understood yet. Instead, much of former investigation in seismology evaluated earthquake characteristics in terms of kinematics that does not directly treat such dynamic aspects and usually excludes the influence of high-frequency wave components over 1 Hz. There are countless valuable research outcomes obtained through this kinematics-based approach, but "extraordinary" phenomena that are difficult to be explained by this conventional description have been found, for instance, on the occasion of the 1995 Hyogo-ken Nanbu, Japan, earthquake, and more detailed study on rupture and wave dynamics, namely, possible mechanical characteristics of (1) rupture development around seismic sources, (2) earthquake-induced structural failures and (3) wave interaction that connects rupture (1) and failures (2), would be indispensable.

  4. Recurrence Statistics of Great Earthquakes

    CERN Document Server

    Ben-Naim, E; Johnson, P A

    2013-01-01

    We investigate the sequence of great earthquakes over the past century. To examine whether the earthquake record includes temporal clustering, we identify aftershocks and remove those from the record. We focus on the recurrence time, defined as the time between two consecutive earthquakes. We study the variance in the recurrence time and the maximal recurrence time. Using these quantities, we compare the earthquake record with sequences of random events, generated by numerical simulations, while systematically varying the minimal earthquake magnitude Mmin. Our analysis shows that the earthquake record is consistent with a random process for magnitude thresholds 7.0<=Mmin<=8.3, where the number of events is larger. Interestingly, the earthquake record deviates from a random process at magnitude threshold 8.4<=Mmin<= 8.5, where the number of events is smaller; however, this deviation is not strong enough to conclude that great earthquakes are clustered. Overall, the findings are robust both qualitat...

  5. Earthquake Damage to Transportation Systems

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Earthquakes represent one of the most destructive natural hazards known to man. A serious result of large-magnitude earthquakes is the disruption of transportation...

  6. Earthquakes, March-April 1989

    Science.gov (United States)

    Person, W.J.

    1989-01-01

    The first major earthquake (7.0-7.9) of the year hit Mexico on April 25, killing three people and causing some damage. Earthquake-related deaths were also reported from Malawi, China, and New Britain. 

  7. Early earthquakes of the Americas

    Institute of Scientific and Technical Information of China (English)

    Niu Zhijun

    2006-01-01

    @@ In recent decades the science of seismology,in particular the study of individual earthquakes, has expanded dramatically. A seismologist can look for evidence of past earthquakes in the material remains that have been excavated by archaeologists.

  8. Is magnitude variability on North-Anatolian and San-Andreas fault segments a consequence of geometry and resultant irregular tectonic loading?

    Science.gov (United States)

    Parsons, T.

    2006-12-01

    Large earthquakes of varying magnitude are observed rupturing the same fault segments on the North Anatolian fault in Turkey, and on the San Andreas fault in California. In Turkey there enough reports of historical earthquake damage [Ambraseys, 2002] to assemble a ~500-yr catalog of M greater than 7 events along the Marmara-Sea portion of the right-lateral obliquely divergent North Anatolian fault. In California, analysis by Weldon et al. [2004, 2005] from paleoseismology on the right-lateral obliquely convergent southern San Andreas fault enabled a long slip-history at the Wrightwood site. In both cases there is resolvable magnitude variation on fault segments where at least two large earthquakes ruptured the same point(s). Characteristic earthquake models posit that repeated versions of the same earthquake rupture fault segments over time, and form the basis for time-dependent probability calculations. Finite element models of the North Anatolian and San Andreas fault systems driven by geodetically-determined displacements show variable long- term stress-loading on these faults. Stressing-rate variability comes from changes in fault geometry along strike, non-uniform motions of crustal blocks, and fault interactions. The North Anatolian and San Andreas finite element models show parts of faults achieving failure stresses sooner than others. Modeled heterogeneous fault loading suggests complex rupture sequences that are consistent with observations.

  9. San Diego's Capital Planning Process

    Science.gov (United States)

    Lytton, Michael

    2009-01-01

    This article describes San Diego's capital planning process. As part of its capital planning process, the San Diego Unified School District has developed a systematic analysis of functional quality at each of its school sites. The advantage of this approach is that it seeks to develop and apply quantifiable metrics and standards for the more…

  10. Los Angeles og San Francisco

    DEFF Research Database (Denmark)

    Ørstrup, Finn Rude

    1998-01-01

    Kompendium udarbejdet til en studierejse til Los Angeles og San Francisco april-maj 1998 Kunstakademiets Arkitektskole, Institut 3H......Kompendium udarbejdet til en studierejse til Los Angeles og San Francisco april-maj 1998 Kunstakademiets Arkitektskole, Institut 3H...

  11. Tsunamigenic Aftershocks From Large Strike-Slip Earthquakes: An Example From the November 16, 2000 Mw=8.0 New Ireland, Papua New Guinea, Earthquake

    Science.gov (United States)

    Geist, E.; Parsons, T.; Hirata, K.; Hirata, K.

    2001-12-01

    Two reverse mechanism earthquakes (M > 7) were triggered by the November 16, 2000 Mw=8.0 New Ireland (Papua New Guinea) left-lateral, strike-slip earthquake. The mainshock rupture initiated in the Bismarck Sea and propagated unilaterally to the southeast through the island of New Ireland and into the Solomon Sea. Although the mainshock caused a local seiche in the bay near Rabaul (New Britain) with a maximum runup of 0.9 m, the main tsunami observed on the south coast of New Britain, New Ireland, and Bougainville (maximum runup approximately 2.5-3 m), appears to have been caused by the Mw=7.4 aftershock 2.8 hours following the mainshock. It is unclear whether the second Mw=7.6 aftershock on November 17, 2000 (40 hours after the mainshock) also generated a tsunami. Analysis and modeling of the available tsunami information can constrain the source parameters of the tsunamigenic aftershock(s) and further elucidated the triggering mechanism. Preliminary stress modeling indicates that because the location of the first Mw=7.4 aftershock is located near the rupture termination of the mainshock, stress calculations are especially sensitive to the location of both ruptures and the assumed coefficient of friction. A similar example of a triggered tsunamigenic earthquake occurred following the 1812 Wrightwood (M ~7.5) earthquake in southern California as discussed by Deng and Sykes (1996, GRL, p. 1155-1158). In this case, they show that strike-slip rupture on the San Andreas fault produced coseismic stress changes that triggered the Santa Barbara Channel earthquake (M ~7.1), 13 days later. The mechanism for the Santa Barbara Channel event appears to have been an oblique thrust event. The November 2000 New Ireland earthquake sequence provides an important analog for studying the potential for tsunamigenic aftershocks following large San Andreas earthquakes in southern California.

  12. Australia: historical earthquake studies

    Directory of Open Access Journals (Sweden)

    K. McCue

    2004-06-01

    Full Text Available Historical studies of earthquakes in Australia using information dating back to 1788 have been comprehensive, if not exhaustive. Newspapers have been the main source of historical earthquake studies. A brief review is given here with an introduction to the pre-European aboriginal dreamtime information. Some of the anecdotal information of the last two centuries has been compiled as isoseismal maps. Relationships between isoseismal radii and magnitude have been established using post-instrumental data allowing magnitudes to be assigned to the pre-instrumental data, which can then be incorporated into the national earthquake database. The studies have contributed to hazard analyses for the building codes and stimulated research into microzonation and paleo-seismology.

  13. Modelling earthquake interaction and seismicity statistics

    Science.gov (United States)

    Steacy, S.; Hetherington, A.

    2009-04-01

    The effects of earthquake interaction and fault complexity on seismicity statistics are investigated in a 3D model composed of a number of cellular automata (each representing an individual fault) distributed in a volume. Each automaton is assigned a fractal distribution of strength. Failure occurs when the 3D Coulomb stress on any cell exceeds its strength and stress transfer during simulated earthquake rupture is via nearest-neighbor rules formulated to give realistic stress concentrations. An event continues until all neighboring cells whose stresses exceed their strengths have ruptured and the size of the event is determined from its area and stress drop. Long-range stress interactions are computed following the termination of simulated ruptures using a boundary element code. In practice, these stress perturbations are only computed for events above a certain size (e.g. a threshold length of 10 km) and stresses are updated on nearby structures. Events which occur as a result of these stress interactions are considered to be "triggered" earthquakes and they, in turn, can trigger further seismic activity. The threshold length for computing interaction stresses is a free parameter and hence interaction can be "turned off" by setting this to an unrealistically high value. We consider 3 synthetic fault networks of increasing degrees of complexity - modelled on the North Anatolian fault system, the structures in the San Francisco Bay Area, and the Southern California fault network. We find that the effect of interaction is dramatically different in networks of differing complexity. In the North Anatolian analogue, for example, interaction leads to a decreased number of events, increased b-values, and an increase in recurrence intervals. In the Bay Area model, by contrast, we observe that interaction increases the number of events, decreases the b-values, and has little effect on recurrence intervals. For all networks, we find that interaction can activate mis

  14. Organizational changes at Earthquakes & Volcanoes

    Science.gov (United States)

    Gordon, David W.

    1992-01-01

    Primary responsibility for the preparation of Earthquakes & Volcanoes within the Geological Survey has shifted from the Office of Scientific Publications to the Office of Earthquakes, Volcanoes, and Engineering (OEVE). As a consequence of this reorganization, Henry Spall has stepepd down as Science Editor for Earthquakes & Volcanoes(E&V).

  15. Sensing the earthquake

    Science.gov (United States)

    Bichisao, Marta; Stallone, Angela

    2017-04-01

    Making science visual plays a crucial role in the process of building knowledge. In this view, art can considerably facilitate the representation of the scientific content, by offering a different perspective on how a specific problem could be approached. Here we explore the possibility of presenting the earthquake process through visual dance. From a choreographer's point of view, the focus is always on the dynamic relationships between moving objects. The observed spatial patterns (coincidences, repetitions, double and rhythmic configurations) suggest how objects organize themselves in the environment and what are the principles underlying that organization. The identified set of rules is then implemented as a basis for the creation of a complex rhythmic and visual dance system. Recently, scientists have turned seismic waves into sound and animations, introducing the possibility of "feeling" the earthquakes. We try to implement these results into a choreographic model with the aim to convert earthquake sound to a visual dance system, which could return a transmedia representation of the earthquake process. In particular, we focus on a possible method to translate and transfer the metric language of seismic sound and animations into body language. The objective is to involve the audience into a multisensory exploration of the earthquake phenomenon, through the stimulation of the hearing, eyesight and perception of the movements (neuromotor system). In essence, the main goal of this work is to develop a method for a simultaneous visual and auditory representation of a seismic event by means of a structured choreographic model. This artistic representation could provide an original entryway into the physics of earthquakes.

  16. Permeability, storage and hydraulic diffusivity controlled by earthquakes

    Science.gov (United States)

    Brodsky, E. E.; Fulton, P. M.; Xue, L.

    2016-12-01

    Earthquakes can increase permeability in fractured rocks. In the farfield, such permeability increases are attributed to seismic waves and can last for months after the initial earthquake. Laboratory studies suggest that unclogging of fractures by the transient flow driven by seismic waves is a viable mechanism. These dynamic permeability increases may contribute to permeability enhancement in the seismic clouds accompanying hydraulic fracking. Permeability enhancement by seismic waves could potentially be engineered and the experiments suggest the process will be most effective at a preferred frequency. We have recently observed similar processes inside active fault zones after major earthquakes. A borehole observatory in the fault that generated the M9.0 2011 Tohoku earthquake reveals a sequence of temperature pulses during the secondary aftershock sequence of an M7.3 aftershock. The pulses are attributed to fluid advection by a flow through a zone of transiently increased permeability. Directly after the M7.3 earthquake, the newly damaged fault zone is highly susceptible to further permeability enhancement, but ultimately heals within a month and becomes no longer as sensitive. The observation suggests that the newly damaged fault zone is more prone to fluid pulsing than would be expected based on the long-term permeability structure. Even longer term healing is seen inside the fault zone of the 2008 M7.9 Wenchuan earthquake. The competition between damage and healing (or clogging and unclogging) results in dynamically controlled permeability, storage and hydraulic diffusivity. Recent measurements of in situ fault zone architecture at the 1-10 meter scale suggest that active fault zones often have hydraulic diffusivities near 10-2 m2/s. This uniformity is true even within the damage zone of the San Andreas fault where permeability and storage increases balance each other to achieve this value of diffusivity over a 400 m wide region. We speculate that fault zones

  17. Broadband Waveform Modeling to Evaluate the USGS Seismic Velocity Model for the San Francisco Bay Area

    Science.gov (United States)

    Rodgers, A.; Petersson, A.; Nilsson, S.; Sjogreen, B.; McCandless, K.

    2006-12-01

    As part of the 1906 San Francisco earthquake centenary, the USGS developed a three-dimensional seismic velocity and attenuation model for Northern California based on detailed geologic and geophysical constraints. The model was used to predict ground motions for the 1906 rupture. In this study we evaluate the model to assess its ability to accurately predict ground motions from moderate earthquakes recorded on broadband stations. Satisfactory prediction of ground motions from these events will provide hope for accurate modeling of future scenario earthquakes. Simulations were performed on large parallel computer(s) with a new elastic finite difference code developed at LLNL. We simulated broadband ground motions (0-0.25 Hz) for several moderate (magnitude 3.5-5.0) earthquakes in the region observed at Berkeley Digital Seismic Network (BDSN) broadband stations. These events are well located and can be modeled with simple point moment tensor sources (taken from the Berkeley Seismological Laboratory catalog), helping to isolate the effects of structure on the waveforms. These data sample the region's diverse tectonic structures, such as the bay muds, sedimentary basins and hard rock complexes. Preliminary results indicate that the simulations reproduce many important features in the data. For example, observed long duration surface waves are often predicted for complex paths (traveling across contrasting structures) and through sedimentary basins. Excellent waveform fits were frequently obtained for long-period comparisons (0.02-0.1) and good fits were often obtained for shorter periods. We will attempt higher frequency simulations to test the ability of the model to match the high frequency response. Finally, we performed large scenario earthquake simulations for the Hayward Fault. These simulations predict large amplifications across the Santa Clara and San Ramon/Livermore Valley sedimentary basins and with the Sacramento/San Joaquin River Delta.

  18. Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Eisses, A.; Kell, A.; Kent, G. [UNR; Driscoll, N. [UCSD; Karlin, R.; Baskin, R. [USGS; Louie, J.; Pullammanappallil, S. [Optim

    2016-08-01

    Amy Eisses, Annie M. Kell, Graham Kent, Neal W. Driscoll, Robert E. Karlin, Robert L. Baskin, John N. Louie, Kenneth D. Smith, Sathish Pullammanappallil, 2011, Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada: presented at American Geophysical Union Fall Meeting, San Francisco, Dec. 5-9, abstract NS14A-08.

  19. Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Eisses, A.; Kell, A.; Kent, G. [UNR; Driscoll, N. [UCSD; Karlin, R.; Baskin, R. [USGS; Louie, J. [UNR; Pullammanappallil, S. [Optim

    2016-08-01

    Amy Eisses, Annie M. Kell, Graham Kent, Neal W. Driscoll, Robert E. Karlin, Robert L. Baskin, John N. Louie, Kenneth D. Smith, Sathish Pullammanappallil, 2011, Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada: presented at American Geophysical Union Fall Meeting, San Francisco, Dec. 5-9, abstract NS14A-08.

  20. Complex rupture during the 12 January 2010 Haiti earthquake

    Science.gov (United States)

    Hayes, G.P.; Briggs, R.W.; Sladen, A.; Fielding, E.J.; Prentice, C.; Hudnut, K.; Mann, P.; Taylor, F.W.; Crone, A.J.; Gold, R.; Ito, T.; Simons, M.

    2010-01-01

    Initially, the devastating Mw 7.0, 12 January 2010 Haiti earthquake seemed to involve straightforward accommodation of oblique relative motion between the Caribbean and North American plates along the Enriquillog-Plantain Garden fault zone. Here, we combine seismological observations, geologic field data and space geodetic measurements to show that, instead, the rupture process may have involved slip on multiple faults. Primary surface deformation was driven by rupture on blind thrust faults with only minor, deep, lateral slip along or near the main Enriquillog-Plantain Garden fault zone; thus the event only partially relieved centuries of accumulated left-lateral strain on a small part of the plate-boundary system. Together with the predominance of shallow off-fault thrusting, the lack of surface deformation implies that remaining shallow shear strain will be released in future surface-rupturing earthquakes on the Enriquillog-Plantain Garden fault zone, as occurred in inferred Holocene and probable historic events. We suggest that the geological signature of this earthquakeg-broad warping and coastal deformation rather than surface rupture along the main fault zoneg-will not be easily recognized by standard palaeoseismic studies. We conclude that similarly complex earthquakes in tectonic environments that accommodate both translation and convergenceg-such as the San Andreas fault through the Transverse Ranges of Californiag-may be missing from the prehistoric earthquake record. ?? 2010 Macmillan Publishers Limited. All rights reserved.

  1. Chapter F. The Loma Prieta, California, Earthquake of October 17, 1989 - Tectonic Processes and Models

    Science.gov (United States)

    Simpson, Robert W.

    1994-01-01

    If there is a single theme that unifies the diverse papers in this chapter, it is the attempt to understand the role of the Loma Prieta earthquake in the context of the earthquake 'machine' in northern California: as the latest event in a long history of shocks in the San Francisco Bay region, as an incremental contributor to the regional deformation pattern, and as a possible harbinger of future large earthquakes. One of the surprises generated by the earthquake was the rather large amount of uplift that occurred as a result of the reverse component of slip on the southwest-dipping fault plane. Preearthquake conventional wisdom had been that large earthquakes in the region would probably be caused by horizontal, right-lateral, strike-slip motion on vertical fault planes. In retrospect, the high topography of the Santa Cruz Mountains and the elevated marine terraces along the coast should have provided some clues. With the observed ocean retreat and the obvious uplift of the coast near Santa Cruz that accompanied the earthquake, Mother Nature was finally caught in the act. Several investigators quickly saw the connection between the earthquake uplift and the long-term evolution of the Santa Cruz Mountains and realized that important insights were to be gained by attempting to quantify the process of crustal deformation in terms of Loma Prieta-type increments of northward transport and fault-normal shortening.

  2. Evaluating earthquake hazards in the Los Angeles region; an earth-science perspective

    Science.gov (United States)

    Ziony, Joseph I.

    1985-01-01

    Potentially destructive earthquakes are inevitable in the Los Angeles region of California, but hazards prediction can provide a basis for reducing damage and loss. This volume identifies the principal geologically controlled earthquake hazards of the region (surface faulting, strong shaking, ground failure, and tsunamis), summarizes methods for characterizing their extent and severity, and suggests opportunities for their reduction. Two systems of active faults generate earthquakes in the Los Angeles region: northwest-trending, chiefly horizontal-slip faults, such as the San Andreas, and west-trending, chiefly vertical-slip faults, such as those of the Transverse Ranges. Faults in these two systems have produced more than 40 damaging earthquakes since 1800. Ninety-five faults have slipped in late Quaternary time (approximately the past 750,000 yr) and are judged capable of generating future moderate to large earthquakes and displacing the ground surface. Average rates of late Quaternary slip or separation along these faults provide an index of their relative activity. The San Andreas and San Jacinto faults have slip rates measured in tens of millimeters per year, but most other faults have rates of about 1 mm/yr or less. Intermediate rates of as much as 6 mm/yr characterize a belt of Transverse Ranges faults that extends from near Santa Barbara to near San Bernardino. The dimensions of late Quaternary faults provide a basis for estimating the maximum sizes of likely future earthquakes in the Los Angeles region: moment magnitude .(M) 8 for the San Andreas, M 7 for the other northwest-trending elements of that fault system, and M 7.5 for the Transverse Ranges faults. Geologic and seismologic evidence along these faults, however, suggests that, for planning and designing noncritical facilities, appropriate sizes would be M 8 for the San Andreas, M 7 for the San Jacinto, M 6.5 for other northwest-trending faults, and M 6.5 to 7 for the Transverse Ranges faults. The

  3. How does the 2010 El Mayor - Cucapah Earthquake Rupture Connect to the Southern California Plate Boundary Fault System

    Science.gov (United States)

    Donnellan, A.; Ben-Zion, Y.; Arrowsmith, R.

    2016-12-01

    The Pacific - North American plate boundary in southern California is marked by several major strike slip faults. The 2010 M7.2 El Mayor - Cucapah earthquake ruptured 120 km of upper crust in Baja California to the US-Mexico border. The earthquake triggered slip along an extensive network of faults in the Salton Trough from the Mexican border to the southern end of the San Andreas fault. Earthquakes >M5 were triggered in the gap between the Laguna Salada and Elsinore faults at Ocotillo and on the Coyote Creek segment of the San Jacinto fault 20 km northwest of Borrego Springs. UAVSAR observations, collected since October of 2009, measure slip associated with the M5.7 Ocotillo aftershock with deformation continuing into 2014. The Elsinore fault has been remarkably quiet, however, with only M5.0 and M5.2 earthquakes occurring on the Coyote Mountains segment of the fault in 1940 and 1968 respectively. In contrast, the Imperial Valley has been quite active historically with numerous moderate events occurring since 1935. Moderate event activity is increasing along the San Jacinto fault zone (SJFZ), especially the trifurcation area, where 6 of 12 historic earthquakes in this 20 km long fault zone have occurred since 2000. However, no recent deformation has been detected using UAVSAR measurements in this area, including the recent M5.2 June 2016 Borrego earthquake. Does the El Mayor - Cucapah rupture connect to and transfer stress primarily to a single southern California fault or several? What is its role relative to the background plate motion? UAVSAR observations indicate that the southward extension of the Elsinore fault has recently experienced the most localized deformation. Seismicity suggests that the San Jacinto fault is more active than neighboring major faults, and geologic evidence suggests that the Southern San Andreas fault has been the major plate boundary fault in southern California. Topographic data with 3-4 cm resolution using structure from motion from

  4. Lithospheric rheology constrained from twenty-five years of postseismic deformation following the 1989 Mw 6.9 Loma Prieta earthquake

    Science.gov (United States)

    Huang, Mong-Han; Burgmann, Roland; Pollitz, Fred

    2016-01-01

    The October 17, 1989 Mw 6.9 Loma Prieta earthquake provides the first opportunity of probing the crustal and upper mantle rheology in the San Francisco Bay Area since the 1906 Mw 7.9 San Francisco earthquake. Here we use geodetic observations including GPS and InSAR to characterize the Loma Prieta earthquake postseismic displacements from 1989 to 2013. Pre-earthquake deformation rates are constrained by nearly 20 yr of USGS trilateration measurements and removed from the postseismic measurements prior to the analysis. We observe GPS horizontal displacements at mean rates of 1–4 mm/yr toward Loma Prieta Mountain until 2000, and ∼2 mm/yr surface subsidence of the northern Santa Cruz Mountains between 1992 and 2002 shown by InSAR, which is not associated with the seasonal and longer-term hydrological deformation in the adjoining Santa Clara Valley. Previous work indicates afterslip dominated in the early (1989–1994) postseismic period, so we focus on modeling the postseismic viscoelastic relaxation constrained by the geodetic observations after 1994. The best fitting model shows an elastic 19-km-thick upper crust above an 11-km-thick viscoelastic lower crust with viscosity of ∼6 × 1018 Pas, underlain by a viscous upper mantle with viscosity between 3 × 1018 and 2 × 1019 Pas. The millimeter-scale postseismic deformation does not resolve the viscosity in the different layers very well, and the lower-crustal relaxation may be localized in a narrow shear zone. However, the inferred lithospheric rheology is consistent with previous estimates based on post-1906 San Francisco earthquake measurements along the San Andreas fault system. The viscoelastic relaxation may also contribute to the enduring increase of aseismic slip and repeating earthquake activity on the San Andreas fault near San Juan Bautista, which continued for at least a decade after the Loma Prieta event.

  5. Lithospheric rheology constrained from twenty-five years of postseismic deformation following the 1989 Mw 6.9 Loma Prieta earthquake

    Science.gov (United States)

    Huang, Mong-Han; Bürgmann, Roland; Pollitz, Fred

    2016-02-01

    The October 17, 1989 Mw 6.9 Loma Prieta earthquake provides the first opportunity of probing the crustal and upper mantle rheology in the San Francisco Bay Area since the 1906 Mw 7.9 San Francisco earthquake. Here we use geodetic observations including GPS and InSAR to characterize the Loma Prieta earthquake postseismic displacements from 1989 to 2013. Pre-earthquake deformation rates are constrained by nearly 20 yr of USGS trilateration measurements and removed from the postseismic measurements prior to the analysis. We observe GPS horizontal displacements at mean rates of 1-4 mm/yr toward Loma Prieta Mountain until 2000, and ˜2 mm/yr surface subsidence of the northern Santa Cruz Mountains between 1992 and 2002 shown by InSAR, which is not associated with the seasonal and longer-term hydrological deformation in the adjoining Santa Clara Valley. Previous work indicates afterslip dominated in the early (1989-1994) postseismic period, so we focus on modeling the postseismic viscoelastic relaxation constrained by the geodetic observations after 1994. The best fitting model shows an elastic 19-km-thick upper crust above an 11-km-thick viscoelastic lower crust with viscosity of ˜ 6 ×1018 Pas, underlain by a viscous upper mantle with viscosity between 3 ×1018 and 2 ×1019 Pas. The millimeter-scale postseismic deformation does not resolve the viscosity in the different layers very well, and the lower-crustal relaxation may be localized in a narrow shear zone. However, the inferred lithospheric rheology is consistent with previous estimates based on post-1906 San Francisco earthquake measurements along the San Andreas fault system. The viscoelastic relaxation may also contribute to the enduring increase of aseismic slip and repeating earthquake activity on the San Andreas fault near San Juan Bautista, which continued for at least a decade after the Loma Prieta event.

  6. Earthquake alarm; operating the seismograph station at the University of California, Berkeley.

    Science.gov (United States)

    Stump, B.

    1980-01-01

    An alarm bell rings at the seismographic station and at the office of the campus police. It is 3:00 on a foggy San Francisco morning. Somewhere in the world an earthquake has occurred. The police telephone the duty seismologist at home telling him that the alarm has triggered. He makes his way into the seismograph station, bathrobe and all, to locate the earthquake and determine its magnitude. In this way, many seismology graduate students have been initiated into the responsibilities of running a seismographic station. 

  7. Quasi-Resonance Effects Observed in The 1994 Northridge Earthquake, and Others

    Directory of Open Access Journals (Sweden)

    Edward G. Fischer

    1998-01-01

    Full Text Available Sine-beat phenomena have been found in the 1994 Northridge earthquake records, and they are capable of producing time-history responses and damaging quasi-resonance effects in structures. Linear, single DOF (degree of freedom oscillators, in lieu of nonlinear, multiple DOF systems, have been found adequate to discuss the failures of tall circuit breakers during the 1971 San Fernando and the 1989 Loma Prieta quakes in California. The use of sine-beat excitation for seismic-shaking-table tests of equipment continues to be a conservative simulation of earthquakes.

  8. The Loma Prieta Earthquake of October 17, 1989, A UCSC Student Oral History Documentary Projec

    OpenAIRE

    Reti, Irene; Regional History Project, UCSC Library

    2006-01-01

    On October 17, 1989 at 5:04 p.m. a 6.9 magnitude earthquake on the San Andreas Fault shook the Central Coast of California and lasted for fifteen seconds. The epicenter of the quake lay near Loma Prieta Peak in the Santa Cruz Mountains, about ten miles northeast of the city of Santa Cruz, deep in the redwoods of Forest of Nisene Marks State Park. The focus point was at a depth of ten miles. This earthquake killed sixty-three people and injured 3,757 others, and caused an estimated six billion...

  9. Chapter A. The Loma Prieta, California, Earthquake of October 17, 1989 - Strong Ground Motion

    Science.gov (United States)

    Borcherdt, Roger D.

    1994-01-01

    Strong ground motion generated by the Loma Prieta, Calif., earthquake (MS~7.1) of October 17, 1989, resulted in at least 63 deaths, more than 3,757 injuries, and damage estimated to exceed $5.9 billion. Strong ground motion severely damaged critical lifelines (freeway overpasses, bridges, and pipelines), caused severe damage to poorly constructed buildings, and induced a significant number of ground failures associated with liquefaction and landsliding. It also caused a significant proportion of the damage and loss of life at distances as far as 100 km from the epicenter. Consequently, understanding the characteristics of the strong ground motion associated with the earthquake is fundamental to understanding the earthquake's devastating impact on society. The papers assembled in this chapter address this problem. Damage to vulnerable structures from the earthquake varied substantially with the distance from the causative fault and the type of underlying geologic deposits. Most of the damage and loss of life occurred in areas underlain by 'soft soil'. Quantifying these effects is important for understanding the tragic concentrations of damage in such areas as Santa Cruz and the Marina and Embarcadero Districts of San Francisco, and the failures of the San Francisco-Oakland Bay Bridge and the Interstate Highway 880 overpass. Most importantly, understanding these effects is a necessary prerequisite for improving mitigation measures for larger earthquakes likely to occur much closer to densely urbanized areas in the San Francisco Bay region. The earthquake generated an especially important data set for understanding variations in the severity of strong ground motion. Instrumental strong-motion recordings were obtained at 131 sites located from about 6 to 175 km from the rupture zone. This set of recordings, the largest yet collected for an event of this size, was obtained from sites on various geologic deposits, including a unique set on 'soft soil' deposits

  10. Indonesian Earthquake Decision Support System

    CERN Document Server

    Warnars, Spits

    2010-01-01

    Earthquake DSS is an information technology environment which can be used by government to sharpen, make faster and better the earthquake mitigation decision. Earthquake DSS can be delivered as E-government which is not only for government itself but in order to guarantee each citizen's rights for education, training and information about earthquake and how to overcome the earthquake. Knowledge can be managed for future use and would become mining by saving and maintain all the data and information about earthquake and earthquake mitigation in Indonesia. Using Web technology will enhance global access and easy to use. Datawarehouse as unNormalized database for multidimensional analysis will speed the query process and increase reports variation. Link with other Disaster DSS in one national disaster DSS, link with other government information system and international will enhance the knowledge and sharpen the reports.

  11. Episodic tremor triggers small earthquakes

    Science.gov (United States)

    Balcerak, Ernie

    2011-08-01

    It has been suggested that episodic tremor and slip (ETS), the weak shaking not associated with measurable earthquakes, could trigger nearby earthquakes. However, this had not been confirmed until recently. Vidale et al. monitored seismicity in the 4-month period around a 16-day episode of episodic tremor and slip in March 2010 in the Cascadia region. They observed five small earthquakes within the subducting slab during the ETS episode. They found that the timing and locations of earthquakes near the tremor suggest that the tremor and earthquakes are related. Furthermore, they observed that the rate of earthquakes across the area was several times higher within 2 days of tremor activity than at other times, adding to evidence of a connection between tremor and earthquakes. (Geochemistry, Geophysics, Geosystems, doi:10.1029/2011GC003559, 2011)

  12. ALMA measures Calama earthquake

    Science.gov (United States)

    Brito, R.; Shillue, B.

    2010-04-01

    On 4 March 2010, the ALMA system response to an extraordinarily large disturbance was measured when a magnitude 6.3 earthquake struck near Calama, Chile, relatively close to the ALMA site. Figures 1 through 4 demonstrate the remarkable performance of the ALMA system to a huge disturbance that was more than 100 times the specification for correction accuracy.

  13. Road Damage Following Earthquake

    Science.gov (United States)

    1989-01-01

    Ground shaking triggered liquefaction in a subsurface layer of water-saturated sand, producing differential lateral and vertical movement in a overlying carapace of unliquified sand and slit, which moved from right to left towards the Pajaro River. This mode of ground failure, termed lateral spreading, is a principal cause of liquefaction-related earthquake damage caused by the Oct. 17, 1989, Loma Prieta earthquake. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: S.D. Ellen, U.S. Geological Survey

  14. 78 FR 39610 - Safety Zone; Big Bay Boom, San Diego Bay; San Diego, CA

    Science.gov (United States)

    2013-07-02

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Big Bay Boom, San Diego Bay; San Diego, CA... temporary safety zones upon the navigable waters of the San Diego Bay for the annual Port of San Diego... Sector San Diego, Coast Guard; telephone 619-278-7261, email d11marineeventssd@uscg.mil . If you have...

  15. 75 FR 38412 - Safety Zone; San Diego POPS Fireworks, San Diego, CA

    Science.gov (United States)

    2010-07-02

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego POPS Fireworks, San Diego, CA... zone on the ] navigable waters of San Diego Bay in support of the San Diego POPS Fireworks. This safety.... Coast Guard Sector San Diego, CA; telephone 619-278- 7262, e-mail Shane.E.Jackson@uscg.mil . If you have...

  16. 78 FR 42027 - Safety Zone; San Diego Bayfair; Mission Bay, San Diego, CA

    Science.gov (United States)

    2013-07-15

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Bayfair; Mission Bay, San Diego... proposing a temporary safety zone on the navigable waters of Mission Bay in San Diego, CA for the San Diego..., call or email Lieutenant John Bannon, Waterways Management, U.S. Coast Guard Sector San Diego...

  17. 78 FR 29289 - Safety Zone; Big Bay Boom, San Diego Bay, San Diego, CA

    Science.gov (United States)

    2013-05-20

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Big Bay Boom, San Diego Bay, San Diego, CA... establish four temporary safety zones upon the navigable waters of San Diego ] Bay for the Port of San Diego... Management, U.S. Coast Guard Sector San Diego; telephone (619) 278-7261, email John.E.Bannon@uscg.mil . If...

