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, Brad 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.

Tilt Precursors before Earthquakes on the San Andreas Fault, California.

Science.gov (United States)

Johnston, M J; Mortensen, C E

1974-12-13

An array of 14 biaxial shallow-borehole tiltmeters (at 1O(-7) radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (> 10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.

Quasi-periodic recurrence of large earthquakes on the southern San Andreas fault

Science.gov (United States)

Scharer, Katherine M.; Biasi, Glenn P.; Weldon, Ray J.; Fumal, Tom E.

2010-01-01

It has been 153 yr since the last large earthquake on the southern San Andreas fault (California, United States), but the average interseismic interval is only ~100 yr. If the recurrence of large earthquakes is periodic, rather than random or clustered, the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses. Unfortunately, robust characterization of a distribution describing earthquake recurrence on a single fault is limited by the brevity of most earthquake records. Here we use statistical tests on a 3000 yr combined record of 29 ground-rupturing earthquakes from Wrightwood, California. We show that earthquake recurrence there is more regular than expected from a Poisson distribution and is not clustered, leading us to conclude that recurrence is quasi-periodic. The observation of unimodal time dependence is persistent across an observationally based sensitivity analysis that critically examines alternative interpretations of the geologic record. The results support formal forecast efforts that use renewal models to estimate probabilities of future earthquakes on the southern San Andreas fault. Only four intervals (15%) from the record are longer than the present open interval, highlighting the current hazard posed by this fault.

Slip in the 1857 and earlier large earthquakes along the Carrizo Plain, San Andreas Fault.

Science.gov (United States)

Zielke, Olaf; Arrowsmith, J Ramón; Grant Ludwig, Lisa; Akçiz, Sinan O

2010-02-26

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

Electrical resistivity variations associated with earthquakes on the san andreas fault.

Science.gov (United States)

Mazzella, A; Morrison, H F

1974-09-06

A 24 percent precursory change in apparent electrical resistivity was observed before a magnitude 3.9 earthquake of strike-slip nature on the San Andreas fault in central California. The experimental configuration and numerical calculations suggest that the change is associated with a volume at depth rather than some near-surface phenomenon. The character and duration of the precursor period agree well with those of other earthquake studies and support a dilatant earthquake mechanism model.

Impact of a Large San Andreas Fault Earthquake on Tall Buildings in Southern California

Science.gov (United States)

Krishnan, S.; Ji, C.; Komatitsch, D.; Tromp, J.

2004-12-01

In 1857, an earthquake of magnitude 7.9 occurred on the San Andreas fault, starting at Parkfield and rupturing in a southeasterly direction for more than 300~km. Such a unilateral rupture produces significant directivity toward the San Fernando and Los Angeles basins. The strong shaking in the basins due to this earthquake would have had a significant long-period content (2--8~s). If such motions were to happen today, they could have a serious impact on tall buildings in Southern California. In order to study the effects of large San Andreas fault earthquakes on tall buildings in Southern California, we use the finite source of the magnitude 7.9 2001 Denali fault earthquake in Alaska and map it onto the San Andreas fault with the rupture originating at Parkfield and proceeding southward over a distance of 290~km. Using the SPECFEM3D spectral element seismic wave propagation code, we simulate a Denali-like earthquake on the San Andreas fault and compute ground motions at sites located on a grid with a 2.5--5.0~km spacing in the greater Southern California region. We subsequently analyze 3D structural models of an existing tall steel building designed in 1984 as well as one designed according to the current building code (Uniform Building Code, 1997) subjected to the computed ground motion. We use a sophisticated nonlinear building analysis program, FRAME3D, that has the ability to simulate damage in buildings due to three-component ground motion. We summarize the performance of these structural models on contour maps of carefully selected structural performance indices. This study could benefit the city in laying out emergency response strategies in the event of an earthquake on the San Andreas fault, in undertaking appropriate retrofit measures for tall buildings, and in formulating zoning regulations for new construction. In addition, the study would provide risk data associated with existing and new construction to insurance companies, real estate developers, and

Interseismic strain accumulation and the earthquake potential on the southern San Andreas fault system.

Science.gov (United States)

Fialko, Yuri

2006-06-22

The San Andreas fault in California is a mature continental transform fault that accommodates a significant fraction of motion between the North American and Pacific plates. The two most recent great earthquakes on this fault ruptured its northern and central sections in 1906 and 1857, respectively. The southern section of the fault, however, has not produced a great earthquake in historic times (for at least 250 years). Assuming the average slip rate of a few centimetres per year, typical of the rest of the San Andreas fault, the minimum amount of slip deficit accrued on the southern section is of the order of 7-10 metres, comparable to the maximum co-seismic offset ever documented on the fault. Here I present high-resolution measurements of interseismic deformation across the southern San Andreas fault system using a well-populated catalogue of space-borne synthetic aperture radar data. The data reveal a nearly equal partitioning of deformation between the southern San Andreas and San Jacinto faults, with a pronounced asymmetry in strain accumulation with respect to the geologically mapped fault traces. The observed strain rates confirm that the southern section of the San Andreas fault may be approaching the end of the interseismic phase of the earthquake cycle.

When it happens again: impact of future San Francisco Bay area earthquakes

Science.gov (United States)

Zoback, M.; Boatwright, J.; Kornfield, L.; Scawthorn, C.; Rojahn, C.

2005-12-01

San Francisco Bay area earthquakes, like major floods and hurricanes, have the potential for massive damage to dense urban population centers concentrated in vulnerable zones-along active faults, in coastal regions, and along major river arteries. The recent destruction of Hurricane Katrina does have precedent in the destruction following the 1906 "San Francisco" earthquake and fire in which more than 3000 people were killed and 225,000 were left homeless in San Francisco alone, a city of 400,000 at the time. Analysis of a comprehensive set of damage reports from the magnitude (M) 7.9 1906 earthquake indicates a region of ~ 18,000 km2 was subjected to shaking of Modified Mercalli Intensity of VIII or more - motions capable of damaging even modern, well-built structures; more than 60,000 km2 was subjected to shaking of Intensity VII or greater - the threshold for damage to masonry and poorly designed structures. By comparison, Katrina's hurricane force winds and intense rainfall impacted an area of ~100,000 km2 on the Gulf Coast. Thus, the anticipated effects of a future major Bay Area quake to lives, property, and infrastructure are comparable in scale to Katrina. Secondary hazards (levee failure and flooding in the case of Katrina and fire following the 1906 earthquake) greatly compounded the devastation in both disasters. A recent USGS-led study concluded there is a 62% chance of one or more damaging (M6.7 or greater) earthquakes striking the greater San Francisco Bay area over the next 30 years. The USGS prepared HAZUS loss estimates for the 10 most likely forecast earthquakes which range in size from a M6.7 event on a blind thrust to the largest anticipated event, a M7.9 repeat of the 1906 earthquake. The largest economic loss is expected for a repeat of the 1906 quake. Losses in the Bay region for this event are nearly double those predicted for a M6.9 rupture of the entire Hayward Fault in the East Bay. However, because of high density of population along the

Earthquake Swarm Along the San Andreas Fault near Palmdale, Southern California, 1976 to 1977.

Science.gov (United States)

McNally, K C; Kanamori, H; Pechmann, J C; Fuis, G

1978-09-01

Between November 1976 and November 1977 a swarm of small earthquakes (local magnitude foreshock sequences, such as tight clustering of hypocenters and time-dependent rotations of stress axes inferred from focal mechanisms. However, because of our present lack of understanding of the processes that precede earthquake faulting, the implications of the swarm for future large earthquakes on the San Andreas fault are unknown.

Earthquake geology and paleoseismology of major strands of the San Andreas fault system: Chapter 38

Science.gov (United States)

Rockwell, Thomas; Scharer, Katherine M.; Dawson, Timothy E.

2016-01-01

The San Andreas fault system in California is one of the best-studied faults in the world, both in terms of the long-term geologic history and paleoseismic study of past surface ruptures. In this paper, we focus on the Quaternary to historic data that have been collected from the major strands of the San Andreas fault system, both on the San Andreas Fault itself, and the major subparallel strands that comprise the plate boundary, including the Calaveras-Hayward- Rogers Creek-Maacama fault zone and the Concord-Green Valley-Bartlett Springs fault zone in northern California, and the San Jacinto and Elsinore faults in southern California. The majority of the relative motion between the Pacific and North American lithospheric plates is accommodated by these faults, with the San Andreas slipping at about 34 mm/yr in central California, decreasing to about 20 mm/yr in northern California north of its juncture with the Calaveras and Concord faults. The Calaveras-Hayward-Rogers Creek-Maacama fault zone exhibits a slip rate of 10-15 mm/yr, whereas the rate along the Concord-Green Valley-Bartlett Springs fault zone is lower at about 5 mm/yr. In southern California, the San Andreas exhibits a slip rate of about 35 mm/yr along the Mojave section, decreasing to as low as 10-15 mm/yr along its juncture with the San Jacinto fault, and about 20 mm/yr in the Coachella Valley. The San Jacinto and Elsinore fault zones exhibit rates of about 15 and 5 mm/yr, respectively. The average recurrence interval for surface-rupturing earthquakes along individual elements of the San Andreas fault system range from 100-500 years and is consistent with slip rate at those sites: higher slip rates produce more frequent or larger earthquakes. There is also evidence of short-term variations in strain release (slip rate) along various fault sections, as expressed as “flurries” or clusters of earthquakes as well as periods of relatively fewer surface ruptures in these relatively short records. This

Ground-motion modeling of the 1906 San Francisco earthquake, part I: Validation using the 1989 Loma Prieta earthquake

Science.gov (United States)

Aagaard, Brad T.; Brocher, T.M.; Dolenc, D.; Dreger, D.; Graves, R.W.; Harmsen, S.; Hartzell, S.; Larsen, S.; Zoback, M.L.

2008-01-01

We compute ground motions for the Beroza (1991) and Wald et al. (1991) source models of the 1989 magnitude 6.9 Loma Prieta earthquake using four different wave-propagation codes and recently developed 3D geologic and seismic velocity models. In preparation for modeling the 1906 San Francisco earthquake, we use this well-recorded earthquake to characterize how well our ground-motion simulations reproduce the observed shaking intensities and amplitude and durations of recorded motions throughout the San Francisco Bay Area. All of the simulations generate ground motions consistent with the large-scale spatial variations in shaking associated with rupture directivity and the geologic structure. We attribute the small variations among the synthetics to the minimum shear-wave speed permitted in the simulations and how they accommodate topography. Our long-period simulations, on average, under predict shaking intensities by about one-half modified Mercalli intensity (MMI) units (25%-35% in peak velocity), while our broadband simulations, on average, under predict the shaking intensities by one-fourth MMI units (16% in peak velocity). Discrepancies with observations arise due to errors in the source models and geologic structure. The consistency in the synthetic waveforms across the wave-propagation codes for a given source model suggests the uncertainty in the source parameters tends to exceed the uncertainty in the seismic velocity structure. In agreement with earlier studies, we find that a source model with slip more evenly distributed northwest and southeast of the hypocenter would be preferable to both the Beroza and Wald source models. Although the new 3D seismic velocity model improves upon previous velocity models, we identify two areas needing improvement. Nevertheless, we find that the seismic velocity model and the wave-propagation codes are suitable for modeling the 1906 earthquake and scenario events in the San Francisco Bay Area.

Periodic, chaotic, and doubled earthquake recurrence intervals on the deep San Andreas fault.

Science.gov (United States)

Shelly, David R

2010-06-11

Earthquake recurrence histories may provide clues to the timing of future events, but long intervals between large events obscure full recurrence variability. In contrast, small earthquakes occur frequently, and recurrence intervals are quantifiable on a much shorter time scale. In this work, I examine an 8.5-year sequence of more than 900 recurring low-frequency earthquake bursts composing tremor beneath the San Andreas fault near Parkfield, California. These events exhibit tightly clustered recurrence intervals that, at times, oscillate between approximately 3 and approximately 6 days, but the patterns sometimes change abruptly. Although the environments of large and low-frequency earthquakes are different, these observations suggest that similar complexity might underlie sequences of large earthquakes.

Periodic, chaotic, and doubled earthquake recurrence intervals on the deep San Andreas Fault

Science.gov (United States)

Shelly, David R.

2010-01-01

Earthquake recurrence histories may provide clues to the timing of future events, but long intervals between large events obscure full recurrence variability. In contrast, small earthquakes occur frequently, and recurrence intervals are quantifiable on a much shorter time scale. In this work, I examine an 8.5-year sequence of more than 900 recurring low-frequency earthquake bursts composing tremor beneath the San Andreas fault near Parkfield, California. These events exhibit tightly clustered recurrence intervals that, at times, oscillate between ~3 and ~6 days, but the patterns sometimes change abruptly. Although the environments of large and low-frequency earthquakes are different, these observations suggest that similar complexity might underlie sequences of large earthquakes.

The HayWired Earthquake Scenario—Earthquake Hazards

Science.gov (United States)

Detweiler, Shane T.; Wein, Anne M.

2017-04-24

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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. Lastly, 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.

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

Science.gov (United States)

Delorey, Andrew; Van Der Elst, Nicholas; Johnson, Paul

2017-01-01

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.

Examining and Comparing Earthquake Readiness in East San Francisco Bay Area Communities (Invited)

Science.gov (United States)

Ramirez, N.; Bul, V.; Chavez, A.; Chin, W.; Cuff, K. E.; Girton, C.; Haynes, D.; Kelly, G.; Leon, G.; Ramirez, J.; Ramirez, R.; Rodriquez, F.; Ruiz, D.; Torres, J.

2009-12-01

Based on past experiences, the potential for casualties and mass destruction that can result from a high magnitude earthquake are well known. Nevertheless, given the East San Francisco Bay Area’s proximity to the Hayward and San Andreas faults, learning about earthquakes and disaster preparedness is of particular importance. While basic educational programs and materials are available both through emergency relief agencies and schools, little research has been done on their effectiveness. Because of the wide socioeconomic spread between communities in the East Bay, we decided to investigate understandings of issues related to disaster and earthquake preparedness among local populations based upon average household income. To accomplish this, we created a survey that was later uploaded to and implemented using Palm Treo Smart Phones. Survey locations were selected in such a way that they reflected the understandings of residents in a diverse set of socio-economic settings. Thus, these locations included a grocery store and nearby plaza in the Fruitvale district of Oakland, CA (zip=94601; median household income= 33,152), as well as the nearby town of Alameda, CA (zip=94502, median household income= 87,855). Preliminary results suggest that in terms of the objective questions on the survey, people from Alameda who participated in our study performed significantly better (difference in percentage correct greater than 10%) than the people from Fruitvale on two of the advanced earthquake knowledge questions. Interestingly enough, people in Fruitvale significantly outperformed people in Alameda on two of the basic earthquake knowledge questions. The final important finding was that while houses in Alameda tended to be newer and more often retrofitted than houses in Fruitvale, the people of the latter location tended to have a higher percentage of respondents claim confidence in the ability of their house to withstand a major earthquake. Based on preliminary results we

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%.

Prediction of maximum earthquake intensities for the San Francisco Bay region

Science.gov (United States)

Borcherdt, Roger D.; Gibbs, James F.

1975-01-01

The intensity data for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the empirical relation derived between 1906 intensities and distance perpendicular to the fault for 917 sites underlain by rocks of the Franciscan Formation is: Intensity = 2.69 - 1.90 log (Distance) (km). For sites on other geologic units intensity increments, derived with respect to this empirical relation, correlate strongly with the Average Horizontal Spectral Amplifications (AHSA) determined from 99 three-component recordings of ground motion generated by nuclear explosions in Nevada. The resulting empirical relation is: Intensity Increment = 0.27 +2.70 log (AHSA), and average intensity increments for the various geologic units are -0.29 for granite, 0.19 for Franciscan Formation, 0.64 for the Great Valley Sequence, 0.82 for Santa Clara Formation, 1.34 for alluvium, 2.43 for bay mud. The maximum intensity map predicted from these empirical relations delineates areas in the San Francisco Bay region of potentially high intensity from future earthquakes on either the San Andreas fault or the Hazard fault.

Prediction of maximum earthquake intensities for the San Francisco Bay region

Energy Technology Data Exchange (ETDEWEB)

Borcherdt, R.D.; Gibbs, J.F.

1975-01-01

The intensity data for the California earthquake of Apr 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the empirical relation derived between 1906 intensities and distance perpendicular to the fault for 917 sites underlain by rocks of the Franciscan formation is intensity = 2.69 - 1.90 log (distance) (km). For sites on other geologic units, intensity increments, derived with respect to this empirical relation, correlate strongly with the average horizontal spectral amplifications (AHSA) determined from 99 three-component recordings of ground motion generated by nuclear explosions in Nevada. The resulting empirical relation is intensity increment = 0.27 + 2.70 log (AHSA), and average intensity increments for the various geologic units are -0.29 for granite, 0.19 for Franciscan formation, 0.64 for the Great Valley sequence, 0.82 for Santa Clara formation, 1.34 for alluvium, and 2.43 for bay mud. The maximum intensity map predicted from these empirical relations delineates areas in the San Francisco Bay region of potentially high intensity from future earthquakes on either the San Andreas fault or the Hayward fault.

Earthquakes and Volcanic Processes at San Miguel Volcano, El Salvador, Determined from a Small, Temporary Seismic Network

Science.gov (United States)

Hernandez, S.; Schiek, C. G.; Zeiler, C. P.; Velasco, A. A.; Hurtado, J. M.

2008-12-01

The San Miguel volcano lies within the Central American volcanic chain in eastern El Salvador. The volcano has experienced at least 29 eruptions with Volcano Explosivity Index (VEI) of 2. Since 1970, however, eruptions have decreased in intensity to an average of VEI 1, with the most recent eruption occurring in 2002. Eruptions at San Miguel volcano consist mostly of central vent and phreatic eruptions. A critical challenge related to the explosive nature of this volcano is to understand the relationships between precursory surface deformation, earthquake activity, and volcanic activity. In this project, we seek to determine sub-surface structures within and near the volcano, relate the local deformation to these structures, and better understand the hazard that the volcano presents in the region. To accomplish these goals, we deployed a six station, broadband seismic network around San Miguel volcano in collaboration with researchers from Servicio Nacional de Estudios Territoriales (SNET). This network operated continuously from 23 March 2007 to 15 January 2008 and had a high data recovery rate. The data were processed to determine earthquake locations, magnitudes, and, for some of the larger events, focal mechanisms. We obtained high precision locations using a double-difference approach and identified at least 25 events near the volcano. Ongoing analysis will seek to identify earthquake types (e.g., long period, tectonic, and hybrid events) that occurred in the vicinity of San Miguel volcano. These results will be combined with radar interferometric measurements of surface deformation in order to determine the relationship between surface and subsurface processes at the volcano.

Ground-rupturing earthquakes on the northern Big Bend of the San Andreas Fault, California, 800 A.D. to Present

Science.gov (United States)

Scharer, Katherine M.; Weldon, Ray; Biasi, Glenn; Streig, Ashley; Fumal, Thomas E.

2017-01-01

Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring sites overlap in age and are considered correlative. This study presents the evidence and ages for 11 earthquakes that occurred along the Big Bend section of the southern San Andreas Fault at the Frazier Mountain paleoseismic site. The most recent earthquake to rupture the site was the Mw7.7–7.9 Fort Tejon earthquake of 1857. We use over 30 trench excavations to document the structural and sedimentological evolution of a small pull-apart basin that has been repeatedly faulted and folded by ground-rupturing earthquakes. A sedimentation rate of 0.4 cm/yr and abundant organic material for radiocarbon dating contribute to a record that is considered complete since 800 A.D. and includes 10 paleoearthquakes. Earthquakes have ruptured this location on average every ~100 years over the last 1200 years, but individual intervals range from ~22 to 186 years. The coefficient of variation of the length of time between earthquakes (0.7) indicates quasiperiodic behavior, similar to other sites along the southern San Andreas Fault. Comparison with the earthquake chronology at neighboring sites along the fault indicates that only one other 1857-size earthquake could have occurred since 1350 A.D., and since 800 A.D., the Big Bend and Mojave sections have ruptured together at most 50% of the time in Mw ≥ 7.3 earthquakes.

EFFECTS OF THE 1983 COALINGA, CALIFORNIA, EARTHQUAKE ONCREEP ALONG THE SAN ADREAS FAULT.

Science.gov (United States)

Mavko, Gerald M.; Schulz, Sandra; Brown, Beth D.

1985-01-01

The M//L approximately equals 6. 5 earthquake that occurred near Coalinga, California, on May 2, 1983 induced changes in near-surface fault slip along the San Andreas fault. Coseismic steps were observed by creepmeters along a 200-km section of the San Andreas. some of the larger aftershocks induced additional steps, both right-lateral and left-lateral, and in general the sequence disrupted observed creep at several sites from preseismic long-term patterns. Static dislocation models can approximately explain the magnitudes and distribution of the larger coseismic steps on May 2. The smaller, more distant steps appear to be the abrupt release of accumulated slip, triggered by the coseismic strain changes, but independent of the strain change amplitudes.

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.

Break of slope in earthquake size distribution and creep rate along the San Andreas Fault system

Science.gov (United States)

Shebalin, P.; Narteau, C.; Vorobieva, I.

2017-12-01

Crustal faults accommodate slip either by a succession of earthquakes or continuous slip, andin most instances, both these seismic and aseismic processes coexist. Recorded seismicity and geodeticmeasurements are therefore two complementary data sets that together document ongoing deformationalong active tectonic structures. Here we study the influence of stable sliding on earthquake statistics.We show that creep along the San Andreas Fault is responsible for a break of slope in the earthquake sizedistribution. This slope increases with an increasing creep rate for larger magnitude ranges, whereas itshows no systematic dependence on creep rate for smaller magnitude ranges. This is interpreted as a deficitof large events under conditions of faster creep where seismic ruptures are less likely to propagate. Theseresults suggest that the earthquake size distribution does not only depend on the level of stress but also onthe type of deformation.