  18. 78 FR 53245 - Safety Zone; San Diego Bayfair; Mission Bay, San Diego, CA

    Science.gov (United States)

    2013-08-29

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Bayfair; Mission Bay, San Diego... temporary safety zone upon the navigable waters of Mission Bay in San Diego, CA for the annual San Diego... Management, U.S. Coast Guard Sector San Diego; telephone (619) 278-7261, email John.E.Bannon@uscg.mil . If...

  19. Seismic velocity structure and seismotectonics of the eastern San Francisco Bay region, California

    Science.gov (United States)

    Hardebeck, J.L.; Michael, A.J.; Brocher, T.M.

    2007-01-01

    The Hayward Fault System is considered the most likely fault system in the San Francisco Bay Area, California, to produce a major earthquake in the next 30 years. To better understand this fault system, we use microseismicity to study its structure and kinematics. We present a new 3D seismic-velocity model for the eastern San Francisco Bay region, using microseismicity and controlled sources, which reveals a ???10% velocity contrast across the Hayward fault in the upper 10 km, with higher velocity in the Franciscan Complex to the west relative to the Great Valley Sequence to the east. This contrast is imaged more sharply in our localized model than in previous regional-scale models. Thick Cenozoic sedimentary basins, such as the Livermore basin, which may experience particularly strong shaking during an earthquake, are imaged in the model. The accurate earthquake locations and focal mechanisms obtained by using the 3D model allow us to study fault complexity and its implications for seismic hazard. The relocated hypocenters along the Hayward Fault in general are consistent with a near-vertical or steeply east-dipping fault zone. The southern Hayward fault merges smoothly with the Calaveras fault at depth, suggesting that large earthquakes may rupture across both faults. The use of the 3D velocity model reveals that most earthquakes along the Hayward fault have near-vertical strike-slip focal mechanisms, consistent with the large-scale orientation and sense of slip of the fault, with no evidence for zones of complex fracturing acting as barriers to earthquake rupture.

  20. Riparian Habitat - San Joaquin River

    Data.gov (United States)

    California Department of Resources — The immediate focus of this study is to identify, describe and map the extent and diversity of riparian habitats found along the main stem of the San Joaquin River,...

  1. Bounding Ground Motions for Hayward Fault Scenario Earthquakes Using Suites of Stochastic Rupture Models

    Science.gov (United States)

    Rodgers, A. J.; Xie, X.; Petersson, A.

    2007-12-01

    The next major earthquake in the San Francisco Bay area is likely to occur on the Hayward-Rodgers Creek Fault system. Attention on the southern Hayward section is appropriate given the upcoming 140th anniversary of the 1868 M 7 rupture coinciding with the estimated recurrence interval. This presentation will describe ground motion simulations for large (M > 6.5) earthquakes on the Hayward Fault using a recently developed elastic finite difference code and high-performance computers at Lawrence Livermore National Laboratory. Our code easily reads the recent USGS 3D seismic velocity model of the Bay Area developed in 2005 and used for simulations of the 1906 San Francisco and 1989 Loma Prieta earthquakes. Previous work has shown that the USGS model performs very well when used to model intermediate period (4-33 seconds) ground motions from moderate (M ~ 4-5) earthquakes (Rodgers et al., 2008). Ground motions for large earthquakes are strongly controlled by the hypocenter location, spatial distribution of slip, rise time and directivity effects. These are factors that are impossible to predict in advance of a large earthquake and lead to large epistemic uncertainties in ground motion estimates for scenario earthquakes. To bound this uncertainty, we are performing suites of simulations of scenario events on the Hayward Fault using stochastic rupture models following the method of Liu et al. (Bull. Seism. Soc. Am., 96, 2118-2130, 2006). These rupture models have spatially variable slip, rupture velocity, rise time and rake constrained by characterization of inferred finite fault ruptures and expert opinion. Computed ground motions show variability due to the variability in rupture models and can be used to estimate the average and spread of ground motion measures at any particular site. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No.W-7405-Eng-48. This is

  2. Seismomagnetic effects from the long-awaited 28 September 2004 M 6.0 parkfield earthquake

    Science.gov (United States)

    Johnston, M.J.S.; Sasai, Y.; Egbert, G.D.; Mueller, R.J.

    2006-01-01

    Precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked-to-creeping transition region of the San Andreas fault at Parkfield, California, since 1976. The M 6.0 Parkfield earthquake on 28 September 2004, occurred within this array and generated coseismic magnetic field changes of between 0.2 and 0.5 nT at five sites in the network. No preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month, week, and days before the earthquake (or expected in light of the absence of measurable precursive deformation, seismicity, or pore pressure changes). Observations of electric and magnetic fields from 0.01 to 20 Hz are also made at one site near the end of the earthquake rupture and corrected for common-mode signals from the ionosphere/magnetosphere using a second site some 115 km to the northwest along the fault. These magnetic data show no indications of unusual noise before the earthquake in the ULF band (0.01-20 Hz) as suggested may have preceded the 1989 ML 7.1 Loma Prieta earthquake. Nor do we see electric field changes similar to those suggested to occur before earthquakes of this magnitude from data in Greece. Uniform and variable slip piezomagnetic models of the earthquake, derived from strain, displacement, and seismic data, generate magnetic field perturbations that are consistent with those observed by the magnetometer array. A higher rate of longer-term magnetic field change, consistent with increased loading in the region, is apparent since 1993. This accompanied an increased rate of secular shear strain observed on a two-color EDM network and a small network of borehole tensor strainmeters and increased seismicity dominated by three M 4.5-5 earthquakes roughly a year apart in 1992, 1993, and 1994. Models incorporating all of these data indicate increased slip at depth in the region

  3. Seismomagnetic Effects from the Long-awaited September 28, 2004, M6 Parkfield Earthquake

    Science.gov (United States)

    Johnston, M. J.; Sasai, Y.; Egbert, G. D.; Kappler, K.

    2005-12-01

    Precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked-to-creeping transition region of the San Andreas Fault at Parkfield, CA. since 1984. The M6 Parkfield earthquake on September 28, 2004, occurred within this array and generated coseismic magnetic field changes of between 0.2 and 0.5 nT at five sites in the network. No preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month, week and days before the earthquake (or expected in light of the absence of measurable precursive deformation, seismicity or pore pressure changes). Observations of electric and magnetic fields from 0.01 to 20 Hz are also made at one site near the end of the earthquake rupture and corrected for common-mode signals from the ionosphere/magnetosphere using a second site some 115 km to the northwest along the fault. These magnetic data show no indications of unusual noise before the earthquake in the ULF band (0.01 Hz to 20 Hz) as suggested may have preceded the 1989 Loma Prieta earthquake. Nor do we see electric field changes similar to those believed to occur before earthquakes of this magnitude from data in Greece. Uniform and variable slip piezomagnetic models of the earthquake, derived from strain, displacement and seismic data, generates magnetic field perturbations that are consistent with those observed by the magnetometer array. A higher rate of longer-term magnetic field change, consistent with increased loading in the region, is apparent since 1993. This accompanied an increased rate of secular shear strain observed on a 2-color EDM network and a small network of borehole tensor strainmeters and increased seismicity dominated by three M4.5-5 earthquakes roughly a year apart in 1992, 1993 and 1994. Models incorporating all of these data indicate increased slip at depth in the region and this may have

  4. Surface fault slip associated with the 2004 Parkfield, California, earthquake

    Science.gov (United States)

    Rymer, M.J.; Tinsley, J. C.; Treiman, J.A.; Arrowsmith, J.R.; Ciahan, K.B.; Rosinski, A.M.; Bryant, W.A.; Snyder, H.A.; Fuis, G.S.; Toke, N.A.; Bawden, G.W.

    2006-01-01

    Surface fracturing occurred along the San Andreas fault, the subparallel Southwest Fracture Zone, and six secondary faults in association with the 28 September 2004 (M 6.0) Parkfield earthquake. Fractures formed discontinuous breaks along a 32-km-long stretch of the San Andreas fault. Sense of slip was right lateral; only locally was there a minor (1-11 mm) vertical component of slip. Right-lateral slip in the first few weeks after the event, early in its afterslip period, ranged from 1 to 44 mm. Our observations in the weeks following the earthquake indicated that the highest slip values are in the Middle Mountain area, northwest of the mainshock epicenter (creepmeter measurements indicate a similar distribution of slip). Surface slip along the San Andreas fault developed soon after the mainshock; field checks in the area near Parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event. Slip along the Southwest Fracture Zone developed coseismically and extended about 8 km. Sense of slip was right lateral; locally there was a minor to moderate (1-29 mm) vertical component of slip. Right-lateral slip ranged from 1 to 41 mm. Surface slip along secondary faults was right lateral; the right-lateral component of slip ranged from 3 to 5 mm. Surface slip in the 1966 and 2004 events occurred along both the San Andreas fault and the Southwest Fracture Zone. In 1966 the length of ground breakage along the San Andreas fault extended 5 km longer than that mapped in 2004. In contrast, the length of ground breakage along the Southwest Fracture Zone was the same in both events, yet the surface fractures were more continuous in 2004. Surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the San Andreas fault and the Southwest Fracture Zone, further revealing aspects of the structural setting and fault interactions in the Parkfield area.

  5. Listening to Earthquakes with Infrasound

    Science.gov (United States)

    Mucek, A. E.; Langston, C. A.

    2011-12-01

    A tripartite infrasound array was installed to listen to earthquakes occurring along the Guy-Greenbrier fault in Arkansas. The active earthquake swarm is believed to be caused by deep waste water injections and will allow us to explain the mechanisms causing earthquake "booms" that have been heard during an earthquake. The array has an aperture of 50 meters and is installed next to the X301 seismograph station run by the Center for Earthquake Research and Information (CERI). This arrangement allows simultaneous recording of seismic and acoustic changes from the arrival of an earthquake. Other acoustic and seismic sources that have been found include thunder from thunderstorms, gunshots, quarry explosions and hydraulic fracturing activity from the local gas wells. The duration of the experiment is from the last week of June to the last week of September 2011. During the first month and a half, seven local earthquakes were recorded, along with numerous occurrences of the other infrasound sources. Phase arrival times of the recorded waves allow us to estimate wave slowness and azimuth of infrasound events. Using these two properties, we can determine whether earthquake "booms" occur at a site from the arrival of the P-wave or whether the earthquake "booms" occur elsewhere and travel through the atmosphere. Preliminary results show that the infrasound correlates well to the ground motion during an earthquake for frequencies below 15 Hertz.

  6. Environmental assessment : Rodent control program : San Joaquin river levee : San Luis National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Lower San Joaquin Levee District (LSJLD) requires that six miles of levee situated along the San Joaquin River on San Luis National Wildlife Refuge (SLNWR) be...

  7. Residencia San Pedro, California

    Directory of Open Access Journals (Sweden)

    Neutra, Richard J.

    1961-01-01

    Full Text Available Esta vivienda representa una aproximación más hacia la típica casa grande española, con techos de teca de 7 cm, que los señores Rados han edificado y en la que albergan a su gran familia de hijos, los cuales tienen ya sus propios vástagos. Ambos, el señor y la señora Rados, descienden de familias navieras italianas de Trieste, y el propio señor Rados tiene una compañía constructora de barcos en el puerto de San Pedro, que puede verse desde su propia casa. Los dos son verdaderamente unos abuelos muy sociables, cariñosos y atentos. Por añadidura, la señora Rados se entretiene frecuentemente y le agrada el cuidado de la casa. Por ello ha sido proyectada para facilitar sensiblemente toda esta serie de actividades.

  8. Great earthquakes along the Western United States continental margin: implications for hazards, stratigraphy and turbidite lithology

    Directory of Open Access Journals (Sweden)

    C. H. Nelson

    2012-11-01

    Full Text Available We summarize the importance of great earthquakes (Mw ≳ 8 for hazards, stratigraphy of basin floors, and turbidite lithology along the active tectonic continental margins of the Cascadia subduction zone and the northern San Andreas Transform Fault by utilizing studies of swath bathymetry visual core descriptions, grain size analysis, X-ray radiographs and physical properties. Recurrence times of Holocene turbidites as proxies for earthquakes on the Cascadia and northern California margins are analyzed using two methods: (1 radiometric dating (14C method, and (2 relative dating, using hemipelagic sediment thickness and sedimentation rates (H method. The H method provides (1 the best estimate of minimum recurrence times, which are the most important for seismic hazards risk analysis, and (2 the most complete dataset of recurrence times, which shows a normal distribution pattern for paleoseismic turbidite frequencies. We observe that, on these tectonically active continental margins, during the sea-level highstand of Holocene time, triggering of turbidity currents is controlled dominantly by earthquakes, and paleoseismic turbidites have an average recurrence time of ~550 yr in northern Cascadia Basin and ~200 yr along northern California margin. The minimum recurrence times for great earthquakes are approximately 300 yr for the Cascadia subduction zone and 130 yr for the northern San Andreas Fault, which indicates both fault systems are in (Cascadia or very close (San Andreas to the early window for another great earthquake.

    On active tectonic margins with great earthquakes, the volumes of mass transport deposits (MTDs are limited on basin floors along the margins. The maximum run-out distances of MTD sheets across abyssal-basin floors along active margins are an order of magnitude less (~100 km than on passive margins (~1000 km. The great earthquakes along the Cascadia and northern California margins

  9. Solar activity and earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, J.

    1979-02-26

    Prolonged astronomical observations have discovered that the Sun, which is the nearest star to the Earth, is not calm and serene. On the solar surface, there are often windstorms, electrical lights, and sometimes large flame eruptions; and there are regularly black spots in patches which are also active. The Sun not only disperses light and heat, but also throws out large quantities of currents of charged particles to be scattered in space and to reach the Earth, sometimes, which are called by some solar winds. These activities in the Sun can induce many physical phenomena on earth, including magnetic storms, polar light, sudden disruption or attenuation of medium- and short-wave radio, and many atmospheric changes. Some scientists believe they are perhaps also related to the occurrence of earthquakes. This paper explains these solar activities and their possible relationship to earthquakes.

  10. A 30-year history of earthquake crisis communication in California and lessons for the future

    Science.gov (United States)

    Jones, L.

    2015-12-01

    The first statement from the US Geological Survey to the California Office of Emergency Services quantifying the probability of a possible future earthquake was made in October 1985 about the probability (approximately 5%) that a M4.7 earthquake located directly beneath the Coronado Bay Bridge in San Diego would be a foreshock to a larger earthquake. In the next 30 years, publication of aftershock advisories have become routine and formal statements about the probability of a larger event have been developed in collaboration with the California Earthquake Prediction Evaluation Council (CEPEC) and sent to CalOES more than a dozen times. Most of these were subsequently released to the public. These communications have spanned a variety of approaches, with and without quantification of the probabilities, and using different ways to express the spatial extent and the magnitude distribution of possible future events. The USGS is re-examining its approach to aftershock probability statements and to operational earthquake forecasting with the goal of creating pre-vetted automated statements that can be released quickly after significant earthquakes. All of the previous formal advisories were written during the earthquake crisis. The time to create and release a statement became shorter with experience from the first public advisory (to the 1988 Lake Elsman earthquake) that was released 18 hours after the triggering event, but was never completed in less than 2 hours. As was done for the Parkfield experiment, the process will be reviewed by CEPEC and NEPEC (National Earthquake Prediction Evaluation Council) so the statements can be sent to the public automatically. This talk will review the advisories, the variations in wording and the public response and compare this with social science research about successful crisis communication, to create recommendations for future advisories

  11. Quasi-Resonance Effects Observed in The 1994 Northridge Earthquake, and Others

    OpenAIRE

    Fischer, Edward G.; Thomas P. Fischer

    1998-01-01

    Sine-beat phenomena have been found in the 1994 Northridge earthquake records, and they are capable of producing time-history responses and damaging quasi-resonance effects in structures. Linear, single DOF (degree of freedom) oscillators, in lieu of nonlinear, multiple DOF systems, have been found adequate to discuss the failures of tall circuit breakers during the 1971 San Fernando and the 1989 Loma Prieta quakes in California. The use of sine-beat excitation for seismic-shaking-table tests...

  12. The Negative Binomial Distribution as a Renewal Model for the Recurrence of Large Earthquakes

    Science.gov (United States)

    Tejedor, Alejandro; Gómez, Javier B.; Pacheco, Amalio F.

    2015-01-01

    The negative binomial distribution is presented as the waiting time distribution of a cyclic Markov model. This cycle simulates the seismic cycle in a fault. As an example, this model, which can describe recurrences with aperiodicities between 0 and 0.5, is used to fit the Parkfield, California earthquake series in the San Andreas Fault. The performance of the model in the forecasting is expressed in terms of error diagrams and compared with other recurrence models from literature.

  13. Do Earthquakes Shake Stock Markets?

    Science.gov (United States)

    Ferreira, Susana; Karali, Berna

    2015-01-01

    This paper examines how major earthquakes affected the returns and volatility of aggregate stock market indices in thirty-five financial markets over the last twenty years. Results show that global financial markets are resilient to shocks caused by earthquakes even if these are domestic. Our analysis reveals that, in a few instances, some macroeconomic variables and earthquake characteristics (gross domestic product per capita, trade openness, bilateral trade flows, earthquake magnitude, a tsunami indicator, distance to the epicenter, and number of fatalities) mediate the impact of earthquakes on stock market returns, resulting in a zero net effect. However, the influence of these variables is market-specific, indicating no systematic pattern across global capital markets. Results also demonstrate that stock market volatility is unaffected by earthquakes, except for Japan.

  14. Earthquake engineering for nuclear facilities

    CERN Document Server

    Kuno, Michiya

    2017-01-01

    This book is a comprehensive compilation of earthquake- and tsunami-related technologies and knowledge for the design and construction of nuclear facilities. As such, it covers a wide range of fields including civil engineering, architecture, geotechnical engineering, mechanical engineering, and nuclear engineering, for the development of new technologies providing greater resistance against earthquakes and tsunamis. It is crucial both for students of nuclear energy courses and for young engineers in nuclear power generation industries to understand the basics and principles of earthquake- and tsunami-resistant design of nuclear facilities. In Part I, "Seismic Design of Nuclear Power Plants", the design of nuclear power plants to withstand earthquakes and tsunamis is explained, focusing on buildings, equipment's, and civil engineering structures. In Part II, "Basics of Earthquake Engineering", fundamental knowledge of earthquakes and tsunamis as well as the dynamic response of structures and foundation ground...

  15. Pain after earthquake

    Directory of Open Access Journals (Sweden)

    Angeletti Chiara

    2012-06-01

    Full Text Available Abstract Introduction On 6 April 2009, at 03:32 local time, an Mw 6.3 earthquake hit the Abruzzi region of central Italy causing widespread damage in the City of L Aquila and its nearby villages. The earthquake caused 308 casualties and over 1,500 injuries, displaced more than 25,000 people and induced significant damage to more than 10,000 buildings in the L'Aquila region. Objectives This observational retrospective study evaluated the prevalence and drug treatment of pain in the five weeks following the L'Aquila earthquake (April 6, 2009. Methods 958 triage documents were analysed for patients pain severity, pain type, and treatment efficacy. Results A third of pain patients reported pain with a prevalence of 34.6%. More than half of pain patients reported severe pain (58.8%. Analgesic agents were limited to available drugs: anti-inflammatory agents, paracetamol, and weak opioids. Reduction in verbal numerical pain scores within the first 24 hours after treatment was achieved with the medications at hand. Pain prevalence and characterization exhibited a biphasic pattern with acute pain syndromes owing to trauma occurring in the first 15 days after the earthquake; traumatic pain then decreased and re-surged at around week five, owing to rebuilding efforts. In the second through fourth week, reports of pain occurred mainly owing to relapses of chronic conditions. Conclusions This study indicates that pain is prevalent during natural disasters, may exhibit a discernible pattern over the weeks following the event, and current drug treatments in this region may be adequate for emergency situations.

  16. Geometry and earthquake potential of the shoreline fault, central California

    Science.gov (United States)

    Hardebeck, Jeanne L.

    2013-01-01

    The Shoreline fault is a vertical strike‐slip fault running along the coastline near San Luis Obispo, California. Much is unknown about the Shoreline fault, including its slip rate and the details of its geometry. Here, I study the geometry of the Shoreline fault at seismogenic depth, as well as the adjacent section of the offshore Hosgri fault, using seismicity relocations and earthquake focal mechanisms. The Optimal Anisotropic Dynamic Clustering (OADC) algorithm (Ouillon et al., 2008) is used to objectively identify the simplest planar fault geometry that fits all of the earthquakes to within their location uncertainty. The OADC results show that the Shoreline fault is a single continuous structure that connects to the Hosgri fault. Discontinuities smaller than about 1 km may be undetected, but would be too small to be barriers to earthquake rupture. The Hosgri fault dips steeply to the east, while the Shoreline fault is essentially vertical, so the Hosgri fault dips towards and under the Shoreline fault as the two faults approach their intersection. The focal mechanisms generally agree with pure right‐lateral strike‐slip on the OADC planes, but suggest a non‐planar Hosgri fault or another structure underlying the northern Shoreline fault. The Shoreline fault most likely transfers strike‐slip motion between the Hosgri fault and other faults of the Pacific–North America plate boundary system to the east. A hypothetical earthquake rupturing the entire known length of the Shoreline fault would have a moment magnitude of 6.4–6.8. A hypothetical earthquake rupturing the Shoreline fault and the section of the Hosgri fault north of the Hosgri–Shoreline junction would have a moment magnitude of 7.2–7.5.

  17. Foreshocks of strong earthquakes

    Science.gov (United States)

    Guglielmi, A. V.; Sobisevich, L. E.; Sobisevich, A. L.; Lavrov, I. P.

    2014-07-01

    The specific enhancement of ultra-low-frequency (ULF) electromagnetic oscillations a few hours prior to the strong earthquakes, which was previously mentioned in the literature, motivated us to search for the distinctive features of the mechanical (foreshock) activity of the Earth's crust in the epicentral zones of the future earthquakes. Activation of the foreshocks three hours before the main shock is revealed, which is roughly similar to the enhancement of the specific electromagnetic ULF emission. It is hypothesized that the round-the-world seismic echo signals from the earthquakes, which form the peak of energy release 2 h 50 min before the main events, act as the triggers of the main shocks due to the cumulative action of the surface waves converging to the epicenter. It is established that the frequency of the fluctuations in the foreshock activity decreases at the final stages of the preparation of the main shocks, which probably testifies to the so-called mode softening at the approach of the failure point according to the catastrophe theory.

  18. Earthquake forecasting: Statistics and Information

    CERN Document Server

    Gertsik, V; Krichevets, A

    2013-01-01

    We present an axiomatic approach to earthquake forecasting in terms of multi-component random fields on a lattice. This approach provides a method for constructing point estimates and confidence intervals for conditional probabilities of strong earthquakes under conditions on the levels of precursors. Also, it provides an approach for setting multilevel alarm system and hypothesis testing for binary alarms. We use a method of comparison for different earthquake forecasts in terms of the increase of Shannon information. 'Forecasting' and 'prediction' of earthquakes are equivalent in this approach.

  19. Earthquake forecasting and its verification

    Directory of Open Access Journals (Sweden)

    J. R. Holliday

    2005-01-01

    Full Text Available No proven method is currently available for the reliable short time prediction of earthquakes (minutes to months. However, it is possible to make probabilistic hazard assessments for earthquake risk. In this paper we discuss a new approach to earthquake forecasting based on a pattern informatics (PI method which quantifies temporal variations in seismicity. The output, which is based on an association of small earthquakes with future large earthquakes, is a map of areas in a seismogenic region ('hotspots'' where earthquakes are forecast to occur in a future 10-year time span. This approach has been successfully applied to California, to Japan, and on a worldwide basis. Because a sharp decision threshold is used, these forecasts are binary--an earthquake is forecast either to occur or to not occur. The standard approach to the evaluation of a binary forecast is the use of the relative (or receiver operating characteristic (ROC diagram, which is a more restrictive test and less subject to bias than maximum likelihood tests. To test our PI method, we made two types of retrospective forecasts for California. The first is the PI method and the second is a relative intensity (RI forecast based on the hypothesis that future large earthquakes will occur where most smaller earthquakes have occurred in the recent past. While both retrospective forecasts are for the ten year period 1 January 2000 to 31 December 2009, we performed an interim analysis 5 years into the forecast. The PI method out performs the RI method under most circumstances.

  20. Migrating tremors illuminate complex deformation beneath the seismogenic San Andreas fault

    Science.gov (United States)

    Shelly, D.R.

    2010-01-01

    The San Andreas fault is one of the most extensively studied faults in the world, yet its physical character and deformation mode beneath the relatively shallow earthquake-generating portion remain largely unconstrained. Tectonic non-volcanic tremor, a recently discovered seismic signal probably generated by shear slip on the deep extension of some major faults, can provide new insight into the deep fate of such faults, including that of the San Andreas fault near Parkfield, California. Here I examine continuous seismic data from mid-2001 to 2008, identifying tremor and decomposing the signal into different families of activity based on the shape and timing of the waveforms at multiple stations. This approach allows differentiation between activities from nearby patches of the deep fault and begins to unveil rich and complex patterns of tremor occurrence. I find that tremor exhibits nearly continuous migration, with the most extensive episodes propagating more than 20 kilometres along fault strike at rates of 15-80 kilometres per hour. This suggests that the San Andreas fault remains a localized through-going structure, at least to the base of the crust, in this area. Tremor rates and recurrence behaviour changed markedly in the wake of the 2004 magnitude-6.0 Parkfield earthquake, but these changes were far from uniform within the tremor zone, probably reflecting heterogeneous fault properties and static and dynamic stresses decaying away from the rupture. The systematic recurrence of tremor demonstrated here suggests the potential to monitor detailed time-varying deformation on this portion of the deep San Andreas fault, deformation which unsteadily loads the shallower zone that last ruptured in the 1857 magnitude-7.9 Fort Tejon earthquake. ?? 2010 Macmillan Publishers Limited. All rights reserved.

  1. Scientific drilling into the San Andreas Fault Zone - an overview of SAFOD's first five years

    Science.gov (United States)

    Zoback, Mark; Hickman, Stephen; Ellsworth, William; ,

    2011-01-01

    The San Andreas Fault Observatory at Depth (SAFOD) was drilled to study the physical and chemical processes controlling faulting and earthquake generation along an active, plate-bounding fault at depth. SAFOD is located near Parkfield, California and penetrates a section of the fault that is moving due to a combination of repeating microearthquakes and fault creep. Geophysical logs define the San Andreas Fault Zone to be relatively broad (~200 m), containing several discrete zones only 2–3 m wide that exhibit very low P- and S-wave velocities and low resistivity. Two of these zones have progressively deformed the cemented casing at measured depths of 3192 m and 3302 m. Cores from both deforming zones contain a pervasively sheared, cohesionless, foliated fault gouge that coincides with casing deformation and explains the observed extremely low seismic velocities and resistivity. These cores are being now extensively tested in laboratories around the world, and their composition, deformation mechanisms, physical properties, and rheological behavior are studied. Downhole measurements show that within 200 m (maximum) of the active fault trace, the direction of maximum horizontal stress remains at a high angle to the San Andreas Fault, consistent with other measurements. The results from the SAFOD Main Hole, together with the stress state determined in the Pilot Hole, are consistent with a strong crust/weak fault model of the San Andreas. Seismic instrumentation has been deployed to study physics of faulting—earthquake nucleation, propagation, and arrest—in order to test how laboratory-derived concepts scale up to earthquakes occurring in nature.

  2. The ShakeOut Earthquake Scenario - A Story That Southern Californians Are Writing

    Science.gov (United States)

    Perry, Suzanne; Cox, Dale; Jones, Lucile; Bernknopf, Richard; Goltz, James; Hudnut, Kenneth; Mileti, Dennis; Ponti, Daniel; Porter, Keith; Reichle, Michael; Seligson, Hope; Shoaf, Kimberley; Treiman, Jerry; Wein, Anne

    2008-01-01

    The question is not if but when southern California will be hit by a major earthquake - one so damaging that it will permanently change lives and livelihoods in the region. How severe the changes will be depends on the actions that individuals, schools, businesses, organizations, communities, and governments take to get ready. To help prepare for this event, scientists of the U.S. Geological Survey (USGS) have changed the way that earthquake scenarios are done, uniting a multidisciplinary team that spans an unprecedented number of specialties. The team includes the California Geological Survey, Southern California Earthquake Center, and nearly 200 other partners in government, academia, emergency response, and industry, working to understand the long-term impacts of an enormous earthquake on the complicated social and economic interactions that sustain southern California society. This project, the ShakeOut Scenario, has applied the best current scientific understanding to identify what can be done now to avoid an earthquake catastrophe. More information on the science behind this project will be available in The ShakeOut Scenario (USGS Open-File Report 2008-1150; http://pubs.usgs.gov/of/2008/1150/). The 'what if?' earthquake modeled in the ShakeOut Scenario is a magnitude 7.8 on the southern San Andreas Fault. Geologists selected the details of this hypothetical earthquake by considering the amount of stored strain on that part of the fault with the greatest risk of imminent rupture. From this, seismologists and computer scientists modeled the ground shaking that would occur in this earthquake. Engineers and other professionals used the shaking to produce a realistic picture of this earthquake's damage to buildings, roads, pipelines, and other infrastructure. From these damages, social scientists projected casualties, emergency response, and the impact of the scenario earthquake on southern California's economy and society. The earthquake, its damages, and

  3. THE GREAT SOUTHERN CALIFORNIA SHAKEOUT: Earthquake Science for 22 Million People

    Science.gov (United States)

    Jones, L.; Cox, D.; Perry, S.; Hudnut, K.; Benthien, M.; Bwarie, J.; Vinci, M.; Buchanan, M.; Long, K.; Sinha, S.; Collins, L.

    2008-12-01

    Earthquake science is being communicated to and used by the 22 million residents of southern California to improve resiliency to future earthquakes through the Great Southern California ShakeOut. The ShakeOut began when the USGS partnered with the California Geological Survey, Southern California Earthquake Center and many other organizations to bring 300 scientists and engineers together to formulate a comprehensive description of a plausible major earthquake, released in May 2008, as the ShakeOut Scenario, a description of the impacts and consequences of a M7.8 earthquake on the Southern San Andreas Fault (USGS OFR2008-1150). The Great Southern California ShakeOut was a week of special events featuring the largest earthquake drill in United States history. The ShakeOut drill occurred in houses, businesses, and public spaces throughout southern California at 10AM on November 13, 2008, when southern Californians were asked to pretend that the M7.8 scenario earthquake had occurred and to practice actions that could reduce the impact on their lives. Residents, organizations, schools and businesses registered to participate in the drill through www.shakeout.org where they could get accessible information about the scenario earthquake and share ideas for better reparation. As of September 8, 2008, over 2.7 million confirmed participants had been registered. The primary message of the ShakeOut is that what we do now, before a big earthquake, will determine what our lives will be like after. The goal of the ShakeOut has been to change the culture of earthquake preparedness in southern California, making earthquakes a reality that are regularly discussed. This implements the sociological finding that 'milling,' discussing a problem with loved ones, is a prerequisite to taking action. ShakeOut milling is taking place at all levels from individuals and families, to corporations and governments. Actions taken as a result of the ShakeOut include the adoption of earthquake

  4. Earthquake Declustering via a Nearest-Neighbor Approach in Space-Time-Magnitude Domain

    Science.gov (United States)

    Zaliapin, I. V.; Ben-Zion, Y.

    2016-12-01

    We propose a new method for earthquake declustering based on nearest-neighbor analysis of earthquakes in space-time-magnitude domain. The nearest-neighbor approach was recently applied to a variety of seismological problems that validate the general utility of the technique and reveal the existence of several different robust types of earthquake clusters. Notably, it was demonstrated that clustering associated with the largest earthquakes is statistically different from that of small-to-medium events. In particular, the characteristic bimodality of the nearest-neighbor distances that helps separating clustered and background events is often violated after the largest earthquakes in their vicinity, which is dominated by triggered events. This prevents using a simple threshold between the two modes of the nearest-neighbor distance distribution for declustering. The current study resolves this problem hence extending the nearest-neighbor approach to the problem of earthquake declustering. The proposed technique is applied to seismicity of different areas in California (San Jacinto, Coso, Salton Sea, Parkfield, Ventura, Mojave, etc.), as well as to the global seismicity, to demonstrate its stability and efficiency in treating various clustering types. The results are compared with those of alternative declustering methods.

  5. Marine magnetic survey and onshore gravity and magnetic survey, San Pablo Bay, northern California

    Science.gov (United States)

    Ponce, David A.; Denton, Kevin M.; Watt, Janet T.

    2016-09-12

    IntroductionFrom November 2011 to August 2015, the U.S. Geological Survey (USGS) collected more than 1,000 line-kilometers (length of lines surveyed in kilometers) of marine magnetic data on San Pablo Bay, 98 onshore gravity stations, and over 27 line-kilometers of ground magnetic data in northern California. Combined magnetic and gravity investigations were undertaken to study subsurface geologic structures as an aid in understanding the geologic framework and earthquake hazard potential in the San Francisco Bay Area. Furthermore, marine magnetic data illuminate local subsurface geologic features in the shallow crust beneath San Pablo Bay where geologic exposure is absent.Magnetic and gravity methods, which reflect contrasting physical properties of the subsurface, are ideal for studying San Pablo Bay. Exposed rock units surrounding San Pablo Bay consist mainly of Jurassic Coast Range ophiolite, Great Valley sequence, Franciscan Complex rocks, Miocene sedimentary rocks, and unconsolidated alluvium (Graymer and others, 2006). The contrasting magnetic and density properties of these rocks enable us to map their subsurface extent.

  6. A Study of Current Interseismic Deformation of San Andreas Fault, San Bernardino Mountain section, using Interferometric Synthetic Aperture Radar

    Science.gov (United States)

    Nee, P.; Funning, G. J.

    2010-12-01

    The San Andreas fault (SAF) system accommodates a significant fraction of the relative movement between the Pacific and North American plates. In the past 250 years, no significant earthquake was recorded on the southernmost section of the SAF, and thus there exists a substantial ongoing earthquake hazard. Estimates of its slip deficit rate, made with various geologic and geodetic observations typically fall in the range 15-25 mm/yr, in the vicinity of the San Bernadino Mountains. Assuming the fault system slips at a constant rate of 20mm/yr, a slip deficit of 5 m would have accumulated since the last event, equivalent to a potential Mw 7.5 or larger earthquake. To understand how much strain is accumulating on the southern SAF system during the current interseismic period, we investigate the surface deformation using radar interferometry. We use the entire catalog of ERS and Envisat Synthetic Aperture Radar (SAR) data from a descending track well oriented for the SAF (track 399). 53 images from ERS spanning 1992 to late 2000, and 50 images from Envisat spanning 2003 to 2010 are used. We perform ratemap inversion (Biggs et al. 2007, GJI) to obtain an estimate of interseismic slip deficit rate, and Persistent Scatterer InSAR (PSI) analysis to investigate the tectonic and non-tectonic surface displacements across the region. The ratemap inversion algorithm involves simultaneous estimation of long wavelength orbital errors, construction of a ratemap by finding the best fitting rate of each pixel, and estimation of slip deficit rate using a half-space elastic dislocation model (Okada 1985, BSSA) calculated from a representative fault model. We constructed and tested different conceptual models based on the SCEC rectangular community fault model (CFM-R). We find that our ERS data are strongly affected by the postseismic deformation of the 1992 Mw 7.3 Landers Earthquake. We therefore estimate the slip rate using the Envisat dataset, which is much less affected by the

  7. Wrightwood and the earthquake cycle: What a long recurrence record tells us about how faults work

    Science.gov (United States)

    Weldon, R.; Scharer, K.; Fumal, T.; Biasi, G.

    2004-01-01

    The concept of the earthquake cycle is so well established that one often hears statements in the popular media like, "the Big One is overdue" and "the longer it waits, the bigger it will be." Surprisingly, data to critically test the variability in recurrence intervals, rupture displacements, and relationships between the two are almost nonexistent. To generate a long series of earthquake intervals and offsets, we have conducted paleoseismic investigations across the San Andreas fault near the town of Wrightwood, California, excavating 45 trenches over 18 years, and can now provide some answers to basic questions about recurrence behavior of large earthquakes. To date, we have characterized at least 30 prehistoric earthquakes in a 6000-yr-long record, complete for the past 1500 yr and for the interval 3000-1500 B.C. For the past 1500 yr, the mean recurrence interval is 105 yr (31-165 yr for individual intervals) and the mean slip is 3.2 m (0.7-7 m per event). The series is slightly more ordered than random and has a notable cluster of events, during which strain was released at 3 times the long-term average rate. Slip associated with an earthquake is not well predicted by the interval preceding it, and only the largest two earthquakes appear to affect the time interval to the next earthquake. Generally, short intervals tend to coincide with large displacements and long intervals with small displacements. The most significant correlation we find is that earthquakes are more frequent following periods of net strain accumulation spanning multiple seismic cycles. The extent of paleoearthquake ruptures may be inferred by correlating event ages between different sites along the San Andreas fault. Wrightwood and other nearby sites experience rupture that could be attributed to overlap of relatively independent segments that each behave in a more regular manner. However, the data are equally consistent with a model in which the irregular behavior seen at Wrightwood

  8. GPS coseismic and postseismic surface displacements of the El Mayor-Cucapah earthquake

    Science.gov (United States)

    Gonzalez, A.; Gonzalez-Garcia, J. J.; Sandwell, D. T.; Fialko, Y.; Agnew, D. C.; Lipovsky, B.; Fletcher, J. M.; Nava Pichardo, F. A.

    2010-12-01

    GPS surveys were performed after the El Mayor Cucapah earthquake Mw 7.2 in northern Baja California by scientists from CICESE, UCSD, and UCR. Six of the sites were occupied for several weeks to capture the postseismic deformation within a day of the earthquake. We calculated the coseismic displacement for 22 sites with previous secular velocity in ITRF2005 reference frame and found 1.160±0.016 m of maximum horizontal displacement near the epicentral area at La Puerta location, and 0.636±0.036 m of vertical offset near Ejido Durango. Most of the GPS sites are located East of the main rupture in Mexicali Valley, 5 are located West at Sierra Juarez and South near San Felipe. We present a velocity field before, along with coseismic displacements and early postseismic features related to the El Mayor-Cucapah earthquake.

  9. The San Andreas fault experiment. [gross tectonic plates relative velocity

    Science.gov (United States)

    Smith, D. E.; Vonbun, F. O.

    1973-01-01

    A plan was developed during 1971 to determine gross tectonic plate motions along the San Andreas Fault System in California. Knowledge of the gross motion along the total fault system is an essential component in the construction of realistic deformation models of fault regions. Such mathematical models will be used in the future for studies which will eventually lead to prediction of major earthquakes. The main purpose of the experiment described is the determination of the relative velocity of the North American and the Pacific Plates. This motion being so extremely small, cannot be measured directly but can be deduced from distance measurements between points on opposite sites of the plate boundary taken over a number of years.

  10. Effect of the Loma Prieta Earthquake on surface slip along the Calaveras Fault in the Hollister area

    Science.gov (United States)

    Galehouse, Jon S.

    Over the past ten years we have made over 800 measurements of slip rates at 20 sites on various faults in the San Francisco Bay region. This data set enables us to compare rates and amounts of slip on these various faults before and after the Loma Prieta earthquake (LPEQ) on the San Andreas fault. No surface slip rate changes associated with the earthquake occurred at any of our sites on the San Andreas, Hayward, northern Calaveras, Concord-Green Valley, Seal Cove-San Gregorio, Antioch, Rodgers Creek, or West Napa faults. The LPEQ apparently triggered up to 12-14 mm of right slip on the southern Calaveras fault at our two sites in the Hollister area less than 50 km from the epicenter. Most of this slip was probably coseismic or nearly so. About the same amount of slip was triggered at these sites in 1984 by the Morgan Hill earthquake. This slip, in contrast, occurred as afterslip within about a 2.5-month interval. The Calaveras fault in the Hollister area moves episodically, with shorter times of more rapid slip alternating with longer times of slower slip. The alternation occurs whether or not the times of faster slip are triggered by any nearby seismic event(s).

  11. Effect of the Loma Prieta earthquake on surface slip along the Calaveras fault in the Hollister area

    Energy Technology Data Exchange (ETDEWEB)

    Galehouse, J.S. (San Francisco State Univ., CA (USA))

    1990-07-01

    Over the past ten years the author has made over 800 measurements of slip rates at 20 sites on various faults in the San Francisco Bay region. This data set enables them to compare rates and amounts of slip on these various faults before and after the Loma Prieta earthquake (LPEQ) on the San Andreas fault. No surface slip rate changes associated with the earthquake occurred at any of the sites on the San Andreas, Hayward, northern Calaveras, Concord-Green Valley, Seal Cove-San Gregorio, Antioch, Rodgers Creek, or West Napa faults. The LPEQ apparently triggered up to 12-14 mm of right slip on the southern Calaveras fault at two sites in the Hollister area less than 50 km from the epicenter. Most of this slip was probably coseismic or nearly so. About the same amount of slip was triggered at these sites in 1984 by the Morgan Hill earthquake. This slip, in contrast, occurred as afterslip within about a 2.5-month interval. The Calaveras fault in the Hollister area moves episodically, with shorter times of more rapid slip alternating with longer times of slower slip. The alternation occurs whether or not the times of faster slip are triggered by any nearby seismic event(s).

  12. Seismicity at Fuego, Pacaya, Izalco, and San Cristobal Volcanoes, Central America, 1973-1974

    Science.gov (United States)

    McNutt, S.R.; Harlow, D.H.

    1983-01-01

    Seismic data collected at four volcanoes in Central America during 1973 and 1974 indicate three sources of seismicity: regional earthquakes with hypocentral distances greater than 80 km, earthquakes within 40 km of each volcano, and seismic activity originating at the volcanoes due to eruptive processes. Regional earthquakes generated by the underthrusting and subduction of the Cocos Plate beneath the Caribbean Plate are the most prominent seismic feature in Central America. Earthquakes in the vicinity of the volcanoes occur on faults that appear to be related to volcano formation. Faulting near Fuego and Pacaya volcanoes in Guatemala is more complex due to motion on a major E-W striking transform plate boundary 40 km north of the volcanoes. Volcanic activity produces different kinds of seismic signatures. Shallow tectonic or A-type events originate on nearby faults and occur both singly and in swarms. There are typically from 0 to 6 A-type events per day with b value of about 1.3. At very shallow depths beneath Pacaya, Izalco, and San Cristobal large numbers of low-frequency or B-type events are recorded with predominant frequencies between 2.5 and 4.5 Hz and with b values of 1.7 to 2.9. The relative number of B-type events appears to be related to the eruptive states of the volcanoes; the more active volcanoes have higher levels of seismicity. At Fuego Volcano, however, low-frequency events have unusually long codas and appear to be similar to tremor. High-amplitude volcanic tremor is recorded at Fuego, Pacaya, and San Cristobal during eruptive periods. Large explosion earthquakes at Fuego are well recorded at five stations and yield information on near-surface seismic wave velocities (??=3.0??0.2 km/sec.). ?? 1983 Intern. Association of Volcanology and Chemistry of the Earth's Interior.

  13. Seismic velocities and geologic logs from boreholes at three downhole arrays in San Francisco, California

    Science.gov (United States)

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.; Warrick, Richard E.; Liu, Hsi-Ping; Westerlund, Robert E.

    1994-01-01

    The Loma Prieta earthquake of October 17, 1989 (1704 PST), has reinforced observations made by Wood and others (1908) after the 1906 San Francisco earthquake, that poor ground conditions (soft soil) increase the likelihood of shaking damage to structures. Since 1908 many studies (for example Borcherdt, 1970, Borcherdt and Gibbs, 1976, Borcherdt and Glassmoyer, 1992) have shown that soft soils amplify seismic waves at frequencies that can be damaging to structures. Damage in the City of San Francisco from the Loma Prieta earthquake was concentrated in the Marina District, the Embarcadero, and the China Basin areas. Each of these areas, to some degree, is underlain by soft soil deposits. These concentrations of damage raise important questions regarding the amplification effects of such deposits at damaging levels of motion. Unfortunately, no strong-motion recordings were obtained in these areas during the Loma Prieta earthquake and only a limited number (< 10) have been obtained on other soft soil sites in the United States. Consequently, important questions exist regarding the response of such deposits during damaging earthquakes, especially questions regarding the nonlinear soil response. Towards developing a data set to address these important questions, borehole strong-motion arrays have been installed at three locations. These arrays consist of groups of wide-dynamic-range pore-pressure transducers and three-component accelerometers, the outputs of which are recorded digitally. The arrays are designed to provide an integrated set of data on ground shaking, liquifaction-induced ground failure, and structural response. This report describes the detailed geologic, seismic, and material-property determinations derived at each of these sites.

  14. Response of Olive View Hospital to Northridge and Whittier earthquakes

    Science.gov (United States)

    Celebi, M.

    1997-01-01

    The purpose of this paper is to study the response of the conventionally designed new Olive View Medical Center (OVMC) building at 16 km from the epicenter of the January 17, 1994 Northridge, California earthquake (Ms = 6.8). OVMC is on an alluvial deposit. The building was subjected to design level peak accelerations during the earthquake and suffered only limited structural and nonstructural damage. The recorded motions at different levels of the OVMC building as well as its associated free-field sites are analyzed using spectral analyses and system identification techniques. The new OVMC building was conservatively designed in 1976 with very high lateral load resisting capability - particularly as a reaction to the detrimental fate of the original Olive View Hospital that was heavily damaged during the 1971 San Fernando earthquake. The original hospital building was later razed. The replacement structure, the new cross-shaped OVMC building, experienced peak acceleration of 2.31g at the roof while its peak ground floor acceleration was 0.82g. The free-field peak acceleration was 0.91g. The lateral load resisting system of the OVMC building consists of concrete shear walls in the lower two stories and steel shear walls at the perimeter of the upper four stories. Spectral analysis shows that this stiff structure was not affected by the long duration pulses of the motions recorded at this site.

  15. Earthquakes Threaten Many American Schools

    Science.gov (United States)

    Bailey, Nancy E.

    2010-01-01

    Millions of U.S. children attend schools that are not safe from earthquakes, even though they are in earthquake-prone zones. Several cities and states have worked to identify and repair unsafe buildings, but many others have done little or nothing to fix the problem. The reasons for ignoring the problem include political and financial ones, but…

  16. Make an Earthquake: Ground Shaking!

    Science.gov (United States)

    Savasci, Funda

    2011-01-01

    The main purposes of this activity are to help students explore possible factors affecting the extent of the damage of earthquakes and learn the ways to reduce earthquake damages. In these inquiry-based activities, students have opportunities to develop science process skills and to build an understanding of the relationship among science,…

  17. Make an Earthquake: Ground Shaking!

    Science.gov (United States)

    Savasci, Funda

    2011-01-01

    The main purposes of this activity are to help students explore possible factors affecting the extent of the damage of earthquakes and learn the ways to reduce earthquake damages. In these inquiry-based activities, students have opportunities to develop science process skills and to build an understanding of the relationship among science,…

  18. Anthropogenic triggering of large earthquakes.

    Science.gov (United States)

    Mulargia, Francesco; Bizzarri, Andrea

    2014-08-26

    The physical mechanism of the anthropogenic triggering of large earthquakes on active faults is studied on the basis of experimental phenomenology, i.e., that earthquakes occur on active tectonic faults, that crustal stress values are those measured in situ and, on active faults, comply to the values of the stress drop measured for real earthquakes, that the static friction coefficients are those inferred on faults, and that the effective triggering stresses are those inferred for real earthquakes. Deriving the conditions for earthquake nucleation as a time-dependent solution of the Tresca-Von Mises criterion applied in the framework of poroelasticity yields that active faults can be triggered by fluid overpressures oil and gas production and storage may trigger destructive earthquakes on active faults at a few tens of kilometers. Fluid pressure propagates as slow stress waves along geometric paths operating in a drained condition and can advance the natural occurrence of earthquakes by a substantial amount of time. Furthermore, it is illusory to control earthquake triggering by close monitoring of minor "foreshocks", since the induction may occur with a delay up to several years.

  19. Heavy tails and earthquake probabilities

    Science.gov (United States)

    Ellsworth, William L.

    2012-01-01

    The 21st century has already seen its share of devastating earthquakes, some of which have been labeled as “unexpected,” at least in the eyes of some seismologists and more than a few journalists. A list of seismological surprises could include the 2004 Sumatra-Andaman Islands; 2008 Wenchuan, China; 2009 Haiti; 2011 Christchurch, New Zealand; and 2011 Tohoku, Japan, earthquakes

  20. Earthquakes Threaten Many American Schools

    Science.gov (United States)

    Bailey, Nancy E.

    2010-01-01

    Millions of U.S. children attend schools that are not safe from earthquakes, even though they are in earthquake-prone zones. Several cities and states have worked to identify and repair unsafe buildings, but many others have done little or nothing to fix the problem. The reasons for ignoring the problem include political and financial ones, but…

  1. Can Satellites Aid Earthquake Predictions?

    Institute of Scientific and Technical Information of China (English)

    John Roach; 李晓辉

    2004-01-01

    @@ Earthquake prediction is an imprecise science, and to illustrate the point,many experts point to the story of Tangshen①, China. On July 28, 1976, a magnitude② 7. 6 earthquake struck the city of Tangshen, China, without warning. None of the signs of the successful prediction from a year and half earlier were present. An estimated 250,000 people died.

  2. Ground-motion modeling of Hayward fault scenario earthquakes, part II: Simulation of long-period and broadband ground motions

    Science.gov (United States)

    Aagaard, Brad T.; Graves, Robert W.; Rodgers, Arthur; Brocher, Thomas M.; Simpson, Robert W.; Dreger, Douglas; Petersson, N. Anders; Larsen, Shawn C.; Ma, Shuo; Jachens, Robert C.

    2010-01-01

    We simulate long-period (T>1.0–2.0 s) and broadband (T>0.1 s) ground motions for 39 scenario earthquakes (Mw 6.7–7.2) involving the Hayward, Calaveras, and Rodgers Creek faults. For rupture on the Hayward fault, we consider the effects of creep on coseismic slip using two different approaches, both of which reduce the ground motions, compared with neglecting the influence of creep. Nevertheless, the scenario earthquakes generate strong shaking throughout the San Francisco Bay area, with about 50% of the urban area experiencing modified Mercalli intensity VII or greater for the magnitude 7.0 scenario events. Long-period simulations of the 2007 Mw 4.18 Oakland earthquake and the 2007 Mw 5.45 Alum Rock earthquake show that the U.S. Geological Survey’s Bay Area Velocity Model version 08.3.0 permits simulation of the amplitude and duration of shaking throughout the San Francisco Bay area for Hayward fault earthquakes, with the greatest accuracy in the Santa Clara Valley (San Jose area). The ground motions for the suite of scenarios exhibit a strong sensitivity to the rupture length (or magnitude), hypocenter (or rupture directivity), and slip distribution. The ground motions display a much weaker sensitivity to the rise time and rupture speed. Peak velocities, peak accelerations, and spectral accelerations from the synthetic broadband ground motions are, on average, slightly higher than the Next Generation Attenuation (NGA) ground-motion prediction equations. We attribute much of this difference to the seismic velocity structure in the San Francisco Bay area and how the NGA models account for basin amplification; the NGA relations may underpredict amplification in shallow sedimentary basins. The simulations also suggest that the Spudich and Chiou (2008) directivity corrections to the NGA relations could be improved by increasing the areal extent of rupture directivity with period.

  3. Vegetation - San Felipe Valley [ds172

    Data.gov (United States)

    California Department of Resources — This Vegetation Map of the San Felipe Valley Wildlife Area in San Diego County, California is based on vegetation samples collected in the field in 2002 and 2005 and...

  4. Earthquake Loss Estimation Uncertainties

    Science.gov (United States)

    Frolova, Nina; Bonnin, Jean; Larionov, Valery; Ugarov, Aleksander

    2013-04-01

    The paper addresses the reliability issues of strong earthquakes loss assessment following strong earthquakes with worldwide Systems' application in emergency mode. Timely and correct action just after an event can result in significant benefits in saving lives. In this case the information about possible damage and expected number of casualties is very critical for taking decision about search, rescue operations and offering humanitarian assistance. Such rough information may be provided by, first of all, global systems, in emergency mode. The experience of earthquakes disasters in different earthquake-prone countries shows that the officials who are in charge of emergency response at national and international levels are often lacking prompt and reliable information on the disaster scope. Uncertainties on the parameters used in the estimation process are numerous and large: knowledge about physical phenomena and uncertainties on the parameters used to describe them; global adequacy of modeling techniques to the actual physical phenomena; actual distribution of population at risk at the very time of the shaking (with respect to immediate threat: buildings or the like); knowledge about the source of shaking, etc. Needless to be a sharp specialist to understand, for example, that the way a given building responds to a given shaking obeys mechanical laws which are poorly known (if not out of the reach of engineers for a large portion of the building stock); if a carefully engineered modern building is approximately predictable, this is far not the case for older buildings which make up the bulk of inhabited buildings. The way population, inside the buildings at the time of shaking, is affected by the physical damage caused to the buildings is not precisely known, by far. The paper analyzes the influence of uncertainties in strong event parameters determination by Alert Seismological Surveys, of simulation models used at all stages from, estimating shaking intensity

  5. Testing earthquake source inversion methodologies

    KAUST Repository

    Page, Morgan T.

    2011-01-01

    Source Inversion Validation Workshop; Palm Springs, California, 11-12 September 2010; Nowadays earthquake source inversions are routinely performed after large earthquakes and represent a key connection between recorded seismic and geodetic data and the complex rupture process at depth. The resulting earthquake source models quantify the spatiotemporal evolution of ruptures. They are also used to provide a rapid assessment of the severity of an earthquake and to estimate losses. However, because of uncertainties in the data, assumed fault geometry and velocity structure, and chosen rupture parameterization, it is not clear which features of these source models are robust. Improved understanding of the uncertainty and reliability of earthquake source inversions will allow the scientific community to use the robust features of kinematic inversions to more thoroughly investigate the complexity of the rupture process and to better constrain other earthquakerelated computations, such as ground motion simulations and static stress change calculations.

  6. Earthquake forecasting: statistics and information

    Directory of Open Access Journals (Sweden)

    Vladimir Gertsik

    2016-01-01

    Full Text Available The paper presents a decision rule forming a mathematical basis of earthquake forecasting problem. We develop an axiomatic approach to earthquake forecasting in terms of multicomponent random fields on a lattice. This approach provides a method for constructing point estimates and confidence intervals for conditional probabilities of strong earthquakes under conditions on the levels of precursors. Also, it provides an approach for setting a multilevel alarm system and hypothesis testing for binary alarms. We use a method of comparison for different algorithms of earthquake forecasts in terms of the increase of Shannon information. ‘Forecasting’ (the calculation of the probabilities and ‘prediction’ (the alarm declaring of earthquakes are equivalent in this approach.

  7. Are Earthquakes a Critical Phenomenon?

    Science.gov (United States)

    Ramos, O.

    2014-12-01

    Earthquakes, granular avalanches, superconducting vortices, solar flares, and even stock markets are known to evolve through power-law distributed events. During decades, the formalism of equilibrium phase transition has coined these phenomena as critical, which implies that they are also unpredictable. This work revises these ideas and uses earthquakes as the paradigm to demonstrate that slowly driven systems evolving through uncorrelated and power-law distributed avalanches (UPLA) are not necessarily critical systems, and therefore not necessarily unpredictable. By linking the correlation length to the pdf of the distribution, and comparing it with the one obtained at a critical point, a condition of criticality is introduced. Simulations in the classical Olami-Feder-Christensen (OFC) earthquake model confirm the findings, showing that earthquakes are not a critical phenomenon. However, one single catastrophic earthquake may show critical properties and, paradoxically, the emergence of this temporal critical behaviour may eventually carry precursory signs of catastrophic events.

  8. 75 FR 39166 - Safety Zone; San Francisco Giants Baseball Game Promotion, San Francisco, CA

    Science.gov (United States)

    2010-07-08

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Francisco Giants Baseball Game... Bay off San Francisco, CA in support of the San Francisco Giants Baseball Game Promotion. This safety... Giants will sponsor the San Francisco Giants Baseball Game Promotion on July 16, 2010, on the...

  9. 78 FR 21403 - Notice of Inventory Completion: San Francisco State University NAGPRA Program, San Francisco, CA

    Science.gov (United States)

    2013-04-10

    ... NAGPRA Program, c/o Department of Anthropology, San Francisco State University, 1600 Holloway Avenue, San...: Pursuant to 25 U.S.C. 3001(9), the human remains described in this notice represent the physical remains of... NAGPRA Program, c/o Department of Anthropology, San Francisco State University, 1600 Holloway Avenue, San...

  10. 76 FR 55796 - Safety Zone; TriRock Triathlon, San Diego Bay, San Diego, CA

    Science.gov (United States)

    2011-09-09

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; TriRock Triathlon, San Diego Bay, San Diego.... Basis and Purpose Competitor Group is sponsoring the TriRock Triathlon, consisting of 2000 swimmers....T11-431 Safety Zone; TriRock Triathlon, San Diego Bay, San Diego, CA. (a) Location. The limits of...

  11. 76 FR 45693 - Safety Zone; San Diego POPS Fireworks, San Diego, CA

    Science.gov (United States)

    2011-08-01

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego POPS Fireworks, San Diego, CA... temporary safety zone on the navigable waters of San Diego Bay in support of the San Diego POPS Fireworks... Diego, CA; telephone (619) 278- 7262, e-mail Shane.E.Jakcson@uscg.mil . If you have questions on viewing...

  12. 78 FR 38584 - Safety Zone; San Diego Symphony Summer POPS Fireworks 2013 Season, San Diego, CA

    Science.gov (United States)

    2013-06-27

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Symphony Summer POPS Fireworks 2013 Season, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of San Diego Bay in support of the San Diego...

  13. 76 FR 75908 - Notice of Inventory Completion: The University of California, San Diego, San Diego, CA

    Science.gov (United States)

    2011-12-05

    ... National Park Service Notice of Inventory Completion: The University of California, San Diego, San Diego... California on behalf of the University of California, San Diego, have completed an inventory of human remains... contact the University of California, San Diego. Disposition of the human remains and associated funerary...

  14. 77 FR 42647 - Safety Zone: San Diego Symphony POPS Fireworks; San Diego, CA

    Science.gov (United States)

    2012-07-20

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone: San Diego Symphony POPS Fireworks; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of San Diego Bay in support of the San Diego Symphony POPS...

  15. 75 FR 77756 - Safety Zone; San Diego Parade of Lights Fireworks, San Diego, CA

    Science.gov (United States)

    2010-12-14

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; San Diego Parade of Lights Fireworks, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone upon the navigable water of the San Diego Bay in San Diego, CA in support of the two...

  16. The San Bernabe power substation; La subestacion San Bernabe

    Energy Technology Data Exchange (ETDEWEB)

    Chavez Sanudo, Andres D. [Luz y Fuerza del Centro, Mexico, D. F. (Mexico)

    1997-12-31

    The first planning studies that gave rise to the San Bernabe substation go back to year 1985. The main circumstance that supports this decision is the gradual restriction for electric power generation that has been suffering the Miguel Aleman Hydro System, until its complete disappearance, to give priority to the potable water supply through the Cutzamala pumping system, that feeds in an important way Mexico City and the State of Mexico. In this document the author describes the construction project of the San Bernabe Substation; mention is made of the technological experiences obtained during the construction and its geographical location is shown, as well as the one line diagram of the same [Espanol] Los primeros estudios de planeacion que dieron origen a la subestacion San Bernabe se remontan al ano de 1985. La circunstancia principal que soporta esta decision es la restriccion paulatina para generar energia que ha venido experimentando el Sistema Hidroelectrico Miguel Aleman, hasta su desaparicion total, para dar prioridad al suministro de agua potable por medio del sistema de bombeo Cutzamala, que alimenta en forma importante a la Ciudad de Mexico y al Estado de Mexico. En este documento el autor describe el proyecto de construccion de la subestacion San Bernabe; se mencionan las experiencias tecnologicas obtenidas durante su construccion y se ilustra su ubicacion geografica, asi como un diagrama unifilar de la misma

  17. Injuries and Traumatic Psychological Exposures Associated with the South Napa Earthquake - California, 2014.

    Science.gov (United States)

    Attfield, Kathleen R; Dobson, Christine B; Henn, Jennifer B; Acosta, Meileen; Smorodinsky, Svetlana; Wilken, Jason A; Barreau, Tracy; Schreiber, Merritt; Windham, Gayle C; Materna, Barbara L; Roisman, Rachel

    2015-09-11

    On August 24, 2014, at 3:20 a.m., a magnitude 6.0 earthquake struck California, with its epicenter in Napa County (1). The earthquake was the largest to affect the San Francisco Bay area in 25 years and caused significant damage in Napa and Solano counties, including widespread power outages, five residential fires, and damage to roadways, waterlines, and 1,600 buildings (2). Two deaths resulted (2). On August 25, Napa County Public Health asked the California Department of Public Health (CDPH) for assistance in assessing postdisaster health effects, including earthquake-related injuries and effects on mental health. On September 23, Solano County Public Health requested similar assistance. A household-level Community Assessment for Public Health Emergency Response (CASPER) was conducted for these counties in two cities (Napa, 3 weeks after the earthquake, and Vallejo, 6 weeks after the earthquake). Among households reporting injuries, a substantial proportion (48% in Napa and 37% in western Vallejo) reported that the injuries occurred during the cleanup period, suggesting that increased messaging on safety precautions after a disaster might be needed. One fifth of respondents overall (27% in Napa and 9% in western Vallejo) reported one or more traumatic psychological exposures in their households. These findings were used by Napa County Mental Health to guide immediate-term mental health resource allocations and to conduct public training sessions and education campaigns to support persons with mental health risks following the earthquake. In addition, to promote community resilience and future earthquake preparedness, Napa County Public Health subsequently conducted community events on the earthquake anniversary and provided outreach workers with psychological first aid training.

  18. Subsurface structure of the East Bay Plain ground-water basin: San Francisco Bay to the Hayward fault, Alameda County, California

    Science.gov (United States)

    Catchings, R.D.; Borchers, J.W.; Goldman, M.R.; Gandhok, G.; Ponce, D.A.; Steedman, C.E.

    2006-01-01

    The area of California between the San Francisco Bay, San Pablo Bay, Santa Clara Valley, and the Diablo Ranges (East Bay Hills), commonly referred to as the 'East Bay', contains the East Bay Plain and Niles Cone ground-water basins. The area has a population of 1.46 million (2003 US Census), largely distributed among several cities, including Alameda, Berkeley, Fremont, Hayward, Newark, Oakland, San Leandro, San Lorenzo, and Union City. Major known tectonic structures in the East Bay area include the Hayward Fault and the Diablo Range to the east and a relatively deep sedimentary basin known as the San Leandro Basin beneath the eastern part of the bay. Known active faults, such as the Hayward, Calaveras, and San Andreas pose significant earthquake hazards to the region, and these and related faults also affect ground-water flow in the San Francisco Bay area. Because most of the valley comprising the San Francisco Bay area is covered by Holocene alluvium or water at the surface, our knowledge of the existence and locations of such faults, their potential hazards, and their effects on ground-water flow within the alluvial basins is incomplete. To better understand the subsurface stratigraphy and structures and their effects on ground-water and earthquake hazards, the U.S. Geological Survey (USGS), in cooperation with the East Bay Municipal Utility District (EBMUD), acquired a series of high-resolution seismic reflection and refraction profiles across the East Bay Plain near San Leandro in June 2002. In this report, we present results of the seismic imaging investigations, with emphasis on ground water.

  19. Interrelation of geomagnetic storms and earthquakes: Insight from lab experiments and field observations

    Science.gov (United States)

    Ruzhin, Yuri; Kamogawa, Masashi; Novikov, Victor

    statistical approach for the problem of ionosphere-lithosphere coupling, and in each case the possible behavior of fluids should be considered under electromagnetic impact on lithosphere. Experimental results supporting this idea are obtained at the spring-block model simulating the seismic cycle (slow accumulation and sharp drop of stresses in the fault gauge), as well as from field observations of water level variations in the well during ionospheric disturbances are presented and discussed. In the lab experiments it was shown that the earthquake may be triggered by very small fluid content injected into the simulated fault (earthquake activity and geomagnetic Sq-variations // Natural Hazards and Earth System Sciences, 3, 2003, p.p.171-177. 2. Novikov V.A. Water imbalance in the geological fault as a possible earthquake trigger // AGU 2012 Fall Meeting, Dec. 3-8, San Francisco, USA, Abstract GC42B-08.

  20. The CATDAT damaging earthquakes database

    Directory of Open Access Journals (Sweden)

    J. E. Daniell

    2011-08-01

    Full Text Available The global CATDAT damaging earthquakes and secondary effects (tsunami, fire, landslides, liquefaction and fault rupture database was developed to validate, remove discrepancies, and expand greatly upon existing global databases; and to better understand the trends in vulnerability, exposure, and possible future impacts of such historic earthquakes.

    Lack of consistency and errors in other earthquake loss databases frequently cited and used in analyses was a major shortcoming in the view of the authors which needed to be improved upon.

    Over 17 000 sources of information have been utilised, primarily in the last few years, to present data from over 12 200 damaging earthquakes historically, with over 7000 earthquakes since 1900 examined and validated before insertion into the database. Each validated earthquake includes seismological information, building damage, ranges of social losses to account for varying sources (deaths, injuries, homeless, and affected, and economic losses (direct, indirect, aid, and insured.

    Globally, a slightly increasing trend in economic damage due to earthquakes is not consistent with the greatly increasing exposure. The 1923 Great Kanto ($214 billion USD damage; 2011 HNDECI-adjusted dollars compared to the 2011 Tohoku (>$300 billion USD at time of writing, 2008 Sichuan and 1995 Kobe earthquakes show the increasing concern for economic loss in urban areas as the trend should be expected to increase. Many economic and social loss values not reported in existing databases have been collected. Historical GDP (Gross Domestic Product, exchange rate, wage information, population, HDI (Human Development Index, and insurance information have been collected globally to form comparisons.

    This catalogue is the largest known cross-checked global historic damaging earthquake database and should have far-reaching consequences for earthquake loss estimation, socio-economic analysis, and the global

  1. In-situ measurements of seismic velocities in the San Francisco Bay region...part II

    Science.gov (United States)

    Gibbs, James F.; Fumal, Thomas E.; Borcherdt, Roger D.

    1976-01-01

    Seismic wave velocities (compressional and shear) are important parameters for determining the seismic response characteristics of various geologic units when subjected to strong earthquake ground shaking. Seismic velocities of various units often show a strong correlation with the amounts of damage following large earthquakes and have been used as a basis for certain types of seismic zonation studies. Currently a program is in progress to measure seismic velocities in the San Francisco Bay region at an estimated 150 sites. At each site seismic travel times are measured in drill holes, normally at 2.5-m intervals to a depth of 30 m. Geologic logs are determined from drill hole cuttings, undisturbed samples, and penetrometer samples. The data provide a detailed comparison of geologic and seismic characteristics and provide parameters for estimating strong earthquake ground motions quantitatively at each of the site. A major emphasis of this program is to obtain a detailed comparison of geologic and seismic data on a regional scale for use in seismic zonation. The broad data base available in the San Francisco Bay region suggests using the area as a pilot area for the development of general techniques applicable to other areas.