Does paleoseismology forecast the historic rates of large earthquakes on the San Andreas fault system?

Science.gov (United States)

Biasi, Glenn; Scharer, Katherine M.; Weldon, Ray; Dawson, Timothy E.

2016-01-01

The 98-year open interval since the most recent ground-rupturing earthquake in the greater San Andreas boundary fault system would not be predicted by the quasi-periodic recurrence statistics from paleoseismic data. We examine whether the current hiatus could be explained by uncertainties in earthquake dating. Using seven independent paleoseismic records, 100 year intervals may have occurred circa 1150, 1400, and 1700 AD, but they occur in a third or less of sample records drawn at random. A second method sampling from dates conditioned on the existence of a gap of varying length suggests century-long gaps occur 3-10% of the time. A combined record with more sites would lead to lower probabilities. Systematic data over-interpretation is considered an unlikely explanation. Instead some form of non-stationary behaviour seems required, perhaps through long-range fault interaction. Earthquake occurrence since 1000 AD is not inconsistent with long-term cyclicity suggested from long runs of earthquake simulators.

Kinematics of the 2015 San Ramon, California earthquake swarm: Implications for fault zone structure and driving mechanisms

Science.gov (United States)

Xue, Lian; Bürgmann, Roland; Shelly, David R.; Johnson, Christopher W.; Taira, Taka'aki

2018-05-01

Earthquake swarms represent a sudden increase in seismicity that may indicate a heterogeneous fault-zone, the involvement of crustal fluids and/or slow fault slip. Swarms sometimes precede major earthquake ruptures. An earthquake swarm occurred in October 2015 near San Ramon, California in an extensional right step-over region between the northern Calaveras Fault and the Concord-Mt. Diablo fault zone, which has hosted ten major swarms since 1970. The 2015 San Ramon swarm is examined here from 11 October through 18 November using template matching analysis. The relocated seismicity catalog contains ∼4000 events with magnitudes between - 0.2

Constraints on the source parameters of low-frequency earthquakes on the San Andreas Fault

Science.gov (United States)

Thomas, Amanda M.; Beroza, Gregory C.; Shelly, David R.

2016-01-01

Low-frequency earthquakes (LFEs) are small repeating earthquakes that occur in conjunction with deep slow slip. Like typical earthquakes, LFEs are thought to represent shear slip on crustal faults, but when compared to earthquakes of the same magnitude, LFEs are depleted in high-frequency content and have lower corner frequencies, implying longer duration. Here we exploit this difference to estimate the duration of LFEs on the deep San Andreas Fault (SAF). We find that the M ~ 1 LFEs have typical durations of ~0.2 s. Using the annual slip rate of the deep SAF and the average number of LFEs per year, we estimate average LFE slip rates of ~0.24 mm/s. When combined with the LFE magnitude, this number implies a stress drop of ~104 Pa, 2 to 3 orders of magnitude lower than ordinary earthquakes, and a rupture velocity of 0.7 km/s, 20% of the shear wave speed. Typical earthquakes are thought to have rupture velocities of ~80–90% of the shear wave speed. Together, the slow rupture velocity, low stress drops, and slow slip velocity explain why LFEs are depleted in high-frequency content relative to ordinary earthquakes and suggest that LFE sources represent areas capable of relatively higher slip speed in deep fault zones. Additionally, changes in rheology may not be required to explain both LFEs and slow slip; the same process that governs the slip speed during slow earthquakes may also limit the rupture velocity of LFEs.

Changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992.

Science.gov (United States)

Jaumé, S C; Sykes, L R

1992-11-20

The April to June 1992 Landers earthquake sequence in southern California modified the state of stress along nearby segments of the San Andreas fault, causing a 50-kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near San Gorgonio Pass. The decrease in compressive normal stress may also have reduced fluid pressures along that fault segment. As pressures are reequilibrated by diffusion, that fault segment should move closer to failure with time. That fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years.

A case for historic joint rupture of the San Andreas and San Jacinto faults.

Science.gov (United States)

Lozos, Julian C

2016-03-01

The San Andreas fault is considered to be the primary plate boundary fault in southern California and the most likely fault to produce a major earthquake. I use dynamic rupture modeling to show that the San Jacinto fault is capable of rupturing along with the San Andreas in a single earthquake, and interpret these results along with existing paleoseismic data and historic damage reports to suggest that this has likely occurred in the historic past. In particular, I find that paleoseismic data and historic observations for the ~M7.5 earthquake of 8 December 1812 are best explained by a rupture that begins on the San Jacinto fault and propagates onto the San Andreas fault. This precedent carries the implications that similar joint ruptures are possible in the future and that the San Jacinto fault plays a more significant role in seismic hazard in southern California than previously considered. My work also shows how physics-based modeling can be used for interpreting paleoseismic data sets and understanding prehistoric fault behavior.

A case for historic joint rupture of the San Andreas and San Jacinto faults

Science.gov (United States)

Lozos, Julian C.

2016-01-01

The San Andreas fault is considered to be the primary plate boundary fault in southern California and the most likely fault to produce a major earthquake. I use dynamic rupture modeling to show that the San Jacinto fault is capable of rupturing along with the San Andreas in a single earthquake, and interpret these results along with existing paleoseismic data and historic damage reports to suggest that this has likely occurred in the historic past. In particular, I find that paleoseismic data and historic observations for the ~M7.5 earthquake of 8 December 1812 are best explained by a rupture that begins on the San Jacinto fault and propagates onto the San Andreas fault. This precedent carries the implications that similar joint ruptures are possible in the future and that the San Jacinto fault plays a more significant role in seismic hazard in southern California than previously considered. My work also shows how physics-based modeling can be used for interpreting paleoseismic data sets and understanding prehistoric fault behavior. PMID:27034977

A case for historic joint rupture of the San Andreas and San Jacinto faults

OpenAIRE

Lozos, Julian C.

2016-01-01

The San Andreas fault is considered to be the primary plate boundary fault in southern California and the most likely fault to produce a major earthquake. I use dynamic rupture modeling to show that the San Jacinto fault is capable of rupturing along with the San Andreas in a single earthquake, and interpret these results along with existing paleoseismic data and historic damage reports to suggest that this has likely occurred in the historic past. In particular, I find that paleoseismic data...

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...

Shallow deformation of the San Andreas fault 5 years following the 2004 Parkfield earthquake (Mw6) combining ERS2 and Envisat InSAR.

Science.gov (United States)

Bacques, Guillaume; de Michele, Marcello; Raucoules, Daniel; Aochi, Hideo; Rolandone, Frédérique

2018-04-16

This study focuses on the shallow deformation that occurred during the 5 years following the Parkfield earthquake (28/09/2004, Mw 6, San Andreas Fault, California). We use Synthetic Aperture Radar interferometry (InSAR) to provide precise measurements of transient deformations after the Parkfield earthquake between 2005 and 2010. We propose a method to combine both ERS2 and ENVISAT interferograms to increase the temporal data sampling. Firstly, we combine 5 years of available Synthetic Aperture Radar (SAR) acquisitions including both ERS-2 and Envisat. Secondly, we stack selected interferograms (both from ERS2 and Envisat) for measuring the temporal evolution of the ground velocities at given time intervals. Thanks to its high spatial resolution, InSAR could provide new insights on the surface fault motion behavior over the 5 years following the Parkfield earthquake. As a complement to previous studies in this area, our results suggest that shallow transient deformations affected the Creeping-Parkfield-Cholame sections of the San Andreas Fault after the 2004 Mw6 Parkfield earthquake.

Earthquakes, November-December 1977

Science.gov (United States)

Person, W.J.

1978-01-01

Two major earthquakes occurred in the last 2 months of the year. A magnitude 7.0 earthquake struck San Juan Province, Argentina, on November 23, causing fatalities and damage. The second major earthquake was a magnitude 7.0 in the Bonin Islands region, an unpopulated area. On December 19, Iran experienced a destructive earthquake, which killed over 500.

Facing the great disaster : How the men and women of the U.S. Geological Survey responded to the 1906 "San Francisco Earthquake"

Science.gov (United States)

Colvard, Elizabeth M.; Rogers, James

2006-01-01

It was the most devastating earthquake in California’s history. At 5:12 a.m. on April 18, 1906, the ground under the San Francisco Bay Area shook violently for more than 40 seconds. The magnitude 7.8 earthquake created a rupture along nearly 300 miles of the San Andreas Fault and was felt from southern Oregon to Los Angeles. Because the earthquake’s epicenter was just offshore from San Francisco, the impact on that city was catastrophic. Fragments of broken houses and buildings tumbled into the streets. The pipeline carrying water into the city was severed; fires triggered by broken gas mains raged out of control for 3 days. An area of almost 5 square miles in the heart of the city was destroyed by shaking and fire, and earthquake damage was widespread elsewhere. At least 3,000 people were killed, and 225,000 were left homeless. Drinking water, food, and supplies quickly became scarce.In 1906, the only permanent U.S. Geological Survey (USGS) office in California was the Pacific Division topographic mapping office in Sacramento, 70 miles up the Sacramento River from San Francisco Bay. The office had been established just 3 years earlier and was the only USGS office ever created for the sole function of topographic mapping. At the time of the earthquake, many USGS topographers were in Sacramento preparing for a summer of field work.Although moderate shaking was felt in Sacramento, then a town of about 30,000 people, detailed information about the earthquake was slow to reach the residents there. USGS topographic engineer George R. Davis, not knowing the full extent of the damage, was fearful that his 62-year-old father Edward Davis in San Francisco was caught up in the devastation. George therefore left Sacramento on the first train bound for the San Francisco Bay area. “He was very worried. The phones were down and he wasn’t sure whether or not the hotel his father was living in was damaged,” said George Davis’s daughter Anna (Davis) Rogers, then an

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.

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.

Chemical and Physical Characteristics of Pulverized Granitic Rock Adjacent to the San Andreas, Garlock and San Jacinto Faults: Implications for Earthquake Physics

Science.gov (United States)

Rockwell, T. K.; Sisk, M.; Stillings, M.; Girty, G.; Dor, O.; Wechsler, N.; Ben-Zion, Y.

2008-12-01

We present new detailed analyses of pulverized granitic rocks from sections adjacent to the San Andreas, Garlock and San Jacinto faults in southern California. Along the San Andreas and Garlock faults, the Tejon Lookout Granite is pulverized in all exposures within about 100 m of both faults. Along the Clark strand of the San Jacinto fault in Horse Canyon, the pulverization of granitic rocks is highly asymmetric, with a much broader zone of pulverization along the southwest side of the Clark fault. In areas where the granite is injected as dyke rock into schist, only the granitic rock shows pulverization, demonstrating the control of rock type on the pulverization process. Chemical analyses indicate little or no weathering in the bulk of the rock, although XRD analysis shows the presence of smectite, illite, and minor kaolinite in the clay-sized fraction. Weathering products may dominate in the less than 1 micron fraction. The average grain size in all samples of pulverized granitic rock range between about 20 and 200 microns (silt to fine sand), with the size distribution in part a function of proximity to the primary slip zone. The San Andreas fault samples are generally finer than those collected from along the Garlock or San Jacinto faults. The particle size distribution for all samples is non-fractal, with a distinct slope break in the 60-100 micron range, which suggests that pulverization is not a consequence of direct shear. This average particle size is quite coarser than previous reports, which we attribute to possible measurement errors in the prior work. Our data and observations suggest that dynamic fracturing in the wall rock of these three major faults only accounts for 1% or less of the earthquake energy budget.

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

Real-Time GPS Monitoring for Earthquake Rapid Assessment in the San Francisco Bay Area

Science.gov (United States)

Guillemot, C.; Langbein, J. O.; Murray, J. R.

2012-12-01

The U.S. Geological Survey Earthquake Science Center has deployed a network of eight real-time Global Positioning System (GPS) stations in the San Francisco Bay area and is implementing software applications to continuously evaluate the status of the deformation within the network. Real-time monitoring of the station positions is expected to provide valuable information for rapidly estimating source parameters should a large earthquake occur in the San Francisco Bay area. Because earthquake response applications require robust data access, as a first step we have developed a suite of web-based applications which are now routinely used to monitor the network's operational status and data streaming performance. The web tools provide continuously updated displays of important telemetry parameters such as data latency and receive rates, as well as source voltage and temperature information within each instrument enclosure. Automated software on the backend uses the streaming performance data to mitigate the impact of outages, radio interference and bandwidth congestion on deformation monitoring operations. A separate set of software applications manages the recovery of lost data due to faulty communication links. Displacement estimates are computed in real-time for various combinations of USGS, Plate Boundary Observatory (PBO) and Bay Area Regional Deformation (BARD) network stations. We are currently comparing results from two software packages (one commercial and one open-source) used to process 1-Hz data on the fly and produce estimates of differential positions. The continuous monitoring of telemetry makes it possible to tune the network to minimize the impact of transient interruptions of the data flow, from one or more stations, on the estimated positions. Ongoing work is focused on using data streaming performance history to optimize the quality of the position, reduce drift and outliers by switching to the best set of stations within the network, and

Evaluation of the Pseudostatic Analyses of Earth Dams Using FE Simulation and Observed Earthquake-Induced Deformations: Case Studies of Upper San Fernando and Kitayama Dams

Directory of Open Access Journals (Sweden)

Tohid Akhlaghi

2014-01-01

Full Text Available Evaluation of the accuracy of the pseudostatic approach is governed by the accuracy with which the simple pseudostatic inertial forces represent the complex dynamic inertial forces that actually exist in an earthquake. In this study, the Upper San Fernando and Kitayama earth dams, which have been designed using the pseudostatic approach and damaged during the 1971 San Fernando and 1995 Kobe earthquakes, were investigated and analyzed. The finite element models of the dams were prepared based on the detailed available data and results of in situ and laboratory material tests. Dynamic analyses were conducted to simulate the earthquake-induced deformations of the dams using the computer program Plaxis code. Then the pseudostatic seismic coefficient used in the design and analyses of the dams were compared with the seismic coefficients obtained from dynamic analyses of the simulated model as well as the other available proposed pseudostatic correlations. Based on the comparisons made, the accuracy and reliability of the pseudostatic seismic coefficients are evaluated and discussed.

The ShakeOut scenario: A hypothetical Mw7.8 earthquake on the Southern San Andreas Fault

Science.gov (United States)

Porter, K.; Jones, L.; Cox, D.; Goltz, J.; Hudnut, K.; Mileti, D.; Perry, S.; Ponti, D.; Reichle, M.; Rose, A.Z.; Scawthorn, C.R.; Seligson, H.A.; Shoaf, K.I.; Treiman, J.; Wein, A.

2011-01-01

In 2008, an earthquake-planning scenario document was released by the U.S. Geological Survey (USGS) and California Geological Survey that hypothesizes the occurrence and effects of a Mw7.8 earthquake on the southern San Andreas Fault. It was created by more than 300 scientists and engineers. Fault offsets reach 13 m and up to 8 m at lifeline crossings. Physics-based modeling was used to generate maps of shaking intensity, with peak ground velocities of 3 m/sec near the fault and exceeding 0.5 m/sec over 10,000 km2. A custom HAZUS??MH analysis and 18 special studies were performed to characterize the effects of the earthquake on the built environment. The scenario posits 1,800 deaths and 53,000 injuries requiring emergency room care. Approximately 1,600 fires are ignited, resulting in the destruction of 200 million square feet of the building stock, the equivalent of 133,000 single-family homes. Fire contributes $87 billion in property and business interruption loss, out of the total $191 billion in economic loss, with most of the rest coming from shakerelated building and content damage ($46 billion) and business interruption loss from water outages ($24 billion). Emergency response activities are depicted in detail, in an innovative grid showing activities versus time, a new format introduced in this study. ?? 2011, Earthquake Engineering Research Institute.

Modeling of periodic great earthquakes on the San Andreas fault: Effects of nonlinear crustal rheology

Science.gov (United States)

Reches, Ze'ev; Schubert, Gerald; Anderson, Charles

1994-01-01

We analyze the cycle of great earthquakes along the San Andreas fault with a finite element numerical model of deformation in a crust with a nonlinear viscoelastic rheology. The viscous component of deformation has an effective viscosity that depends exponentially on the inverse absolute temperature and nonlinearity on the shear stress; the elastic deformation is linear. Crustal thickness and temperature are constrained by seismic and heat flow data for California. The models are for anti plane strain in a 25-km-thick crustal layer having a very long, vertical strike-slip fault; the crustal block extends 250 km to either side of the fault. During the earthquake cycle that lasts 160 years, a constant plate velocity v(sub p)/2 = 17.5 mm yr is applied to the base of the crust and to the vertical end of the crustal block 250 km away from the fault. The upper half of the fault is locked during the interseismic period, while its lower half slips at the constant plate velocity. The locked part of the fault is moved abruptly 2.8 m every 160 years to simulate great earthquakes. The results are sensitive to crustal rheology. Models with quartzite-like rheology display profound transient stages in the velocity, displacement, and stress fields. The predicted transient zone extends about 3-4 times the crustal thickness on each side of the fault, significantly wider than the zone of deformation in elastic models. Models with diabase-like rheology behave similarly to elastic models and exhibit no transient stages. The model predictions are compared with geodetic observations of fault-parallel velocities in northern and central California and local rates of shear strain along the San Andreas fault. The observations are best fit by models which are 10-100 times less viscous than a quartzite-like rheology. Since the lower crust in California is composed of intermediate to mafic rocks, the present result suggests that the in situ viscosity of the crustal rock is orders of magnitude

Anomalous Diffuse CO2 Emission Changes at San Vicente Volcano Related to Earthquakes in El Salvador, Central America

Science.gov (United States)

Salazar, J.; Hernandez, P.; Perez, N.; Barahona, F.; Olmos, R.; Cartagena, R.; Soriano, T.; Notsu, K.; Lopez, D.

2001-12-01

San Vicente or Chichontepeque (2,180 m a.s.l.) is a composite andesitic volcano located 50 Km east of San Salvador. Its paired edifice rises from the so-called Central Graben, an extensional structure parallel to the Pacific coast, and has been inactive for the last 3000 yrs. Fumaroles (98.2°C ) and hot spring waters are present along radial faults at two localities on the northern slope of the volcano (Aguas Agrias and El Infiernillo). CO2 is the most abundant component in the dry gas (>90%) and its mean isotopic composition (δ 13C(CO2)=-2.11 ‰ and 3He/4He of 6.9 Ra) suggests a magmatic origin for the CO2. These manifestations are supposed to be linked to a 1,200 m depth 250°C reservoir with a CO2 partial pressure of 14 bar extended beneath the volcano (Aiuppa et al., 1997). In February 13, 2001, a 6.6 magnitude earthquake with epicenter about 20 Km W of San Vicente damaged and destroyed many towns and villages in the north area of the volcano causing some deceases. In addition, two seismic swarms were recorded beneath the northeastern flank of the volcano in April and May 2001. Searching for any link between the actual seismic activity and changes in the diffuse CO2 degassing at San Vicente, an NDIR instrument for continuos monitoring of the diffuse CO2 degassing was set up at Aguas Agrias in March 2001. Soil CO2 efflux and several meteorological and soil physical variables were measured in an hourly basis. Very significative pre-seismic and post-seismic relationships have been found in the observed diffuse CO2 efflux temporal variations related to the May 2001 seismic swarms. A sustained 50% increase on the average diffuse CO2 efflux was observed 8 days before the May 8, 5.1 magnitude earthquake. This pre-seismic behaviour may be considered a precursor of the May 2001 seismic swarm at San Vicente volcano. However, about a three-fold increase in the diffuse CO2 efflux was also observed after the intense seismicity recorded on May 8-9. These preliminary

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

Zemětřesná aktivita na zlomu San Andreas

OpenAIRE

Voroňáková, Jana

2011-01-01

SUMMARY: This work deals with the San Andreas fault as a tectonically active area. It includes basic information about the fracture, its origins and history. The work shows, as scientists are now trying to combat the risk of impending earthquakes. Project of San Andreas Fault Observatory at Depth and individual predictions of the next earthquake rupture are described.

U-Pb geochronology and paleomagnetism of the Neoproterozoic St Simeon dolerite dykes, Quebec: an eastern Laurentian perspective of Ediacaran Rodinia breakup

Science.gov (United States)

Pisarevsky, Sergei; Murphy, Brendan; Hamilton, Mike; Söderlund, Ulf; Hodych, Joseph

2013-04-01

The St Simeon (SS) mafic dykes (150 km NE of Quebec City) are now dated at 548 ± 1 Ma (U-Pb; baddeleyite). This age is similar to a published LA-ICPMS zircon age of 550 ± 7 Ma for the Mt. St-Anselme (MS) basalts, which supports previous inferences of (i) a genetic relationship between them, (ii) the pene-contemporaneity of OIB-type mafic magmatism in East Laurentia and (iii) the existence of two late Ediacaran plumes that attended the final breakup of Rodinia and opening of the Iapetus Ocean and Tornquist Sea. Both the SS dykes and the MS basalts were sampled for paleomagnetic study. The paleomagnetic pole for SS is similar to the previously published pole for coeval basalts (Skinner Cove, SC) from Newfoundland. Unlike SC, the St Simeon pole represents rocks which are unambiguously coherent tectonically with the Laurentian Craton. This new pole is also coeval with high quality poles from the Winter Coast (Baltica) and provides paleomagnetic constraints on the history of the final breakup of Rodinia and opening of Eastern Iapetus and Tornquist Sea.