  2. The 2015 Gorkha Nepal Earthquake: Insights from Earthquake Damage Survey

    Directory of Open Access Journals (Sweden)

    Katsuichiro eGoda

    2015-06-01

    Full Text Available The 2015 Gorkha Nepal earthquake caused tremendous damage and loss. To gain valuable lessons from this tragic event, an earthquake damage investigation team was dispatched to Nepal from 1 May 2015 to 7 May 2015. A unique aspect of the earthquake damage investigation is that first-hand earthquake damage data were obtained 6 to 11 days after the mainshock. To gain deeper understanding of the observed earthquake damage in Nepal, the paper reviews the seismotectonic setting and regional seismicity in Nepal and analyzes available aftershock data and ground motion data. The earthquake damage observations indicate that the majority of the damaged buildings were stone/brick masonry structures with no seismic detailing, whereas the most of RC buildings were undamaged. This indicates that adequate structural design is the key to reduce the earthquake risk in Nepal. To share the gathered damage data widely, the collected damage data (geo-tagged photos and observation comments are organized using Google Earth and the kmz file is made publicly available.

  3. A Spanish Borderlands Community: San Antonio.

    Science.gov (United States)

    Teja, Jesus F. de la

    2000-01-01

    Discusses the founding of San Antonio, originally San Antonio de Bexar, which, in 1718, came into being as a military settlement involved in Spanish imperial defensive measures. Focuses on the development and continued growth of San Antonio, Texas's most populous city in the 19th century. (CMK)

  4. 7th U.S. / Japan Natural Resources (UJNR) Panel on Earthquake Research: Abstract Volume and Technical Program

    Science.gov (United States)

    Detweiler, Shane T.; Ellsworth, William L.

    2008-01-01

    The U.S. / Japan Natural Resources (UJNR) Panel on Earthquake Research promotes advanced study toward a more fundamental understanding of the earthquake process and hazard estimation. The Panel promotes basic and applied research to improve our understanding of the causes and effects of earthquakes and to facilitate the transmission of research results to those who implement hazard reduction measures on both sides of the Pacific and around the world. Meetings are held every other year, and alternate between countries with short presentation on current research and local field trips being the highlights. The 5th Joint Panel meeting was held at Asilomar, California in October, 2004. The technical sessions featured reports on the September 28, 2004 Parkfield, California earthquake, progress on earthquake early warning and rapid post-event assessment technology, probabilistic earthquake forecasting and the newly discovered phenomenon of nonvolcanic tremor. The Panel visited the epicentral region of the M 6.0 Parkfield earthquake and viewed the surface ruptures along the San Andreas Fault. They also visited the San Andreas Fault Observatory at Depth (SAFOD), which had just completed the first phase of drilling into the fault. The 6th Joint Panel meeting was held in Tokushima, Japan in November, 2006. The meeting included very productive exchanges of information on approaches to systematic observation of earthquake processes. Sixty eight technical papers were presented during the meeting on a wide range of subjects, including interplate earthquakes in subduction zones, slow slip and nonvolcanic tremor, crustal deformation, recent earthquake activity and hazard mapping. Through our discussion, we reaffirmed the benefits of working together to achieve our common goal of reducing earthquake hazard, continued cooperation on issues involving densification of observation networks and the open exchange of data among scientific communities. We also reaffirmed the importance of

  5. Subdiffusion of volcanic earthquakes

    CERN Document Server

    Abe, Sumiyoshi

    2016-01-01

    A comparative study is performed on volcanic seismicities at Mt.Eyjafjallajokull in Iceland and Mt. Etna in Sicily, Italy, from the viewpoint of science of complex systems, and the discovery of remarkable similarities between them regarding their exotic spatio-temporal properties is reported. In both of the volcanic seismicities as point processes, the jump probability distributions of earthquakes are found to obey the exponential law, whereas the waiting-time distributions follow the power law. In particular, a careful analysis is made about the finite size effects on the waiting-time distributions, and accordingly, the previously reported results for Mt. Etna [S. Abe and N. Suzuki, EPL 110, 59001 (2015)] are reinterpreted. It is shown that spreads of the volcanic earthquakes are subdiffusive at both of the volcanoes. The aging phenomenon is observed in the "event-time-averaged" mean-squared displacements of the hypocenters. A comment is also made on presence/absence of long term memories in the context of t...

  6. Revised seismic history of the El Pilar fault, Northeastern Venezuela, from the Cariaco 1997 earthquake and recent preliminary paleoseismic results

    Science.gov (United States)

    Audemard, Franck A.

    2007-07-01

    In light of the July 9, 1997, Cariaco earthquake, it is clearly understood now that damage in the city of Cumaná located in northeastern Venezuela and frequently destroyed by the largest earthquakes since the first recorded event in 1530 is strongly enhanced by poor soil conditions that, in turn, are responsible for site amplification and widespread earthquake-induced effects. Therefore, most previous macroseismic studies of historical earthquakes must be revaluated because those localized high-intensity values at Cumaná surely led to the misestimation of past epicenters. Preliminary paleoseismic results, gathered at three exploratory trenches dug across the surface break of the Cariaco 1997 earthquake in 1998, allow us to associate the 1684 earthquake with this recently ruptured fault segment that extends between the towns of San Antonio del Golfo and Río Casanay (roughly between the two gulfs of Cariaco and Paria, state of Sucre). Other major results from the reassessment of the seismic history of this fault are: (a) the 1766 event seems to have generated in a different source to the El Pilar fault because the size of the felt area suggests that it is an intermediate-depth earthquake; (b) damage to Cumaná produced by the 1797 event suggests that this was a local earthquake, perhaps equivalent to the 1929 earthquake, which ruptured for some 30 km just east of Cumaná into the Gulf of Cariaco; and (c) seismogenic association of the 1530 and 1853 earthquakes still remains unclear but it is very likely that these ruptures occurred offshore, as suggested by the rather large tsunami waves that both events have generated, placing their hypocenters west of Cumaná in the Cariaco Trough. This reassessment also sheds light into the El Pilar fault segmentation and the behavior of its seismogenic barriers through time.

  7. Determination of Design Basis Earthquake ground motion

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Muneaki [Japan Atomic Power Co., Tokyo (Japan)

    1997-03-01

    This paper describes principle of determining of Design Basis Earthquake following the Examination Guide, some examples on actual sites including earthquake sources to be considered, earthquake response spectrum and simulated seismic waves. In sppendix of this paper, furthermore, seismic safety review for N.P.P designed before publication of the Examination Guide was summarized with Check Basis Earthquake. (J.P.N.)

  8. Earthquakes: Risk, Monitoring, Notification, and Research

    Science.gov (United States)

    2008-06-19

    far away as Bangladesh , Taiwan, Thailand, and Vietnam. Several large aftershocks have occurred since the main seismic event. The May 12 earthquake...motion of tectonic plates; ! Earthquake geology and paleoseismology: studies of the history, effects, and mechanics of earthquakes; ! Earthquake hazards

  9. Convair Astronautics, San Diego (California

    Directory of Open Access Journals (Sweden)

    Pereira & Luckmam, Arquitectos

    1960-05-01

    Full Text Available Este brillante y espectacular complejo industrial se ha creado especialmente para la investigación y fabricación de cohetes intercontinentales y vehículos del espacio de las Fuerzas Aéreas de los EE. UU., en las proximidades de San Diego y cerca del campo de pruebas de Sycamore Canyon.

  10. 2010 Chile Earthquake Aftershock Response

    Science.gov (United States)

    Barientos, Sergio

    2010-05-01

    The Mw=8.8 earthquake off the coast of Chile on 27 February 2010 is the 5th largest megathrust earthquake ever to be recorded and provides an unprecedented opportunity to advance our understanding of megathrust earthquakes and associated phenomena. The 2010 Chile earthquake ruptured the Concepcion-Constitucion segment of the Nazca/South America plate boundary, south of the Central Chile region and triggered a tsunami along the coast. Following the 2010 earthquake, a very energetic aftershock sequence is being observed in an area that is 600 km along strike from Valparaiso to 150 km south of Concepcion. Within the first three weeks there were over 260 aftershocks with magnitude 5.0 or greater and 18 with magnitude 6.0 or greater (NEIC, USGS). The Concepcion-Constitucion segment lies immediately north of the rupture zone associated with the great magnitude 9.5 Chile earthquake, and south of the 1906 and the 1985 Valparaiso earthquakes. The last great subduction earthquake in the region dates back to the February 1835 event described by Darwin (1871). Since 1835, part of the region was affected in the north by the Talca earthquake in December 1928, interpreted as a shallow dipping thrust event, and by the Chillan earthquake (Mw 7.9, January 1939), a slab-pull intermediate depth earthquake. For the last 30 years, geodetic studies in this area were consistent with a fully coupled elastic loading of the subduction interface at depth; this led to identify the area as a mature seismic gap with potential for an earthquake of magnitude of the order 8.5 or several earthquakes of lesser magnitude. What was less expected was the partial rupturing of the 1985 segment toward north. Today, the 2010 earthquake raises some disturbing questions: Why and how the rupture terminated where it did at the northern end? How did the 2010 earthquake load the adjacent segment to the north and did the 1985 earthquake only partially ruptured the plate interface leaving loaded asperities since

  11. The physics of an earthquake

    Science.gov (United States)

    McCloskey, John

    2008-03-01

    The Sumatra-Andaman earthquake of 26 December 2004 (Boxing Day 2004) and its tsunami will endure in our memories as one of the worst natural disasters of our time. For geophysicists, the scale of the devastation and the likelihood of another equally destructive earthquake set out a series of challenges of how we might use science not only to understand the earthquake and its aftermath but also to help in planning for future earthquakes in the region. In this article a brief account of these efforts is presented. Earthquake prediction is probably impossible, but earth scientists are now able to identify particularly dangerous places for future events by developing an understanding of the physics of stress interaction. Having identified such a dangerous area, a series of numerical Monte Carlo simulations is described which allow us to get an idea of what the most likely consequences of a future earthquake are by modelling the tsunami generated by lots of possible, individually unpredictable, future events. As this article was being written, another earthquake occurred in the region, which had many expected characteristics but was enigmatic in other ways. This has spawned a series of further theories which will contribute to our understanding of this extremely complex problem.

  12. A new reference global instrumental earthquake catalogue (1900-2009)

    Science.gov (United States)

    Di Giacomo, D.; Engdahl, B.; Bondar, I.; Storchak, D. A.; Villasenor, A.; Bormann, P.; Lee, W.; Dando, B.; Harris, J.

    2011-12-01

    For seismic hazard studies on a global and/or regional scale, accurate knowledge of the spatial distribution of seismicity, the magnitude-frequency relation and the maximum magnitudes is of fundamental importance. However, such information is normally not homogeneous (or not available) for the various seismically active regions of the Earth. To achieve the GEM objectives (www.globalquakemodel.org) of calculating and communicating earthquake risk worldwide, an improved reference global instrumental catalogue for large earthquakes spanning the entire 100+ years period of instrumental seismology is an absolute necessity. To accomplish this task, we apply the most up-to-date techniques and standard observatory practices for computing the earthquake location and magnitude. In particular, the re-location procedure benefits both from the depth determination according to Engdahl and Villaseñor (2002), and the advanced technique recently implemented at the ISC (Bondár and Storchak, 2011) to account for correlated error structure. With regard to magnitude, starting from the re-located hypocenters, the classical surface and body-wave magnitudes are determined following the new IASPEI standards and by using amplitude-period data of phases collected from historical station bulletins (up to 1970), which were not available in digital format before the beginning of this work. Finally, the catalogue will provide moment magnitude values (including uncertainty) for each seismic event via seismic moment, via surface wave magnitude or via other magnitude types using empirical relationships. References Engdahl, E.R., and A. Villaseñor (2002). Global seismicity: 1900-1999. In: International Handbook of Earthquake and Engineering Seismology, eds. W.H.K. Lee, H. Kanamori, J.C. Jennings, and C. Kisslinger, Part A, 665-690, Academic Press, San Diego. Bondár, I., and D. Storchak (2011). Improved location procedures at the International Seismological Centre, Geophys. J. Int., doi:10.1111/j

  13. Early aftershock decay rate of the M6 Parkfield earthquake

    Science.gov (United States)

    Peng, Z.; Vidale, J. E.

    2004-12-01

    Mainshock rupture is typically followed by its aftershocks that diminish in rate approximately as the reciprocal of the elapse time. However, it is notoriously difficult to observe aftershock activity in the noisy aftermath of larger earthquakes. Many aftershocks were missed in the existing seismicity catalogs in the initial few minutes (Kagan, 2004). Yet this period holds valuable information about the transition from mainshock rupture to sporadic aftershocks, and the friction laws that control earthquakes. The Parkfield section of the San Andreas fault is one of most densely seismometered places in the world. Many near-fault, non-clipped and continuous recordings of the M6 Parkfield earthquake and its aftermath have been recovered, providing an excellent opportunity for us to study the aftershock decay rates in the first few hundred seconds after the mainshock. We have so far analyzed recordings from station PKD and 13 stations in the Parkfield High Resolution Seismic Network. By scrutinizing the high-frequency signal, we are able to distinguish mainshock coda from early aftershocks. We find up to 10 times more aftershocks in the first 1000 s than in the USGS NCSN catalog. More than 30 events are detected in the first 200 s after the mainshock. None of these events are in the USGS NCSN catalog. Preliminary results suggest a strong deficit of aftershocks in the first 100 s after the mainshock relative to a 1/t aftershock rate decay. This pattern is consistent with a lack of seismicity in the first 120 s following the 10/31/2001 M5.1 Anza earthquake (Kilb et al., 2004), and our study of early aftershock rates using data from HiNet array in Japan (Vidale et al., 2004). Our observations will allow us to test the prediction of such an interval in rate-and-state friction models prior to the onset of the 1/t aftershock decay rate (Dieterich, 1994).

  14. Fracking, wastewater disposal, and earthquakes

    Science.gov (United States)

    McGarr, Arthur

    2016-03-01

    In the modern oil and gas industry, fracking of low-permeability reservoirs has resulted in a considerable increase in the production of oil and natural gas, but these fluid-injection activities also can induce earthquakes. Earthquakes induced by fracking are an inevitable consequence of the injection of fluid at high pressure, where the intent is to enhance permeability by creating a system of cracks and fissures that allow hydrocarbons to flow to the borehole. The micro-earthquakes induced during these highly-controlled procedures are generally much too small to be felt at the surface; indeed, the creation or reactivation of a large fault would be contrary to the goal of enhancing permeability evenly throughout the formation. Accordingly, the few case histories for which fracking has resulted in felt earthquakes have been due to unintended fault reactivation. Of greater consequence for inducing earthquakes, modern techniques for producing hydrocarbons, including fracking, have resulted in considerable quantities of coproduced wastewater, primarily formation brines. This wastewater is commonly disposed by injection into deep aquifers having high permeability and porosity. As reported in many case histories, pore pressure increases due to wastewater injection were channeled from the target aquifers into fault zones that were, in effect, lubricated, resulting in earthquake slip. These fault zones are often located in the brittle crystalline rocks in the basement. Magnitudes of earthquakes induced by wastewater disposal often exceed 4, the threshold for structural damage. Even though only a small fraction of disposal wells induce earthquakes large enough to be of concern to the public, there are so many of these wells that this source of seismicity contributes significantly to the seismic hazard in the United States, especially east of the Rocky Mountains where standards of building construction are generally not designed to resist shaking from large earthquakes.

  15. Ionospheric phenomena before strong earthquakes

    Directory of Open Access Journals (Sweden)

    A. S. Silina

    2001-01-01

    Full Text Available A statistical analysis of several ionospheric parameters before earthquakes with magnitude M > 5.5 located less than 500 km from an ionospheric vertical sounding station is performed. Ionospheric effects preceding "deep" (depth h > 33 km and "crust" (h 33 km earthquakes were analysed separately. Data of nighttime measurements of the critical frequencies foF2 and foEs, the frequency fbEs and Es-spread at the middle latitude station Dushanbe were used. The frequencies foF2 and fbEs are proportional to the square root of the ionization density at heights of 300 km and 100 km, respectively. It is shown that two days before the earthquakes the values of foF2 averaged over the morning hours (00:00 LT–06:00 LT and of fbEs averaged over the nighttime hours (18:00 LT–06:00 LT decrease; the effect is stronger for the "deep" earthquakes. Analysing the coefficient of semitransparency which characterizes the degree of small-scale turbulence, it was shown that this value increases 1–4 days before "crust" earthquakes, and it does not change before "deep" earthquakes. Studying Es-spread which manifests itself as diffuse Es track on ionograms and characterizes the degree of large-scale turbulence, it was found that the number of Es-spread observations increases 1–3 days before the earthquakes; for "deep" earthquakes the effect is more intensive. Thus it may be concluded that different mechanisms of energy transfer from the region of earthquake preparation to the ionosphere occur for "deep" and "crust" events.

  16. The threat of silent earthquakes

    Science.gov (United States)

    Cervelli, Peter

    2004-01-01

    Not all earthquakes shake the ground. The so-called silent types are forcing scientists to rethink their understanding of the way quake-prone faults behave. In rare instances, silent earthquakes that occur along the flakes of seaside volcanoes may cascade into monstrous landslides that crash into the sea and trigger towering tsunamis. Silent earthquakes that take place within fault zones created by one tectonic plate diving under another may increase the chance of ground-shaking shocks. In other locations, however, silent slip may decrease the likelihood of destructive quakes, because they release stress along faults that might otherwise seem ready to snap.

  17. Earthquakes: Thinking about the unpredictable

    Science.gov (United States)

    Geller, Robert J.

    The possibility of predicting earthquakes has been investigated by professionals and amateurs, seismologists and nonseismologists, for over 100 years. More than once, hopes of a workable earthquake prediction scheme have been raised only to be dashed. Such schemes—on some occasions accompanied by claims of an established track record—continue to be proposed, not only by Earth scientists, but also by workers in other fields. The assessment of these claims is not just a scientific or technical question. Public administrators and policy makers must make decisions regarding appropriate action in response to claims that some scheme has a predictive capability, or to specific predictions of imminent earthquakes.

  18. Fractal Models of Earthquake Dynamics

    CERN Document Server

    Bhattacharya, Pathikrit; Kamal,; Samanta, Debashis

    2009-01-01

    Our understanding of earthquakes is based on the theory of plate tectonics. Earthquake dynamics is the study of the interactions of plates (solid disjoint parts of the lithosphere) which produce seismic activity. Over the last about fifty years many models have come up which try to simulate seismic activity by mimicking plate plate interactions. The validity of a given model is subject to the compliance of the synthetic seismic activity it produces to the well known empirical laws which describe the statistical features of observed seismic activity. Here we present a review of two such models of earthquake dynamics with main focus on a relatively new model namely The Two Fractal Overlap Model.

  19. EARTHQUAKE-INDUCED DEFORMATION STRUCTURES AND RELATED TO EARTHQUAKE MAGNITUDES

    Directory of Open Access Journals (Sweden)

    Savaş TOPAL

    2003-02-01

    Full Text Available Earthquake-induced deformation structures which are called seismites may helpful to clasify the paleoseismic history of a location and to estimate the magnitudes of the potention earthquakes in the future. In this paper, seismites were investigated according to the types formed in deep and shallow lake sediments. Seismites are observed forms of sand dikes, introduced and fractured gravels and pillow structures in shallow lakes and pseudonodules, mushroom-like silts protruding laminites, mixed layers, disturbed varved lamination and loop bedding in deep lake sediments. Earthquake-induced deformation structures, by benefiting from previous studies, were ordered according to their formations and earthquake magnitudes. In this order, the lowest eartquake's record is loop bedding and the highest one is introduced and fractured gravels in lacustrine deposits.

  20. Twitter earthquake detection: Earthquake monitoring in a social world

    Science.gov (United States)

    Earle, Paul S.; Bowden, Daniel C.; Guy, Michelle R.

    2011-01-01

    The U.S. Geological Survey (USGS) is investigating how the social networking site Twitter, a popular service for sending and receiving short, public text messages, can augment USGS earthquake response products and the delivery of hazard information. Rapid detection and qualitative assessment of shaking events are possible because people begin sending public Twitter messages (tweets) with in tens of seconds after feeling shaking. Here we present and evaluate an earthquake detection procedure that relies solely on Twitter data. A tweet-frequency time series constructed from tweets containing the word "earthquake" clearly shows large peaks correlated with the origin times of widely felt events. To identify possible earthquakes, we use a short-term-average, long-term-average algorithm. When tuned to a moderate sensitivity, the detector finds 48 globally-distributed earthquakes with only two false triggers in five months of data. The number of detections is small compared to the 5,175 earthquakes in the USGS global earthquake catalog for the same five-month time period, and no accurate location or magnitude can be assigned based on tweet data alone. However, Twitter earthquake detections are not without merit. The detections are generally caused by widely felt events that are of more immediate interest than those with no human impact. The detections are also fast; about 75% occur within two minutes of the origin time. This is considerably faster than seismographic detections in poorly instrumented regions of the world. The tweets triggering the detections also provided very short first-impression narratives from people who experienced the shaking.

  1. Discussion on Earthquake Forecasting and Early Warning

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiaodong; Jiang Haikun; Li Mingxiao

    2008-01-01

    Through analysis of natural and social attributes of earthquake forecasting,the relationship between the natural and social attributes of earthquake forecasting (early warning) has been discussed.Regarding the natural attributes of earthquake forecasting,it only attempts to forecast the magnitude,location and occurrence time of future earthquake based on the aualysis of observational data and relevant theories and taking into consideration the present understanding of seismogeny and earthquake generation.It need not consider the consequences an earthquake forecast involves,and its purpose is to check out the level of scientific understanding of earthquakes.In respect of the social aspect of earthquake forecasting,people also focus on the consequence that the forecasting involves,in addition to its natural aspect,such as the uncertainty of earthquake prediction itself,the impact of earthquake prediction,and the earthquake resistant capability of structures (buildings),lifeline works,etc.In a word,it highlights the risk of earthquake forecasting and tries to mitigate the earthquake hazard as much as possible.In this paper,the authors also discuss the scientific and social challenges faced in earthquake prediction and analyze preliminarily the meanings and content of earthquake early warning.

  2. Earthquakes in cities revisited

    CERN Document Server

    Wirgin, Armand

    2016-01-01

    During the last twenty years, a number of publications of theoretical-numerical nature have appeared which come to the apparently-reassuring conclusion that seismic motion on the ground in cities is smaller than what this motion would be in the absence of the buildings (but for the same underground and seismic load). Other than the fact that this finding tells nothing about the motion within the buildings, it must be confronted with the overwhelming empirical evidence (e.g, earthquakes in Sendai (2011), Kathmandu (2015), Tainan City (2016), etc.) that shaking within buildings of a city is often large enough to damage or even destroy these structures. I show, on several examples, that theory can be reconciled with empirical evidence, and suggest that the crucial subject of seismic response in cities is in need of more thorough research.

  3. Earthquake Breccias (Invited)

    Science.gov (United States)

    Rowe, C. D.; Melosh, B. L.; Lamothe, K.; Schnitzer, V.; Bate, C.

    2013-12-01

    Fault breccias are one of the fundamental classes of fault rocks and are observed in many exhumed faults. Some breccias have long been assumed to form co-seismically, but textural or mechanistic evidence for the association with earthquakes has never been documented. For example, at dilational jogs in brittle faults, it is common to find small bodies of chaotic breccia in lenticular or rhombohedral voids bounded by main slip surfaces and linking segments. Sibson interpreted these 'implosion breccias' as evidence of wall rock fracturing during sudden unloading when the dilational jogs open during earthquake slip (Sibson 1985, PAGEOPH v. 124, n. 1, 159-175). However, the role of dynamic fracturing in forming these breccias has not been tested. Moreover, the criteria for identifying implosion breccia have not been defined - do all breccias in dilational jogs or step-overs represent earthquake slip? We are building a database of breccia and microbreccia textures to develop a strictly observational set of criteria for distinction of breccia texture classes. Here, we present observations from the right-lateral Pofadder Shear Zone, South Africa, and use our textural criteria to identify the relative roles of dynamic and quasi-static fracture patterns, comminution/grinding and attrition, hydrothermal alteration, dissolution, and cementation. Nearly 100% exposure in the hyper-arid region south of the Orange River allowed very detailed mapping of frictional fault traces associated with rupture events, containing one or more right-steps in each rupture trace. Fracture patterns characteristic of on- and off-fault damage associated with propagation of dynamic rupture are observed along straight segments of the faults. The wall rock fractures are regularly spaced, begin at the fault trace and propagate at a high angle to the fault, and locally branch into subsidiary fractures before terminating a few cm away. This pattern of fractures has been previously linked to dynamic

  4. High Resolution Seismic Imaging of Fault Zones: Methods and Examples From The San Andreas Fault

    Science.gov (United States)

    Catchings, R. D.; Rymer, M. J.; Goldman, M.; Prentice, C. S.; Sickler, R. R.; Criley, C.

    2011-12-01

    Seismic imaging of fault zones at shallow depths is challenging. Conventional seismic reflection methods do not work well in fault zones that consist of non-planar strata or that have large variations in velocity structure, two properties that occur in most fault zones. Understanding the structure and geometry of fault zones is important to elucidate the earthquake hazard associated with fault zones and the barrier effect that faults impose on subsurface fluid flow. In collaboration with the San Francisco Public Utilities Commission (SFPUC) at San Andreas Lake on the San Francisco peninsula, we acquired combined seismic P-wave and S-wave reflection, refraction, and guided-wave data to image the principal strand of the San Andreas Fault (SAF) that ruptured the surface during the 1906 San Francisco earthquake and additional fault strands east of the rupture. The locations and geometries of these fault strands are important because the SFPUC is seismically retrofitting the Hetch Hetchy water delivery system, which provides much of the water for the San Francisco Bay area, and the delivery system is close to the SAF at San Andreas Lake. Seismic reflection images did not image the SAF zone well due to the brecciated bedrock, a lack of layered stratigraphy, and widely varying velocities. Tomographic P-wave velocity images clearly delineate the fault zone as a low-velocity zone at about 10 m depth in more competent rock, but due to soil saturation above the rock, the P-waves do not clearly image the fault strands at shallower depths. S-wave velocity images, however, clearly show a diagnostic low-velocity zone at the mapped 1906 surface break. To image the fault zone at greater depths, we utilized guided waves, which exhibit high amplitude seismic energy within fault zones. The guided waves appear to image the fault zone at varying depths depending on the frequency of the seismic waves. At higher frequencies (~30 to 40 Hz), the guided waves show strong amplification at the

  5. Sichuan Earthquake in China

    Science.gov (United States)

    2008-01-01

    The Sichuan earthquake in China occurred on May 12, 2008, along faults within the mountains, but near and almost parallel the mountain front, northwest of the city of Chengdu. This major quake caused immediate and severe damage to many villages and cities in the area. Aftershocks pose a continuing danger, but another continuing hazard is the widespread occurrence of landslides that have formed new natural dams and consequently new lakes. These lakes are submerging roads and flooding previously developed lands. But an even greater concern is the possible rapid release of water as the lakes eventually overflow the new dams. The dams are generally composed of disintegrated rock debris that may easily erode, leading to greater release of water, which may then cause faster erosion and an even greater release of water. This possible 'positive feedback' between increasing erosion and increasing water release could result in catastrophic debris flows and/or flooding. The danger is well known to the Chinese earthquake response teams, which have been building spillways over some of the new natural dams. This ASTER image, acquired on June 1, 2008, shows two of the new large landslide dams and lakes upstream from the town of Chi-Kua-Kan at 32o12'N latitude and 104o50'E longitude. Vegetation is green, water is blue, and soil is grayish brown in this enhanced color view. New landslides appear bright off-white. The northern (top) lake is upstream from the southern lake. Close inspection shows a series of much smaller lakes in an elongated 'S' pattern along the original stream path. Note especially the large landslides that created the dams. Some other landslides in this area, such as the large one in the northeast corner of the image, occur only on the mountain slopes, so do not block streams, and do not form lakes.

  6. Sichuan Earthquake in China

    Science.gov (United States)

    2008-01-01

    The Sichuan earthquake in China occurred on May 12, 2008, along faults within the mountains, but near and almost parallel the mountain front, northwest of the city of Chengdu. This major quake caused immediate and severe damage to many villages and cities in the area. Aftershocks pose a continuing danger, but another continuing hazard is the widespread occurrence of landslides that have formed new natural dams and consequently new lakes. These lakes are submerging roads and flooding previously developed lands. But an even greater concern is the possible rapid release of water as the lakes eventually overflow the new dams. The dams are generally composed of disintegrated rock debris that may easily erode, leading to greater release of water, which may then cause faster erosion and an even greater release of water. This possible 'positive feedback' between increasing erosion and increasing water release could result in catastrophic debris flows and/or flooding. The danger is well known to the Chinese earthquake response teams, which have been building spillways over some of the new natural dams. This ASTER image, acquired on June 1, 2008, shows two of the new large landslide dams and lakes upstream from the town of Chi-Kua-Kan at 32o12'N latitude and 104o50'E longitude. Vegetation is green, water is blue, and soil is grayish brown in this enhanced color view. New landslides appear bright off-white. The northern (top) lake is upstream from the southern lake. Close inspection shows a series of much smaller lakes in an elongated 'S' pattern along the original stream path. Note especially the large landslides that created the dams. Some other landslides in this area, such as the large one in the northeast corner of the image, occur only on the mountain slopes, so do not block streams, and do not form lakes.

  7. Geodetic constraints on the 2014 M 6.0 South Napa earthquake

    Science.gov (United States)

    Barnhart, William D.; Murray, Jessica R.; Yun, S H; Svarc, Jerry L.; Samsonov, SV; Fielding, EJ; Brooks, Benjamin A.; Milillo, Pietro

    2014-01-01

    On 24 August 2014, the M 6.0 South Napa earthquake shook much of the San Francisco Bay area, leading to significant damage in the Napa Valley. The earthquake occurred in the vicinity of the West Napa fault (122.313° W, 38.22° N, 11.3 km), a mapped structure located between the Rodger’s Creek and Green Valley faults, with nearly pure right‐lateral strike‐slip motion (strike 157°, dip 77°, rake –169°; http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#summary, last accessed December 2014) (Fig. 1). The West Napa fault previously experienced an M 5 strike‐slip event in 2000 but otherwise exhibited no previous definitive evidence of historic earthquake rupture (Rodgers et al., 2008; Wesling and Hanson, 2008). Evans et al. (2012) found slip rates of ∼9.5  mm/yr along the West Napa fault, with most slip rate models for the Bay area placing higher slip rates and greater earthquake potential on the Rodger’s Creek and Green Valley faults, respectively (e.g., Savage et al., 1999; d’Alessio et al., 2005; Funning et al., 2007).

  8. Absence of earthquake correlation with Earth tides: An indication of high preseismic fault stress rate

    Science.gov (United States)

    Vidale, J.E.; Agnew, D.C.; Johnston, M.J.S.; Oppenheimer, D.H.

    1998-01-01

    Because the rate of stress change from the Earth tides exceeds that from tectonic stress accumulation, tidal triggering of earthquakes would be expected if the final hours of loading of the fault were at the tectonic rate and if rupture began soon after the achievement of a critical stress level. We analyze the tidal stresses and stress rates on the fault planes and at the times of 13,042 earthquakes which are so close to the San Andreas and Calaveras faults in California that we may take the fault plane to be known. We find that the stresses and stress rates from Earth tides at the times of earthquakes are distributed in the same way as tidal stresses and stress rates at random times. While the rate of earthquakes when the tidal stress promotes failure is 2% higher than when the stress does not, this difference in rate is not statistically significant. This lack of tidal triggering implies that preseismic stress rates in the nucleation zones of earthquakes are at least 0.15 bar/h just preceding seismic failure, much above the long-term tectonic stress rate of 10-4 bar/h.

  9. Extreme value statistics and thermodynamics of earthquakes. Large earthquakes

    Energy Technology Data Exchange (ETDEWEB)

    Lavenda, B. [Camerino Univ., Camerino, MC (Italy); Cipollone, E. [ENEA, Centro Ricerche Casaccia, S. Maria di Galeria, RM (Italy). National Centre for Research on Thermodynamics

    2000-06-01

    A compound Poisson process is used to derive a new shape parameter which can be used to discriminate between large earthquakes and aftershocks sequences. Sample exceedance distributions of large earthquakes are fitted to the Pareto tail and the actual distribution of the maximum to the Frechet distribution, while the sample distribution of aftershocks are fitted to a Beta distribution and the distribution of the minimum to the Weibull distribution for the smallest value. The transition between initial sample distributions and asymptotic extreme value distributions show that self-similar power laws are transformed into non scaling exponential distributions so that neither self-similarity nor the Gutenberg-Richter law can be considered universal. The energy-magnitude transformation converts the Frechet distribution into the Gumbel distribution, originally proposed by Epstein and Lomnitz, and not the Gompertz distribution as in the Lomnitz-Adler and Lomnitz generalization of the Gutenberg-Richter law. Numerical comparison is made with the Lomnitz-Adler and Lomnitz analysis using the same catalogue of Chinese earthquakes. An analogy is drawn between large earthquakes and high energy particle physics. A generalized equation of state is used to transform the Gamma density into the order-statistic Frechet distribution. Earthquake temperature and volume are determined as functions of the energy. Large insurance claims based on the Pareto distribution, which does not have a right endpoint, show why there cannot be a maximum earthquake energy.