Offshore geology and geomorphology from Point Piedras Blancas to Pismo Beach, San Luis Obispo County, California

Science.gov (United States)

Watt, Janet Tilden; Johnson, Samuel Y.; Hartwell, Stephen R.; Roberts, Michelle

2015-01-01

Marine geology and geomorphology were mapped along the continental shelf and upper slope between Point Piedras Blancas and Pismo Beach, California. The map area is divided into the following three (smaller) map areas, listed from north to south: San Simeon, Morro Bay, and Point San Luis. Each smaller map area consists of a geologic map and the corresponding geophysical data that support the geologic mapping. Each geophysical data sheet includes shaded-relief multibeam bathymetry, seismic-reflection-survey tracklines, and residual magnetic anomalies, as well as a smaller version of the geologic map for reference. Offshore geologic units were delineated on the basis of integrated analysis of adjacent onshore geology, seafloor-sediment and rock samples, multibeam bathymetry and backscatter imagery, magnetic data, and high-resolution seismic-reflection profiles. Although the geologic maps are presented here at 1:35,000 scale, map interpretation was conducted at scales of between 1:6,000 and 1:12,000.

Short-period strain (0.1-105 s): Near-source strain field for an earthquake (M L 3.2) near San Juan Bautista, California

Science.gov (United States)

Johnston, M. J. S.; Borcherdt, R. D.; Linde, A. T.

1986-10-01

Measurements of dilational earth strain in the frequency band 25-10-5 Hz have been made on a deep borehole strainmeter installed near the San Andreas fault. These data are used to determine seismic radiation fields during nuclear explosions, teleseisms, local earthquakes, and ground noise during seismically quiet times. Strains of less than 10-10 on these instruments can be clearly resolved at short periods (< 10 s) and are recorded with wide dynamic range digital recorders. This permits measurement of the static and dynamic strain variations in the near field of local earthquakes. Noise spectra for earth strain referenced to 1 (strain)2/Hz show that strain resolution decreases at about 10 dB per decade of frequency from -150 dB at 10-4 Hz to -223 dB at 10 Hz. Exact expressions are derived to relate the volumetric strain and displacement field for a homogeneous P wave in a general viscoelastic solid as observed on colocated dilatometers and seismometers. A rare near-field recording of strain and seismic velocity was obtained on May 26, 1984, from an earthquake (ML 3.2) at a hypocentral distance of 3.2 km near the San Andreas fault at San Juan Bautista, California. While the data indicate no precursory strain release at the 5 × 10-11 strain level, a coseismic strain release of 1.86 nanostrain was observed. This change in strain is consistent with that calculated from a simple dislocation model of the event. Ground displacement spectra, determined from the downhole strain data and instrument-corrected surface seismic data, suggest that source parameters estimated from surface recordings may be contaminated by amplification effects in near-surface low-velocity materials.

The 1911 M ~6.6 Calaveras earthquake: Source parameters and the role of static, viscoelastic, and dynamic coulomb stress changes imparted by the 1906 San Francisco earthquake

Science.gov (United States)

Doser, D.I.; Olsen, K.B.; Pollitz, F.F.; Stein, R.S.; Toda, S.

2009-01-01

The occurrence of a right-lateral strike-slip earthquake in 1911 is inconsistent with the calculated 0.2-2.5 bar static stress decrease imparted by the 1906 rupture at that location on the Calaveras fault, and 5 yr of calculated post-1906 viscoelastic rebound does little to reload the fault. We have used all available first-motion, body-wave, and surface-wave data to explore possible focal mechanisms for the 1911 earthquake. We find that the event was most likely a right-lateral strikeslip event on the Calaveras fault, larger than, but otherwise resembling, the 1984 Mw 6.1 Morgan Hill earthquake in roughly the same location. Unfortunately, we could recover no unambiguous surface fault offset or geodetic strain data to corroborate the seismic analysis despite an exhaustive archival search. We calculated the static and dynamic Coulomb stress changes for three 1906 source models to understand stress transfer to the 1911 site. In contrast to the static stress shadow, the peak dynamic Coulomb stress imparted by the 1906 rupture promoted failure at the site of the 1911 earthquake by 1.4-5.8 bar. Perhaps because the sample is small and the aftershocks are poorly located, we find no correlation of 1906 aftershock frequency or magnitude with the peak dynamic stress, although all aftershocks sustained a calculated dynamic stress of ???3 bar. Just 20 km to the south of the 1911 epicenter, we find that surface creep of the Calaveras fault at Hollister paused for ~17 yr after 1906, about the expected delay for the calculated static stress drop imparted by the 1906 earthquake when San Andreas fault postseismic creep and viscoelastic relaxation are included. Thus, the 1911 earthquake may have been promoted by the transient dynamic stresses, while Calaveras fault creep 20 km to the south appears to have been inhibited by the static stress changes.

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.

The Challenge of Centennial Earthquakes to Improve Modern Earthquake Engineering

International Nuclear Information System (INIS)

Saragoni, G. Rodolfo

2008-01-01

The recent commemoration of the centennial of the San Francisco and Valparaiso 1906 earthquakes has given the opportunity to reanalyze their damages from modern earthquake engineering perspective. These two earthquakes plus Messina Reggio Calabria 1908 had a strong impact in the birth and developing of earthquake engineering. The study of the seismic performance of some up today existing buildings, that survive centennial earthquakes, represent a challenge to better understand the limitations of our in use earthquake design methods. Only Valparaiso 1906 earthquake, of the three considered centennial earthquakes, has been repeated again as the Central Chile, 1985, Ms = 7.8 earthquake. In this paper a comparative study of the damage produced by 1906 and 1985 Valparaiso earthquakes is done in the neighborhood of Valparaiso harbor. In this study the only three centennial buildings of 3 stories that survived both earthquakes almost undamaged were identified. Since for 1985 earthquake accelerogram at El Almendral soil conditions as well as in rock were recoded, the vulnerability analysis of these building is done considering instrumental measurements of the demand. The study concludes that good performance of these buildings in the epicentral zone of large earthquakes can not be well explained by modern earthquake engineering methods. Therefore, it is recommended to use in the future of more suitable instrumental parameters, such as the destructiveness potential factor, to describe earthquake demand

Earthquakes-Rattling the Earth's Plumbing System

Science.gov (United States)

Sneed, Michelle; Galloway, Devin L.; Cunningham, William L.

2003-01-01

Hydrogeologic responses to earthquakes have been known for decades, and have occurred both close to, and thousands of miles from earthquake epicenters. Water wells have become turbid, dry or begun flowing, discharge of springs and ground water to streams has increased and new springs have formed, and well and surface-water quality have become degraded as a result of earthquakes. Earthquakes affect our Earth’s intricate plumbing system—whether you live near the notoriously active San Andreas Fault in California, or far from active faults in Florida, an earthquake near or far can affect you and the water resources you depend on.

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.

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.

The Pocatello Valley, Idaho, earthquake

Science.gov (United States)

Rogers, A. M.; Langer, C.J.; Bucknam, R.C.

1975-01-01

A Richter magnitude 6.3 earthquake occurred at 8:31 p.m mountain daylight time on March 27, 1975, near the Utah-Idaho border in Pocatello Valley. The epicenter of the main shock was located at 42.094° N, 112.478° W, and had a focal depth of 5.5 km. This earthquake was the largest in the continental United States since the destructive San Fernando earthquake of February 1971. The main shock was preceded by a magnitude 4.5 foreshock on March 26. 

Study of responses of 64-story Rincon Building to Napa, Fremont, Piedmont, San Ramon earthquakes and ambient motions

Science.gov (United States)

Çelebi, Mehmet; Hooper, John; Klemencic, Ron

2017-01-01

We analyze the recorded responses of a 64-story, instrumented, concrete core shear wall building in San Francisco, California, equipped with tuned sloshing liquid dampers (TSDs) and buckling restraining braces (BRBs). Previously, only ambient data from the 72-channel array in the building were studied (Çelebi et al. 2013). Recently, the 24 August 2014 Mw 6.0 Napa and three other earthquakes were recorded. The peak accelerations of ambient and the larger Napa earthquake responses at the basement are 0.12 cm/s/s and 5.2 cm/s/s respectively—a factor of ~42. At the 61st level, they are 0.30 cm/s/s (ambient) and 16.8 cm/s/s (Napa), respectively—a factor of ~56. Fundamental frequencies (NS ~ 0.3, EW ~ 0.27 Hz) from earthquake responses vary within an insignificant frequency band of ~0.02–0.03 Hz when compared to those from ambient data. In the absence of soil-structure interaction (SSI), these small and insignificant differences may be attributed to (1) identification errors, (2) any nonlinear behavior, and (3) shaking levels that are not large enough to activate the BRBs and TSDs to make significant shifts in frequencies and increase damping.

Chapter A. The Loma Prieta, California, Earthquake of October 17, 1989 - Lifelines

Science.gov (United States)

Schiff, Anshel J.

1998-01-01

To the general public who had their televisions tuned to watch the World Series, the 1989 Loma Prieta earthquake was a lifelines earthquake. It was the images seen around the world of the collapsed Cypress Street viaduct, with the frantic and heroic efforts to pull survivors from the structure that was billowing smoke; the collapsed section of the San Francisco-Oakland Bay Bridge and subsequent home video of a car plunging off the open span; and the spectacular fire in the Marina District of San Francisco fed by a broken gasline. To many of the residents of the San Francisco Bay region, the relation of lifelines to the earthquake was characterized by sitting in the dark because of power outage, the inability to make telephone calls because of network congestion, and the slow and snarled traffic. Had the public been aware of the actions of the engineers and tradespeople working for the utilities and other lifeline organizations on the emergency response and restoration of lifelines, the lifeline characteristics of this earthquake would have been even more significant. Unobserved by the public were the warlike devastation in several electrical-power substations, the 13 miles of gas-distribution lines that had to be replaced in several communities, and the more than 1,200 leaks and breaks in water mains and service connections that had to be excavated and repaired. Like the 1971 San Fernando, Calif., earthquake, which was a seminal event for activity to improve the earthquake performance of lifelines, the 1989 Loma Prieta earthquake demonstrated that the tasks of preparing lifelines in 'earthquake country' were incomplete-indeed, new lessons had to be learned.

Expectable Earthquakes and their ground motions in the Van Norman Reservoirs Area

Science.gov (United States)

Wesson, R.L.; Page, R.A.; Boore, D.M.; Yerkes, R.F.

1974-01-01

The upper and lower Van Norman dams, in northwesternmost San Fernando Valley about 20 mi (32 km) northwest of downtown Los Angeles, were severely damaged during the 1971 San Fernando earthquake. An investigation of the geologic-seismologic setting of the Van Norman area indicates that an earthquake of at least M 7.7 may be expected in the Van Norman area. The expectable transitory effects in the Van Norman area of such an earthquake are as follows: peak horizontal acceleration of at least 1.15 g, peak velocity of displacement of 4.43 ft/sec (135 cm/sec), peak displacement of 2.3 ft (70 cm), and duration of shaking at accelerations greater than 0.05 g, 40 sec. A great earthquake (M 8+) on the San Andreas fault, 25 mi distant, also is expectable. Transitory effects in the Van Norman area from such an earthquake are estimated as follows: peak horizontal acceleration of 0.5 g, peak velocity of 1.97 ft/sec (60 cm/sec), displacement of 1.31 ft (40 cm), and duration of shaking at accelerations greater than 0.05 g, 80 sec. The permanent effects of the expectable local earthquake could include simultaneous fault movement at the lower damsite, the upper damsite, and the site proposed for a replacement dam halfway between the upper and lower dams. The maximum differential displacements due to such movements are estimated at 16.4 ft (5 m) at the lower damsite and about 9.6 ft (2.93 m) at the upper and proposed damsites. The 1971 San Fernando earthquake (M 6?) was accompanied by the most intense ground motions ever recorded instrumentally for a natural earthquake. At the lower Van Norman dam, horizontal accelerations exceeded 0.6 g, and shaking greater than 0.25 g lasted for about 13 see; at Pacoima dam, 6 mi (10 km) northeast of the lower dam, high-frequency peak horizontal accelerations of 1.25 g were recorded in two directions, and shaking greater than 0.25 g lasted for about 7 sec. Permanent effects of the earthquake include slope failures in the embankments of the upper

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

Climate-modulated channel incision and rupture history of the San Andreas Fault in the Carrizo Plain.

Science.gov (United States)

Grant Ludwig, Lisa; Akçiz, Sinan O; Noriega, Gabriela R; Zielke, Olaf; Arrowsmith, J Ramón

2010-02-26

The spatial and temporal distribution of fault slip is a critical parameter in earthquake source models. Previous geomorphic and geologic studies of channel offset along the Carrizo section of the south central San Andreas Fault assumed that channels form more frequently than earthquakes occur and suggested that repeated large-slip earthquakes similar to the 1857 Fort Tejon earthquake illustrate typical fault behavior. We found that offset channels in the Carrizo Plain incised less frequently than they were offset by earthquakes. Channels have been offset by successive earthquakes with variable slip since ~1400. This nonuniform slip history reveals a more complex rupture history than previously assumed for the structurally simplest section of the San Andreas Fault.

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.

Imaging the Fine-Scale Structure of the San Andreas Fault in the Northern Gabilan Range with Explosion and Earthquake Sources

Science.gov (United States)

Xin, H.; Thurber, C. H.; Zhang, H.; Wang, F.

2014-12-01

A number of geophysical studies have been carried out along the San Andreas Fault (SAF) in the Northern Gabilan Range (NGR) with the purpose of characterizing in detail the fault zone structure. Previous seismic research has revealed the complex structure of the crustal volume in the NGR region in two-dimensions (Thurber et al., 1996, 1997), and there has been some work on the three-dimensional (3D) structure at a coarser scale (Lin and Roecker, 1997). In our study we use earthquake body-wave arrival times and differential times (P and S) and explosion arrival times (only P) to image the 3D P- and S-wave velocity structure of the upper crust along the SAF in the NGR using double-difference (DD) tomography. The earthquake and explosion data types have complementary strengths - the earthquake data have good resolution at depth and resolve both Vp and Vs structure, although only where there are sufficient seismic rays between hypocenter and stations, whereas the explosions contribute very good near-surface resolution but for P waves only. The original dataset analyzed by Thurber et al. (1996, 1997) included data from 77 local earthquakes and 8 explosions. We enlarge the dataset with 114 more earthquakes that occurred in the study area, obtain improved S-wave picks using an automated picker, and include absolute and cross-correlation differential times. The inversion code we use is the algorithm tomoDD (Zhang and Thurber, 2003). We assess how the P and S velocity models and earthquake locations vary as we alter the inversion parameters and the inversion grid. The new inversion results show clearly the fine-scale structure of the SAF at depth in 3D, sharpening the image of the velocity contrast from the southwest side to the northeast side.

4D stress evolution models of the San Andreas Fault System: Investigating time- and depth-dependent stress thresholds over multiple earthquake cycles

Science.gov (United States)

Burkhard, L. M.; Smith-Konter, B. R.

2017-12-01

4D simulations of stress evolution provide a rare insight into earthquake cycle crustal stress variations at seismogenic depths where earthquake ruptures nucleate. Paleoseismic estimates of earthquake offset and chronology, spanning multiple earthquakes cycles, are available for many well-studied segments of the San Andreas Fault System (SAFS). Here we construct new 4D earthquake cycle time-series simulations to further study the temporally and spatially varying stress threshold conditions of the SAFS throughout the paleoseismic record. Interseismic strain accumulation, co-seismic stress drop, and postseismic viscoelastic relaxation processes are evaluated as a function of variable slip and locking depths along 42 major fault segments. Paleoseismic earthquake rupture histories provide a slip chronology dating back over 1000 years. Using GAGE Facility GPS and new Sentinel-1A InSAR data, we tune model locking depths and slip rates to compute the 4D stress accumulation within the seismogenic crust. Revised estimates of stress accumulation rate are most significant along the Imperial (2.8 MPa/100yr) and Coachella (1.2 MPa/100yr) faults, with a maximum change in stress rate along some segments of 11-17% in comparison with our previous estimates. Revised estimates of earthquake cycle stress accumulation are most significant along the Imperial (2.25 MPa), Coachella (2.9 MPa), and Carrizo (3.2 MPa) segments, with a 15-29% decrease in stress due to locking depth and slip rate updates, and also postseismic relaxation from the El Mayor-Cucapah earthquake. Because stress drops of major strike-slip earthquakes rarely exceed 10 MPa, these models may provide a lower bound on estimates of stress evolution throughout the historical era, and perhaps an upper bound on the expected recurrence interval of a particular fault segment. Furthermore, time-series stress models reveal temporally varying stress concentrations at 5-10 km depths, due to the interaction of neighboring fault

April 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...

Fundamental questions of earthquake statistics, source behavior, and the estimation of earthquake probabilities from possible foreshocks

Science.gov (United States)

Michael, Andrew J.

2012-01-01

Estimates of the probability that an ML 4.8 earthquake, which occurred near the southern end of the San Andreas fault on 24 March 2009, would be followed by an M 7 mainshock over the following three days vary from 0.0009 using a Gutenberg–Richter model of aftershock statistics (Reasenberg and Jones, 1989) to 0.04 using a statistical model of foreshock behavior and long‐term estimates of large earthquake probabilities, including characteristic earthquakes (Agnew and Jones, 1991). I demonstrate that the disparity between the existing approaches depends on whether or not they conform to Gutenberg–Richter behavior. While Gutenberg–Richter behavior is well established over large regions, it could be violated on individual faults if they have characteristic earthquakes or over small areas if the spatial distribution of large‐event nucleations is disproportional to the rate of smaller events. I develop a new form of the aftershock model that includes characteristic behavior and combines the features of both models. This new model and the older foreshock model yield the same results when given the same inputs, but the new model has the advantage of producing probabilities for events of all magnitudes, rather than just for events larger than the initial one. Compared with the aftershock model, the new model has the advantage of taking into account long‐term earthquake probability models. Using consistent parameters, the probability of an M 7 mainshock on the southernmost San Andreas fault is 0.0001 for three days from long‐term models and the clustering probabilities following the ML 4.8 event are 0.00035 for a Gutenberg–Richter distribution and 0.013 for a characteristic‐earthquake magnitude–frequency distribution. Our decisions about the existence of characteristic earthquakes and how large earthquakes nucleate have a first‐order effect on the probabilities obtained from short‐term clustering models for these large events.

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.

Aftershocks and triggered events of the Great 1906 California earthquake

Science.gov (United States)

Meltzner, A.J.; Wald, D.J.

2003-01-01

The San Andreas fault is the longest fault in California and one of the longest strike-slip faults in the world, yet little is known about the aftershocks following the most recent great event on the San Andreas, the Mw 7.8 San Francisco earthquake on 18 April 1906. We conducted a study to locate and to estimate magnitudes for the largest aftershocks and triggered events of this earthquake. We examined existing catalogs and historical documents for the period April 1906 to December 1907, compiling data on the first 20 months of the aftershock sequence. We grouped felt reports temporally and assigned modified Mercalli intensities for the larger events based on the descriptions judged to be the most reliable. For onshore and near-shore events, a grid-search algorithm (derived from empirical analysis of modern earthquakes) was used to find the epicentral location and magnitude most consistent with the assigned intensities. For one event identified as far offshore, the event's intensity distribution was compared with those of modern events, in order to contrain the event's location and magnitude. The largest aftershock within the study period, an M ???6.7 event, occurred ???100 km west of Eureka on 23 April 1906. Although not within our study period, another M ???6.7 aftershock occurred near Cape Mendocino on 28 October 1909. Other significant aftershocks included an M ???5.6 event near San Juan Bautista on 17 May 1906 and an M ???6.3 event near Shelter Cove on 11 August 1907. An M ???4.9 aftershock occurred on the creeping segment of the San Andreas fault (southeast of the mainshock rupture) on 6 July 1906. The 1906 San Francisco earthquake also triggered events in southern California (including separate events in or near the Imperial Valley, the Pomona Valley, and Santa Monica Bay), in western Nevada, in southern central Oregon, and in western Arizona, all within 2 days of the mainshock. Of these trigerred events, the largest were an M ???6.1 earthquake near Brawley

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, Edward; 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.

Cholinesterase Structure: Identification of Mechanisms and Residues Involved in Organophosphate Inhibition and Enzyme Reactivation

Science.gov (United States)

2005-05-01

analysed by combinatorial mutations and enantiomeric phosphonates Zrinka KOVARIK*t1, Zoran RADI6*, Harvey A. BERMANf, Vera SIMEON-RUDOLFt, Elsa REINERt and...Harvey A. Berman,1’ Vera Simeon-Rudolf,§ Elsa Reiner,§ and Palmer Taylbr*4’ Department qf Pharmacology, Univeitirv ofCalffornia at San Diego, La...and refinement statistics A N TZ2PA6 isomer complexed to mAChE anti1 synl Data collection* Beamline (European Synchrotron ID14-EH1 ID14-EH2 Radiation

Nonvolcanic tremors deep beneath the San Andreas Fault.

Science.gov (United States)

Nadeau, Robert M; Dolenc, David

2005-01-21

We have discovered nonvolcanic tremor activity (i.e., long-duration seismic signals with no clear P or S waves) within a transform plate boundary zone along the San Andreas Fault near Cholame, California, the inferred epicentral region of the 1857 Fort Tejon earthquake (moment magnitude approximately 7.8). The tremors occur between 20 to 40 kilometers' depth, below the seismogenic zone (the upper approximately 15 kilometers of Earth's crust where earthquakes occur), and their activity rates may correlate with variations in local earthquake activity.