  10. Effects of Hayward fault interactions with the Rodgers Creek and San Andreas faults

    Science.gov (United States)

    Parsons, T.; Geist, E.; Jachens, R.; Sliter, R.; Jaffe, B.

    2003-12-01

    Finite-element and crustal-structure models of the Hayward fault emphasize its position within a network of interacting faults, and indicate a number of expected influences from other faults. For example, a new structural cross section across San Pablo Bay in association with potential field maps allows us to map and model detailed interactions between the Hayward and Rodgers Creek faults. The two faults do not appear to connect at depth, and finite-element models indicate growing extensional stress in the stepover between the two faults. A model consequence of extensional stress in the stepover, combined with long-term interaction with the San Andreas fault, is normal-stress reduction (unclamping) of the north Hayward fault. If this occurs in the real Earth, then substantial reduction in frictional resistance on the north Hayward fault is expected, which might in turn be expected to influence the distribution of creep. Interaction effects on a shorter time scale are also evident. The 1906 San Francisco, and 1989 Loma Prieta earthquakes are calculated to have reduced stress on the Hayward fault at seismogenic depths. Models of the 1906 earthquake show complex interactions; coseismic static stress changes drop stress on the north Hayward fault while upper mantle viscoelastic relaxation slightly raises the stressing rate. Stress recovery is calculated to have occurred by ~1980, though earthquake probability is still affected by the delay induced by stress reduction. We conclude that the model Hayward fault is strongly influenced by its neighbors, and it is worth considering these effects when studying and attempting to understand the real fault.

  11. Identification of Necessary Conditions for Super-shear Wave Rupture Speeds: The San Andreas Fault

    Science.gov (United States)

    Das, S.

    2007-12-01

    The 2001 Kunlun, Tibet earthquake taught us that the portion of a strike-slip fault most likely to propagate at super-shear speeds are the long straight portions. This is only a necessary (but not sufficient) condition. That is, once a fault accelerates to the maximum permissible speed, it can continue at this speed provided it is straight and there are no obstacles along the way, and provided the fault friction is low. For the Tibet earthquake, the 100 km region of highest rupture speed also had the highest slip rate, the highest slip and the highest stress drop (Robinson et al., JGR, 2006). Off-fault cracks due to the passage of the Mach cone exists in only that portion of the fault identified as travelling at super-shear speed and not in other places along the fault (Bhat et al., JGR, 2007). Re-examination of earlier reports of super-shear rupture speeds on the North Anatolian fault and the Denali fault show that such speeds did occur on the straight section of these faults. Of course all straight portions of faults will not reach super-shear speeds. So what can the Tibet earthquake teach us about the San Andreas fault? Both the 1906 and the 1857 have long, straight portions, the former having been identified by Song et al. (EOS, 2005) as having reached super-shear speeds to the north of San Francisco, the region of highest slip. If the repeat of the 1857 starts in the central valley, as it is believed to have done in 1857, it has the potential to propagate at super-shear speeds through the long, straight portion of the San Andread fault in the Carrizo Plain, the region believed to have had the largest displacement in 1857 based on paleoseismic studies. The resulting shock waves would strike the highly populated regions of Santa Barbara and the Los Angeles Basin (Das, Science, 2007).

  12. Inferences drawn from two decades of alinement array measurements of creep on faults in the San Francisco Bay Region

    Science.gov (United States)

    Galehouse, J.S.; Lienkaemper, J.J.

    2003-01-01

    We summarize over 20 years of monitoring surface creep on faults of the San Andreas system in the San Francisco Bay region using alinement arrays. The San Andreas fault is fully locked at five sites northwest from San Juan Bautista, the southern end of the 1906 earthquake rupture, that is, no creep (San Gregorio, Rodgers Creek, and West Napa faults show no creep. The measured creep rate on the Calaveras-Paicines fault from Hollister southward is either 6 or ??? 10 mm/yr, depending on whether the arrays cross all of the creeping traces. Northward of Hollister, the central Calaveras creep rate reaches 14 ?? 2 mm/yr but drops to ??? 2 mm/yr near Calaveras Reservoir, where slip transfers to the southern Hayward fault at a maximum creep rate of 9 mm/yr at its south end. However, the Hayward fault averages only 4.6 mm/yr over most of its length. The Northern Calaveras fault, now creeping at 3-4 mm/yr, steps right to the Concord fault, which has a similar rate, 2.5-3.5 mm/yr, which is slightly slower than the 4.4 mm/yr rate on its northward continuation, the Green Valley fault. The Maacama fault creeps at 4.4 mm/yr near Ukiah and 6.5 mm/yr in Willits. The central and southern segments of the Calaveras fault are predominantly creeping, whereas the Hayward, Northern Calaveras, and Maacama faults are partly locked and, along with the Rodgers Creek and San Andreas, have high potential for major earthquakes.

  13. Asymmetric motion along the San Franciso Bay Area faults. Implication for the magnitude of future seismic events

    Science.gov (United States)

    Houlie, N.; Romanowicz, B.

    2007-12-01

    The San Francisco Bay area is one of the tectonically most deformed areas in the world. This deformation is the result of relative motion of the Pacific and North-America plates. A large part of the strain (75 %) is accommodated along structures lying in a 50 km wide land strip. At least two major seismic events (Mw>6.5) are expected along the San Andreas (SAF) and Hayward faults (HAY) within the next decades. Triggering effects between the two seismic events may not be excluded. The BARD network is a permanent GPS network comprising 40 GPS sites, installed since 1994 in Northern California. Originally started as a collaborative effort of different Bay Area institutions, since the establishment of the Plate Boundary Observatory it has focused on real-time data acquisition from stations operated by UC Berkeley, with plans for expansion in collaboration with USGS/Menlo Park. The BARD network is streaming data to the Berkeley Seismological Laboratory in real-time (sampling rates of 1s and 15s, depending on the site). All sites are transmitting data using Frame Relay technology which makes them safer in case of earthquake occurrence. Data are archived at the Northern California Earthquake Data Center (NCEDC, http://www.ncedc.org) and are freely available. The BARD network is currently able to provide high accuracy (errorSan Andreas fault may be asymmetric. Therefore, the common assumption that the deformation is symmetric across the fault could lead to a biased location of the region of maximum strain in the San Francisco Bay Area. The new location of the maximum static strain based on asymmetry influences estimates of the response of the Hayward Fault to deformation associated with the San Andreas fault. We also present preliminary velocities for PBO sites located in the San Francisco Bay Area and discuss them in the light of a BARD reference frame.

  14. Geometrical impact of the San Andreas Fault on stress and seismicity in California

    Science.gov (United States)

    Li, Qingsong; Liu, Mian

    2006-04-01

    Most large earthquakes in northern and central California clustered along the main trace of the San Andreas Fault (SAF), the North American-Pacific plate boundary. However, in southern California earthquakes were rather scattered. Here we suggest that such along-strike variation of seismicity may largely reflect the geometrical impact of the SAF. Using a dynamic finite element model that includes the first-order geometric features of the SAF, we show that strain partitioning and crustal deformation in California are closely related to the geometry of the SAF. In particular, the Big Bend is shown to reduce slip rate on southern SAF and cause high shear stress and strain energy over a broad region in southern California, and a belt of high strain energy in the Eastern California Shear Zone.

  15. Behavior of Columns During Earthquakes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The behavior of columns during earthquakes is very important since column failures may lead to additional structural failures and result in total building collapses....

  16. Medical complications associated with earthquakes.

    Science.gov (United States)

    Bartels, Susan A; VanRooyen, Michael J

    2012-02-25

    Major earthquakes are some of the most devastating natural disasters. The epidemiology of earthquake-related injuries and mortality is unique for these disasters. Because earthquakes frequently affect populous urban areas with poor structural standards, they often result in high death rates and mass casualties with many traumatic injuries. These injuries are highly mechanical and often multisystem, requiring intensive curative medical and surgical care at a time when the local and regional medical response capacities have been at least partly disrupted. Many patients surviving blunt and penetrating trauma and crush injuries have subsequent complications that lead to additional morbidity and mortality. Here, we review and summarise earthquake-induced injuries and medical complications affecting major organ systems.

  17. Statistical earthquake focal mechanism forecasts

    CERN Document Server

    Kagan, Yan Y

    2013-01-01

    Forecasts of the focal mechanisms of future earthquakes are important for seismic hazard estimates and Coulomb stress and other models of earthquake occurrence. Here we report on a high-resolution global forecast of earthquake rate density as a function of location, magnitude, and focal mechanism. In previous publications we reported forecasts of 0.5 degree spatial resolution, covering the latitude range magnitude, and focal mechanism. In previous publications we reported forecasts of 0.5 degree spatial resolution, covering the latitude range from -75 to +75 degrees, based on the Global Central Moment Tensor earthquake catalog. In the new forecasts we've improved the spatial resolution to 0.1 degree and the latitude range from pole to pole. Our focal mechanism estimates require distance-weighted combinations of observed focal mechanisms within 1000 km of each grid point. Simultaneously we calculate an average rotation angle between the forecasted mechanism and all the surrounding mechanisms, using the method ...

  18. Low strength of deep San Andreas fault gouge from SAFOD core

    Science.gov (United States)

    Lockner, David A.; Morrow, Carolyn A.; Moore, Diane E.; Hickman, Stephen H.

    2011-01-01

    The San Andreas fault accommodates 28–34 mm yr−1 of right lateral motion of the Pacific crustal plate northwestward past the North American plate. In California, the fault is composed of two distinct locked segments that have produced great earthquakes in historical times, separated by a 150-km-long creeping zone. The San Andreas Fault Observatory at Depth (SAFOD) is a scientific borehole located northwest of Parkfield, California, near the southern end of the creeping zone. Core was recovered from across the actively deforming San Andreas fault at a vertical depth of 2.7 km (ref. 1). Here we report laboratory strength measurements of these fault core materials at in situ conditions, demonstrating that at this locality and this depth the San Andreas fault is profoundly weak (coefficient of friction, 0.15) owing to the presence of the smectite clay mineral saponite, which is one of the weakest phyllosilicates known. This Mg-rich clay is the low-temperature product of metasomatic reactions between the quartzofeldspathic wall rocks and serpentinite blocks in the fault2, 3. These findings provide strong evidence that deformation of the mechanically unusual creeping portions of the San Andreas fault system is controlled by the presence of weak minerals rather than by high fluid pressure or other proposed mechanisms1. The combination of these measurements of fault core strength with borehole observations1, 4, 5 yields a self-consistent picture of the stress state of the San Andreas fault at the SAFOD site, in which the fault is intrinsically weak in an otherwise strong crust.

  19. The GIS and analysis of earthquake damage distribution of the 1303 Hongtong M=8 earthquake

    Institute of Scientific and Technical Information of China (English)

    高孟潭; 金学申; 安卫平; 吕晓健

    2004-01-01

    The geography information system of the 1303 Hongtong M=8 earthquake has been established. Using the spatial analysis function of GIS, the spatial distribution characteristics of damage and isoseismal of the earthquake are studied. By comparing with the standard earthquake intensity attenuation relationship, the abnormal damage distribution of the earthquake is found, so the relationship of the abnormal distribution with tectonics, site condition and basin are analyzed. In this paper, the influence on the ground motion generated by earthquake source and the underground structures near source also are studied. The influence on seismic zonation, anti-earthquake design, earthquake prediction and earthquake emergency responding produced by the abnormal density distribution are discussed.

  20. Causes of hospitalisation before and after the 2009 L'Aquila earthquake.

    Science.gov (United States)

    Petrazzi, L; Striuli, R; Polidoro, L; Petrarca, M; Scipioni, R; Struglia, M; Giorgini, P; Necozione, S; Festuccia, V; Ferri, C

    2013-09-01

    On 6 April 2009, an earthquake struck L'Aquila. The San Salvatore Hospital was evacuated, and a field hospital was built. The study aimed to assess the epidemiologic impact of the earthquake through the analysis of patient population admitted to the field hospital during a 2-month period following the disaster. We retrospectively evaluated causes of hospitalisation and demographic data of patients admitted to (i) the Division of Internal Medicine and (ii) the Division of Emergency Medicine of the field hospital from 6 April, 2009 to 29 May, 2009. All data were compared with the admissions made at the same divisions of the San Salvatore Hospital during the same period of previous year. (i) Patient group (n = 102) and comparison group (n = 108). Mean patient age was higher, patients living in L'Aquila were more numerous, while mean length of stay was lower after than before the earthquake. Infectious diseases increased, while 'other' diseases decreased after the disaster both in admission and in discharge diagnoses. Gastroenterological diseases decreased with the earthquake but only in admission diagnoses. (ii) Patient group (n = 5255) and comparison group (n = 6564). Triage codes changed with the earthquake. Cardiovascular, psychiatric, gynaecological, infectious and chronic diseases increased, while pneumologic, gastroenterological, traumatic and 'other' diseases decreased after the quake. The number of hospitalised patients decreased with the tremor, while those discharged transferred to other hospitals and those who rejected hospitalisation increased. A natural disaster completely changes causes of hospitalisation in the Divisions of Internal and Emergency Medicine. These findings can be useful for the design of specific intervention programmes and for softening the detrimental effects of quakes.

  1. Earthquakes - Volcanoes (Causes and Forecast)

    Science.gov (United States)

    Tsiapas, E.

    2009-04-01

    EARTHQUAKES - VOLCANOES (CAUSES AND FORECAST) ELIAS TSIAPAS RESEARCHER NEA STYRA, EVIA,GREECE TEL.0302224041057 tsiapas@hol.gr The earthquakes are caused by large quantities of liquids (e.g. H2O, H2S, SO2, ect.) moving through lithosphere and pyrosphere (MOHO discontinuity) till they meet projections (mountains negative projections or projections coming from sinking lithosphere). The liquids are moved from West Eastward carried away by the pyrosphere because of differential speed of rotation of the pyrosphere by the lithosphere. With starting point an earthquake which was noticed at an area and from statistical studies, we know when, where and what rate an earthquake may be, which earthquake is caused by the same quantity of liquids, at the next east region. The forecast of an earthquake ceases to be valid if these components meet a crack in the lithosphere (e.g. limits of lithosphere plates) or a volcano crater. In this case the liquids come out into the atmosphere by the form of gasses carrying small quantities of lava with them (volcano explosion).

  2. Two models for earthquake forerunners

    Science.gov (United States)

    Mjachkin, V.I.; Brace, W.F.; Sobolev, G.A.; Dieterich, J.H.

    1975-01-01

    Similar precursory phenomena have been observed before earthquakes in the United States, the Soviet Union, Japan, and China. Two quite different physical models are used to explain these phenomena. According to a model developed by US seismologists, the so-called dilatancy diffusion model, the earthquake occurs near maximum stress, following a period of dilatant crack expansion. Diffusion of water in and out of the dilatant volume is required to explain the recovery of seismic velocity before the earthquake. According to a model developed by Soviet scientists growth of cracks is also involved but diffusion of water in and out of the focal region is not required. With this model, the earthquake is assumed to occur during a period of falling stress and recovery of velocity here is due to crack closure as stress relaxes. In general, the dilatancy diffusion model gives a peaked precursor form, whereas the dry model gives a bay form, in which recovery is well under way before the earthquake. A number of field observations should help to distinguish between the two models: study of post-earthquake recovery, time variation of stress and pore pressure in the focal region, the occurrence of pre-existing faults, and any changes in direction of precursory phenomena during the anomalous period. ?? 1975 Birkha??user Verlag.

  3. Earthquake damage to underground facilities

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, H.R.; Hustrulid, W.A. Stephenson, D.E.

    1978-11-01

    The potential seismic risk for an underground nuclear waste repository will be one of the considerations in evaluating its ultimate location. However, the risk to subsurface facilities cannot be judged by applying intensity ratings derived from the surface effects of an earthquake. A literature review and analysis were performed to document the damage and non-damage due to earthquakes to underground facilities. Damage from earthquakes to tunnels, s, and wells and damage (rock bursts) from mining operations were investigated. Damage from documented nuclear events was also included in the study where applicable. There are very few data on damage in the subsurface due to earthquakes. This fact itself attests to the lessened effect of earthquakes in the subsurface because mines exist in areas where strong earthquakes have done extensive surface damage. More damage is reported in shallow tunnels near the surface than in deep mines. In mines and tunnels, large displacements occur primarily along pre-existing faults and fractures or at the surface entrance to these facilities.Data indicate vertical structures such as wells and shafts are less susceptible to damage than surface facilities. More analysis is required before seismic criteria can be formulated for the siting of a nuclear waste repository.

  4. Large earthquakes and creeping faults

    Science.gov (United States)

    Harris, Ruth A.

    2017-01-01

    Faults are ubiquitous throughout the Earth's crust. The majority are silent for decades to centuries, until they suddenly rupture and produce earthquakes. With a focus on shallow continental active-tectonic regions, this paper reviews a subset of faults that have a different behavior. These unusual faults slowly creep for long periods of time and produce many small earthquakes. The presence of fault creep and the related microseismicity helps illuminate faults that might not otherwise be located in fine detail, but there is also the question of how creeping faults contribute to seismic hazard. It appears that well-recorded creeping fault earthquakes of up to magnitude 6.6 that have occurred in shallow continental regions produce similar fault-surface rupture areas and similar peak ground shaking as their locked fault counterparts of the same earthquake magnitude. The behavior of much larger earthquakes on shallow creeping continental faults is less well known, because there is a dearth of comprehensive observations. Computational simulations provide an opportunity to fill the gaps in our understanding, particularly of the dynamic processes that occur during large earthquake rupture and arrest.

  5. Intracontinental basins and strong earthquakes

    Institute of Scientific and Technical Information of China (English)

    邓起东; 高孟潭; 赵新平; 吴建春

    2004-01-01

    The September 17, 1303 Hongtong M=8 earthquake occurred in Linfen basin of Shanxi down-faulted basin zone. It is the first recorded M=8 earthquake since the Chinese historical seismic records had started and is a great earthquake occurring in the active intracontinental basin. We had held a Meeting of the 700th Anniversary of the 1303 Hongtong M=8 Earthquake in Shanxi and a Symposium on Intracontinental Basins and Strong Earthquakes in Taiyuan City of Shanxi Province on September 17~18, 2003. The articles presented on the symposium discussed the relationships between active intracontinental basins of different properties, developed in different regions, including tensional graben and semi-graben basins in tensile tectonic regions, compression-depression basins and foreland basins in compressive tectonic regions and pull-apart basins in strike-slip tectonic zones, and strong earthquakes in China. In this article we make a brief summary of some problems. The articles published in this special issue are a part of the articles presented on the symposium.

  6. Potential Effects of a Scenario Earthquake on the Economy of Southern California: Small Business Exposure and Sensitivity Analysis to a Magnitude 7.8 Earthquake

    Science.gov (United States)

    Sherrouse, Benson C.; Hester, David J.; Wein, Anne M.

    2008-01-01

    The Multi-Hazards Demonstration Project (MHDP) is a collaboration between the U.S. Geological Survey (USGS) and various partners from the public and private sectors and academia, meant to improve Southern California's resiliency to natural hazards (Jones and others, 2007). In support of the MHDP objectives, the ShakeOut Scenario was developed. It describes a magnitude 7.8 (M7.8) earthquake along the southernmost 300 kilometers (200 miles) of the San Andreas Fault, identified by geoscientists as a plausible event that will cause moderate to strong shaking over much of the eight-county (Imperial, Kern, Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura) Southern California region. This report contains an exposure and sensitivity analysis of small businesses in terms of labor and employment statistics. Exposure is measured as the absolute counts of labor market variables anticipated to experience each level of Instrumental Intensity (a proxy measure of damage). Sensitivity is the percentage of the exposure of each business establishment size category to each Instrumental Intensity level. The analysis concerns the direct effect of the earthquake on small businesses. The analysis is inspired by the Bureau of Labor Statistics (BLS) report that analyzed the labor market losses (exposure) of a M6.9 earthquake on the Hayward fault by overlaying geocoded labor market data on Instrumental Intensity values. The method used here is influenced by the ZIP-code-level data provided by the California Employment Development Department (CA EDD), which requires the assignment of Instrumental Intensities to ZIP codes. The ZIP-code-level labor market data includes the number of business establishments, employees, and quarterly payroll categorized by business establishment size.

  7. Triggering of volcanic eruptions by large earthquakes

    Science.gov (United States)

    Nishimura, Takeshi

    2017-08-01

    When a large earthquake occurs near an active volcano, there is often concern that volcanic eruptions may be triggered by the earthquake. In this study, recently accumulated, reliable data were analyzed to quantitatively evaluate the probability of the occurrence of new eruptions of volcanoes located near the epicenters of large earthquakes. For volcanoes located within 200 km of large earthquakes of magnitude 7.5 or greater, the eruption occurrence probability increases by approximately 50% for 5 years after the earthquake origin time. However, no significant increase in the occurrence probability of new eruptions was observed at distant volcanoes or for smaller earthquakes. The present results strongly suggest that new eruptions are likely triggered by static stress changes and/or strong ground motions caused by nearby large earthquakes. This is not similar to the previously presented evidence that volcanic earthquakes at distant volcanoes are remotely triggered by surface waves generated by large earthquakes.

  8. Twitter earthquake detection: earthquake monitoring in a social world

    Directory of Open Access Journals (Sweden)

    Daniel C. Bowden

    2011-06-01

    Full Text Available The U.S. Geological Survey (USGS is investigating how the social networking site Twitter, a popular service for sending and receiving short, public text messages, can augment USGS earthquake response products and the delivery of hazard information. Rapid detection and qualitative assessment of shaking events are possible because people begin sending public Twitter messages (tweets with in tens of seconds after feeling shaking. Here we present and evaluate an earthquake detection procedure that relies solely on Twitter data. A tweet-frequency time series constructed from tweets containing the word “earthquake” clearly shows large peaks correlated with the origin times of widely felt events. To identify possible earthquakes, we use a short-term-average, long-term-average algorithm. When tuned to a moderate sensitivity, the detector finds 48 globally-distributed earthquakes with only two false triggers in five months of data. The number of detections is small compared to the 5,175 earthquakes in the USGS global earthquake catalog for the same five-month time period, and no accurate location or magnitude can be assigned based on tweet data alone. However, Twitter earthquake detections are not without merit. The detections are generally caused by widely felt events that are of more immediate interest than those with no human impact. The detections are also fast; about 75% occur within two minutes of the origin time. This is considerably faster than seismographic detections in poorly instrumented regions of the world. The tweets triggering the detections also provided very short first-impression narratives from people who experienced the shaking.

  9. Earthquake Early Warning: A Prospective User's Perspective (Invited)

    Science.gov (United States)

    Nishenko, S. P.; Savage, W. U.; Johnson, T.

    2009-12-01

    With more than 25 million people at risk from high hazard faults in California alone, Earthquake Early Warning (EEW) presents a promising public safety and emergency response tool. EEW represents the real-time end of an earthquake information spectrum which also includes near real-time notifications of earthquake location, magnitude, and shaking levels; as well as geographic information system (GIS)-based products for compiling and visually displaying processed earthquake data such as ShakeMap and ShakeCast. Improvements to and increased multi-national implementation of EEW have stimulated interest in how such information products could be used in the future. Lifeline organizations, consisting of utilities and transportation systems, can use both onsite and regional EEW information as part of their risk management and public safety programs. Regional EEW information can provide improved situational awareness to system operators before automatic system protection devices activate, and allow trained personnel to take precautionary measures. On-site EEW is used for earthquake-actuated automatic gas shutoff valves, triggered garage door openers at fire stations, system controls, etc. While there is no public policy framework for preemptive, precautionary electricity or gas service shutdowns by utilities in the United States, gas shut-off devices are being required at the building owner level by some local governments. In the transportation sector, high-speed rail systems have already demonstrated the ‘proof of concept’ for EEW in several countries, and more EEW systems are being installed. Recently the Bay Area Rapid Transit District (BART) began collaborating with the California Integrated Seismic Network (CISN) and others to assess the potential benefits of EEW technology to mass transit operations and emergency response in the San Francisco Bay region. A key issue in this assessment is that significant earthquakes are likely to occur close to or within the BART

  10. Natural gas network resiliency to a "shakeout scenario" earthquake.

    Energy Technology Data Exchange (ETDEWEB)

    Ellison, James F.; Corbet, Thomas Frank,; Brooks, Robert E.

    2013-06-01

    A natural gas network model was used to assess the likely impact of a scenario San Andreas Fault earthquake on the natural gas network. Two disruption scenarios were examined. The more extensive damage scenario assumes the disruption of all three major corridors bringing gas into southern California. If withdrawals from the Aliso Canyon storage facility are limited to keep the amount of stored gas within historical levels, the disruption reduces Los Angeles Basin gas supplies by 50%. If Aliso Canyon withdrawals are only constrained by the physical capacity of the storage system to withdraw gas, the shortfall is reduced to 25%. This result suggests that it is important for stakeholders to put agreements in place facilitating the withdrawal of Aliso Canyon gas in the event of an emergency.

  11. Earthquake recovery of historic buildings: exploring cost and time needs.

    Science.gov (United States)

    Al-Nammari, Fatima M; Lindell, Michael K

    2009-07-01

    Disaster recovery of historic buildings has rarely been investigated even though the available literature indicates that they face special challenges. This study examines buildings' recovery time and cost to determine whether their functions (that is, their use) and their status (historic or non-historic) affect these outcomes. The study uses data from the city of San Francisco after the 1989 Loma Prieta earthquake to examine the recovery of historic buildings owned by public agencies and non-governmental organisations. The results show that recovery cost is affected by damage level, construction type and historic status, whereas recovery time is affected by the same variables and also by building function. The study points to the importance of pre-incident recovery planning, especially for building functions that have shown delayed recovery. Also, the study calls attention to the importance of further investigations into the challenges facing historic building recovery.

  12. The Electronic Encyclopedia of Earthquakes

    Science.gov (United States)

    Benthien, M.; Marquis, J.; Jordan, T.

    2003-12-01

    The Electronic Encyclopedia of Earthquakes is a collaborative project of the Southern California Earthquake Center (SCEC), the Consortia of Universities for Research in Earthquake Engineering (CUREE) and the Incorporated Research Institutions for Seismology (IRIS). This digital library organizes earthquake information online as a partner with the NSF-funded National Science, Technology, Engineering and Mathematics (STEM) Digital Library (NSDL) and the Digital Library for Earth System Education (DLESE). When complete, information and resources for over 500 Earth science and engineering topics will be included, with connections to curricular materials useful for teaching Earth Science, engineering, physics and mathematics. Although conceived primarily as an educational resource, the Encyclopedia is also a valuable portal to anyone seeking up-to-date earthquake information and authoritative technical sources. "E3" is a unique collaboration among earthquake scientists and engineers to articulate and document a common knowledge base with a shared terminology and conceptual framework. It is a platform for cross-training scientists and engineers in these complementary fields and will provide a basis for sustained communication and resource-building between major education and outreach activities. For example, the E3 collaborating organizations have leadership roles in the two largest earthquake engineering and earth science projects ever sponsored by NSF: the George E. Brown Network for Earthquake Engineering Simulation (CUREE) and the EarthScope Project (IRIS and SCEC). The E3 vocabulary and definitions are also being connected to a formal ontology under development by the SCEC/ITR project for knowledge management within the SCEC Collaboratory. The E3 development system is now fully operational, 165 entries are in the pipeline, and the development teams are capable of producing 20 new, fully reviewed encyclopedia entries each month. Over the next two years teams will

  13. Evidence for Ancient Mesoamerican Earthquakes

    Science.gov (United States)

    Kovach, R. L.; Garcia, B.

    2001-12-01

    Evidence for past earthquake damage at Mesoamerican ruins is often overlooked because of the invasive effects of tropical vegetation and is usually not considered as a casual factor when restoration and reconstruction of many archaeological sites are undertaken. Yet the proximity of many ruins to zones of seismic activity would argue otherwise. Clues as to the types of damage which should be soughtwere offered in September 1999 when the M = 7.5 Oaxaca earthquake struck the ruins of Monte Alban, Mexico, where archaeological renovations were underway. More than 20 structures were damaged, 5 of them seriously. Damage features noted were walls out of plumb, fractures in walls, floors, basal platforms and tableros, toppling of columns, and deformation, settling and tumbling of walls. A Modified Mercalli Intensity of VII (ground accelerations 18-34 %b) occurred at the site. Within the diffuse landward extension of the Caribbean plate boundary zone M = 7+ earthquakes occur with repeat times of hundreds of years arguing that many Maya sites were subjected to earthquakes. Damage to re-erected and reinforced stelae, walls, and buildings were witnessed at Quirigua, Guatemala, during an expedition underway when then 1976 M = 7.5 Guatemala earthquake on the Motagua fault struck. Excavations also revealed evidence (domestic pttery vessels and skeleton of a child crushed under fallen walls) of an ancient earthquake occurring about the teim of the demise and abandonment of Quirigua in the late 9th century. Striking evidence for sudden earthquake building collapse at the end of the Mayan Classic Period ~A.D. 889 was found at Benque Viejo (Xunantunich), Belize, located 210 north of Quirigua. It is argued that a M = 7.5 to 7.9 earthquake at the end of the Maya Classic period centered in the vicinity of the Chixoy-Polochic and Motagua fault zones cound have produced the contemporaneous earthquake damage to the above sites. As a consequences this earthquake may have accelerated the

  14. A Prospect of Earthquake Prediction Research

    CERN Document Server

    Ogata, Yosihiko

    2013-01-01

    Earthquakes occur because of abrupt slips on faults due to accumulated stress in the Earth's crust. Because most of these faults and their mechanisms are not readily apparent, deterministic earthquake prediction is difficult. For effective prediction, complex conditions and uncertain elements must be considered, which necessitates stochastic prediction. In particular, a large amount of uncertainty lies in identifying whether abnormal phenomena are precursors to large earthquakes, as well as in assigning urgency to the earthquake. Any discovery of potentially useful information for earthquake prediction is incomplete unless quantitative modeling of risk is considered. Therefore, this manuscript describes the prospect of earthquake predictability research to realize practical operational forecasting in the near future.

  15. Effects of a major earthquake on calls to regional poison control centers.

    Science.gov (United States)

    Nathan, A R; Olson, K R; Everson, G W; Kearney, T E; Blanc, P D

    1992-03-01

    We retrospectively evaluated the effect of the Loma Prieta earthquake on calls to 2 designated regional poison control centers (San Francisco and Santa Clara) in the area. In the immediate 12 hours after the earthquake, there was an initial drop (31%) in call volume, related to telephone system overload and other technical problems. Calls from Bay Area counties outside of San Francisco and Santa Clara decreased more dramatically than those from within the host counties where the poison control centers are located. In the next 2 days, each poison control center then handled a 27% increase in call volume. Requests for information regarding safety of water supplies and other environmental concerns were significantly increased. The number of cases of actual poisoning exposure decreased, particularly poison and drug ingestions in children. Most calls directly related to the earthquake included spills and leaks of hazardous materials and questions about water and food safety. Regional poison control centers play an essential role in the emergency medical response to major disasters and are critically dependent on an operational telephone system.

  16. Comparison of two large earthquakes: the 2008 Sichuan Earthquake and the 2011 East Japan Earthquake.

    Science.gov (United States)

    Otani, Yuki; Ando, Takayuki; Atobe, Kaori; Haiden, Akina; Kao, Sheng-Yuan; Saito, Kohei; Shimanuki, Marie; Yoshimoto, Norifumi; Fukunaga, Koichi

    2012-01-01

    Between August 15th and 19th, 2011, eight 5th-year medical students from the Keio University School of Medicine had the opportunity to visit the Peking University School of Medicine and hold a discussion session titled "What is the most effective way to educate people for survival in an acute disaster situation (before the mental health care stage)?" During the session, we discussed the following six points: basic information regarding the Sichuan Earthquake and the East Japan Earthquake, differences in preparedness for earthquakes, government actions, acceptance of medical rescue teams, earthquake-induced secondary effects, and media restrictions. Although comparison of the two earthquakes was not simple, we concluded that three major points should be emphasized to facilitate the most effective course of disaster planning and action. First, all relevant agencies should formulate emergency plans and should supply information regarding the emergency to the general public and health professionals on a normal basis. Second, each citizen should be educated and trained in how to minimize the risks from earthquake-induced secondary effects. Finally, the central government should establish a single headquarters responsible for command, control, and coordination during a natural disaster emergency and should centralize all powers in this single authority. We hope this discussion may be of some use in future natural disasters in China, Japan, and worldwide.

  17. Viscoelasticity, Postseismic Slip, Fault Interactions, and the Recurrence of Large Earthquakes

    Science.gov (United States)

    Michael, A. J.

    2003-12-01

    of variability of the inter-event time distribution changes depending on the shape of the loading function. For a given level of noise in the loading process, transient deformation generally has the effect of increasing the coefficient of variability of earthquake inter-event times. Conversely, the level of noise needed to achieve a given level of variability is reduced when transient deformation is included. This would then increase the effect of known fault-interactions modeled as steps in state due to changes in stress or strain because the steps in state due to the known fault-interactions would be larger with respect to the "noise." If earthquake probabilities are estimated solely by empirically fitting inter-event times, the transient loading effect need not be modeled because it produces a similar-shaped distribution as the standard BPT model. However, if the goal is to estimate earthquake probabilities based on the physics of seismogenic processes, then transient deformation must be included. For example, a transient-loading BPT model for the 1906 San Francisco earthquake produces a 60% greater variability in earthquake recurrence when compared to a uniform loading model and the same level of noise. Thus, if transient deformation is included in a BPT model for the faults of the San Francisco Bay region and the noise level is reduced to maintain the same variability in earthquake recurrence, then the effect of the stress change of the 1906 earthquake is greater than for a constant-loading BPT model. Prior work may therefore underestimate the effect of the 1906 stress shadow.

  18. Earthquake Source and Ground Motion Characteristics of Great Kanto Earthquakes

    Science.gov (United States)

    Somerville, P. G.; Sato, T.; Wald, D. J.; Graves, R. W.; Dan, K.

    2003-12-01

    This paper describes the derivation of a rupture model of the 1923 Kanto earthquake, and the estimation of ground motions that occurred during that earthquake and that might occur during future great Kanto earthquakes. The rupture model was derived from the joint inversion of geodetic and teleseismic data. The leveling and triangulation data place strong constraints on the distribution and orientation of slip on the fault. The most concentrated slip is in the shallow central and western part of the fault. The location of the hypocenter on the western part of the fault gives rise to strong near fault rupture directivity effects, which are largest toward the east in the Boso Peninsula. To estimate the ground motions caused by this earthquake, we first calibrated 1D and 3D wave propagation path effects using the Odawara earthquake of 5 August 1990 (M 5.1), the first earthquake larger than M 5 in the last 60 years near the hypocenter of the 1923 Kanto earthquake. The simulation of the moderate-sized Odawara earthquake demonstrates that the 3D velocity model works quite well at reproducing the recorded long-period (T > 3.33 sec) strong motions, including basin-generated surface waves, for a number of sites located throughout the Kanto basin region. Using this validated 3D model along with the rupture model described above, we simulated the long-period (T > 4 sec) ground motions in this region for the 1923 Kanto earthquake. The largest ground motions occur east of the epicenter along the central and southern part of the Boso Peninsula. These large motions arise from strong rupture directivity effects and are comprised of relatively simple, source-controlled pulses with a dominant period of about 10 sec. Other rupture models and hypocenter locations generally produce smaller long period ground motion levels in this region that those of the 1923 event. North of the epicentral region, in the Tokyo area, 3D basin-generated phases are quite significant, and these phases

  19. The 1980 Irpinia-Basilicata earthquake: the environmental phenomena and the choices of reconstruction.

    Science.gov (United States)

    Porfido, Sabina; Alessio, Giuliana; Avallone, Paola; Gaudiosi, Germana; Lombardi, Giovanni; Nappi, Rosa; Salvemini, Raffaella; Spiga, Efisio

    2016-04-01

    This paper, by means of a multidisciplinary approach, deals with changes of the urban and territorial setting in many localities of the epicentral area of the 23 November 1980 Irpinia earthquake. The 23 November 1980 earthquake, known as the "Irpinia-Basilicata earthquake" was the strongest seismic event of the last 80 years in the Southern Apennines of Italy (Mw 6.9, I0=X MCS). It was felt nearly everywhere in Italy, from Sicily in the South, to Emilia Romagna and Liguria in the North. This earthquake was characterized by a complex main rupture, composed of three major sub-events, interpreted as a succession of normal faulting events. Many localities in the Avellino, Salerno and Potenza provinces were nearly completely destroyed (I=IX-X MSK, Postpischl et al., 1985); among them Castelnuovo di Conza, Conza della Campania, Lioni, Santomenna, San Mango sul Calore, San Michele di Serino and Sant'Angelo dei Lombardi. About 800 localities suffered serious damage (Balvano, Bisaccia, Calitri, etc); 75,000 houses collapsed totally and 275,000 were badly damaged. Casualties were 3000, and 10,000 people were wounded. A large amount of information on primary and secondary environmental effects, over all slope movements, was available on the basis of several geological surveys of the area affected by this earthquake. The amount of surface faulting was about 40 km in length and the maximum displacement about 100 cm, while the total area interested by slope movements was estimated in 7400 km2 (Porfido et al., 2002, 2007; Serva et al.2009). In this study we aim to describe trends and specific effects that have taken place in the 35 years following the 1980 earthquake: how the urban and territorial setting have changed, especially in the villages located in the epicentral area; the consequences of the environmental effects on the choices of reconstruction, both in situ, and far from the original historical centre. Therefore, some case histories as San Mango sul Calore and Calitri

  20. Uranium concentrations and 234U/238U activity ratios in fault-associated groundwater as possible earthquake precursors

    Science.gov (United States)

    Finkel, R. C.

    In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and 234U/238U activity ratios have been monitored on a monthly or bimonthly basis in water from 24 wells and springs associated with Southern California fault zones. Uranium concentrations vary from 0.002 ppb at Indian Canyon Springs on the San Jacinto fault to 8.3 ppb at Lake Hughes well on the San Andreas fault in the Palmdale area. 234U/238U activity ratios vary from 0.88 at Agua Caliente Springs on the Elsinore fault to 5.4 at Niland Slab well on the San Andreas fault in the Imperial Valley. There was one large earthquake in the study area during 1979, the 15 October 1979 M=6.6 Imperial Valley earthquake. Correlated with this event, uranium concentrations varied by a factor of more than 60 and activity ratios by a factor of 3 at the Niland Slab site, about 70 km from the epicenter. At the other sites monitored, uranium concentrations varied in time, but with no apparent pattern, while uranium activity ratios remained essentially constant throughout the monitoring period.

  1. San Pascual (1991) Año XXVIII, n. 284

    OpenAIRE

    Pérez, María Dolores, O.S.C. (Directora)

    1991-01-01

    Editorial. Documento de la Santa sede. San Pascual y la Virgen de Gracia. Nueva revista dedicada a San Pascual. Adoración nocturna. Desde la clausura. Vida en el santuario de San Pascual. Orden Franciscana. Coplas a San Pascual Baylón. San Pascual en el arte. Rutas pascualinas. A l'ombra del claustre.

  2. San Pascual (1991) Año XXVIII, n. 284

    OpenAIRE

    Pérez, María Dolores, O.S.C. (Directora)

    1991-01-01

    Editorial. Documento de la Santa sede. San Pascual y la Virgen de Gracia. Nueva revista dedicada a San Pascual. Adoración nocturna. Desde la clausura. Vida en el santuario de San Pascual. Orden Franciscana. Coplas a San Pascual Baylón. San Pascual en el arte. Rutas pascualinas. A l'ombra del claustre.

  3. Extreme value statistics and thermodynamics of earthquakes: large earthquakes

    Directory of Open Access Journals (Sweden)

    B. H. Lavenda

    2000-06-01

    Full Text Available A compound Poisson process is used to derive a new shape parameter which can be used to discriminate between large earthquakes and aftershock sequences. Sample exceedance distributions of large earthquakes are fitted to the Pareto tail and the actual distribution of the maximum to the Fréchet distribution, while the sample distribution of aftershocks are fitted to a Beta distribution and the distribution of the minimum to the Weibull distribution for the smallest value. The transition between initial sample distributions and asymptotic extreme value distributions shows that self-similar power laws are transformed into nonscaling exponential distributions so that neither self-similarity nor the Gutenberg-Richter law can be considered universal. The energy-magnitude transformation converts the Fréchet distribution into the Gumbel distribution, originally proposed by Epstein and Lomnitz, and not the Gompertz distribution as in the Lomnitz-Adler and Lomnitz generalization of the Gutenberg-Richter law. Numerical comparison is made with the Lomnitz-Adler and Lomnitz analysis using the same Catalogue of Chinese Earthquakes. An analogy is drawn between large earthquakes and high energy particle physics. A generalized equation of state is used to transform the Gamma density into the order-statistic Fréchet distribution. Earthquaketemperature and volume are determined as functions of the energy. Large insurance claims based on the Pareto distribution, which does not have a right endpoint, show why there cannot be a maximum earthquake energy.

  4. Earthquake, GIS and multimedia. The 1883 Casamicciola earthquake

    Directory of Open Access Journals (Sweden)

    M. Rebuffat

    1995-06-01

    Full Text Available A series of multimedia monographs concerning the main seismic events that have affected the Italian territory are in the process of being produced for the Documental Integrated Multimedia Project (DIMP started by the Italian National Seismic Survey (NSS. The purpose of the project is to reconstruct the historical record of earthquakes and promote an earthquake public education. Producing the monographs. developed in ARC INFO and working in UNIX. involved designing a special filing and management methodology to integrate heterogeneous information (images, papers, cartographies, etc.. This paper describes the possibilities of a GIS (Geographic Information System in the filing and management of documental information. As an example we present the first monograph on the 1883 Casamicciola earthquake. on the island of Ischia (Campania, Italy. This earthquake is particularly interesting for the following reasons: I historical-cultural context (first destructive seismic event after the unification of Italy; 2 its features (volcanic earthquake; 3 the socioeconomic consequences caused at such an important seaside resort.

  5. Triggered surface slips in southern California associated with the 2010 El Mayor-Cucapah, Baja California, Mexico, earthquake

    Science.gov (United States)

    Rymer, Michael J.; Treiman, Jerome A.; Kendrick, Katherine J.; Lienkaemper, James J.; Weldon, Ray J.; Bilham, Roger; Wei, Meng; Fielding, Eric J.; Hernandez, Janis L.; Olson, Brian P.E.; Irvine, Pamela J.; Knepprath, Nichole; Sickler, Robert R.; Tong, Xiaopeng; Siem, Martin E.

    2011-01-01

    The April 4, 2010 (Mw7.2), El Mayor-Cucapah, Baja California, Mexico, earthquake is the strongest earthquake to shake the Salton Trough area since the 1992 (Mw7.3) Landers earthquake. Similar to the Landers event, ground-surface fracturing occurred on multiple faults in the trough. However, the 2010 event triggered surface slip on more faults in the central Salton Trough than previous earthquakes, including multiple faults in the Yuha Desert area, the southwestern section of the Salton Trough. In the central Salton Trough, surface fracturing occurred along the southern San Andreas, Coyote Creek, Superstition Hills, Wienert, Kalin, and Imperial Faults and along the Brawley Fault Zone, all of which are known to have slipped in historical time, either in primary (tectonic) slip and/or in triggered slip. Surface slip in association with the El Mayor-Cucapah earthquake is at least the eighth time in the past 42 years that a local or regional earthquake has triggered slip along faults in the central Salton Trough. In the southwestern part of the Salton Trough, surface fractures (triggered slip) occurred in a broad area of the Yuha Desert. This is the first time that triggered slip has been observed in the southwestern Salton Trough.

  6. Post-1906 stress recovery of the San Andreas fault system calculated from three-dimensional finite element analysis

    Science.gov (United States)

    Parsons, T.

    2002-01-01

    The M = 7.8 1906 San Francisco earthquake cast a stress shadow across the San Andreas fault system, inhibiting other large earthquakes for at least 75 years. The duration of the stress shadow is a key question in San Francisco Bay area seismic hazard assessment. This study presents a three-dimensional (3-D) finite element simulation of post-1906 stress recovery. The model reproduces observed geologic slip rates on major strike-slip faults and produces surface velocity vectors comparable to geodetic measurements. Fault stressing rates calculated with the finite element model are evaluated against numbers calculated using deep dislocation slip. In the finite element model, tectonic stressing is distributed throughout the crust and upper mantle, whereas tectonic stressing calculated with dislocations is focused mostly on faults. In addition, the finite element model incorporates postseismic effects such as deep afterslip and viscoelastic relaxation in the upper mantle. More distributed stressing and postseismic effects in the finite element model lead to lower calculated tectonic stressing rates and longer stress shadow durations (17-74 years compared with 7-54 years). All models considered indicate that the 1906 stress shadow was completely erased by tectonic loading no later than 1980. However, the stress shadow still affects present-day earthquake probability. Use of stressing rate parameters calculated with the finite element model yields a 7-12% reduction in 30-year probability caused by the 1906 stress shadow as compared with calculations not incorporating interactions. The aggregate interaction-based probability on selected segments (not including the ruptured San Andreas fault) is 53-70% versus the noninteraction range of 65-77%.

  7. Scientific Drilling Into the San Andreas Fault Zone —An Overview of SAFOD’s First Five Years

    Directory of Open Access Journals (Sweden)

    Stephen Hickman

    2011-03-01

    Full Text Available The San Andreas Fault Observatory at Depth (SAFODwas drilled to study the physical and chemical processes controlling faulting and earthquake generation along an active, plate-bounding fault at depth. SAFOD is located near Parkfield, California and penetrates a section of the fault that is moving due to a combination of repeating microearthquakes and fault creep. Geophysical logs define the SanAndreas Fault Zone to be relatively broad (~200 m, containing several discrete zones only 2–3 m wide that exhibit very low P- and S-wave velocities and low resistivity. Two of these zones have progressively deformed the cemented casing at measured depths of 3192 m and 3302 m. Cores from both deforming zones contain a pervasively sheared, cohesionless, foliated fault gouge that coincides with casing deformation and explains the observed extremely low seismic velocities and resistivity. These cores are being now extensivelytested in laboratories around the world, and their composition, deformation mechanisms, physical properties, and rheological behavior are studied. Downhole measurements show that within 200 m (maximum of the active fault trace, the direction of maximum horizontal stress remains at a high angle to the San Andreas Fault, consistent with other measurements. The results from the SAFOD Main Hole, together with the stress state determined in the Pilot Hole, are consistent with a strong crust/weak fault model of the San Andreas. Seismic instrumentation has been deployed to study physics of faulting—earthquake nucleation, propagation, and arrest—in order to test how laboratory-derived concepts scale up to earthquakes occurring in nature.

  8. Species - San Diego Co. [ds121

    Data.gov (United States)

    California Department of Resources — This is the Biological Observation Database point layer representing baseline observations of sensitive species (as defined by the MSCP) throughout San Diego County....

  9. 33 CFR 165.1102 - Security Zone; Naval Base Point Loma; San Diego Bay, San Diego, CA.

    Science.gov (United States)

    2010-07-01

    ... Loma; San Diego Bay, San Diego, CA. 165.1102 Section 165.1102 Navigation and Navigable Waters COAST... Guard District § 165.1102 Security Zone; Naval Base Point Loma; San Diego Bay, San Diego, CA. (a) Location. The following area is a security zone: The water adjacent to the Naval Base Point Loma, San Diego...

  10. The music of earthquakes and Earthquake Quartet #1

    Science.gov (United States)

    Michael, Andrew J.

    2013-01-01

    Earthquake Quartet #1, my composition for voice, trombone, cello, and seismograms, is the intersection of listening to earthquakes as a seismologist and performing music as a trombonist. Along the way, I realized there is a close relationship between what I do as a scientist and what I do as a musician. A musician controls the source of the sound and the path it travels through their instrument in order to make sound waves that we hear as music. An earthquake is the source of waves that travel along a path through the earth until reaching us as shaking. It is almost as if the earth is a musician and people, including seismologists, are metaphorically listening and trying to understand what the music means.

  11. Using earthquake intensities to forecast earthquake occurrence times

    Directory of Open Access Journals (Sweden)

    J. R. Holliday

    2006-01-01

    Full Text Available It is well known that earthquakes do not occur randomly in space and time. Foreshocks, aftershocks, precursory activation, and quiescence are just some of the patterns recognized by seismologists. Using the Pattern Informatics technique along with relative intensity analysis, we create a scoring method based on time dependent relative operating characteristic diagrams and show that the occurrences of large earthquakes in California correlate with time intervals where fluctuations in small earthquakes are suppressed relative to the long term average. We estimate a probability of less than 1% that this coincidence is due to random clustering. Furthermore, we show that the methods used to obtain these results may be applicable to other parts of the world.

  12. 77 FR 57494 - Safety Zone; Fleet Week Fireworks, San Francisco Bay, San Francisco, CA

    Science.gov (United States)

    2012-09-18

    ... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; Fleet Week Fireworks, San Francisco Bay, San Francisco... will enforce the safety zone for the Fleet Week Fireworks in the Captain of the Port, San Francisco...'' W (NAD83) for the Fleet Week Fireworks in 33 CFR 165.1191, Table 1, item number 25. This safety...

  13. 78 FR 10062 - Safety Zone; Sea World San Diego Fireworks, Mission Bay; San Diego, CA

    Science.gov (United States)

    2013-02-13

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Sea World San Diego Fireworks, Mission Bay; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of Mission Bay in support of the Sea World San Diego...

  14. 77 FR 42649 - Safety Zone: Sea World San Diego Fireworks, Mission Bay; San Diego, CA

    Science.gov (United States)

    2012-07-20

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone: Sea World San Diego Fireworks, Mission Bay; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is... rule, call or email Petty Officer David Varela, Waterways Management, U.S. Coast Guard Sector San Diego...

  15. 77 FR 60899 - Safety Zone; Sea World San Diego Fireworks, Mission Bay; San Diego, CA

    Science.gov (United States)

    2012-10-05

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Sea World San Diego Fireworks, Mission Bay; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of Mission Bay in support of the Sea World San Diego...

  16. 77 FR 42638 - Safety Zone: Sea World San Diego Fireworks, Mission Bay; San Diego, CA

    Science.gov (United States)

    2012-07-20

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone: Sea World San Diego Fireworks, Mission Bay; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of Mission Bay in support of the Sea World San Diego...

  17. 78 FR 29025 - Sea World San Diego Fireworks 2013 Season; Mission Bay, San Diego, CA

    Science.gov (United States)

    2013-05-17

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Sea World San Diego Fireworks 2013 Season; Mission Bay, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a safety zone on the navigable waters of Mission Bay in support of the Sea World San Diego...

  18. 76 FR 46352 - Approval of Noise Compatibility Program for San Diego International, San Diego, CA

    Science.gov (United States)

    2011-08-02

    ... Federal Aviation Administration Approval of Noise Compatibility Program for San Diego International, San Diego, CA AGENCY: Federal Aviation Administration, DOT. ACTION: Notice . SUMMARY: The Federal Aviation Administration (FAA) announces its findings on the noise compatibility program submitted by San Diego Regional...

  19. 78 FR 77597 - Safety Zone; Allied PRA-Solid Works, San Diego Bay; San Diego, CA

    Science.gov (United States)

    2013-12-24

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Allied PRA-Solid Works, San Diego Bay; San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone on the navigable waters of the San Diego Bay in support of a fireworks...

  20. Retrospection on the Conclusions of Earthquake Tendency Forecast before the Wenchuan Ms8.0 Earthquake

    Institute of Scientific and Technical Information of China (English)

    Liu Jie; Guo Tieshuan; Yang Liming; Su Youjin; Li Gang

    2009-01-01

    The reason for the failure to forecast the Wenchuan Ms8.0 earthquake is under study, based on the systematically collection of the seismicity anomalies and their analysis results from annual earthquake tendency forecasts between the 2001 Western Kuulun Mountains Pass Ms8.1 earthquake and the 2008 Wenchuan Ms8.0 earthquake. The results show that the earthquake tendency estimation of Chinese Mainland is for strong earthquakes to occur in the active stage, and that there is still potential for the occurrence of a Ms8.0 large earthquake in Chinese Mainland after the 2001 Western Kunlun Mountains Pass earthquake. However the phenomena that many large earthquakes occurred around Chinese Mainland, and the 6-year long quietude of Ms7.0 earthquake and an obvious quietude of Ms5.0 and Ms6.0 earthquakes during 2002 ~2007 led to the distinctly lower forecast estimation of earthquake tendency in Chinese Mainland after 2006. The middle part in the north-south seismic belt has been designated a seismic risk area of strong earthquake in recent years, but, the estimation of the risk degree in Southwestern China is insufficient after the Ning'er Ms6.4 earthquake in Yunnan in 2007. There are no records of earthquakes with Ms≥7.0 in the Longmenshan fault, which is one of reasons that this fault was not considered a seismic risk area of strong earthquakes in recent years.

  1. LLNL-Generated Content for the California Academy of Sciences, Morrison Planetarium Full-Dome Show: Earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, A J; Petersson, N A; Morency, C E; Simmons, N A; Sjogreen, B

    2012-01-23

    The California Academy of Sciences (CAS) Morrison Planetarium is producing a 'full-dome' planetarium show on earthquakes and asked LLNL to produce content for the show. Specifically the show features numerical ground motion simulations of the M 7.9 1906 San Francisco and a possible future M 7.05 Hayward fault scenario earthquake. The show also features concepts of plate tectonics and mantle convection using images from LLNL's G3D global seismic tomography. This document describes the data that was provided to the CAS in support of production of the 'Earthquake' show. The CAS is located in Golden Gate Park, San Francisco and hosts over 1.6 million visitors. The Morrison Planetarium, within the CAS, is the largest all digital planetarium in the world. It features a 75-foot diameter spherical section projection screen tilted at a 30-degree angle. Six projectors cover the entire field of view and give a three-dimensional immersive experience. CAS shows strive to use scientifically accurate digital data in their productions. The show, entitled simply 'Earthquake', will debut on 26 May 2012. They are working on graphics and animations based on the same data sets for display on LLNL powerwalls and flat-screens as well as for public release.

  2. Earthquake forecast via neutrino tomography

    Institute of Scientific and Technical Information of China (English)

    WANG Bin; CHEN Ya-Zheng; LI Xue-Qian

    2011-01-01

    We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. An- tineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomog- raphy of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for ν emitted from a reactor. The case for a ν beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.

  3. Potential Effects of a Scenario Earthquake on the Economy of Southern California: Intraregional Commuter, Worker, and Earnings Flow Analysis

    Science.gov (United States)

    Sherrouse, Benson C.; Hester, David J.

    2008-01-01

    The Multi-Hazards Demonstration Project (MHDP) is a collaboration between the U.S. Geological Survey (USGS) and various partners from the public and private sectors and academia, meant to improve Southern California's resiliency to natural hazards (Jones and others, 2007). In support of the MHDP objectives, the ShakeOut Scenario was developed. It describes a magnitude 7.8 (M7.8) earthquake along the southernmost 300 kilometers (200 miles) of the San Andreas Fault, identified by geoscientists as a plausible event that will cause moderate to strong shaking over much of the eight-county (Imperial, Kern, Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura) Southern California region (Jones and others, 2008). This report uses selected datasets from the U.S. Census Bureau and the State of California's Employment Development Department to develop preliminary estimates of the number and spatial distribution of commuters who cross the San Andreas Fault and to characterize these commuters by the industries in which they work and their total earnings. The analysis concerns the relative exposure of the region's economy to the effects of the earthquake as described by the location, volume, and earnings of those commuters who work in each of the region's economic sectors. It is anticipated that damage to transportation corridors traversing the fault would lead to at least short-term disruptions in the ability of commuters to travel between their places of residence and work.

  4. Extreme value distribution of earthquake magnitude

    Science.gov (United States)

    Zi, Jun Gan; Tung, C. C.

    1983-07-01

    Probability distribution of maximum earthquake magnitude is first derived for an unspecified probability distribution of earthquake magnitude. A model for energy release of large earthquakes, similar to that of Adler-Lomnitz and Lomnitz, is introduced from which the probability distribution of earthquake magnitude is obtained. An extensive set of world data for shallow earthquakes, covering the period from 1904 to 1980, is used to determine the parameters of the probability distribution of maximum earthquake magnitude. Because of the special form of probability distribution of earthquake magnitude, a simple iterative scheme is devised to facilitate the estimation of these parameters by the method of least-squares. The agreement between the empirical and derived probability distributions of maximum earthquake magnitude is excellent.

  5. Earthquakes in Central California, 1980-1984

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — There have been many earthquake occurrences in central California. This set of slides shows earthquake damage from the following events: Livermore, 1980, Coalinga,...

  6. The SCEC TeraShake Earthquake Simulation

    Science.gov (United States)

    Minster, J.; Olsen, K. B.; Moore, R.; Day, S.; Maechling, P.; Jordan, T.; Faerman, M.; Cui, Y.; Ely, G.; Hu, Y.; Shkoller, B.; Marcinkovich, C.; Bielak, J.; Okaya, D.; Archuleta, R.; Wilkins-Diehr, N.; Cutchin, S.; Chourasia, A.; Kremenek, G.; Jagatheesan, A.; Brieger, L.; Majundar, A.; Chukkapalli, G.; Xin, Q.; Moore, R.; Banister, B.; Thorp, D.; Kovatch, P.; Diegel, L.; Sherwin, T.; Jordan, C.; Thiebaux, M.; Lopez, J.

    2004-12-01

    The southern portion of the San Andreas fault, between Cajon Creek and Bombay Beach has not seen a major event since 1690, and has therefore accumulated a slip deficit of 5-6 m. The potential for this portion of the fault to rupture in a single M7.7 event is a major component of seismic hazard in southern California and northern Mexico. TeraShake is a large-scale finite-difference (fourth-order) simulation of such an event based on Olsen's Anelastic Wave Propagation Model (AWM) code, and conducted in the context of the Southern California Earthquake Center Community Modeling Environment (CME). The fault geometry is taken from the 2002 USGS National Hazard Maps. The kinematic slip function is transported and scaled from published inversions for the 2002 Denali (M7.9) earthquake. The three-dimensional crustal structure is the SCEC Community Velocity model. The 600km x 300km x 80km simulation domain extends from the Ventura Basin and Tehachapi region to the north and to Mexicali and Tijuana to the south. It includes all major population centers in southern California, and is modeled at 200m resolution using a rectangular, 1.8 giganode, 3000 x 1500 x 400 mesh. The simulated duration is 200 seconds, with a temporal resolution of 0.01seconds, maximum frequency of 0.5Hz, for a total of 20,000 time steps. The simulation is planned to run at the San Diego Supercomputer Center (SDSC) on 240 processors of the IBM Power4, DataStar machine. Validation runs conducted at one sixteenth (4D) resolution have shown that this is the optimal configuration in the trade-off between computational and I/O demands. The full run will consume about 18,000 CPU.hours. Each time step produces a 21.6GByte mesh snapshot of the entire ground motion velocity vectors. A 4D wavefield containing 2,000 time steps, amounting to 43 Tbytes of data, will be stored at SDSC. Surface data will be archived for every time step for synthetic seismogram engineering analysis, totaling 1 Tbyte. The data will be

  7. Cuartel San Carlos. Yacimiento veterano

    Directory of Open Access Journals (Sweden)

    Mariana Flores

    2007-01-01

    Full Text Available El Cuartel San Carlos es un monumento histórico nacional (1986 de finales del siglo XVIII (1785-1790, caracterizado por sufrir diversas adversidades en su construcción y soportar los terremotos de 1812 y 1900. En el año 2006, el organismo encargado de su custodia, el Instituto de Patrimonio Cultural del Ministerio de Cultura, ejecutó tres etapas de exploración arqueológica, que abarcaron las áreas Traspatio, Patio Central y las Naves Este y Oeste de la edificación. Este trabajo reseña el análisis de la documentación arqueológica obtenida en el sitio, a partir de la realización de dicho proyecto, denominado EACUSAC (Estudio Arqueológico del Cuartel San Carlos, que representa además, la tercera campaña realizada en el sitio. La importancia de este yacimiento histórico, radica en su participación en los acontecimientos que propiciaron conflictos de poder durante el surgimiento de la República y en los sucesos políticos del siglo XX. De igual manera, se encontró en el sitio una amplia muestra de materiales arqueológicos que reseñan un estilo de vida cotidiana militar, así como las dinámicas sociales internas ocurridas en el San Carlos, como lugar estratégico para la defensa de los diferentes regímenes que atravesó el país, desde la época del imperialismo español hasta nuestros días.

  8. Ground fracturing at the southern end of Summit Ridge caused by October 17, 1989 Loma Prieta, California, earthquake sequence (maps of Summit Ridge Shear Zones, en echelon tension cracks, complex and compound fractures, and small faults that formed coactively with the earthquake sequence)

    Energy Technology Data Exchange (ETDEWEB)

    Martosudarmo, S.Y. [BPP Technologi, Jakarta (Indonesia); Johnson, A.M. [Purdue Univ., West Lafayette, IN (United States). Harry Fielding Reid Earthquake Research Lab.; Fleming, R.W. [Geological Survey, Denver, CO (United States)

    1997-12-31

    The Loma Prieta earthquake of 17 October 1989 was the first of three large earthquakes that occurred in California in less than 5 years. The main shock of the Loma Prieta earthquake was deep-seated, the rupture zones of the main shock did not reach the surface, and the earthquake produced enigmatic surface ruptures along the frontal faults of the Coast Range and in the epicentral area that were explained in several quite different ways. The Landers earthquake of 28 June 1992 was near surface and produced more than 80 km of spectacular surface rupture of many different kinematic expressions. Detailed study of fractures at Landers has provided a basis for re-evaluating earlier work on fractures produced by the Loma Prieta earthquake. This paper is a description of some of the fractures produced by the Loma Prieta earthquake and a discussion of their causes. Detailed mapping (scale of 1:250) in an area on either side of Summit Road and between Morrell Cutoff Road in the northwest and the intersection of Summit Road and San Jose-Soquel Road in the southeast has provided documentation of fracture orientations and differential displacements required to decipher the ground deformation in that area during the Loma Prieta earthquake.

  9. Nonstationary ETAS models for nonstandard earthquakes

    OpenAIRE

    Kumazawa, Takao; Ogata, Yosihiko

    2014-01-01

    The conditional intensity function of a point process is a useful tool for generating probability forecasts of earthquakes. The epidemic-type aftershock sequence (ETAS) model is defined by a conditional intensity function, and the corresponding point process is equivalent to a branching process, assuming that an earthquake generates a cluster of offspring earthquakes (triggered earthquakes or so-called aftershocks). Further, the size of the first-generation cluster depends on the magnitude of...

  10. The October 12, 1992, Dahshur, Egypt, Earthquake

    Science.gov (United States)

    Thenhaus, P.C.; Celebi, M.; Sharp, R.V.

    1993-01-01

    Cairo and northeastern Egypt experienced a rare, damaging earthquake on October 12, 1992. The earthquake, which measured 5.9 on the Richter magnitude scale, was centered near the village of Dahshur, about 18 km south of Cairo. The computed hypocentral depth of the earthquake, about 25 km, is consistent with the fact that fault rupture associated with the earthquake did not reach the surface. 

  11. PRECURSORS OF EARTHQUAKES: VLF SIGNALSIONOSPHERE IONOSPHERE RELATION

    Directory of Open Access Journals (Sweden)

    Mustafa ULAS

    2013-01-01

    Full Text Available lot of people have died because of earthquakes every year. Therefore It is crucial to predict the time of the earthquakes reasonable time before it had happed. This paper presents recent information published in the literature about precursors of earthquakes. The relationships between earthquakes and ionosphere are targeted to guide new researches in order to study further to find novel prediction methods.

  12. Downtown revitalization in San Salvador

    OpenAIRE

    Ejeborn, Elisabet; Nedersjö, Julia

    2012-01-01

    The aim of this master’s thesis in spatial planning is to research the conditions in the historic city centre of San Salvador and make a strategy and urban design proposal for the area, but also to investigate the relationship between economic development, public institutions and the public space in this area. The research has been done through literature studies on El Salvador and formal/informal economy, onsite inventory, studies of good examples and interviews with people in the area. In t...

  13. Downtown revitalization in San Salvador

    OpenAIRE

    Ejeborn, Elisabet; Nedersjö, Julia

    2012-01-01

    The aim of this master’s thesis in spatial planning is to research the conditions in the historic city centre of San Salvador and make a strategy and urban design proposal for the area, but also to investigate the relationship between economic development, public institutions and the public space in this area. The research has been done through literature studies on El Salvador and formal/informal economy, onsite inventory, studies of good examples and interviews with people in the area. In t...

  14. Are "uncharacteristic" earthquakes spatially linked to strike-slip restraining bends?

    Science.gov (United States)

    Mann, P.

    2011-12-01

    On the basis of a compilation of paleoseismological data from the Wasatch and San Andreas faults, Schwartz and Coppersmith (1984) proposed that both plate boundary and intraplate faults tend to generate essentially same size earthquakes having a relatively narrow range of magnitudes near the maximum. They referred to these earthquakes as "characteristic earthquakes". Their hypothesis suggests that the historical record of earthquakes documented for periods of time ranging from centuries to millennia in different parts of the world that could allow predictions of future ruptures. The characteristic earthquake model works surprisingly well for major strike-slip faults like the North Anatolian fault of Turkey and the North Tabriz strike-slip fault in Iran which both show a progressive, uni-direction pattern of rupture starting at one point and "unzippering" over a distance of hundreds of kilometers in a series of earthquakes. This regular periodicity has been attributed to systematic changes in Coulomb failure stress on individual faults or interconnected fault networks defined by distinctive changes in fault strike, or stepover faults, or by the intersection of a neighboring fault. However, studies of the San Andreas, Wasatch, and Dead Sea faults show that earthquake ruptures are not periodic and instead form clusters of events with no obvious "recurrence interval" as predicted by the characteristic earthquake model. Some of these hard-to-forecast "uncharacteristic" earthquakes initiate as blind thrust faults formed at deeper levels in the crust near the brittle-plastic transition zone as illustrated by the 1989 M 6.9 Loma Prieta earthquake of California. Such events would produce little or no surface rupture of the main fault plane so the effects of this type of earthquake would remain impossible for future paleoseismologists to discern (other than from shaking effects and the broad vertical uplift related to vertical motions on deeply buried faults). More recently

  15. Dynamically Triggered Earthquakes in the Geysers Region following the 2014 M6.0 South Napa Earthquake

    Science.gov (United States)

    Meng, X.; Peng, Z.; Aiken, C.; Kilb, D.