Prediction of spectral acceleration response ordinates based on PGA attenuation

Science.gov (United States)

Graizer, V.; Kalkan, E.

2009-01-01

Developed herein is a new peak ground acceleration (PGA)-based predictive model for 5% damped pseudospectral acceleration (SA) ordinates of free-field horizontal component of ground motion from shallow-crustal earthquakes. The predictive model of ground motion spectral shape (i.e., normalized spectrum) is generated as a continuous function of few parameters. The proposed model eliminates the classical exhausted matrix of estimator coefficients, and provides significant ease in its implementation. It is structured on the Next Generation Attenuation (NGA) database with a number of additions from recent Californian events including 2003 San Simeon and 2004 Parkfield earthquakes. A unique feature of the model is its new functional form explicitly integrating PGA as a scaling factor. The spectral shape model is parameterized within an approximation function using moment magnitude, closest distance to the fault (fault distance) and VS30 (average shear-wave velocity in the upper 30 m) as independent variables. Mean values of its estimator coefficients were computed by fitting an approximation function to spectral shape of each record using robust nonlinear optimization. Proposed spectral shape model is independent of the PGA attenuation, allowing utilization of various PGA attenuation relations to estimate the response spectrum of earthquake recordings.

Delayed dynamic triggering of deep tremor along the Parkfield-Cholame section of the San Andreas Fault following the 2014 M6.0 South Napa earthquake

Science.gov (United States)

Peng, Zhigang; Shelly, David R.; Ellsworth, William L.

2015-01-01

Large, distant earthquakes are known to trigger deep tectonic tremor along the San Andreas Fault and in subduction zones. However, there are relatively few observations of triggering from regional distance earthquakes. Here we show that a small tremor episode about 12–18 km NW of Parkfield was triggered during and immediately following the passage of surface waves from the 2014 Mw 6.0 South Napa main shock. More notably, a major tremor episode followed, beginning about 12 h later, and centered SE of Parkfield near Cholame. This major episode is one of the largest seen over the past several years, containing intense activity for ~3 days and taking more than 3 weeks to return to background levels. This episode showed systematic along-strike migration at ~5 km/d, suggesting that it was driven by a slow-slip event. Our results suggest that moderate-size earthquakes are capable of triggering major tremor and deep slow slip at regional distances.

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.

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

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.

Protecting your family from earthquakes: The seven steps to earthquake safety

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

Triggered creep as a possible mechanism for delayed dynamic triggering of tremor and earthquakes

Science.gov (United States)

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

2011-01-01

The passage of radiating seismic waves generates transient stresses in the Earth's crust that can trigger slip on faults far away from the original earthquake source. The triggered fault slip is detectable in the form of earthquakes and seismic tremor. However, the significance of these triggered events remains controversial, in part because they often occur with some delay, long after the triggering stress has passed. Here we scrutinize the location and timing of tremor on the San Andreas fault between 2001 and 2010 in relation to distant earthquakes. We observe tremor on the San Andreas fault that is initiated by passing seismic waves, yet migrates along the fault at a much slower velocity than the radiating seismic waves. We suggest that the migrating tremor records triggered slow slip of the San Andreas fault as a propagating creep event. We find that the triggered tremor and fault creep can be initiated by distant earthquakes as small as magnitude 5.4 and can persist for several days after the seismic waves have passed. Our observations of prolonged tremor activity provide a clear example of the delayed dynamic triggering of seismic events. Fault creep has been shown to trigger earthquakes, and we therefore suggest that the dynamic triggering of prolonged fault creep could provide a mechanism for the delayed triggering of earthquakes. ?? 2011 Macmillan Publishers Limited. All rights reserved.

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.

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.

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.

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...

Tidal Sensitivity of Declustered Low Frequency Earthquake Families and Inferred Creep Episodes on the San Andreas Fault

Science.gov (United States)

Babb, A.; Thomas, A.; Bletery, Q.

2017-12-01

Low frequency earthquakes (LFEs) are detected at depths of 16-30 km on a 150 km section of the San Andreas Fault centered at Parkfield, CA. The LFEs are divided into 88 families based on waveform similarity. Each family is thought to represent a brittle asperity on the fault surface that repeatedly slips during aseismic slip of the surrounding fault. LFE occurrence is irregular which allows families to be divided into continuous and episodic. In continuous families a burst of a few LFE events recurs every few days while episodic families experience essentially quiescent periods often lasting months followed by bursts of hundreds of events over a few days. The occurrence of LFEs has also been shown to be sensitive to extremely small ( 1kPa) tidal stress perturbations. However, the clustered nature of LFE occurrence could potentially bias estimates of tidal sensitivity. Here we re-evaluate the tidal sensitivity of LFE families on the deep San Andreas using a declustered catalog. In this catalog LFE bursts are isolated based on the recurrence intervals between individual LFE events for each family. Preliminary analysis suggests that declustered LFE families are still highly sensitive to tidal stress perturbations, primarily right-lateral shear stress (RLSS) and to a lesser extent fault normal stress (FNS). We also find inferred creep episodes initiate preferentially during times of positive RLSS.

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.

Searching for evidence of a preferred rupture direction in small earthquakes at Parkfield

Science.gov (United States)

Kane, D. L.; Shearer, P. M.; Allmann, B.; Vernon, F. L.

2009-12-01

Theoretical modeling of strike-slip ruptures along a bimaterial interface suggests that the interface will have a preferred rupture direction and will produce asymmetric ground motion (Shi and Ben-Zion, 2006). This could have widespread implications for earthquake source physics and for hazard analysis on mature faults because larger ground motions would be expected in the direction of rupture propagation. Studies have shown that many large global earthquakes exhibit unilateral rupture, but a consistently preferred rupture direction along faults has not been observed. Some researchers have argued that the bimaterial interface model does not apply to natural faults, noting that the rupture of the M 6 2004 Parkfield earthquake propagated in the opposite direction from previous M 6 earthquakes along that section of the San Andreas Fault (Harris and Day, 2005). We analyze earthquake spectra from the Parkfield area to look for evidence of consistent rupture directivity along the San Andreas Fault. We separate the earthquakes into spatially defined clusters and quantify the differences in high-frequency energy among earthquakes recorded at each station. Propagation path effects are minimized in this analysis because we compare earthquakes located within a small volume and recorded by the same stations. By considering a number of potential end-member models, we seek to determine if a preferred rupture direction is present among small earthquakes at Parkfield.

San Miguel Volcanic Seismic and Structure in Central America: Insight into the Physical Processes of Volcanoes

Science.gov (United States)

Patlan, E.; Velasco, A.; Konter, J. G.

2010-12-01

The San Miguel volcano lies near the city of San Miguel, El Salvador (13.43N and - 88.26W). San Miguel volcano, an active stratovolcano, presents a significant natural hazard for the city of San Miguel. In general, the internal state and activity of volcanoes remains an important component to understanding volcanic hazard. The main technology for addressing volcanic hazards and processes is through the analysis of data collected from the deployment of seismic sensors that record ground motion. Six UTEP seismic stations were deployed around San Miguel volcano from 2007-2008 to define the magma chamber and assess the seismic and volcanic hazard. We utilize these data to develop images of the earth structure beneath the volcano, studying the volcanic processes by identifying different sources, and investigating the role of earthquakes and faults in controlling the volcanic processes. We initially locate events using automated routines and focus on analyzing local events. We then relocate each seismic event by hand-picking P-wave arrivals, and later refine these picks using waveform cross correlation. Using a double difference earthquake location algorithm (HypoDD), we identify a set of earthquakes that vertically align beneath the edifice of the volcano, suggesting that we have identified a magma conduit feeding the volcano. We also apply a double-difference earthquake tomography approach (tomoDD) to investigate the volcano’s plumbing system. Our preliminary results show the extent of the magma chamber that also aligns with some horizontal seismicity. Overall, this volcano is very active and presents a significant hazard to the region.

1855 and 1991 Surveys of the San Andreas Fault: Implications for Fault Machanics

Science.gov (United States)

Grant, Lisa B.; Donnellan, Andrea

1993-01-01

Two monuments from an 1855 survey that spans the San Andreas fault in the Carrizo Plain have been displaced 11.0+/-2.5m right-laterally by the 1857 Fort Tejon earthquake and associated seismicity and afterslip by the 1857 Fort Tejon earthquake and associated seismicity and afterslip.

Using an Earthquake Simulator to Model Tremor Along a Strike Slip Fault

Science.gov (United States)

Cochran, E. S.; Richards-Dinger, K. B.; Kroll, K.; Harrington, R. M.; Dieterich, J. H.

2013-12-01

We employ the earthquake simulator, RSQSim, to investigate the conditions under which tremor occurs in the transition zone of the San Andreas fault. RSQSim is a computationally efficient method that uses rate- and state- dependent friction to simulate a wide range of event sizes for long time histories of slip [Dieterich and Richards-Dinger, 2010; Richards-Dinger and Dieterich, 2012]. RSQSim has been previously used to investigate slow slip events in Cascadia [Colella et al., 2011; 2012]. Earthquakes, tremor, slow slip, and creep occurrence are primarily controlled by the rate and state constants a and b and slip speed. We will report the preliminary results of using RSQSim to vary fault frictional properties in order to better understand rupture dynamics in the transition zone using observed characteristics of tremor along the San Andreas fault. Recent studies of tremor along the San Andreas fault provide information on tremor characteristics including precise locations, peak amplitudes, duration of tremor episodes, and tremor migration. We use these observations to constrain numerical simulations that examine the slip conditions in the transition zone of the San Andreas Fault. Here, we use the earthquake simulator, RSQSim, to conduct multi-event simulations of tremor for a strike slip fault modeled on Cholame section of the San Andreas fault. Tremor was first observed on the San Andreas fault near Cholame, California near the southern edge of the 2004 Parkfield rupture [Nadeau and Dolenc, 2005]. Since then, tremor has been observed across a 150 km section of the San Andreas with depths between 16-28 km and peak amplitudes that vary by a factor of 7 [Shelly and Hardebeck, 2010]. Tremor episodes, comprised of multiple low frequency earthquakes (LFEs), tend to be relatively short, lasting tens of seconds to as long as 1-2 hours [Horstmann et al., in review, 2013]; tremor occurs regularly with some tremor observed almost daily [Shelly and Hardebeck, 2010; Horstmann

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

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

The Quantitative Grammar and Poetics of Finite Verb Forms in the Guslʹ Dobroglasnaia by Simeon Polotsky

Directory of Open Access Journals (Sweden)

Fedor N. Dviniatin

2015-08-01

Full Text Available The paper offers data on the quantity and structure of finite verbal forms in Simeon Polotsky’s collection Guslʹ Dobroglasnaia. The results are compared to data from twenty epinician odes by Mikhail Lomonosov and ten odes by Gavriil Derzhavin. We find 851 personal forms in Simeon’s collection, of which 214 belong to past tenses (73 to imperfect, 92 to aorist, 49 to past tense with l morpheme; 363 belong to present tense; 99 to future tense; 51 to imperative mood; 6 to conjunctive mood; and 118 to the forms with the da particle. The total percentage of past tenses in Simeon’s texts (25.1% is close to the parameters appearing in Lomonosov’s and Derzhavin’s texts (21.4% and 23.5%, respectively, and the same is true for the percentages of non-indicative moods (20.5% vs. 19.1% and 20.5%. Simeon Polotsky’s texts contain fewer present tense forms than those written by the 18th-century poets (42.8% vs. 50.6% and 49.5%, but they contain more future tense forms (11.6% vs. 8.9% and 6.5%. Past tense forms in Simeon’s texts with l suffix include 29 forms of the third person with the auxiliary iestʹ verb, usually given in a rhyme position. In the aorist, the proportion of imperfective and perfective forms to the forms of the byti verb is 9:72:11; in imperfect, this proportion is 52:6:15; and in past tenses with l suffix, it is 8:38:3. We find 99 forms of the future tense, broken down as follows: 69 are forms of simple future; 12 are accompanied by imatʹ and similar forms; and 18 are accompanied by budet and similar forms (there is no semantic difference between these two last cases. Of the forms containing the da particle, 65 belong to present tense, 37 belong to future tense, and 16 are accompanied by byti forms.

The October 1992 Parkfield, California, earthquake prediction

Science.gov (United States)

Langbein, J.

1992-01-01

A magnitude 4.7 earthquake occurred near Parkfield, California, on October 20, 992, at 05:28 UTC (October 19 at 10:28 p.m. local or Pacific Daylight Time).This moderate shock, interpreted as the potential foreshock of a damaging earthquake on the San Andreas fault, triggered long-standing federal, state and local government plans to issue a public warning of an imminent magnitude 6 earthquake near Parkfield. Although the predicted earthquake did not take place, sophisticated suites of instruments deployed as part of the Parkfield Earthquake Prediction Experiment recorded valuable data associated with an unusual series of events. this article describes the geological aspects of these events, which occurred near Parkfield in October 1992. The accompnaying article, an edited version of a press conference b Richard Andrews, the Director of the California Office of Emergency Service (OES), describes governmental response to the prediction.   

The accommodation of relative motion at depth on the San Andreas fault system in California

Science.gov (United States)

Prescott, W. H.; Nur, A.

1981-01-01

Plate motion below the seismogenic layer along the San Andreas fault system in California is assumed to form by aseismic slip along a deeper extension of the fault or may result from lateral distribution of deformation below the seismogenic layer. The shallow depth of California earthquakes, the depth of the coseismic slip during the 1906 San Francisco earthquake, and the presence of widely separated parallel faults indicate that relative motion is distributed below the seismogenic zone, occurring by inelastic flow rather than by aseismic slip on discrete fault planes.

Simulating Earthquakes for Science and Society: Earthquake Visualizations Ideal for use in Science Communication and Education

Science.gov (United States)

de Groot, R.

2008-12-01

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 gained visibility via television news coverage in Southern California. 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). For example, The Great Southern California ShakeOut was based on a potential magnitude 7.8 earthquake on the southern San Andreas fault. The visualization created for the ShakeOut was a key scientific and communication tool for the earthquake drill. This presentation will also feature SCEC Virtual Display of Objects visualization software developed by SCEC Undergraduate Studies in Earthquake Information Technology interns. 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.

Seismic velocity structure in the lower crust beneath the seismic belt in the San-in district, Southwest Japan

Science.gov (United States)

Tsuda, H.; Iio, Y.; Shibutani, T.

2017-12-01

In the San-in district in Southwest Japan, a linear distribution of the epicenters of microearthquakes is seen along the coast of the Japan Sea (Fig. 1). The linear distribution is known as the seismic belt in the San-in district. Large earthquakes also occurred in the seismic belt. What localizes the earthquake distribution in the San-in district which is located far from the plate boundary? We thought that the model proposed by Iio et al. (2002, 2004) could answer this question. The model is as follows. Viscosity is low in a part of the lower crust, which is called `weak zone'. Stress and strain are concentrated in the upper crust right above the weak zone, due to concentrated deformation in the weak zone, and thus earthquakes occur there. To verify whether the weak zone exists in the lower crust beneath the seismic belt, we estimated the seismic velocity structure there by travel-time tomography. We used the tomography program, FMTOMO (Rawlinson et al., 2006). For the model space, we set the latitude range of 33°-36°N, the longitude range of 131°-136°E (Fig. 1), and the depth range of 0-81 km. The grid intervals are 0.1°×0.1°×7 km. We used arrival times picked by Japan Meteorological Agency (JMA) for earthquakes that occurred in the study area. In addition, we used arrival times manually picked at stations in and around the San-in district for earthquakes that occurred within the Philippine Sea Slab, because they are not included in the JMA data. Since the seismic waves from those earthquakes to the stations in the San-in district pass through the lower crust beneath the San-in district, we expect that these data can improve the resolution there. We revealed that low velocity anomalies exist in the lower crust beneath the seismic belt (Fig. 1). It is inferred that the region of low velocity anomalies is characterized by low viscosity, since velocities of rocks decrease with temperature and/or water content. Therefore, the results of this study support

The HayWired earthquake scenario—We can outsmart disaster

Science.gov (United States)

Hudnut, Kenneth W.; Wein, Anne M.; Cox, Dale A.; Porter, Keith A.; Johnson, Laurie A.; Perry, Suzanne C.; Bruce, Jennifer L.; LaPointe, Drew

2018-04-18

The HayWired earthquake scenario, led by the U.S. Geological Survey (USGS), anticipates the impacts of a hypothetical magnitude-7.0 earthquake on the Hayward Fault. The fault is along the east side of California’s San Francisco Bay and is among the most active and dangerous in the United States, because it runs through a densely urbanized and interconnected region. One way to learn about a large earthquake without experiencing it is to conduct a scientifically realistic scenario. The USGS and its partners in the HayWired Coalition and the HayWired Campaign are working to energize residents and businesses to engage in ongoing and new efforts to prepare the region for such a future earthquake.

Earthquake experience suggests new approach to seismic criteria

International Nuclear Information System (INIS)

Knox, R.

1983-01-01

Progress in seismic qualification of nuclear power plants as reviewed at the 4th Pacific Basin Nuclear Conference in Vancouver, September 1983, is discussed. The lack of experience of earthquakes in existing nuclear plants can be compensated by the growing experience of actual earthquake effects in conventional power plants and similar installations. A survey of the effects on four power stations, with a total of twenty generating units, in the area strongly shaken by the San Fernando earthquake in California in 1971 is reported. The Canadian approach to seismic qualification, international criteria, Canadian/Korean experience, safety related equipment, the Tadotsu test facility and seismic tests are discussed. (U.K.)

Periodic pulsing of characteristic microearthquakes on the San Andreas fault.

Science.gov (United States)

Nadeau, Robert M; McEvilly, Thomas V

2004-01-09

Deep fault slip information from characteristically repeating microearthquakes reveals previously unrecognized patterns of extensive, large-amplitude, long-duration, quasiperiodic repetition of aseismic events along much of a 175-kilometer segment of the central San Andreas fault. Pulsing occurs both in conjunction with and independent of transient slip from larger earthquakes. It extends to depths of approximately 10 to 11 kilometers but may be deeper, and it may be related to similar phenomena occurring in subduction zones. Over much of the study area, pulse onset periods also show a higher probability of larger earthquakes, which may provide useful information for earthquake forecasting.

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.

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

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

Science.gov (United States)

Shelly, David R

2010-02-04

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.

Foreshocks and aftershocks of the Great 1857 California earthquake

Science.gov (United States)

Meltzner, A.J.; Wald, D.J.

1999-01-01

The San Andreas fault is the longest fault in California and one of the longest strike-slip faults anywhere in the world, yet we know little about many aspects of its behavior before, during, and after large earthquakes. We conducted a study to locate and to estimate magnitudes for the largest foreshocks and aftershocks of the 1857 M 7.9 Fort Tejon earthquake on the central and southern segments of the fault. We began by searching archived first-hand accounts from 1857 through 1862, by grouping felt reports temporally, and by assigning modified Mercalli intensities to each site. We then used a modified form of the grid-search algorithm of Bakum and Wentworth, derived from empirical analysis of modern earthquakes, to find the location and magnitude most consistent with the assigned intensities for each of the largest events. The result confirms a conclusion of Sieh that at least two foreshocks ('dawn' and 'sunrise') located on or near the Parkfield segment of the San Andreas fault preceded the mainshock. We estimate their magnitudes to be M ~ 6.1 and M ~ 5.6, respectively. The aftershock rate was below average but within one standard deviation of the number of aftershocks expected based on statistics of modern southern California mainshock-aftershock sequences. The aftershocks included two significant events during the first eight days of the sequence, with magnitudes M ~ 6.25 and M ~ 6.7, near the southern half of the rupture; later aftershocks included a M ~ 6 event near San Bernardino in December 1858 and a M ~ 6.3 event near the Parkfield segment in April 1860. From earthquake logs at Fort Tejon, we conclude that the aftershock sequence lasted a minimum of 3.75 years.

Physics of Earthquake Rupture Propagation

Science.gov (United States)

Xu, Shiqing; Fukuyama, Eiichi; Sagy, Amir; Doan, Mai-Linh

2018-05-01

A comprehensive understanding of earthquake rupture propagation requires the study of not only the sudden release of elastic strain energy during co-seismic slip, but also of other processes that operate at a variety of spatiotemporal scales. For example, the accumulation of the elastic strain energy usually takes decades to hundreds of years, and rupture propagation and termination modify the bulk properties of the surrounding medium that can influence the behavior of future earthquakes. To share recent findings in the multiscale investigation of earthquake rupture propagation, we held a session entitled "Physics of Earthquake Rupture Propagation" during the 2016 American Geophysical Union (AGU) Fall Meeting in San Francisco. The session included 46 poster and 32 oral presentations, reporting observations of natural earthquakes, numerical and experimental simulations of earthquake ruptures, and studies of earthquake fault friction. These presentations and discussions during and after the session suggested a need to document more formally the research findings, particularly new observations and views different from conventional ones, complexities in fault zone properties and loading conditions, the diversity of fault slip modes and their interactions, the evaluation of observational and model uncertainties, and comparison between empirical and physics-based models. Therefore, we organize this Special Issue (SI) of Tectonophysics under the same title as our AGU session, hoping to inspire future investigations. Eighteen articles (marked with "this issue") are included in this SI and grouped into the following six categories.

Technical features of a low-cost earthquake alert system

International Nuclear Information System (INIS)

Harben, P.