    2014-12-01

    The 08/24/2014 M6.0 South Napa earthquake is the largest seismic event to strike the San Francisco Bay Area since the 10/17/1989 M6.9 Loma Prieta earthquake. The South Napa event caused severe damage near the epicenter. Based on the Northern California Seismic Network (NCSN) catalog, we find a clear increase of seismicity near the Geysers Geothermal Field following the South Napa event, which is located along its rupture directivity path ~50 km NNW from the hypocenter. Visually inspecting 10 Hz high-pass filtered waveforms at seismic stations near Geysers, we can identify many local earthquakes during the surface waves of the mainshock event that are missing from the NCSN catalog. To obtain a more complete catalog, we apply a recently developed matched filter technique to detect new events within continuous seismic recordings from 74 seismic stations near the Geysers. We use 4000 local earthquakes listed in the NCSN catalog from 06/01/2014 to 09/10/2014 as templates and systematically scan continuous data within ±7 days from the South Napa mainshock. As a result, we detect ~10 times more earthquakes than in the NCSN catalog, and the magnitude of completeness reduces from 0.75 to -0.6. Of the 8091 new events, 28 occurred within the mainshock wavetrain. Depending on the filter used, the first triggered event has an inferred magnitude in the range 3.6-4.0. The intensive seismic activity near the Geysers gradually decays with a p-value of ~0.7 and returns to pre-shock level in about one day. We fit the seismicity rate in the week prior to the South Napa event with the Epidemic Type Aftershock Sequence (ETAS) model and extrapolate to obtain a post-mainshock rate. The observed post-mainshock seismicity rate clearly deviates from the ETAS prediction, which suggests that not all increased seismicity near the Geysers can be explained as aftershocks of the first triggered event. Instead these new events may be associated with stress transients (e.g. creep) or fluid

  16. Southern California Earthquake Center - SCEC1: Final Report Summary Alternative Earthquake Source Characterization for the Los Angeles Region

    Energy Technology Data Exchange (ETDEWEB)

    Foxall, B

    2003-02-26

    The objective my research has been to synthesize current understanding of the tectonics and faults of the Los Angeles Basin and surrounding region to quantify uncertainty in the characterization of earthquake sources used for geologically- and geodetically-based regional earthquake likelihood models. This work has focused on capturing epistemic uncertainty; i.e. uncertainty stemming from ignorance of the true characteristics of the active faults in the region and of the tectonic forces that drive them. In the present context, epistemic uncertainty has two components: First, the uncertainty in source geometrical and occurrence rate parameters deduced from the limited geological, geophysical and geodetic observations available; and second. uncertainties that result from fundamentally different interpretations of regional tectonic deformation and faulting. Characterization of the large number of active and potentially active faults that need to be included in estimating earthquake occurrence likelihoods for the Los Angeles region requires synthesis and evaluation of large amounts of data and numerous interpretations. This was accomplished primarily through a series of carefully facilitated workshops, smaller meetings involving key researchers, and email groups. The workshops and meetings were made possible by the unique logistical and financial resources available through SCEC, and proved to be extremely effective forums for the exchange and critical debate of data and interpretations that are essential in constructing fully representative source models. The main products from this work are a complete source model that characterizes all know or potentially active faults in the greater Los Angeles region. which includes the continental borderland as far south as San Diego, the Ventura Basin, and the Santa Barbara Channel. The model constitutes a series of maps and representative cross-sections that define alternative fault geometries, a table containing rault

  17. Fault geometry and earthquake mechanics

    Directory of Open Access Journals (Sweden)

    D. J. Andrews

    1994-06-01

    Full Text Available Earthquake mechanics may be determined by the geometry of a fault system. Slip on a fractal branching fault surface can explain: 1 regeneration of stress irregularities in an earthquake; 2 the concentration of stress drop in an earthquake into asperities; 3 starting and stopping of earthquake slip at fault junctions, and 4 self-similar scaling of earthquakes. Slip at fault junctions provides a natural realization of barrier and asperity models without appealing to variations of fault strength. Fault systems are observed to have a branching fractal structure, and slip may occur at many fault junctions in an earthquake. Consider the mechanics of slip at one fault junction. In order to avoid a stress singularity of order 1/r, an intersection of faults must be a triple junction and the Burgers vectors on the three fault segments at the junction must sum to zero. In other words, to lowest order the deformation consists of rigid block displacement, which ensures that the local stress due to the dislocations is zero. The elastic dislocation solution, however, ignores the fact that the configuration of the blocks changes at the scale of the displacement. A volume change occurs at the junction; either a void opens or intense local deformation is required to avoid material overlap. The volume change is proportional to the product of the slip increment and the total slip since the formation of the junction. Energy absorbed at the junction, equal to confining pressure times the volume change, is not large enongh to prevent slip at a new junction. The ratio of energy absorbed at a new junction to elastic energy released in an earthquake is no larger than P/µ where P is confining pressure and µ is the shear modulus. At a depth of 10 km this dimensionless ratio has th value P/µ= 0.01. As slip accumulates at a fault junction in a number of earthquakes, the fault segments are displaced such that they no longer meet at a single point. For this reason the

  18. EARTHQUAKES - VOLCANOES (Causes - Forecast - Counteraction)

    Science.gov (United States)

    Tsiapas, Elias

    2014-05-01

    Earthquakes and volcanoes are caused by: 1)Various liquid elements (e.g. H20, H2S, S02) which emerge from the pyrosphere and are trapped in the space between the solid crust and the pyrosphere (Moho discontinuity). 2)Protrusions of the solid crust at the Moho discontinuity (mountain range roots, sinking of the lithosphere's plates). 3)The differential movement of crust and pyrosphere. The crust misses one full rotation for approximately every 100 pyrosphere rotations, mostly because of the lunar pull. The above mentioned elements can be found in small quantities all over the Moho discontinuity, and they are constantly causing minor earthquakes and small volcanic eruptions. When large quantities of these elements (H20, H2S, SO2, etc) concentrate, they are carried away by the pyrosphere, moving from west to east under the crust. When this movement takes place under flat surfaces of the solid crust, it does not cause earthquakes. But when these elements come along a protrusion (a mountain root) they concentrate on its western side, displacing the pyrosphere until they fill the space created. Due to the differential movement of pyrosphere and solid crust, a vacuum is created on the eastern side of these protrusions and when the aforementioned liquids overfill this space, they explode, escaping to the east. At the point of their escape, these liquids are vaporized and compressed, their flow accelerates, their temperature rises due to fluid friction and they are ionized. On the Earth's surface, a powerful rumbling sound and electrical discharges in the atmosphere, caused by the movement of the gasses, are noticeable. When these elements escape, the space on the west side of the protrusion is violently taken up by the pyrosphere, which collides with the protrusion, causing a major earthquake, attenuation of the protrusions, cracks on the solid crust and damages to structures on the Earth's surface. It is easy to foresee when an earthquake will occur and how big it is

  19. Historical earthquake investigations in Greece

    Directory of Open Access Journals (Sweden)

    K. Makropoulos

    2004-06-01

    Full Text Available The active tectonics of the area of Greece and its seismic activity have always been present in the country?s history. Many researchers, tempted to work on Greek historical earthquakes, have realized that this is a task not easily fulfilled. The existing catalogues of strong historical earthquakes are useful tools to perform general SHA studies. However, a variety of supporting datasets, non-uniformly distributed in space and time, need to be further investigated. In the present paper, a review of historical earthquake studies in Greece is attempted. The seismic history of the country is divided into four main periods. In each one of them, characteristic examples, studies and approaches are presented.

  20. 13 CFR 120.174 - Earthquake hazards.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Earthquake hazards. 120.174... Applying to All Business Loans Requirements Imposed Under Other Laws and Orders § 120.174 Earthquake..., the construction must conform with the “National Earthquake Hazards Reduction Program (“NEHRP...

  1. Hoy hace: El Sismo de San Antolín, el 2 de septiembre de 1841, un desastre en el desarrollo libre de Costa Rica

    OpenAIRE

    Peraldo Huertas, Giovanni

    2005-01-01

    Hace un recuento sobre el principal temblor del siglo XIX, conocido como el terremoto de San Antolín, en el año 1841, basado en algunos documentos históricos. Expone características del sismo como las zonas donde se sintió y que además tuvieron daños. Comenta sobre las políticas de mitigación que el Estado proclamó y hace una reflexión sobre una de las características sociales de la época It does a re-count of the main earthquake of the 19th Century known as the San Antolín earthquake, ye...

  2. Aseismic slip on the San Andreas Fault south of Loma Prieta

    Science.gov (United States)

    Behr, J.; Bilham, R.; Bodin, P.; Burfoid, R. O.; Bürgmann, R.

    Two digital creepmeters installed within the San Andreas fault zone after the 18 Oct 1989 Loma Prieta main shock show less than 1 cm of post seismic right-lateral slip in the four months following the earthquake. At Mt. Madonna road a 23 mm coseismic fracture slipped a further 3 mm after heavy rain, and at Nyland Ranch near San Juan Bautista the fault slipped approximately 9 mm starting 42 days after the main shock. If the current trend at Nyland Ranch persists, more than 2 cm of post seismic slip will develop by 1991. At both sites minor left-lateral displacements occurred which are attributed to near-surface soil effects. The abutments of the railroad bridge across the Pajaro River at Chittenden, which were extended by the 1906 earthquake, were not extended during the Loma Prieta event although they have evidently moved apart by more than 7 cm since bridge reconstruction in 1940. This corresponds to 10 cm of right-lateral slip which could be related to M>5 events in mid-century or could be due to aseismic slip at a mean rate of 2.1 mm/a. The absence of significant surface slip within the fault zone in the decades before and the months following the Loma Prieta event suggests either that near-surface deformation is distributed over a wide zone or that a slip deficit remains. Several authors have proposed this region as a future location for M≈5 events.

  3. Scaling relation for earthquake networks

    CERN Document Server

    Abe, Sumiyoshi

    2008-01-01

    The scaling relation derived by Dorogovtsev, Goltsev, Mendes and Samukhin [Phys. Rev. E, 68 (2003) 046109] states that the exponents of the power-law connectivity distribution, gamma, and the power-law eigenvalue distribution of the adjacency matrix, delta, of a locally treelike scale-free network satisfy 2*gamma - delta = 1 in the mean field approximation. Here, it is shown that this relation holds well for the reduced simple earthquake networks (without tadpole-loops and multiple edges) constructed from the seismic data taken from California and Japan. The result is interpreted from the viewpoint of the hierarchical organization of the earthquake networks.

  4. Computational methods in earthquake engineering

    CERN Document Server

    Plevris, Vagelis; Lagaros, Nikos

    2017-01-01

    This is the third book in a series on Computational Methods in Earthquake Engineering. The purpose of this volume is to bring together the scientific communities of Computational Mechanics and Structural Dynamics, offering a wide coverage of timely issues on contemporary Earthquake Engineering. This volume will facilitate the exchange of ideas in topics of mutual interest and can serve as a platform for establishing links between research groups with complementary activities. The computational aspects are emphasized in order to address difficult engineering problems of great social and economic importance. .

  5. Earthquakes triggered by fluid extraction

    Science.gov (United States)

    Segall, P.

    1989-01-01

    Seismicity is correlated in space and time with production from some oil and gas fields where pore pressures have declined by several tens of megapascals. Reverse faulting has occurred both above and below petroleum reservoirs, and normal faulting has occurred on the flanks of at least one reservoir. The theory of poroelasticity requires that fluid extraction locally alter the state of stress. Calculations with simple geometries predict stress perturbations that are consistent with observed earthquake locations and focal mechanisms. Measurements of surface displacement and strain, pore pressure, stress, and poroelastic rock properties in such areas could be used to test theoretical predictions and improve our understanding of earthquake mechanics. -Author

  6. Three-dimensional crustal structure influences on wave propagation and generation of strong ground motion in the greater San Francisco Bay region

    Science.gov (United States)

    Stidham, Christiane Wilson

    Recent development of three-dimensional finite-difference codes allows simulation of earthquakes using realistic three-dimensional earth models. These and other developments have shifted emphasis in seismology from earthquake prediction to estimation of location and magnitude of damage in future earthquakes. The accurate calculation of ground motions for future large earthquakes depends upon detailed knowledge of three-dimensional (3D) geologic structure and the earthquake source process, as well as sufficient computational resources. Knowledge of subsurface geologic structure in the San Francisco Bay Area is quite good relative to many areas, and this knowledge has been incorporated into a 3D velocity model of the Bay Area. With access to a 3D finite-difference code (E3D) developed by Shawn Larsen at Lawrence Livermore National Laboratory and use of super-computing resources at Livermore, we are able to complete calculations for simulations of a number of San Francisco Bay Area earthquakes. These include a small 1993 Rodgers Creek event recorded at Berkeley Seismological Laboratory, the 1989 Loma Prieta event recorded on the U.S. Geological Survey and Calif. Div. of Mines and Geology network of strong motion stations, and a number of small South Bay events (including the 8/12/98 San Juan Bautista EQ) recorded on a temporary USGS/UCB/PASSCAL Santa Clara array. In each of these cases, comparison of synthetic results (synthetic seismograms and plots of maximum horizontal ground velocity) from E3D to recorded data from the event gives an excellent opportunity to both judge the usefulness and the constraints necessary in using finite-difference modeling and the validity of the velocity model as it is now constructed. Results show that 3D finite-difference modeling produces waveforms that are often quite comparable to recorded data, and that fit the data considerably better than synthetics waveforms derived with a 1D velocity model. It is also possible to explore the

  7. Broadband records of earthquakes in deep gold mines and a comparison with results from SAFOD, California

    Science.gov (United States)

    McGarr, A.; Boettcher, M.; Fletcher, Joe B.; Sell, R.; Johnston, M.J.S.; Durrheim, R.; Spottiswoode, S.; Milev, A.

    2009-01-01

    For one week during September 2007, we deployed a temporary network of field recorders and accelerometers at four sites within two deep, seismically active mines. The ground-motion data, recorded at 200 samples/sec, are well suited to determining source and ground-motion parameters for the mining-induced earthquakes within and adjacent to our network. Four earthquakes with magnitudes close to 2 were recorded with high signal/noise at all four sites. Analysis of seismic moments and peak velocities, in conjunction with the results of laboratory stick-slip friction experiments, were used to estimate source processes that are key to understanding source physics and to assessing underground seismic hazard. The maximum displacements on the rupture surfaces can be estimated from the parameter Rv, where v is the peak ground velocity at a given recording site, and R is the hypocentral distance. For each earthquake, the maximum slip and seismic moment can be combined with results from laboratory friction experiments to estimate the maximum slip rate within the rupture zone. Analysis of the four M 2 earthquakes recorded during our deployment and one of special interest recorded by the in-mine seismic network in 2004 revealed maximum slips ranging from 4 to 27 mm and maximum slip rates from 1.1 to 6:3 m=sec. Applying the same analyses to an M 2.1 earthquake within a cluster of repeating earthquakes near the San Andreas Fault Observatory at Depth site, California, yielded similar results for maximum slip and slip rate, 14 mm and 4:0 m=sec.

  8. The 18 May 2012 (Ms 4.5) Chapala Lake, Jalisco, Mexico Earthquake

    Science.gov (United States)

    Yamamoto, J.; Espindola, J. M.

    2015-12-01

    The central part of Jalisco, Mexico has experienced at different times the occurrence of low magnitude earthquakes series. Although the effect of these earthquakes have been limited to relatively small areas have caused general alarm within the population and even in some cases true catastrophes (e.g. San Cristobal 1875). These groups of earthquakes that have lasted for weeks and even months have greater importance because they affect the most populous state area including the capital city of Guadalajara. An extraordinary example of these series of earthquakes occurred on 8 may 1912 that lasted until September. In the first 18 days 64 events were felt by residents of Guadalajara. Since then, there has been a relative seismic activity calm in the region. This paper analyzes the earthquake of May 18, 2012 (03:07 UT) occurred at the West edge of Lake Chapala. While it's an event of low magnitude (4.5 Ms) it has the importance of having occurred just 60 km to the South of Guadalajara and for which instrumental data of first quality is available. The focus of the earthquake was located at 20.30 ° N and 103.49 ° W at a depth of 0 km using arrivals of P and S waves at 16 regional seismic stations. However, by the errors of localization inherent in the method focus could be in a range of 0 to 5 km deep. The mechanism of failure using the polarities of the first arrivals favors a clear faulting of dip slip type along a plane with strike = 227 °, Dip = 80 °, and Rake = 93 °. Waveforms analysis is being used to corroborate these results.

  9. Trouble Brewing in San Francisco. Policy Brief

    Science.gov (United States)

    Buck, Stuart

    2010-01-01

    The city of San Francisco will face enormous budgetary pressures from the growing deficits in public pensions, both at a state and local level. In this policy brief, the author estimates that San Francisco faces an aggregate $22.4 billion liability for pensions and retiree health benefits that are underfunded--including $14.1 billion for the city…

  10. The Hayward Fault - Is It Due for a Repeat of the Powerful 1868 Earthquake?

    Science.gov (United States)

    Brocher, Thomas M.; Boatwright, Jack; Lienkaemper, James J.; Prentice, Carol S.; Schwartz, David P.; Bundock, Howard

    2008-01-01

    On October 21, 1868, a magnitude 6.8 earthquake struck the San Francisco Bay region. Although the region was then sparsely populated, this quake on the Hayward Fault was one of the most destructive in California?s history. Recent studies show that such powerful Hayward Fault quakes have repeatedly jolted the region in the past. U.S. Geological Survey (USGS) scientists describe this fault as a tectonic time bomb, due anytime for another magnitude 6.8 to 7.0 earthquake. Because such a quake could cause hundreds of deaths, leave thousands homeless, and devastate the region?s economy, the USGS and other organizations are working together with new urgency to help prepare Bay Area communities for this certain future quake.

  11. Dancing Earthquake Science Assists Recovery from the Christchurch Earthquakes

    Science.gov (United States)

    Egan, Candice J.; Quigley, Mark C.

    2015-01-01

    The 2010-2012 Christchurch (Canterbury) earthquakes in New Zealand caused loss of life and psychological distress in residents throughout the region. In 2011, student dancers of the Hagley Dance Company and dance professionals choreographed the performance "Move: A Seismic Journey" for the Christchurch Body Festival that explored…

  12. Dancing Earthquake Science Assists Recovery from the Christchurch Earthquakes

    Science.gov (United States)

    Egan, Candice J.; Quigley, Mark C.

    2015-01-01

    The 2010-2012 Christchurch (Canterbury) earthquakes in New Zealand caused loss of life and psychological distress in residents throughout the region. In 2011, student dancers of the Hagley Dance Company and dance professionals choreographed the performance "Move: A Seismic Journey" for the Christchurch Body Festival that explored…

  13. The role of a keystone fault in triggering the complex El Mayor-Cucapah earthquake rupture

    Science.gov (United States)

    Fletcher, John M.; Oskin, Michael E.; Teran, Orlando J.

    2016-04-01

    The 2010 Mw 7.2 El Mayor-Cucapah earthquake in Baja California, Mexico activated slip on multiple faults of diverse orientations, which is commonly the case for large earthquakes. The critical stress level for fault failure depends on fault orientation and is lowest for optimally oriented faults positioned approximately 30° to the greatest principal compressive stress. Yet, misoriented faults whose positioning is not conducive to rupture are also common. Here we use stress inversions of surface displacement and seismic data to show that the El Mayor-Cucapah earthquake initiated on a fault that, owing to its orientation, was among those that required the greatest stress for failure. Although other optimally oriented faults must have reached critical stress earlier in the interseismic period, Coulomb stress modelling shows that slip on these faults was initially muted because they were pinned, held in place by misoriented faults that helped regulate their slip. In this way, faults of diverse orientations could be maintained at critical stress without destabilizing the network. We propose that regional stress build-up continues until a misoriented keystone fault reaches its threshold and its failure then spreads spontaneously across the network in a large earthquake. Our keystone fault hypothesis explains seismogenic failure of severely misoriented faults such as the San Andreas fault and the entire class of low-angle normal faults.

  14. Documentation and virtual reconstruction of historical objects in Peru damaged by an earthquake and climatic events

    Science.gov (United States)

    Hanzalová, K.; Pavelka, K.

    2013-07-01

    This paper deals with the possibilities of creating a 3-D model and a visualization technique for a presentation of historical buildings and sites in Peru. The project Nasca/CTU is documenting historical objects by using several techniques. This paper describes the documentation and the visualization of two historical churches (San Jose and San Xavier Churches) and the pre-Hispanic archaeological site La Ciudad Perdida de Huayuri (Abandoned town near Huayuri) in Nasca region by using photogrammetry and remote sensing. Both churches were damaged by an earthquake. We use different process for the documentation of these objects. Firstly, PhotoModeler software was used for the photogrammetric data processing of the acquired images. The subsequent making models of both churches were different too. Google SketchUp software was used for the San Jose Church and the 3-D model of San Xavier Church was created in MicroStation software. While in the modelling of the "Abandoned town" near Huayuri, which was destroyed by a climatic event (El Niño), the terrestrial photogrammetry, satellite data and GNSS measurement were applied. The general output of the project is a thematic map of this archaeological site; C14 method was used for dating.

  15. Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California

    Science.gov (United States)

    Witter, Robert C.; Knudsen, Keith L.; Sowers, Janet M.; Wentworth, Carl M.; Koehler, Richard D.; Randolph, Carolyn E.; Brooks, Suzanna K.; Gans, Kathleen D.

    2006-01-01

    This report presents a map and database of Quaternary deposits and liquefaction susceptibility for the urban core of the San Francisco Bay region. It supercedes the equivalent area of U.S. Geological Survey Open-File Report 00-444 (Knudsen and others, 2000), which covers the larger 9-county San Francisco Bay region. The report consists of (1) a spatial database, (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map and liquefaction interpretation (part 3), and (4) a text introducing the report and describing the database (part 1). All parts of the report are digital; part 1 describes the database and digital files and how to obtain them by downloading across the internet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. This new map provides a consistent detailed treatment of the central part of the 9-county region in which much of the mapping of Open-File Report 00-444 was either at smaller (less detailed) scale or represented only preliminary revision of earlier work. Like Open-File Report 00-444, the current mapping uses geomorphic expression, pedogenic soils, inferred depositional environments, and geologic age to define and distinguish the map units. Further scrutiny of the factors controlling liquefaction susceptibility has led to some changes relative to Open-File Report 00-444: particularly the reclassification of San Francisco Bay mud (Qhbm) to have only MODERATE susceptibility and the rating of artificial fills according to the Quaternary map units inferred to underlie them (other than dams - adf). The two colored

  16. Preliminary Geologic Map of the San Fernando 7.5' Quadrangle, Southern California: A Digital Database

    Science.gov (United States)

    Yerkes, R.F.

    1997-01-01

    The city of San Fernando sits atop a structurally complex, sedimentologically diverse, and tectonically evolving late Tertiary-Quaternary basin situated within the Transverse Ranges of southern California. The surrounding San Fernando Valley (SFV) contains the headwaters of the Los Angeles River and its tributaries. Prior to the advent of flood control, the valley floor was composed of active alluvial fans and floodplains. Seasonal streams emanating from Pacoima and Big Tujunga Canyons drain the complex western San Gabriel Mountains and deposit coarse, highly permeable alluvium that contains generally high-quality ground water. The more shallow western part derives mainly from Tertiary and pre-Tertiary sedimentary rocks, and is underlain by less permeable, fine-grained deposits containing persistent shallow ground water and poorer water quality. Home of the 1971 San Fernando and the 1994 Northridge earthquakes, the SFV experienced near-record levels of strong ground motion in 1994 that caused widespread damage from strong shaking and ground failure. A new map of late Quaternary deposits of the San Fernando area shows that the SFV is a structural trough that has been filled from the sides, with the major source of sediment being large drainages in the San Gabriel Mountains. Deposition on the major alluvial fan of Tujunga Wash and Pacoima Wash, which issues from the San Gabriel Mountains, and on smaller fans, has been influenced by ongoing compressional tectonics in the valley. Late Pleistocene deposits have been cut by active faults and warped over growing folds. Holocene alluvial fans are locally ponded behind active uplifts. The resulting complex pattern of deposits has a major effect on liquefaction hazards. Young sandy sediments generally are highly susceptible to liquefaction where they are saturated, but the distribution of young deposits, their grain size characteristics, and the level of ground water all are complexly dependent on the tectonics of the valley

  17. Automatic earthquake confirmation for early warning system

    Science.gov (United States)

    Kuyuk, H. S.; Colombelli, S.; Zollo, A.; Allen, R. M.; Erdik, M. O.

    2015-07-01

    Earthquake early warning studies are shifting real-time seismology in earthquake science. They provide methods to rapidly assess earthquakes to predict damaging ground shaking. Preventing false alarms from these systems is key. Here we developed a simple, robust algorithm, Authorizing GRound shaking for Earthquake Early warning Systems (AGREEs), to reduce falsely issued alarms. This is a network threshold-based algorithm, which differs from existing approaches based on apparent velocity of P and S waves. AGREEs is designed to function as an external module to support existing earthquake early warning systems (EEWSs) and filters out the false events, by evaluating actual shaking near the epicenter. Our retrospective analyses of the 2009 L'Aquila and 2012 Emilia earthquakes show that AGREEs could help an EEWS by confirming the epicentral intensity. Furthermore, AGREEs is able to effectively identify three false events due to a storm, a teleseismic earthquake, and broken sensors in Irpinia Seismic Network, Italy.

  18. 2011 Pacific Gas and Electric Diablo Canyon Power Plant (DCPP): Los Osos, CA Central Coast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Diablo Canyon Power Plant (DCPP) LiDAR and Imagery datasets are comprised of three separate LiDAR surveys: Diablo Canyon (2010), Los Osos (2011), and San Simeon...

  19. Earthquake design for controlled structures

    Directory of Open Access Journals (Sweden)

    Nikos G. Pnevmatikos

    2017-04-01

    Full Text Available An alternative design philosophy, for structures equipped with control devices, capable to resist an expected earthquake while remaining in the elastic range, is described. The idea is that a portion of the earthquake loading is under¬taken by the control system and the remaining by the structure which is designed to resist elastically. The earthquake forces assuming elastic behavior (elastic forces and elastoplastic behavior (design forces are first calculated ac¬cording to the codes. The required control forces are calculated as the difference from elastic to design forces. The maximum value of capacity of control devices is then compared to the required control force. If the capacity of the control devices is larger than the required control force then the control devices are accepted and installed in the structure and the structure is designed according to the design forces. If the capacity is smaller than the required control force then a scale factor, α, reducing the elastic forces to new design forces is calculated. The structure is redesigned and devices are installed. The proposed procedure ensures that the structure behaves elastically (without damage for the expected earthquake at no additional cost, excluding that of buying and installing the control devices.

  20. Using Smartphones to Detect Earthquakes

    Science.gov (United States)

    Kong, Q.; Allen, R. M.

    2012-12-01

    We are using the accelerometers in smartphones to record earthquakes. In the future, these smartphones may work as a supplement network to the current traditional network for scientific research and real-time applications. Given the potential number of smartphones, and small separation of sensors, this new type of seismic dataset has significant potential provides that the signal can be separated from the noise. We developed an application for android phones to record the acceleration in real time. These records can be saved on the local phone or transmitted back to a server in real time. The accelerometers in the phones were evaluated by comparing performance with a high quality accelerometer while located on controlled shake tables for a variety of tests. The results show that the accelerometer in the smartphone can reproduce the characteristic of the shaking very well, even the phone left freely on the shake table. The nature of these datasets is also quite different from traditional networks due to the fact that smartphones are moving around with their owners. Therefore, we must distinguish earthquake signals from other daily use. In addition to the shake table tests that accumulated earthquake records, we also recorded different human activities such as running, walking, driving etc. An artificial neural network based approach was developed to distinguish these different records. It shows a 99.7% successful rate of distinguishing earthquakes from the other typical human activities in our database. We are now at the stage ready to develop the basic infrastructure for a smartphone seismic network.

  1. Seismicity dynamics and earthquake predictability

    Directory of Open Access Journals (Sweden)

    G. A. Sobolev

    2011-02-01

    Full Text Available Many factors complicate earthquake sequences, including the heterogeneity and self-similarity of the geological medium, the hierarchical structure of faults and stresses, and small-scale variations in the stresses from different sources. A seismic process is a type of nonlinear dissipative system demonstrating opposing trends towards order and chaos. Transitions from equilibrium to unstable equilibrium and local dynamic instability appear when there is an inflow of energy; reverse transitions appear when energy is dissipating. Several metastable areas of a different scale exist in the seismically active region before an earthquake. Some earthquakes are preceded by precursory phenomena of a different scale in space and time. These include long-term activation, seismic quiescence, foreshocks in the broad and narrow sense, hidden periodical vibrations, effects of the synchronization of seismic activity, and others. Such phenomena indicate that the dynamic system of lithosphere is moving to a new state – catastrophe. A number of examples of medium-term and short-term precursors is shown in this paper. However, no precursors identified to date are clear and unambiguous: the percentage of missed targets and false alarms is high. The weak fluctuations from outer and internal sources play a great role on the eve of an earthquake and the occurrence time of the future event depends on the collective behavior of triggers. The main task is to improve the methods of metastable zone detection and probabilistic forecasting.

  2. Earthquake swarms in South America

    Science.gov (United States)

    Holtkamp, S. G.; Pritchard, M. E.; Lohman, R. B.

    2011-10-01

    We searched for earthquake swarms in South America between 1973 and 2009 using the global Preliminary Determination of Epicenters (PDE) catalogue. Seismicity rates vary greatly over the South American continent, so we employ a manual search approach that aims to be insensitive to spatial and temporal scales or to the number of earthquakes in a potential swarm. We identify 29 possible swarms involving 5-180 earthquakes each (with total swarm moment magnitudes between 4.7 and 6.9) within a range of tectonic and volcanic locations. Some of the earthquake swarms on the subduction megathrust occur as foreshocks and delineate the limits of main shock rupture propagation for large earthquakes, including the 2010 Mw 8.8 Maule, Chile and 2007 Mw 8.1 Pisco, Peru earthquakes. Also, subduction megathrust swarms commonly occur at the location of subduction of aseismic ridges, including areas of long-standing seismic gaps in Peru and Ecuador. The magnitude-frequency relationship of swarms we observe appears to agree with previously determined magnitude-frequency scaling for swarms in Japan. We examine geodetic data covering five of the swarms to search for an aseismic component. Only two of these swarms (at Copiapó, Chile, in 2006 and near Ticsani Volcano, Peru, in 2005) have suitable satellite-based Interferometric Synthetic Aperture Radar (InSAR) observations. We invert the InSAR geodetic signal and find that the ground deformation associated with these swarms does not require a significant component of aseismic fault slip or magmatic intrusion. Three swarms in the vicinity of the volcanic arc in southern Peru appear to be triggered by the Mw= 8.5 2001 Peru earthquake, but predicted static Coulomb stress changes due to the main shock were very small at the swarm locations, suggesting that dynamic triggering processes may have had a role in their occurrence. Although we identified few swarms in volcanic regions, we suggest that particularly large volcanic swarms (those that

  3. The kinematics of faults in the San Francisco Bay area inferred from geodetic and seismic data

    Science.gov (United States)

    Schmidt, David Andrew

    2002-01-01

    The work presented in this dissertation focuses on the kinematics and mechanics of the Hayward fault, the Loma Prieta earthquake rupture, and the Silver Creek fault. To better understand their behavior and geometry, geodetic and seismic data are used in conjunction with elastic models of the crust. Along the northern and central segments of the Hayward fault, a steady interseismic deformation rate is observed. Variations in this rate along strike suggest a variable slip-rate distribution at depth indicative of locked and creeping patches. A locked patch that correlates with the presumed source region of the 1868 earthquake on the Hayward fault implies that elastic strain is accumulating at this location. The southern Hayward fault exhibits complex time-dependent slip. Interferometric Synthetic Aperture Radar (InSAR) is employed to visualize the crustal deformation signal by utilizing over 100 interferograms. Results suggest that the observed surface deformation is best explained by a combination of transient fault slip and land subsidence. This is in contrast to the Silver Creek fault in the Santa Clara Valley where all of the deformation is attributed to differential aquifer compaction and expansion across the fault. Regional faults interact through the redistribution of stress in the crust and upper mantle. The effect of this change in stress on the creeping portion of the Hayward fault following the 1906 San Francisco earthquake is explored using a rate-and-state friction model. The predicted surface creep response, driven by the postseismic relaxation of the mantle following the 1906 event, is used to constrain the rheology of the lower crust. Rheologies that include a horizontal shear zone underpredict the surface creep response observed from offset cultural features. Inversions for the coseismic slip distribution of the 1989 Loma Prieta earthquake are performed to evaluate the sensitivity of the inversion to the prescribed fault geometry. Models the

  4. Geomorphic evidence of active tectonics in the San Gorgonio Pass region of the San Andreas Fault system: an example of discovery-based research in undergraduate teaching

    Science.gov (United States)

    Reinen, L. A.; Yule, J. D.

    2014-12-01

    Student-conducted research in courses during the first two undergraduate years can increase learning and improve student self-confidence in scientific study, and is recommended for engaging and retaining students in STEM fields (PCAST, 2012). At Pomona College, incorporating student research throughout the geology curriculum tripled the number of students conducting research prior to their senior year that culminated in a professional conference presentation (Reinen et al., 2006). Here we present an example of discovery-based research in Neotectonics, a second-tier course predominantly enrolling first-and second-year students; describe the steps involved in the four week project; and discuss early outcomes of student confidence, engagement and retention. In the San Gorgonio Pass region (SGPR) in southern California, the San Andreas fault undergoes a transition from predominantly strike-slip to a complex system of faults with significant dip-slip, resulting in diffuse deformation and raising the question of whether a large earthquake on the San Andreas could propagate through the region (Yule, 2009). In spring 2014, seven students in the Neotectonics course conducted original research investigating quantifiable geomorphic evidence of tectonic activity in the SGPR. Students addressed questions of [1] unequal uplift in the San Bernardino Mountains, [2] fault activity indicated by stream knick points, [3] the role of fault style on mountain front sinuosity, and [4] characteristic earthquake slip determined via fault scarp degradation models. Students developed and revised individual projects, collaborated with each other on methods, and presented results in a public forum. A final class day was spent reviewing the projects and planning future research directions. Pre- and post-course surveys show increases in students' self-confidence in the design, implementation, and presentation of original scientific inquiries. 5 of 6 eligible students participated in research the

  5. Strong motions and engineering structure performances in recent major earthquakes

    Institute of Scientific and Technical Information of China (English)

    Xiaojun Li

    2010-01-01

    @@ In recent years, a series of major earthquakes occurred, which resulted in considerable engineering damage and collapse, triggered heavy geological hazards, and caused extremely high casualties and huge property and economic loss. The earthquakes include the 1994 Northridge earthquake (M6.8), the 1995 Kobe earthquake (M6.8), the 1999 Izmit earthquake (M7.6), the 1999 Jiji (Chi-Chi) earthquake (M7.6), the 2005 northern Pakistan earthquake (M7.6), the 2008 Wenchuan earthquake (M8.0) and the 2010 Haiti earthquake (M7.0). Some villages, towns and even cities were devastated in the earthquakes, especially in the 2005 northern Pakistan earthquake, the 2008 Wenchuan earthquake and the 2010 Haiti earthquake.

  6. Gravity and magnetic expression of the San Leandro gabbro with implications for the geometry and evolution of the Hayward Fault zone, northern California

    Science.gov (United States)

    Ponce, D.A.; Hildenbrand, T.G.; Jachens, R.C.

    2003-01-01

    The Hayward Fault, one of the most hazardous faults in northern California, trends north-northwest and extends for about 90 km along the eastern San Francisco Bay region. At numerous locations along its length, distinct and elongate gravity and magnetic anomalies correlate with mapped mafic and ultramafic rocks. The most prominent of these anomalies reflects the 16-km-long San Leandro gabbroic block. Inversion of magnetic and gravity data constrained with physical property measurements is used to define the subsurface extent of the San Leandro gabbro body and to speculate on its origin and relationship to the Hayward Fault Zone. Modeling indicates that the San Leandro gabbro body is about 3 km wide, dips about 75??-80?? northeast, and extends to a depth of at least 6 km. One of the most striking results of the modeling, which was performed independently of seismicity data, is that accurately relocated seismicity is concentrated along the western edge or stratigraphically lower bounding surface of the San Leandro gabbro. The western boundary of the San Leandro gabbro block is the base of an incomplete ophiolite sequence and represented at one time, a low-angle roof thrust related to the tectonic wedging of the Franciscan Complex. After repeated episodes of extension and attenuation, the roof thrust of this tectonic wedge was rotated to near vertical, and in places, the strike-slip Hayward Fault probably reactivated or preferentially followed this pre-existing feature. Because earthquakes concentrate near the edge of the San Leandro gabbro but tend to avoid its interior, we qualitatively explore mechanical models to explain how this massive igneous block may influence the distribution of stress. The microseismicity cluster along the western flank of the San Leandro gabbro leads us to suggest that this stressed volume may be the site of future moderate to large earthquakes. Improved understanding of the three-dimensional geometry and physical properties along the

  7. Remotely triggered microearthquakes and tremor in central California following the 2010 Mw 8.8 Chile earthquake

    Science.gov (United States)

    Peng, Zhigang; Hill, David P.; Shelly, David R.; Aiken, Chastity

    2010-01-01

    We examine remotely triggered microearthquakes and tectonic tremor in central California following the 2010 Mw 8.8 Chile earthquake. Several microearthquakes near the Coso Geothermal Field were apparently triggered, with the largest earthquake (Ml 3.5) occurring during the large-amplitude Love surface waves. The Chile mainshock also triggered numerous tremor bursts near the Parkfield-Cholame section of the San Andreas Fault (SAF). The locally triggered tremor bursts are partially masked at lower frequencies by the regionally triggered earthquake signals from Coso, but can be identified by applying high-pass or matched filters. Both triggered tremor along the SAF and the Ml 3.5 earthquake in Coso are consistent with frictional failure at different depths on critically-stressed faults under the Coulomb failure criteria. The triggered tremor, however, appears to be more phase-correlated with the surface waves than the triggered earthquakes, likely reflecting differences in constitutive properties between the brittle, seismogenic crust and the underlying lower crust.

  8. PBO Southwest Region: Baja Earthquake Response and Network Operations

    Science.gov (United States)

    Walls, C. P.; Basset, A.; Mann, D.; Lawrence, S.; Jarvis, C.; Feaux, K.; Jackson, M. E.

    2011-12-01

    The SW region of the Plate Boundary Observatory consists of 455 continuously operating GPS stations located principally along the transform system of the San Andreas fault and Eastern California Shear Zone. In the past year network uptime exceeded an average of 97% with greater than 99% data acquisition. Communications range from CDMA modem (307), radio (92), Vsat (30), DSL/T1/other (25) to manual downloads (1). Sixty-three stations stream 1 Hz data over the VRS3Net typically with vandalism (solar panel stolen) with one total loss of receiver and communications gear. Security was enhanced at these sites through fencing and more secure station configurations. In the past 12 months, 4 new stations were installed to replace removed stations or to augment the network at strategic locations. Following the M7.2 El Mayor-Cucapah earthquake CGPS station P796, a deep-drilled braced monument, was constructed in San Luis, AZ along the border within 5 weeks of the event. In addition, UNAVCO participated in a successful University of Arizona-led RAPID proposal for the installation of six continuous GPS stations for post-seismic observations. Six stations are installed and telemetered through a UNAM relay at the Sierra San Pedro Martir. Four of these stations have Vaisala WXT520 meteorological sensors. An additional site in the Sierra Cucapah (PTAX) that was built by CICESE, an Associate UNAVCO Member institution in Mexico, and Caltech has been integrated into PBO dataflow. The stations will be maintained as part of the PBO network in coordination with CICESE. UNAVCO is working with NOAA to upgrade PBO stations with WXT520 meteorological sensors and communications systems capable of streaming real-time GPS and met data. The real-time GPS and meteorological sensor data streaming support watershed and flood analyses for regional early-warning systems related to NOAA's work with California Department of Water Resources. Currently 19 stations are online and streaming with 7 more in

  9. The Characteristics of Earthquake Swarms in and around Jiangsu Province

    Institute of Scientific and Technical Information of China (English)

    Huang Yun; Tian Jianming; Miao Ali

    2011-01-01

    This paper systematically analyzed 36 earthquake swarms in and around Jiangsu Province, summarized their characteristics and discussed the relationship between earthquske swarms and subsequent strong earthquakes. It also analyzed the judgment criteria for precursory earthquake swarms. Earthquake swarms in Jiangsu Province are concentrated in several areas. Most of them were of magnitude ML2. 0 ~ 3. 9. For most earthquake swarms, the number of earthquakes was less than 30. Time duration for about 55% of earthquake swarms was less than 15 days. The biggest magnitude of one earthquake swarm was not proportional to the number of earthquakes and time duration. There are 78% of earthquake swarms corresponded to the forthcoming earthquakes of M 〉 4. 6 in which there're 57% occured in one year, This shows a medium- and short-term criterion. Distance between earthquake swarm and future earthquake was distributed dispersedly. There were no earthquakes occurring in the same location as earthquake swarms. There was no good correlation between the magnitude and the corresponding rate of future earthquakes and the intensity of earthquake swarms. There was also no good correlation between the number of earthquakes in an earthquake swarm and the corresponding rate. The study also shows that it's better to use U-p or whole-combination to determine the type of earthquake swarm.

  10. TremorScope: A Tool to Image the Deep Workings of the San Andreas Fault near Cholame, CA

    Science.gov (United States)

    Hellweg, M.; Burgmann, R.; Taira, T.; Nadeau, R. M.; Dreger, D. S.; Allen, R. M.

    2015-12-01

    Until recently, active fault zones were thought to deform via seismic slip during earthquakes in the upper, brittle portion of the crust, and by steady, aseismic shear below. However, since 2000, this view has been shaken by seismological observations of seismic tremor deep in the roots of active fault zones, including on the section of the San Andreas to the southeast of Parkfield, CA, deep (~20-30 km) beneath the nucleation zone of the great 1857 Fort Tejon earthquake. With funding from the Gordon and Betty Moore Foundation, we have improved the seismic network in the area above the tremor source by installing four new broadband/strong motion surface stations and four borehole sites with uphole accelerometers and downhole geophones, broadband and strong motion sensors. Data from all stations are telemetered in real-time. They are analysed as part of normal earthquake monitoring, and archived and distributed through the Northern California Earthquake Data Center (NCEDC). Data from the TremorScope project is improving earthquake monitoring in the region south of Parkfield, including allowing empirical Greens function finite fault analysis of moderate events in the area. Locations and characterization of tremor episodes are improved by the data recorded by TremorScope stations. For example, the rate of ambient tremor activity in the TremorScope area increased by a factor of ~8 within ~12 hours of the 2014 Napa M6.0 earthquake and remained elevated for ~ 100 days, exceeding the tremor rate increase following the 2004 Parkfield M6.0 quake despite the differences in epicentral distance (~300 km vs. ~15 km). No comparable increases in tremor rates have been observed between the Parkfield and Napa events. This suggests that the sensitivity to external stressing in the in the deep tremor zone of the TremorScope region may have increased since 2004. We also show how this network's strong motion instrumentation will provide unprecedented and exciting insights into the

  11. Small angle neutron scattering (SANS and V-SANS) study of asphaltene aggregates in crude oil.

    Science.gov (United States)

    Headen, Thomas F; Boek, Edo S; Stellbrink, Jörg; Scheven, Ulrich M

    2009-01-06

    We report small angle neutron scattering (SANS) experiments on two crude oils. Analysis of the high-Q SANS region has probed the asphaltene aggregates in the nanometer length scale. We find that the radius of gyration decreases with increasing temperature. We show that SANS measurements on crude oils give similar aggregate sizes to those found from SANS measurements of asphaltenes redispersed in deuterated toluene. The combined use of SANS and V-SANS on crude oil samples has allowed the determination of the radius of gyration of large scale asphaltene aggregates of approximately 0.45 microm. This has been achieved by the fitting of Beaucage functions over two size regimes. Analysis of the fitted Beaucage functions at very low-Q has shown that the large scale aggregates are not simply made by aggregation of all the smaller nanoaggregates. Instead, they are two different aggregates coexisting.

  12. Relation between the characteristics of strong earthquake activities in Chinese mainland and the Wenchuan earthquake

    Institute of Scientific and Technical Information of China (English)

    Xiaodong Zhang; Guohua Yang; Xian Lu; Mingxiao Li; Zhigao Yang

    2009-01-01

    This paper studies the relations between the great Wenchuan earthquake and the active-quiet periodic characteristics of strong earthquakes, the rhythmic feature of great earthquakes, and the grouped spatial distribution of MS8.0 earthquakes in Chinese mainland. We also studied the relation between the Wenchuan earthquake and the stepwise migration characteristics of MS≥7.0 earthquakes on the North-South seismic belt, the features of the energy releasing acceleration in the active crustal blocks related to the Wenchuan earthquake and the relation between the Wenchuan earthquake and the so called second-arc fault zone. The results can be summarized as follows: ① the occurrence of the Wenchuan earthquake was consistent with the active-quiet periodic characteristics of strong earthquakes; ② its occurrence is consistent with the features of grouped occurrence of MS8.0 earthquakes and follows the 25 years rhythm (each circulation experiences the same time) of great earthquakes; ③ the Wenchuan MS8.0 earthquake follows the well known stepwise migration feature of strong earthquakes on the North-South seismic belt; ④ the location where the Wenchuan MS8.0 earthquake took place has an obvious consistency with the temporal and spatial characteristic of grouped activity of MS≥7.0 strong earthquakes on the second-arc fault zone; ⑤ the second-arc fault zone is not only the lower boundary for earthquakes with more than 30 km focal depth, but also looks like a lower boundary for deep substance movement; and ⑥ there are obvious seismic accelerations nearby the Qaidam and Qiangtang active crustal blocks (the northern and southern neighbors of the Bayan Har active block, respectively), which agrees with the GPS observation data.

  13. Update earthquake risk assessment in Cairo, Egypt

    Science.gov (United States)

    Badawy, Ahmed; Korrat, Ibrahim; El-Hadidy, Mahmoud; Gaber, Hanan

    2016-12-01

    The Cairo earthquake (12 October 1992; m b = 5.8) is still and after 25 years one of the most painful events and is dug into the Egyptians memory. This is not due to the strength of the earthquake but due to the accompanied losses and damages (561 dead; 10,000 injured and 3000 families lost their homes). Nowadays, the most frequent and important question that should rise is "what if this earthquake is repeated today." In this study, we simulate the same size earthquake (12 October 1992) ground motion shaking and the consequent social-economic impacts in terms of losses and damages. Seismic hazard, earthquake catalogs, soil types, demographics, and building inventories were integrated into HAZUS-MH to produce a sound earthquake risk assessment for Cairo including economic and social losses. Generally, the earthquake risk assessment clearly indicates that "the losses and damages may be increased twice or three times" in Cairo compared to the 1992 earthquake. The earthquake risk profile reveals that five districts (Al-Sahel, El Basateen, Dar El-Salam, Gharb, and Madinat Nasr sharq) lie in high seismic risks, and three districts (Manshiyat Naser, El-Waily, and Wassat (center)) are in low seismic risk level. Moreover, the building damage estimations reflect that Gharb is the highest vulnerable district. The analysis shows that the Cairo urban area faces high risk. Deteriorating buildings and infrastructure make the city particularly vulnerable to earthquake risks. For instance, more than 90 % of the estimated buildings damages are concentrated within the most densely populated (El Basateen, Dar El-Salam, Gharb, and Madinat Nasr Gharb) districts. Moreover, about 75 % of casualties are in the same districts. Actually, an earthquake risk assessment for Cairo represents a crucial application of the HAZUS earthquake loss estimation model for risk management. Finally, for mitigation, risk reduction, and to improve the seismic performance of structures and assure life safety

  14. Update earthquake risk assessment in Cairo, Egypt

    Science.gov (United States)

    Badawy, Ahmed; Korrat, Ibrahim; El-Hadidy, Mahmoud; Gaber, Hanan

    2017-07-01

    The Cairo earthquake (12 October 1992; m b = 5.8) is still and after 25 years one of the most painful events and is dug into the Egyptians memory. This is not due to the strength of the earthquake but due to the accompanied losses and damages (561 dead; 10,000 injured and 3000 families lost their homes). Nowadays, the most frequent and important question that should rise is "what if this earthquake is repeated today." In this study, we simulate the same size earthquake (12 October 1992) ground motion shaking and the consequent social-economic impacts in terms of losses and damages. Seismic hazard, earthquake catalogs, soil types, demographics, and building inventories were integrated into HAZUS-MH to produce a sound earthquake risk assessment for Cairo including economic and social losses. Generally, the earthquake risk assessment clearly indicates that "the losses and damages may be increased twice or three times" in Cairo compared to the 1992 earthquake. The earthquake risk profile reveals that five districts (Al-Sahel, El Basateen, Dar El-Salam, Gharb, and Madinat Nasr sharq) lie in high seismic risks, and three districts (Manshiyat Naser, El-Waily, and Wassat (center)) are in low seismic risk level. Moreover, the building damage estimations reflect that Gharb is the highest vulnerable district. The analysis shows that the Cairo urban area faces high risk. Deteriorating buildings and infrastructure make the city particularly vulnerable to earthquake risks. For instance, more than 90 % of the estimated buildings damages are concentrated within the most densely populated (El Basateen, Dar El-Salam, Gharb, and Madinat Nasr Gharb) districts. Moreover, about 75 % of casualties are in the same districts. Actually, an earthquake risk assessment for Cairo represents a crucial application of the HAZUS earthquake loss estimation model for risk management. Finally, for mitigation, risk reduction, and to improve the seismic performance of structures and assure life safety

  15. Integrated geomorphic and geodynamic modeling of a potential blind thrust in the San Francisco Bay area, California

    Science.gov (United States)

    Johnson, Courtney B.; Furlong, Kevin P.; Kirby, Eric

    2009-06-01

    Geometries and slip budgets of the faults in the San Francisco Bay area imply previously unrecognized fault linkages, including examples of blind thrust structures that appear to connect segments of strike-slip faults and accommodate along-strike variations in slip rate along these structures. Displacement along linking faults may be associated with the development of topography and also may serve as earthquake sources. In Marin County, California, systematic spatial patterns in landscape topography and geomorphic indices suggest that the region north of Mt. Tamalpais is experiencing differential rock uplift. We suggest that a blind thrust underlies the elevated area, creating the observed topography and possibly resolving a slip discrepancy between the Hayward and San Andreas Fault in this region. We have developed and implemented an integrative approach that combines observations from tectonic deformation and geomorphic properties to identify a potential blind thrust beneath Marin County. Elastic displacement modeling has been tested for compatibility with the blind thrust hypothesis and to assess the sensitivity of observables to fault geometry and orientation; from this, a set of plausible blind thrust structures are defined. We use a range of empirical relationships between channel steepness index and erosion rate to estimate spatial variations in erosion rate along Bolinas Ridge. By coupling these erosion estimates with elastic displacement fault modeling, we can use the resulting topographic envelopes to constrain the rate and duration of deformation. These constraints, along with spatial bounds on the possible fault models, are used to calculate potential seismic moment and moment magnitude. With an assumed recurrence interval of ~ 100 years, such blind thrusts can produce a Mw ~ 6.3 earthquake, while a longer recurrence time (~ 1000 years) results in a maximum Mw ~ 7.0 earthquake. Although such events are not likely to be catastrophic, they are large

  16. A smartphone application for earthquakes that matter!

    Science.gov (United States)

    Bossu, Rémy; Etivant, Caroline; Roussel, Fréderic; Mazet-Roux, Gilles; Steed, Robert

    2014-05-01

    Smartphone applications have swiftly become one of the most popular tools for rapid reception of earthquake information for the public, some of them having been downloaded more than 1 million times! The advantages are obvious: wherever someone's own location is, they can be automatically informed when an earthquake has struck. Just by setting a magnitude threshold and an area of interest, there is no longer the need to browse the internet as the information reaches you automatically and instantaneously! One question remains: are the provided earthquake notifications always relevant for the public? What are the earthquakes that really matters to laypeople? One clue may be derived from some newspaper reports that show that a while after damaging earthquakes many eyewitnesses scrap the application they installed just after the mainshock. Why? Because either the magnitude threshold is set too high and many felt earthquakes are missed, or it is set too low and the majority of the notifications are related to unfelt earthquakes thereby only increasing anxiety among the population at each new update. Felt and damaging earthquakes are the ones that matter the most for the public (and authorities). They are the ones of societal importance even when of small magnitude. A smartphone application developed by EMSC (Euro-Med Seismological Centre) with the financial support of the Fondation MAIF aims at providing suitable notifications for earthquakes by collating different information threads covering tsunamigenic, potentially damaging and felt earthquakes. Tsunamigenic earthquakes are considered here to be those ones that are the subject of alert or information messages from the PTWC (Pacific Tsunami Warning Centre). While potentially damaging earthquakes are identified through an automated system called EQIA (Earthquake Qualitative Impact Assessment) developed and operated at EMSC. This rapidly assesses earthquake impact by comparing the population exposed to each expected

  17. Should Coulomb stress change calculations be used to forecast aftershocks and to influence earthquake probability estimates? (Invited)

    Science.gov (United States)

    Parsons, T.

    2009-12-01

    After a large earthquake, our concern immediately moves to the likelihood that another large shock could be triggered, threatening an already weakened building stock. A key question is whether it is best to map out Coulomb stress change calculations shortly after mainshocks to potentially highlight the most likely aftershock locations, or whether it is more prudent to wait until the best information is available. It has been shown repeatedly that spatial aftershock patterns can be matched with Coulomb stress change calculations a year or more after mainshocks. However, with the onset of rapid source slip model determinations, the method has produced encouraging results like the M=8.7 earthquake that was forecast using stress change calculations from 2004 great Sumatra earthquake by McCloskey et al. [2005]. Here, I look back at two additional prospective calculations published shortly after the 2005 M=7.6 Kashmir and 2008 M=8.0 Wenchuan earthquakes. With the benefit of 1.5-4 years of additional seismicity, it is possible to assess the performance of rapid Coulomb stress change calculations. In the second part of the talk, within the context of the ongoing Working Group on California Earthquake Probabilities (WGCEP) assessments, uncertainties associated with time-dependent probability calculations are convolved with uncertainties inherent to Coulomb stress change calculations to assess the strength of signal necessary for a physics-based calculation to merit consideration into a formal earthquake forecast. Conclusions are as follows: (1) subsequent aftershock occurrence shows that prospective static stress change calculations both for Kashmir and Wenchuan examples failed to adequately predict the spatial post-mainshock earthquake distributions. (2) For a San Andreas fault example with relatively well-understood recurrence, a static stress change on the order of 30 to 40 times the annual stressing rate would be required to cause a significant (90%) perturbation to the

  18. 75 FR 55270 - Safety Zone; NASSCO Launching of USNS Washington Chambers, San Diego Bay, San Diego, CA

    Science.gov (United States)

    2010-09-10

    ... Chambers, San Diego Bay, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone on the navigable waters of the San Diego Bay in... the Port (COTP) San Diego or his designated representative. DATES: This rule is effective from 9:15 a...

  19. Description of gravity cores from San Pablo Bay and Carquinez Strait, San Francisco Bay, California

    Science.gov (United States)

    Woodrow, Donald L.; John L. Chin,; Wong, Florence L.; Fregoso, Theresa; Jaffe, Bruce E.

    2017-06-27

    Seventy-two gravity cores were collected by the U.S. Geological Survey in 1990, 1991, and 2000 from San Pablo Bay and Carquinez Strait, California. The gravity cores collected within San Pablo Bay contain bioturbated laminated silts and sandy clays, whole and broken bivalve shells (mostly mussels), fossil tube structures, and fine-grained plant or wood fragments. Gravity cores from the channel wall of Carquinez Strait east of San Pablo Bay consist of sand and clay layers, whole and broken bivalve shells (less than in San Pablo Bay), trace fossil tubes, and minute fragments of plant material.

  20. Earthquake Risk, FEMA Earthquake Hazzard Risk Map, Published in 1994, Delaware Geological Survey.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Earthquake Risk dataset, was produced all or in part from Published Reports/Deeds information as of 1994. It is described as 'FEMA Earthquake Hazzard Risk Map'....

  1. Predicted Liquefaction in the Greater Oakland and Northern Santa Clara Valley Areas for a Repeat of the 1868 Hayward Earthquake

    Science.gov (United States)

    Holzer, T. L.; Noce, T. E.; Bennett, M. J.

    2008-12-01

    Probabilities of surface manifestations of liquefaction due to a repeat of the 1868 (M6.7-7.0) earthquake on the southern segment of the Hayward Fault were calculated for two areas along the margin of San Francisco Bay, California: greater Oakland and the northern Santa Clara Valley. Liquefaction is predicted to be more common in the greater Oakland area than in the northern Santa Clara Valley owing to the presence of 57 km2 of susceptible sandy artificial fill. Most of the fills were placed into San Francisco Bay during the first half of the 20th century to build military bases, port facilities, and shoreline communities like Alameda and Bay Farm Island. Probabilities of liquefaction in the area underlain by this sandy artificial fill range from 0.2 to ~0.5 for a M7.0 earthquake, and decrease to 0.1 to ~0.4 for a M6.7 earthquake. In the greater Oakland area, liquefaction probabilities generally are less than 0.05 for Holocene alluvial fan deposits, which underlie most of the remaining flat-lying urban area. In the northern Santa Clara Valley for a M7.0 earthquake on the Hayward Fault and an assumed water-table depth of 1.5 m (the historically shallowest water level), liquefaction probabilities range from 0.1 to 0.2 along Coyote and Guadalupe Creeks, but are less than 0.05 elsewhere. For a M6.7 earthquake, probabilities are greater than 0.1 along Coyote Creek but decrease along Guadalupe Creek to less than 0.1. Areas with high probabilities in the Santa Clara Valley are underlain by latest Holocene alluvial fan levee deposits where liquefaction and lateral spreading occurred during large earthquakes in 1868 and 1906. The liquefaction scenario maps were created with ArcGIS ModelBuilder. Peak ground accelerations first were computed with the new Boore and Atkinson NGA attenuation relation (2008, Earthquake Spectra, 24:1, p. 99-138), using VS30 to account for local site response. Spatial liquefaction probabilities were then estimated using the predicted ground motions

  2. San Luis Valley waterbird plan : Draft

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The goal of this plan is "to provide and protect a habitat base of sufficient quality and quantity to maintain healthy viable populations of waterbirds in the San...

  3. Historical methyl mercury in San Francisco Bay

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — San Francisco Bay, California is considered a mercury-impaired watershed. Elevated concentrations of mercury are found in water and sediment as well as fish and...

  4. Bathymetry--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the bathymetry and shaded-relief maps of Offshore of San Francisco, California (raster data file is included in...

  5. Backscatter A [8101]--Offshore San Gregorio, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3306 presents data for the acoustic-backscatter map (see sheet 3, SIM 3306) of the Offshore of San Gregorio map area, California. Backscatter data...

  6. Habitat--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Offshore of San Francisco map area, California. The vector data file is included in...

  7. San Antonio Bay 1986-1989

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The effect of salinity on utilization of shallow-water nursery habitats by aquatic fauna was assessed in San Antonio Bay, Texas. Overall, 272 samples were collected...

  8. Habitat--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Offshore of San Francisco map area, California. The vector data file is included in...

  9. Contours--Offshore of San Francisco, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the bathymetric contours for several seafloor maps of the Offshore of San Francisco map area, California. The vector data file...

  10. Backscatter B [7125]--Offshore San Gregorio, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of SIM 3306 presents data for the acoustic-backscatter map (see sheet 3, SIM 3306) of the Offshore of San Gregorio map area, California. Backscatter data...

  11. San Bernardino National Wildlife Refuge contaminant study

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The San Bernardino National Wildlife Refuge was established in 1982 for the protection and management of endangered desert fishes which are indigenous to the Rio...

  12. An Archeological Survey of the San Diego River

    Science.gov (United States)

    1975-08-27

    Indian populations and to arable landa and water, Father Serra moved Mission San Diego de Aleala ------ to the site of Nipoguay, an Indian village located...NN ARCHAEOLOGICAL SRE OF THE ~i7 SAN DIEGORIE I If SAN DIEGO STATE UNIVERSITY FOUNDATION DEPARTMENT OF THE ARMY, CORPS OF ENGINEERS kSAN DIEGO STATE...the San Diego River Archeological Survey A. PERFORMING ORG.ý REPORT NUM§ER na 7. AUTHOR(s) 6. CONTRACT OR GRANT NUMBER(*) - I- PERFORMING ORGANIZATION

  13. A resonance mechanism of earthquakes

    CERN Document Server

    Flambaum, V V

    2015-01-01

    It had been observed in [1] that there are periodic 4-6 hours pulses of ? 200 ?Hz seismogravita- tional oscillations ( SGO ) before 95 % of powerful earthquakes. We explain this by beating between an oscillation eigenmode of a whole tectonic plate and a local eigenmode of an active zone which tranfers the oscillation energy from the tectonic plate to the active zone causing the eathrquake. Oscillation frequencies of the plate and ones of the active zone are tuned to a resonance by an additional pressure applied to the active zone due to collision of neighboring plates or convection in the upper mantia (plume). Corresponding theory may be used for short-term prediction of the earthquakes and tsunami.

  14. Pre-earthquake Magnetic Pulses

    CERN Document Server

    Scoville, John; Freund, Friedemann

    2014-01-01

    A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are observable because their extremely long wavelength allows them to pass through the Earth's crust. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stress is building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  15. Great East Japan Earthquake Tsunami

    Science.gov (United States)

    Iijima, Y.; Minoura, K.; Hirano, S.; Yamada, T.

    2011-12-01

    The 11 March 2011, Mw 9.0 Great East Japan Earthquake, already among the most destructive earthquakes in modern history, emanated from a fault rupture that extended an estimated 500 km along the Pacific coast of Honshu. This earthquake is the fourth among five of the strongest temblors since AD 1900 and the largest in Japan since modern instrumental recordings began 130 years ago. The earthquake triggered a huge tsunami, which invaded the seaside areas of the Pacific coast of East Japan, causing devastating damages on the coast. Artificial structures were destroyed and planted forests were thoroughly eroded. Inrush of turbulent flows washed backshore areas and dunes. Coastal materials including beach sand were transported onto inland areas by going-up currents. Just after the occurrence of the tsunami, we started field investigation of measuring thickness and distribution of sediment layers by the tsunami and the inundation depth of water in Sendai plain. Ripple marks showing direction of sediment transport were the important object of observation. We used a soil auger for collecting sediments in the field, and sediment samples were submitted for analyzing grain size and interstitial water chemistry. Satellite images and aerial photographs are very useful for estimating the hydrogeological effects of tsunami inundation. We checked the correspondence of micro-topography, vegetation and sediment covering between before and after the tsunami. The most conspicuous phenomenon is the damage of pine forests planted in the purpose of preventing sand shifting. About ninety-five percent of vegetation coverage was lost during the period of rapid currents changed from first wave. The landward slopes of seawalls were mostly damaged and destroyed. Some aerial photographs leave detailed records of wave destruction just behind seawalls, which shows the occurrence of supercritical flows. The large-scale erosion of backshore behind seawalls is interpreted to have been caused by

  16. Local versus regional active stress field in 5900m San Gregorio Magno 1 well (southern Apennines, Italy).

    Science.gov (United States)

    Pierdominici, S.; Montone, P.; Mariucci, M. T.

    2009-04-01

    The aim of this work is to characterize the local stress field in a peculiar sector of the southern Apennines by analyzing borehole breakouts, fractures and logging data along the San Gregorio Magno 1 deep well, and to compare the achieved stress field with the regional one. The study area is characterized by diffuse low-Magnitude seismicity, although in historical times it has been repeatedly struck by moderate to large earthquakes. We have analyzed in detail the 5900m San Gregorio Magno 1 well drilled in 1996-97 by ENI S.p.A. and located very close (1.3 km away) to the Irpinia Fault. This fault was responsible of the strongest earthquake happened in this area, the 23rd November 1980 M6.9 earthquake that produced the first unequivocal historical surface faulting ever documented in Italy. The mainshock enucleated on a fault 38 km-long with a strike of 308° and 60-70° northeast-dipping, consistent with a NE-SW T-axis and a normal faulting tectonic regime. Borehole breakouts, active faults and focal mechanism solutions have allowed to define the present-day stress along and around the San Gregorio Magno 1 well and other analysis (logging data) to discriminate the presence of fracture zones and/or faults at depth. We have considered data from 1200m to the bottom of San Gregorio Magno 1 well. Our analysis of stress-induced wellbore breakouts shows an inhomogeneous direction of minimum horizontal stress (N359+-31°) orientation along the well. This direction is moderately consistent with the Shmin-trend determined from breakouts in other wells in this region and also with the regional active stress field inferred from active faults and earthquake focal plane solutions (N44 Shmin oriented). For this reason we have computed for each breakout zone the difference between the local trend and the regional one; comparing these breakout rotations with the spikes or changing trend of logs we have identified possible fractures or faults at different depths. We have correlated

  17. 15 CFR 922.130 - Boundary.

    Science.gov (United States)

    2010-01-01

    ... a small area between Point Bonita and Point San Pedro. Pillar Point Harbor, Santa Cruz Harbor... Cambria, in San Luis Obispo County. The Sanctuary boundary then extends eastward towards shore until it... portion of the Sanctuary is located approximately 65 nmi off the coast of San Simeon in San Luis...

  18. The physics of rock failure and earthquakes

    CERN Document Server

    Ohnaka, Mitiyasu

    2013-01-01

    Despite significant advances in the understanding of earthquake generation processes and derivation of underlying physical laws, controversy remains regarding the constitutive law for earthquake ruptures and how it should be formulated. Laboratory experiments are necessary to obtain high-resolution measurements that allow the physical nature of shear rupture processes to be deduced, and to resolve the controversy. This important book provides a deeper understanding of earthquake processes from nucleation to their dynamic propagation. Its key focus is a deductive approach based on laboratory-derived physical laws and formulae, such as a unifying constitutive law, a constitutive scaling law, and a physical model of shear rupture nucleation. Topics covered include: the fundamentals of rock failure physics, earthquake generation processes, physical scale dependence, and large-earthquake generation cycles. Designed for researchers and professionals in earthquake seismology, rock failure physics, geology and earthq...

  19. Is There An Earthquake Migration Global Pattern?

    Science.gov (United States)

    dos Santos, A. M.; Franca, G. S.; da Silveira, A. G.; Frigeri, G. V.; Marotta, G. S.

    2012-12-01

    Earthquake migration patterns before large earthquake were proposed by Mogi (1968) and existence of the correlation between earthquakes over distances that show probable global interdependence and this theme is certainly one of the most intriguing in field of seismology. In this job, we will present the phenomenology of earthquake migration global seismic pattern empirically, in order to ensure statistically the correlation of long range and lead to confrontation these seismic patterns. We used the international catalog available, such as, NEIC-USGS. We find that the pair of events that have a good correlation are confirmed statistically. As Shebalin (1996) has shown the earthquake chain, we show this first stage of the earthquake prediction correlation for large distances.

  20. Earthquake Hazard Mitigation Strategy in Indonesia

    Science.gov (United States)

    Karnawati, D.; Anderson, R.; Pramumijoyo, S.

    2008-05-01

    Because of the active tectonic setting of the region, the risks of geological hazards inevitably increase in Indonesian Archipelagoes and other ASIAN countries. Encouraging community living in the vulnerable area to adapt with the nature of geology will be the most appropriate strategy for earthquake risk reduction. Updating the Earth