1991-01-01

The concept and features of an Earthquake Alert System (EAS) involving a distributed network of strong motion sensors is discussed. The EAS analyzes real-time data telemetered to a central facility and issues an areawide warning of a large earthquake in advance of the spreading elastic wave energy. A low-cost solution to high-cost estimates for installation and maintenance of a dedicated EAS is presented that makes use of existing microseismic stations. Using the San Francisco Bay area as an example, we show that existing US Geological Survey microseismic monitoring stations are of sufficient density to form the elements of a prototype EAS. By installing strong motion instrumentation and a specially developed switching device, strong ground motion can be telemetered in real-time to the central microseismic station on the existing communication channels. When a large earthquake occurs, a dedicated real-time central processing unit at the central microseismic station digitizes and analyzes the incoming data and issues a warning containing location and magnitude estimations. A 50-station EAS of this type in the San Francisco Bay area should cost under $70,000 to install and less than $5,000 annually to maintain

Precursory diffuse carbon dioxide degassing signature related to a 5.1 magnitude earthquake in El Salvador, Central America

Science.gov (United States)

Salazar, J. M. L.; Pérez, N. M.; Hernández, P. A.; Soriano, T.; Barahona, F.; Olmos, R.; Cartagena, R.; López, D. L.; Lima, R. N.; Melián, G.; Galindo, I.; Padrón, E.; Sumino, H.; Notsu, K.

2002-12-01

Anomalous changes in the diffuse emission of carbon dioxide have been observed before some of the aftershocks of the 13 February 2001 El Salvador earthquake (magnitude 6.6). A significant increase in soil CO 2 efflux was detected 8 days before a 5.1 magnitude earthquake on 8 May 2001 25 km away from the observation site. In addition, pre- and co-seismic CO 2 efflux variations have also been observed related to the onset of a seismic swarm beneath San Vicente volcano on May 2001. Strain changes and/or fluid pressure fluctuations prior to earthquakes in the crust are hypothesized to be responsible for the observed variations in gas efflux at the surface environment of San Vicente volcano.

Keeping the History in Historical Seismology: The 1872 Owens Valley, California Earthquake

International Nuclear Information System (INIS)

Hough, Susan E.

2008-01-01

The importance of historical earthquakes is being increasingly recognized. Careful investigations of key pre-instrumental earthquakes can provide critical information and insights for not only seismic hazard assessment but also for earthquake science. In recent years, with the explosive growth in computational sophistication in Earth sciences, researchers have developed increasingly sophisticated methods to analyze macroseismic data quantitatively. These methodological developments can be extremely useful to exploit fully the temporally and spatially rich information source that seismic intensities often represent. For example, the exhaustive and painstaking investigations done by Ambraseys and his colleagues of early Himalayan earthquakes provides information that can be used to map out site response in the Ganges basin. In any investigation of macroseismic data, however, one must stay mindful that intensity values are not data but rather interpretations. The results of any subsequent analysis, regardless of the degree of sophistication of the methodology, will be only as reliable as the interpretations of available accounts - and only as complete as the research done to ferret out, and in many cases translate, these accounts. When intensities are assigned without an appreciation of historical setting and context, seemingly careful subsequent analysis can yield grossly inaccurate results. As a case study, I report here on the results of a recent investigation of the 1872 Owen's Valley, California earthquake. Careful consideration of macroseismic observations reveals that this event was probably larger than the great San Francisco earthquake of 1906, and possibly the largest historical earthquake in California. The results suggest that some large earthquakes in California will generate significantly larger ground motions than San Andreas fault events of comparable magnitude

The impact of Hurricane Hugo and the San Francisco earthquake on a sample of people with rheumatoid arthritis.

Science.gov (United States)

Grady, K E; Reisine, S T; Fifield, J; Lee, N R; McVay, J; Kelsey, M E

1991-06-01

The health effects of two natural disasters on 32 people with rheumatoid arthritis (RA) were assessed during the second-year wave of interviews in an ongoing 3-year study. Although the severity of Hurricane Hugo exceeded that of the San Francisco earthquake, no significant differences in health impacts were found. Both groups reported significantly increased ratings of RA activity, pain, and depression compared with ratings during the first year. However, comparison with the rest of the sample (n = 767) showed that increases in disease activity and pain were a general phenomenon but that the increase in depression was unique to the disaster subsample. Physician health status assessments also indicated that those who experienced the disaster were more likely to be classified in later stages of the disease subsequent to the disaster and were more likely to experience flares. These results suggest that people with RA may constitute a special high-risk population for adverse health effects after natural disasters.

What Can Sounds Tell Us About Earthquake Interactions?

Science.gov (United States)

Aiken, C.; Peng, Z.

2012-12-01

It is important not only for seismologists but also for educators to effectively convey information about earthquakes and the influences earthquakes can have on each other. Recent studies using auditory display [e.g. Kilb et al., 2012; Peng et al. 2012] have depicted catastrophic earthquakes and the effects large earthquakes can have on other parts of the world. Auditory display of earthquakes, which combines static images with time-compressed sound of recorded seismic data, is a new approach to disseminating information to a general audience about earthquakes and earthquake interactions. Earthquake interactions are influential to understanding the underlying physics of earthquakes and other seismic phenomena such as tremors in addition to their source characteristics (e.g. frequency contents, amplitudes). Earthquake interactions can include, for example, a large, shallow earthquake followed by increased seismicity around the mainshock rupture (i.e. aftershocks) or even a large earthquake triggering earthquakes or tremors several hundreds to thousands of kilometers away [Hill and Prejean, 2007; Peng and Gomberg, 2010]. We use standard tools like MATLAB, QuickTime Pro, and Python to produce animations that illustrate earthquake interactions. Our efforts are focused on producing animations that depict cross-section (side) views of tremors triggered along the San Andreas Fault by distant earthquakes, as well as map (bird's eye) views of mainshock-aftershock sequences such as the 2011/08/23 Mw5.8 Virginia earthquake sequence. These examples of earthquake interactions include sonifying earthquake and tremor catalogs as musical notes (e.g. piano keys) as well as audifying seismic data using time-compression. Our overall goal is to use auditory display to invigorate a general interest in earthquake seismology that leads to the understanding of how earthquakes occur, how earthquakes influence one another as well as tremors, and what the musical properties of these

Surface deformation associated with the November 23, 1977, Caucete, Argentina, earthquake sequence

Science.gov (United States)

Kadinsky-Cade, K.; Reilinger, R.; Isacks, B.

1985-01-01

The 1977 Caucete (San Juan) earthquake considered in the present paper occurred near the Sierra Pie de Palo in the Sierras Pampeanas tectonic province of western Argentina. In the study reported, coseismic surface deformation is combined with seismic observations (main shock and aftershocks, both teleseismic and local data) to place constraints on the geometry and slip of the main fault responsible for the 1977 earthquake. The implications of the 1977 event for long-term crustal shortening and earthquake recurrence rates in this region are also discussed. It is concluded that the 1977 Caucete earthquake was accompanied by more than 1 m of vertical uplift.

Echo-sounding method aids earthquake hazard studies

Science.gov (United States)

,

1995-01-01

Dramatic examples of catastrophic damage from an earthquake occurred in 1989, when the M 7.1 Lorna Prieta rocked the San Francisco Bay area, and in 1994, when the M 6.6 Northridge earthquake jolted southern California. The surprising amount and distribution of damage to private property and infrastructure emphasizes the importance of seismic-hazard research in urbanized areas, where the potential for damage and loss of life is greatest. During April 1995, a group of scientists from the U.S. Geological Survey and the University of Tennessee, using an echo-sounding method described below, is collecting data in San Antonio Park, California, to examine the Monte Vista fault which runs through this park. The Monte Vista fault in this vicinity shows evidence of movement within the last 10,000 years or so. The data will give them a "picture" of the subsurface rock deformation near this fault. The data will also be used to help locate a trench that will be dug across the fault by scientists from William Lettis & Associates.

Rupture Propagation through the Big Bend of the San Andreas Fault: A Dynamic Modeling Case Study of the Great Earthquake of 1857

Science.gov (United States)

Lozos, J.

2017-12-01

The great San Andreas Fault (SAF) earthquake of 9 January 1857, estimated at M7.9, was one of California's largest historic earthquakes. Its 360 km rupture trace follows the Carrizo and Mojave segments of the SAF, including the 30° compressional Big Bend in the fault. If 1857 were a characteristic rupture, the hazard implications for southern California would be dire, especially given the inferred 150 year recurrence interval for this section of the fault. However, recent paleoseismic studies in this region suggest that 1857-type events occur less frequently than single-segment Carrizo or Mojave ruptures, and that the hinge of the Big Bend is a barrier to through-going rupture. Here, I use 3D dynamic rupture modeling to attempt to reproduce the rupture length and surface slip distribution of the 1857 earthquake, to determine which physical conditions allow rupture to negotiate the Big Bend of the SAF. These models incorporate the nonplanar geometry of the SAF, an observation-based heterogeneous regional velocity structure (SCEC CVM), and a regional stress field from seismicity literature. Under regional stress conditions, I am unable to produce model events that both match the observed surface slip on the Carrizo and Mojave segments of the SAF and include rupture through the hinge of the Big Bend. I suggest that accumulated stresses at the bend hinge from multiple smaller Carrizo or Mojave ruptures may be required to allow rupture through the bend — a concept consistent with paleoseismic observations. This study may contribute to understanding the cyclicity of hazard associated with the southern-central SAF.

Earthquake ground-motion in presence of source and medium heterogeneities

KAUST Repository

Vyas, Jagdish Chandra

2017-01-01

-motion variability associated with unilateral ruptures based on ground-motion simulations of the MW 7.3 1992 Landers earthquake, eight simplified source models, and a MW 7.8 rupture simulation (ShakeOut) for the San Andreas fault. Our numerical modeling reveals

Deeper penetration of large earthquakes on seismically quiescent faults.

Science.gov (United States)

Jiang, Junle; Lapusta, Nadia

2016-06-10

Why many major strike-slip faults known to have had large earthquakes are silent in the interseismic period is a long-standing enigma. One would expect small earthquakes to occur at least at the bottom of the seismogenic zone, where deeper aseismic deformation concentrates loading. We suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes. We support this conclusion with numerical simulations of fault behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas Fault in Southern California penetrated below the seismogenic zone by at least 3 to 5 kilometers. Our findings suggest that such deeper ruptures may occur on other major fault segments, potentially increasing the associated seismic hazard. Copyright © 2016, American Association for the Advancement of Science.

Clustering and periodic recurrence of microearthquakes on the san andreas fault at parkfield, california.

Science.gov (United States)

Nadeau, R M; Foxall, W; McEvilly, T V

1995-01-27

The San Andreas fault at Parkfield, California, apparently late in an interval between repeating magnitude 6 earthquakes, is yielding to tectonic loading partly by seismic slip concentrated in a relatively sparse distribution of small clusters (<20-meter radius) of microearthquakes. Within these clusters, which account for 63% of the earthquakes in a 1987-92 study interval, virtually identical small earthquakes occurred with a regularity that can be described by the statistical model used previously in forecasting large characteristic earthquakes. Sympathetic occurrence of microearthquakes in nearby clusters was observed within a range of about 200 meters at communication speeds of 10 to 100 centimeters per second. The rate of earthquake occurrence, particularly at depth, increased significantly during the study period, but the fraction of earthquakes that were cluster members decreased.

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

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.

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.

Short presentation on some researches activities about near field earthquakes

International Nuclear Information System (INIS)

Donald, John

2002-01-01

The major hazard posed by earthquakes is often thought to be due to moderate to large magnitude events. However, there have been many cases where earthquakes of moderate and even small magnitude have caused very significant destruction when they have coincided with population centres. Even though the area of intense ground shaking caused by such events is generally small, the epicentral motions can be severe enough to cause damage even in well-engineered structures. Two issues are addressed here, the first being the identification of the minimum earthquake magnitude likely to cause damage to engineered structures and the limits of the near-field for small-to-moderate magnitude earthquakes. The second issue addressed is whether features of near-field ground motions such as directivity, which can significantly enhance the destructive potential, occur in small-to-moderate magnitude events. The accelerograms from the 1986 San Salvador (El Salvador) earthquake indicate that it may be non conservative to assume that near-field directivity effects only need to be considered for earthquakes of moment magnitude M 6.5 and greater. (author)

Using Low-Frequency Earthquake Families on the San Andreas Fault as Deep Creepmeters

Science.gov (United States)

Thomas, A. M.; Beeler, N. M.; Bletery, Q.; Burgmann, R.; Shelly, D. R.

2018-01-01

The central section of the San Andreas Fault hosts tectonic tremor and low-frequency earthquakes (LFEs) similar to subduction zone environments. LFEs are often interpreted as persistent regions that repeatedly fail during the aseismic shear of the surrounding fault allowing them to be used as creepmeters. We test this idea by using the recurrence intervals of individual LFEs within LFE families to estimate the timing, duration, recurrence interval, slip, and slip rate associated with inferred slow slip events. We formalize the definition of a creepmeter and determine whether this definition is consistent with our observations. We find that episodic families reflect surrounding creep over the interevent time, while the continuous families and the short time scale bursts that occur as part of the episodic families do not. However, when these families are evaluated on time scales longer than the interevent time these events can also be used to meter slip. A straightforward interpretation of episodic families is that they define sections of the fault where slip is distinctly episodic in well-defined slow slip events that slip 16 times the long-term rate. In contrast, the frequent short-term bursts of the continuous and short time scale episodic families likely do not represent individual creep events but rather are persistent asperities that are driven to failure by quasi-continuous creep on the surrounding fault. Finally, we find that the moment-duration scaling of our inferred creep events are inconsistent with the proposed linear moment-duration scaling. However, caution must be exercised when attempting to determine scaling with incomplete knowledge of scale.

Uranium concentrations and 234U/238U activity ratios in fault-associated groundwater as possible earthquake precursors

International Nuclear Information System (INIS)

Finkel, R.C.

1981-01-01

In order to assess the utility of uranium isotopes as fluid phase earthquake precursors, uranium concentrations and 234 U/ 238 U 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. 234 U/ 238 U 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

Discovery of amorphous carbon veins in the 2008 Wenchuan earthquake fault zone: implications for the fault weakening mechanism

Science.gov (United States)

Liu, J.; Zhang, J.; Zhang, B.; Li, H.

2013-12-01

The 2008 Wenchuan earthquake generated 270- and 80-km-long surface ruptures along Yingxiu-Beichuan fault and Guanxian-Anxian fault, respectively. At the outcrop near Hongkou village, southwest segment of Yingxiu-Beichuan rupture, network black amorphous carbon veins were discovered near fault planes in the 190-m-wide earthquake fault zone. These veins are mainly composed of ultrafine- and fine-grained amorphous carbon, usually narrower than 5mm and injected into faults and cracks as far as several meter. Flowage structures like asymmetrical structures around few stiff rock fragments indicate materials flew when the veins formed. Fluidization of cataclastic amorphous carbon and the powerful driving force in the veins imply high pore pressure built up during earthquakes. High pore pressure solution and graphite reported in the fault gouge (Togo et al., 2011) can lead very low dynamic friction during the Wenchuan earthquake. This deduction hypothesis is in accordance with the very low thermal abnormal measured on the principle fault zone following the Wenchuan earthquake (Mori et al., 2010). Furthermore, network amorphous carbon veins of different generations suggest similar weakening mechanism also worked on historical earthquakes in Longmenshan fault zone. Reference: Brodsky, E. E., Li, H., Mori, J. J., Kano, Y., and Xue, L., 2012, Frictional Stress Measured Through Temperature Profiles in the Wenchuan Scientific Fault Zone Drilling Project. American Geophysical Union, Fall Meeting. San Francisco, T44B-07 Li, H., Xu, Z., Si, J., Pei, J., Song, S., Sun, Z., and Chevalier, M., 2012, Wenchuan Earthquake Fault Scientific Drilling program (WFSD): Overview and Results. American Geophysical Union, Fall Meeting. San Francisco, T44B-01 Mori, J. J., Li, H., Wang, H., Kano, Y., Pei, J., Xu, Z., and Brodsky, E. E., 2010, Temperature measurements in the WFSD-1 borehole following the 2008 Wenchuan earthquake (MW7.9). American Geophysical Union, Fall Meeting. San Francisco, T53E

Stress diffusion along the san andreas fault at parkfield, california.

Science.gov (United States)

Malin, P E; Alvarez, M G

1992-05-15

Beginning in January 1990, the epicenters of microearthquakes associated with a 12-month increase in seismicity near Parkfield, California, moved northwest to southeast along the San Andreas fault. During this sequence of events, the locally variable rate of cumulative seismic moment increased. This increase implies a local increase in fault slip. These data suggest that a southeastwardly diffusing stress front propagated along the San Andreas fault at a speed of 30 to 50 kilometers per year. Evidently, this front did not load the Parkfield asperities fast enough to produce a moderate earthquake; however, a future front might do so.

Fracture surface energy of the Punchbowl fault, San Andreas system.

Science.gov (United States)

Chester, Judith S; Chester, Frederick M; Kronenberg, Andreas K

2005-09-01

Fracture energy is a form of latent heat required to create an earthquake rupture surface and is related to parameters governing rupture propagation and processes of slip weakening. Fracture energy has been estimated from seismological and experimental rock deformation data, yet its magnitude, mechanisms of rupture surface formation and processes leading to slip weakening are not well defined. Here we quantify structural observations of the Punchbowl fault, a large-displacement exhumed fault in the San Andreas fault system, and show that the energy required to create the fracture surface area in the fault is about 300 times greater than seismological estimates would predict for a single large earthquake. If fracture energy is attributed entirely to the production of fracture surfaces, then all of the fracture surface area in the Punchbowl fault could have been produced by earthquake displacements totalling <1 km. But this would only account for a small fraction of the total energy budget, and therefore additional processes probably contributed to slip weakening during earthquake rupture.

Seismic resistance of equipment and building service systems: review of earthquake damage design requirements, and research applications in the USA

International Nuclear Information System (INIS)

Skjei, R.E.; Chakravartula, B.C.; Yanev, P.I.

1979-01-01

The history of earthquake damage and the resulting code design requirements for earthquake hazard mitigation for equipment in the USA is reviewed. Earthquake damage to essential service systems is summarized; observations for the 1964 Alaska and the 1971 San Fernando, California, earthquakes are stressed, and information from other events is included. USA building codes that reflect lessons learned from these earthquakes are discussed; brief summaries of widely used codes are presented. In conclusion there is a discussion of the desirability of adapting advanced technological concepts from the nuclear industry to equipment in conventional structures. (author)

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.

Paleoseismic analysis of the San Vicente segment of the El Salvador Fault Zone, El Salvador, Central America

OpenAIRE

Canora Catalán, Carolina; Villamor Pérez, María Pilar; Martínez Díaz, José J.; Berryman, K.R.; Álvarez Gómez, José Antonio; Capote del Villar, Ramón; Hernández, Walter

2012-01-01

The El Salvador earthquake of February 13th 2001 (Mw 6.6) was associated with the tectonic rupture of the El Salvador Fault Zone. Paleoseismic studies of the El Salvador Fault Zone undertaken after this earthquake provide a basis for examining the longer history of surface rupturing earthquakes on the fault. Trenching at five sites along the San Vicente segment, a 21km-long and up to 2km-wide central section of the El Salvador Fault Zone, shows that surface fault rupture has occurred at least...

Satellite Geodetic Constraints On Earthquake Processes: Implications of the 1999 Turkish Earthquakes for Fault Mechanics and Seismic Hazards on the San Andreas Fault

Science.gov (United States)

Reilinger, Robert

2005-01-01

Our principal activities during the initial phase of this project include: 1) Continued monitoring of postseismic deformation for the 1999 Izmit and Duzce, Turkey earthquakes from repeated GPS survey measurements and expansion of the Marmara Continuous GPS Network (MAGNET), 2) Establishing three North Anatolian fault crossing profiles (10 sitedprofile) at locations that experienced major surface-fault earthquakes at different times in the past to examine strain accumulation as a function of time in the earthquake cycle (2004), 3) Repeat observations of selected sites in the fault-crossing profiles (2005), 4) Repeat surveys of the Marmara GPS network to continue to monitor postseismic deformation, 5) Refining block models for the Marmara Sea seismic gap area to better understand earthquake hazards in the Greater Istanbul area, 6) Continuing development of models for afterslip and distributed viscoelastic deformation for the earthquake cycle. We are keeping close contact with MIT colleagues (Brad Hager, and Eric Hetland) who are developing models for S. California and for the earthquake cycle in general (Hetland, 2006). In addition, our Turkish partners at the Marmara Research Center have undertaken repeat, micro-gravity measurements at the MAGNET sites and have provided us estimates of gravity change during the period 2003 - 2005.

Telegraph Canyon Creek, City of Chula Vista, San Diego County, California. Detailed Report for Flood Control. Volume 1. Main Report.

Science.gov (United States)

1983-07-01

SECURITY CLASS. (of chi* report) Los Angeles District, Corps of Engineers Ucasfe P.O. Box 2711, Los Angeles, CA 90053 15&. DEL SI F1CATION/OWNGRAOI...greater potential for the possible occurrence of a large earthquake include the Whittier-Elsinore, Agua Caliente, San Jacinto, and the San Andreas...about 900,000 motor vehicles used within the county. 2.20 Air contaminants monitored within the San Diego Bay air basin include carbon monoxide (CO

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.

Self-potential variations preceding earthquakes in central california

International Nuclear Information System (INIS)

Corwin, R.F.; Morrison, H.G.

1977-01-01

Two earthquakes in central California were preceded by anomalous variations in the horizontal electric field (self-potential) of the earth. The first variation was an anomaly of 90 mV amplitude across electrode dipoles of 630 and 640 m, which began 55 days before an earthquake of M=5, located 37 km NW of the dipoles. The second variation had an amplitude of 4 mV across a 300 m dipole, and began 110 hours before an event of M=2.4 located on the San Andreas fault, 2.5 km from the dipole. Streaming potentials generated by the flow of groundwater into a dilatant zone are proposed as a possible mechanism for the observed variations

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.

Low Velocity Zones along the San Jacinto Fault, Southern California, inferred from Local Earthquakes

Science.gov (United States)

Li, Z.; Yang, H.; Peng, Z.; Ben-Zion, Y.; Vernon, F.

2013-12-01

Natural fault zones have regions of brittle damage leading to a low-velocity zone (LVZ) in the immediate vicinity of the main fault interface. The LVZ may amplify ground motion, modify rupture propagation, and impact derivation of earthquke properties. Here we image low-velocity fault zone structures along the San Jacinto Fault (SJF), southern California, using waveforms of local earthquakes that are recorded at several dense arrays across the SJFZ. We use generalized ray theory to compute synthetic travel times to track the direct and FZ-reflected waves bouncing from the FZ boundaries. This method can effectively reduce the trade-off between FZ width and velocity reduction relative to the host rock. Our preliminary results from travel time modeling show the clear signature of LVZs along the SJF, including the segment of the Anza seismic gap. At the southern part near the trifrication area, the LVZ of the Clark Valley branch (array JF) has a width of ~200 m with ~55% reduction in Vp and Vs. This is consistent with what have been suggested from previous studies. In comparison, we find that the velocity reduction relative to the host rock across the Anza seismic gap (array RA) is ~50% for both Vp and Vs, nearly as prominent as that on the southern branches. The width of the LVZ is ~230 m. In addition, the LVZ across the Anza gap appears to locate in the northeast side of the RA array, implying potential preferred propagation direction of past ruptures.

Computational Approach for Improving Three-Dimensional Sub-Surface Earth Structure for Regional Earthquake Hazard Simulations in the San Francisco Bay Area

Energy Technology Data Exchange (ETDEWEB)

Rodgers, A. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-09-25

In our Exascale Computing Project (ECP) we seek to simulate earthquake ground motions at much higher frequency than is currently possible. Previous simulations in the SFBA were limited to 0.5-1 Hz or lower (Aagaard et al. 2008, 2010), while we have recently simulated the response to 5 Hz. In order to improve confidence in simulated ground motions, we must accurately represent the three-dimensional (3D) sub-surface material properties that govern seismic wave propagation over a broad region. We are currently focusing on the San Francisco Bay Area (SFBA) with a Cartesian domain of size 120 x 80 x 35 km, but this area will be expanded to cover a larger domain. Currently, the United States Geologic Survey (USGS) has a 3D model of the SFBA for seismic simulations. However, this model suffers from two serious shortcomings relative to our application: 1) it does not fit most of the available low frequency (< 1 Hz) seismic waveforms from moderate (magnitude M 3.5-5.0) earthquakes; and 2) it is represented with much lower resolution than necessary for the high frequency simulations (> 5 Hz) we seek to perform. The current model will serve as a starting model for full waveform tomography based on 3D sensitivity kernels. This report serves as the deliverable for our ECP FY2017 Quarter 4 milestone to FY 2018 “Computational approach to developing model updates”. We summarize the current state of 3D seismic simulations in the SFBA and demonstrate the performance of the USGS 3D model for a few selected paths. We show the available open-source waveform data sets for model updates, based on moderate earthquakes recorded in the region. We present a plan for improving the 3D model utilizing the available data and further development of our SW4 application. We project how the model could be improved and present options for further improvements focused on the shallow geotechnical layers using dense passive recordings of ambient and human-induced noise.

San Andreas tremor cascades define deep fault zone complexity

Science.gov (United States)

Shelly, David R.

2015-01-01

Weak seismic vibrations - tectonic tremor - can be used to delineate some plate boundary faults. Tremor on the deep San Andreas Fault, located at the boundary between the Pacific and North American plates, is thought to be a passive indicator of slow fault slip. San Andreas Fault tremor migrates at up to 30 m s-1, but the processes regulating tremor migration are unclear. Here I use a 12-year catalogue of more than 850,000 low-frequency earthquakes to systematically analyse the high-speed migration of tremor along the San Andreas Fault. I find that tremor migrates most effectively through regions of greatest tremor production and does not propagate through regions with gaps in tremor production. I interpret the rapid tremor migration as a self-regulating cascade of seismic ruptures along the fault, which implies that tremor may be an active, rather than passive participant in the slip propagation. I also identify an isolated group of tremor sources that are offset eastwards beneath the San Andreas Fault, possibly indicative of the interface between the Monterey Microplate, a hypothesized remnant of the subducted Farallon Plate, and the North American Plate. These observations illustrate a possible link between the central San Andreas Fault and tremor-producing subduction zones.

Triggered surface slips in the Coachella Valley area associated with the 1992 Joshua Tree and Landers, California, Earthquakes

Science.gov (United States)

Rymer, M.J.

2000-01-01

The Coachella Valley area was strongly shaken by the 1992 Joshua Tree (23 April) and Landers (28 June) earthquakes, and both events caused triggered slip on active faults within the area. Triggered slip associated with the Joshua Tree earthquake was on a newly recognized fault, the East Wide Canyon fault, near the southwestern edge of the Little San Bernardino Mountains. Slip associated with the Landers earthquake formed along the San Andreas fault in the southeastern Coachella Valley. Surface fractures formed along the East Wide Canyon fault in association with the Joshua Tree earthquake. The fractures extended discontinuously over a 1.5-km stretch of the fault, near its southern end. Sense of slip was consistently right-oblique, west side down, similar to the long-term style of faulting. Measured offset values were small, with right-lateral and vertical components of slip ranging from 1 to 6 mm and 1 to 4 mm, respectively. This is the first documented historic slip on the East Wide Canyon fault, which was first mapped only months before the Joshua Tree earthquake. Surface slip associated with the Joshua Tree earthquake most likely developed as triggered slip given its 5 km distance from the Joshua Tree epicenter and aftershocks. As revealed in a trench investigation, slip formed in an area with only a thin (Salton Trough. A paleoseismic trench study in an area of 1992 surface slip revealed evidence of two and possibly three surface faulting events on the East Wide Canyon fault during the late Quaternary, probably latest Pleistocene (first event) and mid- to late Holocene (second two events). About two months after the Joshua Tree earthquake, the Landers earthquake then triggered slip on many faults, including the San Andreas fault in the southeastern Coachella Valley. Surface fractures associated with this event formed discontinuous breaks over a 54-km-long stretch of the fault, from the Indio Hills southeastward to Durmid Hill. Sense of slip was right

Distribution of creep in the northern San Francisco Bay Area illuminated by repeating earthquakes and InSAR

Science.gov (United States)

Funning, G.; Shakibay Senobari, N.; Swiatlowski, J. L.

2017-12-01

Surface observations of fault creep in the region north of San Francisco Bay are sporadic. While there are long-standing instances of creep-affected infrastructure on the Maacama and Bartlett Springs faults, the lateral and depth extents of creep on these and other faults in the region remain a question. Here, we supplement this sparse existing observation set with additional information from repeating earthquake sequences (REs) and InSAR, to illuminate, and significantly improve our knowledge of, creep across the region. Repeating earthquakes have long been considered indicators of creep on faults. We present the results of an extensive similarity search through over 600,000 archived waveforms from 43,000 events using a fast algorithm; from this we can identify 39 periodic repeating sequences and over 80 nonperiodic repeated event groups. We compare these with decadal line-of-sight velocity measurements made by applying the StaMPS time series InSAR code to ERS and Envisat data covering the region, that can be used to identify surface creep on faults. On the Rodgers Creek, Maacama and Bartlett Springs faults, both InSAR and REs show corroborating evidence for creep at locations where it was previously inferred. The REs additionally provide information on its depth extent. On the Maacama fault, we find REs extending almost to the southern limit of the mapped fault trace, south of Cloverdale, suggesting that creep may be pervasive on the fault. We can also identify structural complexity both in the stepover region with the Rodgers Creek fault, and in the northern segment of the fault close to Willits, potentially indicating parallel and/or down-dip branching creeping structures in both locations. REs on the Bartlett Springs fault indicate creep that extends across the full down-dip width of the brittle fault; here the proximity of InSAR creep rate estimates and a shallow RE sequence may permit a calibration of the RE `creepmeter', allowing us to estimate creep rates

The HayWired earthquake scenario—Engineering implications

Science.gov (United States)

Detweiler, Shane T.; Wein, Anne M.

2018-04-18

The HayWired Earthquake Scenario—Engineering Implications is the second volume of U.S. Geological Survey (USGS) Scientific Investigations Report 2017–5013, which describes the HayWired scenario, developed by USGS and its partners. The scenario is a hypothetical yet scientifically realistic earthquake sequence that is being used to better understand hazards for the San Francisco Bay region during and after a magnitude-7 earthquake (mainshock) on the Hayward Fault and its aftershocks.Analyses in this volume suggest that (1) 800 deaths and 16,000 nonfatal injuries result from shaking alone, plus property and direct business interruption losses of more than $82 billion from shaking, liquefaction, and landslides; (2) the building code is designed to protect lives, but even if all buildings in the region complied with current building codes, 0.4 percent could collapse, 5 percent could be unsafe to occupy, and 19 percent could have restricted use; (3) people expect, prefer, and would be willing to pay for greater resilience of buildings; (4) more than 22,000 people could require extrication from stalled elevators, and more than 2,400 people could require rescue from collapsed buildings; (5) the average east-bay resident could lose water service for 6 weeks, some for as long as 6 months; (6) older steel-frame high-rise office buildings and new reinforced-concrete residential buildings in downtown San Francisco and Oakland could be unusable for as long as 10 months; (7) about 450 large fires could result in a loss of residential and commercial building floor area equivalent to more than 52,000 single-family homes and cause property (building and content) losses approaching $30 billion; and (8) combining earthquake early warning (ShakeAlert) with “drop, cover, and hold on” actions could prevent as many as 1,500 nonfatal injuries out of 18,000 total estimated nonfatal injuries from shaking and liquefaction hazards.

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.

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

Relocating San Miguel Volcanic Seismic Events for Receiver Functions and Tomographic Models

Science.gov (United States)

Patlan, E.; Velasco, A. A.; Konter, J.

2009-12-01

The San Miguel volcano lies near the city of San Miguel, El Salvador (13.43N and -88.26W). San Miguel volcano, an active stratovolcano, presents a significant natural hazard for the city of San Miguel. Furthermore, the internal state and activity of volcanoes remains an important component to understanding volcanic hazard. The main technology for addressing volcanic hazards and processes is through the analysis of data collected from the deployment of seismic sensors that record ground motion. Six UTEP seismic stations were deployed around San Miguel volcano from 2007-2008 to define the magma chamber and assess the seismic and volcanic hazard. We utilize these data to develop images of the earth structure beneath the volcano, studying the volcanic processes by identifying different sources, and investigating the role of earthquakes and faults in controlling the volcanic processes. We will calculate receiver functions to determine the thickness of San Miguel volcano internal structure, within the Caribbean plate. Crustal thicknesses will be modeled using calculated receiver functions from both theoretical and hand-picked P-wave arrivals. We will use this information derived from receiver functions, along with P-wave delay times, to map the location of the magma chamber.

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.

Magnitude of shear stress on the san andreas fault: implications of a stress measurement profile at shallow depth.

Science.gov (United States)

Zoback, M D; Roller, J C

1979-10-26

A profile of measurements of shear stress perpendicular to the San Andreas fault near Palmdale, California, shows a marked increase in stress with distance from the fault. The pattern suggests that shear stress on the fault increases slowly with depth and reaches a value on the order of the average stress released during earthquakes. This result has important implications for both long- and shortterm prediction of large earthquakes.

San Onofre/Zion auxiliary feedwater system seismic fault tree modeling

International Nuclear Information System (INIS)

Najafi, B.; Eide, S.

1982-02-01

As part of the study for the seismic evaluation of the San Onofre Unit 1 Auxiliary Feedwater System (AFWS), a fault tree model was developed capable of handling the effect of structural failure of the plant (in the event of an earthquake) on the availability of the AFWS. A compatible fault tree model was developed for the Zion Unit 1 AFWS in order to compare the results of the two systems. It was concluded that if a single failure of the San Onofre Unit 1 AFWS is to be prevented, some weight existing, locally operated locked open manual valves have to be used for isolation of a rupture in specific parts of the AFWS pipings

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

Off-fault seismicity suggests creep below 10 km on the northern San Jacinto Fault

Science.gov (United States)

Cooke, M. L.; Beyer, J. L.

2017-12-01

Within the San Bernardino basin, CA, south of the juncture of the San Jacinto (SJF) and San Andreas faults (SAF), focal mechanisms show normal slip events that are inconsistent with the interseismic strike-slip loading of the region. High-quality (nodal plane uncertainty faults [Anderson et al., 2004]. However, the loading of these normal slip events remains enigmatic because the region is expected to have dextral loading between large earthquake events. These enigmatic normal slip events may be loaded by deep (> 10 km depth) spatially creep along the northern SJF. Steady state models show that over many earthquake cycles, the dextral slip rate on the northern SJF increases southward, placing the San Bernardino basin in extension. In the absence of recent large seismic events that could produce off-fault normal focal mechanisms in the San Bernardino basin, non-uniform deep aseismic slip on the SJF could account for this seismicity. We develop interseismic models that incorporate spatially non-uniform creep below 10 km on the SJF based on steady-state slip distribution. These model results match the pattern of deep normal slip events within the San Bernardino basin. Such deep creep on the SJF may not be detectable from the geodetic signal due to the close proximity of the SAF, whose lack of seismicity suggests that it is locked to 20 km. Interseismic models with 15 km locking depth on both faults are indistinguishable from models with 10 km locking depth on the SJF and 20 km locking depth on the SAF. This analysis suggests that the microseismicity in our multi-decadal catalog may record both the interseismic dextral loading of the region as well as off-fault deformation associated with deep aseismic creep on the northern SJF. If the enigmatic normal slip events of the San Bernardino basin are included in stress inversions from the seismic catalog used to assess seismic hazard, the results may provide inaccurate information about fault loading in this region.

The 2001 January 13th M {W}7.7 and February 13th M {W}6.6 El Salvador Earthquakes: Deformation and Stress Triggering

Science.gov (United States)

Hreinsdóttir, S.; Freymueller, J. T.

2001-12-01

On the 13th of January 2001, an M {W} 7.7 normal fault earthquake occurred offshore El Salvador. The earthquake occurred in the subducting Cocos plate and was followed by high seismic activity and several earthquakes exceeding magnitude 5. On the 13th of February, an M {W} 6.6 strike slip earthquake occurred in the overriding Caribbean plate, about 75 km NNW from the epicenter of the large January earthquake. Deformation due to these earthquakes was observed at six continuous CORS GPS stations in Central America. In the M {W} 7.7 earthquake about 10 mm displacement was measured at GPS stations in El Salvador and Honduras. A smaller but significant dispacement was also observed at GPS stations in Nicaragua, more then 200 km from the earthquake's epicenter. In the M {W} 6.6 earthquake 41+/- 1 mm displacement in direction N111oE was measured at the GPS station in San Salvador, El Salvador. Other CORS GPS stations were not affected by that earthquake. A postsesmic signal is detectable at the San Salvador GPS station, strongest right after the earthquake and then decays. On average we see 0.3 +/- 0.1 mm/day of SSW motion of the station in the first twenty days following the earthquake. Using seismic and geodetic data, we calculated Coulomb stress changes following the January 13th, M {W} 7.7 earthquake. Of special interest were six 5.4 earthquake that occurred in the overriding Caribean plate. The location and focal mechanism of these earthquakes correlate with areas of calculated increase in static stress thus indicating stress triggering. The thrust events occurred 2 to 20 days after the M {W} 7.7 earthquake, in increasing distance from the M {W} 7.7 event with time.

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

The Landers earthquake; preliminary instrumental results

Science.gov (United States)

Jones, L.; Mori, J.; Hauksson, E.

1992-01-01

Early on the morning of June 28, 1992, millions of people in southern California were awakened by the largest earthquake to occur in the western United States in the past 40 yrs. At 4:58 a.m PDT (local time), faulting associated with the magnitude 7.3 earthquake broke through to earth's surface near the town of Landers, California. the surface rupture then propagated 70km (45 mi) to the north and northwest along a band of faults passing through the middle of the Mojave Desert. Fortunately, the strongest shaking occurred in uninhabited regions of the Mojave Desert. Still one child was killed in Yucca Valley, and about 400 people were injured in the surrounding area. the desert communities of Landers, Yucca Valley, and Joshua Tree in San Bernardino Country suffered considerable damage to buildings and roads. Damage to water and power lines caused problems in many areas. 

Style and rate of quaternary deformation of the Hosgri Fault Zone, offshore south-central coastal California

Science.gov (United States)

Hanson, Kathryn L.; Lettis, William R.; McLaren, Marcia; Savage, William U.; Hall, N. Timothy; Keller, Mararget A.

2004-01-01

The Hosgri Fault Zone is the southernmost component of a complex system of right-slip faults in south-central coastal California that includes the San Gregorio, Sur, and San Simeon Faults. We have characterized the contemporary style of faulting along the zone on the basis of an integrated analysis of a broad spectrum of data, including shallow high-resolution and deep penetration seismic reflection data; geologic and geomorphic data along the Hosgri and San Simeon Fault Zones and the intervening San Simeon/Hosgri pull-apart basin; the distribution and nature of near-coast seismicity; regional tectonic kinematics; and comparison of the Hosgri Fault Zone with worldwide strike-slip, oblique-slip, and reverse-slip fault zones. These data show that the modern Hosgri Fault Zone is a convergent right-slip (transpressional) fault having a late Quaternary slip rate of 1 to 3 mm/yr. Evidence supporting predominantly strike-slip deformation includes (1) a long, narrow, linear zone of faulting and associated deformation; (2) the presence of asymmetric flower structures; (3) kinematically consistent localized extensional and compressional deformation at releasing and restraining bends or steps, respectively, in the fault zone; (4) changes in the sense and magnitude of vertical separation both along trend of the fault zone and vertically within the fault zone; (5) strike-slip focal mechanisms along the fault trace; (6) a distribution of seismicity that delineates a high-angle fault extending through the seismogenic crust; (7) high ratios of lateral to vertical slip along the fault zone; and (8) the separation by the fault of two tectonic domains (offshore Santa Maria Basin, onshore Los Osos domain) that are undergoing contrasting styles of deformation and orientations of crustal shortening. The convergent component of slip is evidenced by the deformation of the early-late Pliocene unconformity. In characterizing the style of faulting along the Hosgri Fault Zone, we assessed

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

Science.gov (United States)

Nelson, C. H.; Gutiérrez Pastor, J.; Goldfinger, C.; Escutia, C.

2012-11-01

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 cause seismic strengthening of the sediment, which

Disaster preparedness and response improvement: comparison of the 2010 Haiti earthquake-related diagnoses with baseline medical data.

Science.gov (United States)

van Berlaer, Gerlant; Staes, Tom; Danschutter, Dirk; Ackermans, Ronald; Zannini, Stefano; Rossi, Gabriele; Buyl, Ronald; Gijs, Geert; Debacker, Michel; Hubloue, Ives

2017-10-01

Disaster medicine research generally lacks control groups. This study aims to describe categories of diagnoses encountered by the Belgian First Aid and Support Team after the 2010 Haiti earthquake and extract earthquake-related changes from comparison with comparable baseline data. The hypothesis is that besides earthquake-related trauma, medical problems emerge soon, questioning an appropriate composition of Foreign Medical Teams and Interagency Emergency Health Kits. Using a descriptive cohort study design, diagnoses of patients presenting to the Belgian field hospital were prospectively registered during 4 weeks after the earthquake and compared with those recorded similarly by Médecins Sans Frontières in the same area and time span in previous and later years. Of 7000 triaged postearthquake patients, 3500 were admitted, of whom 2795 were included and analysed. In the fortnight after the earthquake, 90% suffered from injury. In the following fortnight, medical diseases emerged, particularly respiratory (23%) and digestive (14%). More than 53% developed infections within 3 weeks after the event. Médecins Sans Frontières registered 6407 patients in 2009; 6033 in 2011; and 7300 in 2012. A comparison indicates that postearthquake patients suffered significantly less from violence, but more from wounds, respiratory, digestive and ophthalmological diseases. This is the first comparison of postearthquake diagnoses with baseline data. Within 2 weeks after the acute phase of an earthquake, respiratory, digestive and ophthalmological problems will emerge to the prejudice of trauma. This fact should be anticipated when composing Foreign Medical Teams and Interagency Emergency Health Kits to be sent to the disaster site.

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

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.

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 (M_w ≳ 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

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

Solar eruptions - soil radon - earthquakes

International Nuclear Information System (INIS)

Saghatelyan, E.; Petrosyan, L.; Aghbalyan, Yu.; Baburyan, M.; Araratyan, L.

2004-01-01

For the first time a new natural phenomenon was established: a contrasting increase in the soil radon level under the influence of solar flares. Such an increase is one of geochemical indicators of earthquakes. Most researchers consider this a phenomenon of exclusively terrestrial processes. Investigations regarding the link of earthquakes to solar activity carried out during the last decade in different countries are based on the analysis of statistical data ΣΕ (t) and W (t). As established, the overall seismicity of the Earth and its separate regions depends of an 11-year long cycle of solar activity. Data provided in the paper based on experimental studies serve the first step on the way of experimental data on revealing cause-and-reason solar-terrestrials bonds in a series s olar eruption-lithosphere radon-earthquakes . They need further collection of experimental data. For the first time, through radon constituent of terrestrial radiation objectification has been made of elementary lattice of the Hartmann's network contoured out by bio location method. As found out, radon concentration variations in Hartmann's network nodes determine the dynamics of solar-terrestrial relationships. Of the three types of rapidly running processes conditioned by solar-terrestrial bonds earthquakes are attributed to rapidly running destructive processes that occur in the most intense way at the juncture of tectonic massifs, along transformed and deep failures. The basic factors provoking the earthquakes are both magnetic-structural effects and a long-term (over 5 months) bombing of the surface of lithosphere by highly energetic particles of corpuscular solar flows, this being approved by photometry. As a result of solar flares that occurred from 29 October to 4 November 2003, a sharply contrasting increase in soil radon was established which is an earthquake indicator on the territory of Yerevan City. A month and a half later, earthquakes occurred in San-Francisco, Iran, Turkey

Determining Volcanic Deformation at San Miguel Volcano, El Salvador by Integrating Radar Interferometry and Seismic Analyses

Science.gov (United States)

Schiek, C. G.; Hurtado, J. M.; Velasco, A. A.; Buckley, S. M.; Escobar, D.

2008-12-01

From the early 1900's to the present day, San Miguel volcano has experienced many small eruptions and several periods of heightened seismic activity, making it one of the most active volcanoes in the El Salvadoran volcanic chain. Prior to 1969, the volcano experienced many explosive eruptions with Volcano Explosivity Indices (VEI) of 2. Since then, eruptions have decreased in intensity to an average VEI of 1. Eruptions mostly consist of phreatic explosions and central vent eruptions. Due to the explosive nature of this volcano, it is important to study the origins of the volcanism and its relationship to surface deformation and earthquake activity. We analyze these interactions by integrating interferometric synthetic aperture radar (InSAR) results with earthquake source location data from a ten-month (March 2007-January 2008) seismic deployment. The InSAR results show a maximum of 7 cm of volcanic inflation from March 2007 to mid-October 2007. During this time, seismic activity increased to a Real-time Seismic-Amplitude Measurement (RSAM) value of >400. Normal RSAM values for this volcano are earthquakes that occurred between March 2007 and January 2008 suggests a fault zone through the center of the San Miguel volcanic cone. This fault zone is most likely where dyke propagation is occurring. Source mechanisms will be determined for the earthquakes associated with this fault zone, and they will be compared to the InSAR deformation field to determine if the mid-October seismic activity and observed surface deformation are compatible.

Paleoearthquakes at Frazier Mountain, California delimit extent and frequency of past San Andreas Fault ruptures along 1857 trace

Science.gov (United States)

Scharer, Katherine M.; Weldon, Ray; Streig, Ashley; Fumal, Thomas

2014-01-01

Large earthquakes are infrequent along a single fault, and therefore historic, well-characterized earthquakes exert a strong influence on fault behavior models. This is true of the 1857 Fort Tejon earthquake (estimated M7.7–7.9) on the southern San Andreas Fault (SSAF), but an outstanding question is whether the 330 km long rupture was typical. New paleoseismic data for six to seven ground-rupturing earthquakes on the Big Bend of the SSAF restrict the pattern of possible ruptures on the 1857 stretch of the fault. In conjunction with existing sites, we show that over the last ~650 years, at least 75% of the surface ruptures are shorter than the 1857 earthquake, with estimated rupture lengths of 100 to <300 km. These results suggest that the 1857 rupture was unusual, perhaps leading to the long open interval, and that a return to pre-1857 behavior would increase the rate of M7.3–M7.7 earthquakes.

Roles of Radon-222 and other natural radionuclides in earthquake prediction

International Nuclear Information System (INIS)

Smith, A.R.; Wollenberg, H.A.; Mosier, D.F.

1980-01-01

The concentration of 222 Rn in subsurface waters is one of the natural parameters being investigated to help develop the capability to predict destructive earthquakes. Since 1966, scientists in several nations have sought to link radon variations with ongoing seismic activity, primarily through the dilatancy model for earthquake occurrences. Within the range of these studies, alpha-, beta-, and gamma-radiation detection techniques have been used in both discrete-sampling and continiuous-monitoring programs. These measured techniques are reviewed in terms of instrumentation adapted to seismic-monitoring purposes. A recent Lawrence Berkeley Laboratory study conducted in central California incorporated discrete sampling of wells in the aftershock area of the 1975 Oroville earthquake and continuous monitoring of water radon in a well on the San Andreas Fault. The results presented show short-term radon variations that may be associated with aftershocks and diurnal changes that may reflect earth tidal forces

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.

Analysis of Earthquake Source Spectra in Salton Trough

Science.gov (United States)

Chen, X.; Shearer, P. M.

2009-12-01

Previous studies of the source spectra of small earthquakes in southern California show that average Brune-type stress drops vary among different regions, with particularly low stress drops observed in the Salton Trough (Shearer et al., 2006). The Salton Trough marks the southern end of the San Andreas Fault and is prone to earthquake swarms, some of which are driven by aseismic creep events (Lohman and McGuire, 2007). In order to learn the stress state and understand the physical mechanisms of swarms and slow slip events, we analyze the source spectra of earthquakes in this region. We obtain Southern California Seismic Network (SCSN) waveforms for earthquakes from 1977 to 2009 archived at the Southern California Earthquake Center (SCEC) data center, which includes over 17,000 events. After resampling the data to a uniform 100 Hz sample rate, we compute spectra for both signal and noise windows for each seismogram, and select traces with a P-wave signal-to-noise ratio greater than 5 between 5 Hz and 15 Hz. Using selected displacement spectra, we isolate the source spectra from station terms and path effects using an empirical Green’s function approach. From the corrected source spectra, we compute corner frequencies and estimate moments and stress drops. Finally we analyze spatial and temporal variations in stress drop in the Salton Trough and compare them with studies of swarms and creep events to assess the evolution of faulting and stress in the region. References: Lohman, R. B., and J. J. McGuire (2007), Earthquake swarms driven by aseismic creep in the Salton Trough, California, J. Geophys. Res., 112, B04405, doi:10.1029/2006JB004596 Shearer, P. M., G. A. Prieto, and E. Hauksson (2006), Comprehensive analysis of earthquake source spectra in southern California, J. Geophys. Res., 111, B06303, doi:10.1029/2005JB003979.

The use of radon gas techniques for earthquake prediction

International Nuclear Information System (INIS)

Al-Hilal, M.

1993-01-01

This scientific article explains the applications of radon gas measurements in water and soil for monitoring fault activities and earthquake prediction. It also emphasizes, through some worldwide examples presented from Tashkent Basin in U.S.S.R. and from San Andreas fault in U.S.A, that the use of radon gas technique in fault originated water as well as in soil gases can be considered as an important geological-tool, within the general framework of earthquake prediction because of the coherent and time anomalous relationship between the density of alpha particles due to radon decay and between the tectonic activity level along fault zones. The article also indicates, and through the practical experience of the author, to the possibility of applying such techniques in certain parts of Syria. (author). 6 refs., 4 figs

Effects of local geological conditions in the San Francisco Bay region on ground motions and the intensities of the 1906 earthquake

International Nuclear Information System (INIS)

Borcherdt, R.D.; Gibbs, J.F.

1976-01-01

Measurements of ground motion generated by nuclear explosions in Nevada have been completed for 99 locations in the San Francisco Bay region, California. The recordings show marked amplitude variations in the frequency band 0.25 to 3.0 Hz that are consistently related to the local geological conditions of the recording site. The average spectral amplifications observed for vertical and horizontal ground motions are, respectively: (1,1) for granite, (1.5, 1.6) for the Franciscan Formation, (3.0, 2.7) for the Santa Clara Formation, (3.3, 4.4) for alluvium, and (3.7, 11.3) for bay mud. Spectral amplification curves define predominant ground frequencies in the band 0.25 to 3.0 H for bay mud sites and for some alluvial sites. Amplitude spectra computed from recordings of seismic background noise at 50 sites do not generally define predominant ground frequencies. The intensities ascribed to various sites in the San Francisco Bay region for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the intensities for 917 sites on Franciscan rocks generally decrease with the logarithm of distance as Intensity = 2.69 -- 1.90 log (Distance in kilometers). For sites on other geological units, intensity increments, derived from this empirical relation, correlate strongly with the Average Horizontal Spectral Amplifications (AHSA) according to the empirical relation Intensity Increment = 0.27 + 2.70 log (AHSA). Average intensity increments predicted for the various geological units are --0.3 for granite, 0.2 for the Franciscan Formation, 0.6 for the Great Valley sequence, 0.8 for the Santa Clara Formation, 1.3 for alluvium, and 2.4 for bay mud

Effects of local geological conditions in the San Francisco Bay region on ground motions and the intensities of the 1906 earthquake

Energy Technology Data Exchange (ETDEWEB)

Borcherdt, R.D.; Gibbs, J.F.

1976-04-01

Measurements of ground motion generated by nuclear explosions in Nevada have been completed for 99 locations in the San Francisco Bay region, California. The recordings show marked amplitude variations in the frequency band 0.25 to 3.0 Hz that are consistently related to the local geological conditions of the recording site. The average spectral amplifications observed for vertical and horizontal ground motions are, respectively: (1,1) for granite, (1.5, 1.6) for the Franciscan Formation, (3.0, 2.7) for the Santa Clara Formation, (3.3, 4.4) for alluvium, and (3.7, 11.3) for bay mud. Spectral amplification curves define predominant ground frequencies in the band 0.25 to 3.0 H for bay mud sites and for some alluvial sites. Amplitude spectra computed from recordings of seismic background noise at 50 sites do not generally define predominant ground frequencies. The intensities ascribed to various sites in the San Francisco Bay region for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the intensities for 917 sites on Franciscan rocks generally decrease with the logarithm of distance as Intensity = 2.69 -- 1.90 log (Distance in kilometers). For sites on other geological units, intensity increments, derived from this empirical relation, correlate strongly with the Average Horizontal Spectral Amplifications (AHSA) according to the empirical relation Intensity Increment = 0.27 + 2.70 log (AHSA). Average intensity increments predicted for the various geological units are --0.3 for granite, 0.2 for the Franciscan Formation, 0.6 for the Great Valley sequence, 0.8 for the Santa Clara Formation, 1.3 for alluvium, and 2.4 for bay mud.

Seismogeodetic monitoring techniques for tsunami and earthquake early warning and rapid assessment of structural damage

Science.gov (United States)

Haase, J. S.; Bock, Y.; Saunders, J. K.; Goldberg, D.; Restrepo, J. I.

2016-12-01

As part of an effort to promote the use of NASA-sponsored Earth science information for disaster risk reduction, real-time high-rate seismogeodetic data are being incorporated into early warning and structural monitoring systems. Seismogeodesy combines seismic acceleration and GPS displacement measurements using a tightly-coupled Kalman filter to provide absolute estimates of seismic acceleration, velocity and displacement. Traditionally, the monitoring of earthquakes and tsunamis has been based on seismic networks for estimating earthquake magnitude and slip, and tide gauges and deep-ocean buoys for direct measurement of tsunami waves. Real-time seismogeodetic observations at subduction zones allow for more robust and rapid magnitude and slip estimation that increase warning time in the near-source region. A NASA-funded effort to utilize GPS and seismogeodesy in NOAA's Tsunami Warning Centers in Alaska and Hawaii integrates new modules for picking, locating, and estimating magnitudes and moment tensors for earthquakes into the USGS earthworm environment at the TWCs. In a related project, NASA supports the transition of this research to seismogeodetic tools for disaster preparedness, specifically by implementing GPS and low-cost MEMS accelerometers for structural monitoring in partnership with earthquake engineers. Real-time high-rate seismogeodetic structural monitoring has been implemented on two structures. The first is a parking garage at the Autonomous University of Baja California Faculty of Medicine in Mexicali, not far from the rupture of the 2011 Mw 7.2 El Mayor Cucapah earthquake enabled through a UCMexus collaboration. The second is the 8-story Geisel Library at University of California, San Diego (UCSD). The system has also been installed for several proof-of-concept experiments at the UCSD Network for Earthquake Engineering Simulation (NEES) Large High Performance Outdoor Shake Table. We present MEMS-based seismogeodetic observations from the 10 June

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

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

Southern San Andreas Fault evaluation field activity: approaches to measuring small geomorphic offsets--challenges and recommendations for active fault studies

Science.gov (United States)

Scharer, Katherine M.; Salisbury, J. Barrett; Arrowsmith, J. Ramon; Rockwell, Thomas K.

2014-01-01

In southern California, where fast slip rates and sparse vegetation contribute to crisp expression of faults and microtopography, field and high‐resolution topographic data (fault, analyze the offset values for concentrations or trends along strike, and infer that the common magnitudes reflect successive surface‐rupturing earthquakes along that fault section. Wallace (1968) introduced the use of such offsets, and the challenges in interpreting their “unique complex history” with offsets on the Carrizo section of the San Andreas fault; these were more fully mapped by Sieh (1978) and followed by similar field studies along other faults (e.g., Lindvall et al., 1989; McGill and Sieh, 1991). Results from such compilations spurred the development of classic fault behavior models, notably the characteristic earthquake and slip‐patch models, and thus constitute an important component of the long‐standing contrast between magnitude–frequency models (Schwartz and Coppersmith, 1984; Sieh, 1996; Hecker et al., 2013). The proliferation of offset datasets has led earthquake geologists to examine the methods and approaches for measuring these offsets, uncertainties associated with measurement of such features, and quality ranking schemes (Arrowsmith and Rockwell, 2012; Salisbury, Arrowsmith, et al., 2012; Gold et al., 2013; Madden et al., 2013). In light of this, the Southern San Andreas Fault Evaluation (SoSAFE) project at the Southern California Earthquake Center (SCEC) organized a combined field activity and workshop (the “Fieldshop”) to measure offsets, compare techniques, and explore differences in interpretation. A thorough analysis of the measurements from the field activity will be provided separately; this paper discusses the complications presented by such offset measurements using two channels from the San Andreas fault as illustrative cases. We conclude with best approaches for future data collection efforts based on input from the Fieldshop.

Off-fault ground ruptures in the Santa Cruz Mountains, California: Ridge-top spreading versus tectonic extension during the 1989 Loma Prieta earthquake

Science.gov (United States)

Ponti, Daniel J.; Wells, Ray E.

1991-01-01

The Ms 7.1 Loma Prieta earthquake of 18 October 1989 produced abundant ground ruptures in an 8 by 4 km area along Summit Road and Skyland Ridge in the Santa Cruz Mountains. Predominantly extensional fissures formed a left-stepping, crudely en echelon pattern along ridges of the hanging-wall block southwest of the San Andreas fault, about 12 km northwest of the epicenter. The fissures are subparallel to the San Andreas fault and appear to be controlled by bedding planes, faults, joints, and other weak zones in the underlying Tertiary sedimentary strata of the hanging-wall block. The pattern of extensional fissures is generally consistent with tectonic extension across the crest of the uplifted hanging-wall block. Also, many displacements in Laurel Creek canyon and along the San Andreas and Sargent faults are consistent with right-lateral reverse faulting inferred for the mainshock. Additional small tensile failures along the axis of the Laurel anticline may reflect growth of the fold during deep-seated compression. However, the larger ridge-top fissures commonly have displacements that are parallel to the north-northeast regional slope directions and appear inconsistent with east-northeast extension expected from this earthquake. Measured cumulative displacements across the ridge crests are at least 35 times larger than that predicted by the geodetically determined surface deformation. These fissures also occur in association with ubiquitous landslide complexes that were reactivated by the earthquake to produce the largest concentration of co-seismic slope failures in the epicentral region. The anomalously large displacements and the apparent slope control of the geometry and displacement of many co-seismic surface ruptures lead us to conclude that gravity is an important driving force in the formation of the ridge-top fissures. Shaking-induced gravitational spreading of ridges and downslope movement may account for 90¿ or more of the observed displacements on

San andreas fault zone head waves near parkfield, california.

Science.gov (United States)

Ben-Zion, Y; Malin, P

1991-03-29

Microearthquake seismograms from the borehole seismic network on the San Andreas fault near Parkfield, California, provide three lines of evidence that first P arrivals are "head" waves refracted along the cross-fault material contrast. First, the travel time difference between these arrivals and secondary phases identified as direct P waves scales linearly with the source-receiver distance. Second, these arrivals have the emergent wave character associated in theory and practice with refracted head waves instead of the sharp first breaks associated with direct P arrivals. Third, the first motion polarities of the emergent arrivals are reversed from those of the direct P waves as predicted by the theory of fault zone head waves for slip on the San Andreas fault. The presence of fault zone head waves in local seismic network data may help account for scatter in earthquake locations and source mechanisms. The fault zone head waves indicate that the velocity contrast across the San Andreas fault near Parkfield is approximately 4 percent. Further studies of these waves may provide a way of assessing changes in the physical state of the fault system.

Investigation of radon-222 in subsurface waters as an earthquake predictor

International Nuclear Information System (INIS)

Smith, A.R.; Bowman, H.R.; Mosier, D.F.; Asaro, F.; Wollenberg, H.A.; King, C.Y.

1975-11-01

Changes of radon-222 content of well waters in seismically active regions may provide earthquake precursor signals, according to reports of recent Chinese and Russian work. A high-precision γ-ray system for continuous monitoring of radon in wells and springs has been developed at the Lawrence Berkeley Laboratory, where monitoring began in April 1975, and has been extended to other sites including the San Andreas fault zone

Investigation of 222Rn in subsurface waters as an earthquake predictor

International Nuclear Information System (INIS)

Smith, A.R.; Bowman, H.R.; Mosier, D.F.; Asaro, F.; Wollenberg, H.A.; King, C.Y.

1976-01-01

Changes of 222 Ra content of well waters in seismically active regions may provide earthquake precursor signals, according to reports of recent Chinese and Russian work. A high-precision γ-ray system for continuous monitoring of radon in wells and springs has been developed at the Lawrence Berkeley Laboratory, where monitoring began in April 1975, and has been extended to other sites including the San Andreas fault zone

Deterministic Earthquake Hazard Assessment by Public Agencies in California

Science.gov (United States)

Mualchin, L.

2005-12-01

Even in its short recorded history, California has experienced a number of damaging earthquakes that have resulted in new codes and other legislation for public safety. In particular, the 1971 San Fernando earthquake produced some of the most lasting results such as the Hospital Safety Act, the Strong Motion Instrumentation Program, the Alquist-Priolo Special Studies Zone Act, and the California Department of Transportation (Caltrans') fault-based deterministic seismic hazard (DSH) map. The latter product provides values for earthquake ground motions based on Maximum Credible Earthquakes (MCEs), defined as the largest earthquakes that can reasonably be expected on faults in the current tectonic regime. For surface fault rupture displacement hazards, detailed study of the same faults apply. Originally, hospital, dam, and other critical facilities used seismic design criteria based on deterministic seismic hazard analyses (DSHA). However, probabilistic methods grew and took hold by introducing earthquake design criteria based on time factors and quantifying "uncertainties", by procedures such as logic trees. These probabilistic seismic hazard analyses (PSHA) ignored the DSH approach. Some agencies were influenced to adopt only the PSHA method. However, deficiencies in the PSHA method are becoming recognized, and the use of the method is now becoming a focus of strong debate. Caltrans is in the process of producing the fourth edition of its DSH map. The reason for preferring the DSH method is that Caltrans believes it is more realistic than the probabilistic method for assessing earthquake hazards that may affect critical facilities, and is the best available method for insuring public safety. Its time-invariant values help to produce robust design criteria that are soundly based on physical evidence. And it is the method for which there is the least opportunity for unwelcome surprises.

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.

Volcano hazards in the San Salvador region, El Salvador

Science.gov (United States)

Major, J.J.; Schilling, S.P.; Sofield, D.J.; Escobar, C.D.; Pullinger, C.R.

2001-01-01

communities. Another concern is a landslide and an associated debris flow (a watery flow of mud, rock, and debris--also known as a lahar) that could occur during periods of no volcanic activity. An event of this type occurred in 1998 at Casita volcano in Nicaragua when extremely heavy rainfall from Hurricane Mitch triggered a landslide that moved down slope and transformed into a rapidly moving debris flow that destroyed two villages and killed more than 2000 people. Historical landslides up to a few hundred thousand cubic meters in volume have been triggered on San Salvador volcano by torrential rainstorms and earthquakes, and some have transformed into debris flows that have inundated populated areas down stream. Destructive rainfall- and earthquake-triggered landslides and debris flows on or near San Salvador volcano in September 1982 and January 2001 demonstrate that such mass movements in El Salvador have also been lethal. This report describes the kinds of hazardous events that occur at volcanoes in general and the kinds of hazardous geologic events that have occurred at San Salvador volcano in the past. The accompanying volcano-hazards-zonation maps show areas that are likely to be at risk when hazardous events occur again.

Los cambios en la política social argentina y el impacto del terremoto de San Juan (1944)

OpenAIRE

Pablo Buchbinder

2014-01-01

El objetivo del artículo consiste en analizar las consecuencias sociales y políticas del terremoto de San Juan. El estudio focaliza en tres aspectos: los relacionados con las colectas de dinero para las víctimas, con las políticas de vivienda y con la aparición de nuevas leyes de adopción de menores. Abstract  The aim of this paper is to analyze the social and political consequences of the earthquake in San Juan. The study focuses on three areas: those related to collecting money for...

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

Science.gov (United States)

Lockner, David A; Morrow, Carolyn; Moore, Diane; Hickman, Stephen

2011-04-07

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 fault. 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 mechanisms. The combination of these measurements of fault core strength with borehole observations 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. ©2011 Macmillan Publishers Limited. All rights reserved

Sensitivity of Earthquake Loss Estimates to Source Modeling Assumptions and Uncertainty

Science.gov (United States)

Reasenberg, Paul A.; Shostak, Nan; Terwilliger, Sharon

2006-01-01

Introduction: This report explores how uncertainty in an earthquake source model may affect estimates of earthquake economic loss. Specifically, it focuses on the earthquake source model for the San Francisco Bay region (SFBR) created by the Working Group on California Earthquake Probabilities. The loss calculations are made using HAZUS-MH, a publicly available computer program developed by the Federal Emergency Management Agency (FEMA) for calculating future losses from earthquakes, floods and hurricanes within the United States. The database built into HAZUS-MH includes a detailed building inventory, population data, data on transportation corridors, bridges, utility lifelines, etc. Earthquake hazard in the loss calculations is based upon expected (median value) ground motion maps called ShakeMaps calculated for the scenario earthquake sources defined in WGCEP. The study considers the effect of relaxing certain assumptions in the WG02 model, and explores the effect of hypothetical reductions in epistemic uncertainty in parts of the model. For example, it addresses questions such as what would happen to the calculated loss distribution if the uncertainty in slip rate in the WG02 model were reduced (say, by obtaining additional geologic data)? What would happen if the geometry or amount of aseismic slip (creep) on the region's faults were better known? And what would be the effect on the calculated loss distribution if the time-dependent earthquake probability were better constrained, either by eliminating certain probability models or by better constraining the inherent randomness in earthquake recurrence? The study does not consider the effect of reducing uncertainty in the hazard introduced through models of attenuation and local site characteristics, although these may have a comparable or greater effect than does source-related uncertainty. Nor does it consider sources of uncertainty in the building inventory, building fragility curves, and other assumptions

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.

A 100-year average recurrence interval for the san andreas fault at wrightwood, california.

Science.gov (United States)

Fumal, T E; Schwartz, D P; Pezzopane, S K; Weldon, R J

1993-01-08

Evidence for five large earthquakes during the past five centuries along the San Andreas fault zone 70 kilometers northeast of Los Angeles, California, indicates that the average recurrence interval and the temporal variability are significantly smaller than previously thought. Rapid sedimentation during the past 5000 years in a 150-meter-wide structural depression has produced a greater than 21-meter-thick sequence of debris flow and stream deposits interbedded with more than 50 datable peat layers. Fault scarps, colluvial wedges, fissure infills, upward termination of ruptures, and tilted and folded deposits above listric faults provide evidence for large earthquakes that occurred in A.D. 1857, 1812, and about 1700, 1610, and 1470.

Simulation of scenario earthquake influenced field by using GIS

Science.gov (United States)

Zuo, Hui-Qiang; Xie, Li-Li; Borcherdt, R. D.

1999-07-01

The method for estimating the site effect on ground motion specified by Borcherdt (1994a, 1994b) is briefly introduced in the paper. This method and the detail geological data and site classification data in San Francisco bay area of California, the United States, are applied to simulate the influenced field of scenario earthquake by GIS technology, and the software for simulating has been drawn up. The paper is a partial result of cooperative research project between China Seismological Bureau and US Geological Survey.

Using low-frequency earthquake families on the San Andreas fault as deep creepmeters

Science.gov (United States)

Thomas, A.; Beeler, N. M.; Bletery, Q.; Burgmann, R.; Shelly, D. R.

2017-12-01

The San Andreas fault hosts tectonic tremor and low-frequency earthquakes (LFEs) similar to those in subduction zone environments. These LFEs are grouped into families based on waveform similarity and locate between 16 and 29 km depth along a 150-km-long section of the fault centered on Parkfield, CA. ­Within individual LFE families event occurrence is not steady. In some families, bursts of a few events recur on timescales of days while in other families there are nearly quiescent periods that often last for months followed by episodes where hundreds of events occur over the course of a few days. These two different styles of LFE occurrence are called continuous and episodic respectively. LFEs are often assumed to reflect persistent regions that periodically fail during the aseismic shear of the surrounding fault allowing them to be used as creepmeters. We test this idea by formalizing the definition of a creepmeter (the LFE occurrence rate is proportional to the local fault slip rate), determining whether this definition is consistent with the observations, and over what timescale. We use the recurrence intervals of LFEs within individual families to create a catalog of LFE bursts. For the episodic families, we consider both longer duration (multiday) inferred creep episodes (dubbed long-timescale episodic) as well as the frequent short-term bursts of events that occur many times during inferred creep episodes (dubbed short-timescale episodic). We then use the recurrence intervals of LFE bursts to estimate the timing, duration, recurrence interval, slip, and slip rate associated with inferred slow slip events. We find that continuous families and the short-timescale episodic families appear to be inconsistent with our definition of a creepmeter (defined on the recurrence interval timescale) because their estimated durations are not physically meaningful. A straight-forward interpretation of the frequent short-term bursts of the continuous and short

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. Copyright © 2016, American Association for the Advancement of Science.

Slip deficit on the san andreas fault at parkfield, california, as revealed by inversion of geodetic data.

Science.gov (United States)

Segall, P; Harris, R

1986-09-26

A network of geodetic lines spanning the San Andreas fault near the rupture zone of the 1966 Parkfield, California, earthquake (magnitude M = 6) has been repeatedly surveyed since 1959. In the study reported here the average rates of line-length change since 1966 were inverted to determine the distribution of interseismic slip rate on the fault. These results indicate that the Parkfield rupture surface has not slipped significantly since 1966. Comparison of the geodetically determined seismic moment of the 1966 earthquake with the interseismic slip-deficit rate suggests that the strain released by the latest shock will most likely be restored between 1984 and 1989, although this may not occur until 1995. These results lend independent support to the earlier forecast of an M = 6 earthquake near Parkfield within 5 years of 1988.

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

Connecting slow earthquakes to huge earthquakes

OpenAIRE

Obara, Kazushige; Kato, Aitaro

2016-01-01

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 th...

Variations in strength and slip rate along the san andreas fault system.

Science.gov (United States)

Jones, C H; Wesnousky, S G

1992-04-03

Convergence across the San Andreas fault (SAF) system is partitioned between strike-slip motion on the vertical SAF and oblique-slip motion on parallel dip-slip faults, as illustrated by the recent magnitude M(s) = 6.0 Palm Springs, M(s) = 6.7 Coalinga, and M(s) = 7.1 Loma Prieta earthquakes. If the partitioning of slip minimizes the work done against friction, the direction of slip during these recent earthquakes depends primarily on fault dip and indicates that the normal stress coefficient and frictional coefficient (micro) vary among the faults. Additionally, accounting for the active dip-slip faults reduces estimates of fault slip rates along the vertical trace of the SAF by about 50 percent in the Loma Prieta and 100 percent in the North Palm Springs segments.

Remote triggering of fault-strength changes on the San Andreas fault at Parkfield.

Science.gov (United States)

Taira, Taka'aki; Silver, Paul G; Niu, Fenglin; Nadeau, Robert M

2009-10-01

Fault strength is a fundamental property of seismogenic zones, and its temporal changes can increase or decrease the likelihood of failure and the ultimate triggering of seismic events. Although changes in fault strength have been suggested to explain various phenomena, such as the remote triggering of seismicity, there has been no means of actually monitoring this important property in situ. Here we argue that approximately 20 years of observation (1987-2008) of the Parkfield area at the San Andreas fault have revealed a means of monitoring fault strength. We have identified two occasions where long-term changes in fault strength have been most probably induced remotely by large seismic events, namely the 2004 magnitude (M) 9.1 Sumatra-Andaman earthquake and the earlier 1992 M = 7.3 Landers earthquake. In both cases, the change possessed two manifestations: temporal variations in the properties of seismic scatterers-probably reflecting the stress-induced migration of fluids-and systematic temporal variations in the characteristics of repeating-earthquake sequences that are most consistent with changes in fault strength. In the case of the 1992 Landers earthquake, a period of reduced strength probably triggered the 1993 Parkfield aseismic transient as well as the accompanying cluster of four M > 4 earthquakes at Parkfield. The fault-strength changes produced by the distant 2004 Sumatra-Andaman earthquake are especially important, as they suggest that the very largest earthquakes may have a global influence on the strength of the Earth's fault systems. As such a perturbation would bring many fault zones closer to failure, it should lead to temporal clustering of global seismicity. This hypothesis seems to be supported by the unusually high number of M >or= 8 earthquakes occurring in the few years following the 2004 Sumatra-Andaman earthquake.

Aseismic Transform Fault Slip at the Mendocino Triple Junction From Characteristically Repeating Earthquakes

Science.gov (United States)

Materna, Kathryn; Taira, Taka'aki; Bürgmann, Roland

2018-01-01

The Mendocino Triple Junction (MTJ), at the northern terminus of the San Andreas Fault system, is an actively deforming plate boundary region with poorly constrained estimates of seismic coupling on most offshore fault surfaces. Characteristically repeating earthquakes provide spatial and temporal descriptions of aseismic creep at the MTJ, including on the oceanic transform Mendocino Fault Zone (MFZ) as it subducts beneath North America. Using a dataset of earthquakes from 2008 to 2017, we find that the easternmost segment of the MFZ displays creep during this period at about 65% of the long-term slip rate. We also find creep at slower rates on the shallower strike-slip interface between the Pacific plate and the North American accretionary wedge, as well as on a fault that accommodates Gorda subplate internal deformation. After a nearby M5.7 earthquake in 2015, we observe a possible decrease in aseismic slip on the near-shore MFZ that lasts from 2015 to at least early 2017.

Golden Gate Bridge response: a study with low-amplitude data from three earthquakes

Science.gov (United States)

Çelebi, Mehmet

2012-01-01

The dynamic response of the Golden Gate Bridge, located north of San Francisco, CA, has been studied previously using ambient vibration data and finite element models. Since permanent seismic instrumentation was installed in 1993, only small earthquakes that originated at distances varying between ~11 to 122 km have been recorded. Nonetheless, these records prompted this study of the response of the bridge to low amplitude shaking caused by three earthquakes. Compared to previous ambient vibration studies, the earthquake response data reveal a slightly higher fundamental frequency (shorter-period) for vertical vibration of the bridge deck center span (~7.7–8.3 s versus 8.2–10.6 s), and a much higher fundamental frequency (shorter period) for the transverse direction of the deck (~11.24–16.3 s versus ~18.2 s). In this study, it is also shown that these two periods are dominant apparent periods representing interaction between tower, cable, and deck.

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

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

Energy Technology Data Exchange (ETDEWEB)

Aagaard, B T; Graves, R W; Rodgers, A; Brocher, T M; Simpson, R W; Dreger, D; Petersson, N A; Larsen, S C; Ma, S; Jachens, R C

2009-11-04

We simulate long-period (T > 1.0-2.0 s) and broadband (T > 0.1 s) ground motions for 39 scenarios 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 MMI VII or greater for the magnitude 7.0 scenario events. Long-period simulations of the 2007 Mw 4.18 Oakland and 2007 Mw 4.5 Alum Rock earthquakes show that the USGS Bay Area Velocity Model version 08.3.0 permits simulation of the amplitude and duration of shaking throughout the San Francisco Bay area, with the greatest accuracy in the Santa Clara Valley (San Jose area). The ground motions 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 at least some of this difference to the relatively narrow width of the Hayward fault ruptures. The simulations suggest that the Spudich and Chiou (2008) directivity corrections to the NGA relations could be improved by including a dependence on the rupture speed and increasing the areal extent of rupture directivity with period. The simulations also indicate that the NGA relations may under-predict amplification in shallow sedimentary basins.

Evolution of the northern santa cruz mountains by advection of crust past a san andreas fault bend.

Science.gov (United States)

Anderson, R S

1990-07-27

The late Quaternary marine terraces near Santa Cruz, California, reflect uplift associated with the nearby restraining bend on the San Andreas fault. Excellent correspondence of the coseismic vertical displacement field caused by the 17 October 1989 magnitude 7.1 Loma Prieta earthquake and the present elevations of these terraces allows calculation of maximum long-term uplift rates 1 to 2 kilometers west of the San Andreas fault of 0.8 millimeters per year. Over several million years, this uplift, in concert with the right lateral translation of the resulting topography, and with continual attack by geomorphic processes, can account for the general topography of the northern Santa Cruz Mountains.

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.

Electromagnetic Imaging of Fluids in the San Andreas Fault; FINAL

International Nuclear Information System (INIS)

Martyn Unsworth

2002-01-01

OAK 270 - Magnetotelluric data were collected on six profiles across the san Andreas Fault at Cholame,Parkfield, and Hollister in Central California. On each profile, high electrical resistivities were imaged west of the fault, and are due to granitic rocks of the Salinian block. East of the fault, lower electrical resistivities are associated with rocks of the Fanciscan formation. On the seismically active Parkfield and Hollister segments, a region of low resistivity was found in the fault zone that extends to a depth of several kilometers. This is due to a zone of fracturing (the damaged zone) that has been infiltrated by saline ground water. The shallowest micro-earthquakers occur at a depth that is coincident with the base of the low resistivity wedge. This strongly suggests that above this depth, the fault rocks are too weak to accumulate sufficient stress for earthquake rupture to occur and fault motion is accommodated through aseismic creep

Filling a gap: Public talks about earthquake preparation and the 'Big One'

Science.gov (United States)

Reinen, L. A.

2013-12-01

Residents of southern California are aware they live in a seismically active area and earthquake drills have trained us to Duck-Cover-Hold On. While many of my acquaintance are familiar with what to do during an earthquake, few have made preparations for living with the aftermath of a large earthquake. The ShakeOut Scenario (Jones et al., USGS Open File Report 2008-1150) describes the physical, social, and economic consequences of a plausible M7.8 earthquake on the southernmost San Andreas Fault. While not detailing an actual event, the ShakeOut Scenario illustrates how individual and community preparation may improve the potential after-affects of a major earthquake in the region. To address the gap between earthquake drills and preparation in my community, for the past several years I have been giving public talks to promote understanding of: the science behind the earthquake predictions; why individual, as well as community, preparation is important; and, ways in which individuals can prepare their home and work environments. The public presentations occur in an array of venues, including elementary school and college classes, a community forum linked with the annual ShakeOut Drill, and local businesses including the local microbrewery. While based on the same fundamental information, each presentation is modified for audience and setting. Assessment of the impact of these talks is primarily anecdotal and includes an increase in the number of venues requesting these talks, repeat invitations, and comments from audience members (sometimes months or years after a talk). I will present elements of these talks, the background information used, and examples of how they have affected change in the earthquake preparedness of audience members. Discussion and suggestions (particularly about effective means of conducting rigorous long-term assessment) are strongly encouraged.

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

Fortnightly modulation of San Andreas tremor and low-frequency earthquakes

Science.gov (United States)

Van Der Elst, Nicholas; Delorey, Andrew; Shelly, David R.; Johnson, Paul

2016-01-01

Earth tides modulate tremor and low-frequency earthquakes (LFEs) on faults in the vicinity of the brittle−ductile (seismic−aseismic) transition. The response to the tidal stress carries otherwise inaccessible information about fault strength and rheology. Here, we analyze the LFE response to the fortnightly tide, which modulates the amplitude of the daily tidal stress over a 14-d cycle. LFE rate is highest during the waxing fortnightly tide, with LFEs most strongly promoted when the daily stress exceeds the previous peak stress by the widest margin. This pattern implies a threshold failure process, with slip initiated when stress exceeds the local fault strength. Variations in sensitivity to the fortnightly modulation may reflect the degree of stress concentration on LFE-producing brittle asperities embedded within an otherwise aseismic fault.

Los cambios en la política social argentina y el impacto del terremoto de San Juan (1944

Directory of Open Access Journals (Sweden)

Pablo Buchbinder

2014-10-01

Full Text Available El objetivo del artículo consiste en analizar las consecuencias sociales y políticas del terremoto de San Juan. El estudio focaliza en tres aspectos: los relacionados con las colectas de dinero para las víctimas, con las políticas de vivienda y con la aparición de nuevas leyes de adopción de menores. Abstract  The aim of this paper is to analyze the social and political consequences of the earthquake in San Juan. The study focuses on three areas: those related to collecting money for victims with housing policies and the emergence of new child adoption laws.

Coulomb Stress Accumulation along the San Andreas Fault System

Science.gov (United States)

Smith, Bridget; Sandwell, David

2003-01-01

Stress accumulation rates along the primary segments of the San Andreas Fault system are computed using a three-dimensional (3-D) elastic half-space model with realistic fault geometry. The model is developed in the Fourier domain by solving for the response of an elastic half-space due to a point vector body force and analytically integrating the force from a locking depth to infinite depth. This approach is then applied to the San Andreas Fault system using published slip rates along 18 major fault strands of the fault zone. GPS-derived horizontal velocity measurements spanning the entire 1700 x 200 km region are then used to solve for apparent locking depth along each primary fault segment. This simple model fits remarkably well (2.43 mm/yr RMS misfit), although some discrepancies occur in the Eastern California Shear Zone. The model also predicts vertical uplift and subsidence rates that are in agreement with independent geologic and geodetic estimates. In addition, shear and normal stresses along the major fault strands are used to compute Coulomb stress accumulation rate. As a result, we find earthquake recurrence intervals along the San Andreas Fault system to be inversely proportional to Coulomb stress accumulation rate, in agreement with typical coseismic stress drops of 1 - 10 MPa. This 3-D deformation model can ultimately be extended to include both time-dependent forcing and viscoelastic response.

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

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.

Nonlinear dynamical triggering of slow slip

Energy Technology Data Exchange (ETDEWEB)

Johnson, Paul A [Los Alamos National Laboratory; Knuth, Matthew W [WISCONSIN; Kaproth, Bryan M [PENN STATE; Carpenter, Brett [PENN STATE; Guyer, Robert A [Los Alamos National Laboratory; Le Bas, Pierre - Yves [Los Alamos National Laboratory; Daub, Eric G [Los Alamos National Laboratory; Marone, Chris [PENN STATE

2010-12-10

triggered slow-slip on the San Andreas Fault at Parkfield, CA., due to December, 2003 Mw6.5 San Simeon Earthquake (Breguier et al., Science 321, p.1478, 2008) shows very similar characteristics to what we observe in the laboratory, suggesting an extremely low in situ effective stress or a weak fault and a nonlinear-dynamical triggering mechanism.

Comparison of the November 2002 Denali and November 2001 Kunlun Earthquakes

Science.gov (United States)

Bufe, C. G.

2002-12-01

Major earthquakes occurred in Tibet on the central Kunlun fault (M 7.8) on November 14, 2001 (Lin and others, 2002) and in Alaska on the central Denali fault (M 7.9) on November 3, 2002. Both earthquakes generated large surface waves (Kunlun Ms 8.0 (USGS) and Denali Ms 8.5). Each event occurred on east-west-trending strike-slip faults and exhibited nearly unilateral rupture propagating several hundred kilometers from west to east. Surface rupture length estimates were about 400 km for Kunlun, 300 km for Denali. Maximum surface faulting and moment release were observed far to the east of the points of rupture initiation. Harvard moment centroids were located east of USGS epicenters by 182 km (Kunlun) and by 126 km (Denali). Maximum surface faulting was observed near 240 km (Kunlun, 16 m left lateral) and near 175 km (Denali, 9 m right lateral) east of the USGS epicenters. Significant thrust components were observed in the initiation of the Denali event (ERI analysis and mapped thrust) and in the termination of the Kunlun rupture, as evidenced by thrust mechanisms of the largest aftershocks which occurred near the eastern part of the Kunlun rupture. In each sequence the largest aftershock was about 2 orders of magnitude smaller than the mainshock. Moment release along the ruptured segments was examined for the 25-year periods preceding the main shocks. The Denali zone shows precursory accelerating moment release with the dominant events occurring on October 22, 1996 (M 5.8) and October 23, 2002 (M 6.7). The Kunlun zone shows nearly constant moment release over time with the last significant event before the main shock occurring on November 26, 2000 (M 5.4). Moment release data are consistent with previous observations of annual periodicity preceding major earthquakes, possibly due to the evolution of a critical state with seasonal and tidal triggering (Varnes and Bufe, 2001). Annual periodicity is also evident for the larger events in the greater San Francisco Bay

Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay region, California: a digital database

Science.gov (United States)

Knudsen, Keith L.; Sowers, Janet M.; Witter, Robert C.; Wentworth, Carl M.; Helley, Edward J.; Nicholson, Robert S.; Wright, Heather M.; Brown, Katherine H.

2000-01-01

This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of fivedata layers (Quaternary deposits, quadrangle index, and three ground effects layers) and two text layers (a labels and leaders layer for Quaternary deposits and for ground effects), (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map, liquefaction interpretation, and the ground effects compendium, and (4) the databse description pamphlet. 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 modern and regionally consistent treatment of Quaternary surficial deposits that builds on the pioneering mapping of Helley and Lajoie (Helley and others, 1979) and such intervening work as Atwater (1982), Helley and others (1994), and Helley and Graymer (1997a and b). Like these earlier studies, the current mapping uses geomorphic expression, pedogenic soils, and inferred depositional environments to define and distinguish the map units. In contrast to the twelve map units of Helley and Lajoie, however, this new map uses a complex stratigraphy of some forty units, which permits a more realistic portrayal of the Quaternary depositional system. The two colored maps provide a regional summary of the new mapping at a scale of 1:275,000, a scale that is sufficient to show the general distribution and relationships of

Analysis of regional deformation and strain accumulation data adjacent to the San Andreas fault

Science.gov (United States)

Turcotte, Donald L.

1991-01-01

A new approach to the understanding of crustal deformation was developed under this grant. This approach combined aspects of fractals, chaos, and self-organized criticality to provide a comprehensive theory for deformation on distributed faults. It is hypothesized that crustal deformation is an example of comminution: Deformation takes place on a fractal distribution of faults resulting in a fractal distribution of seismicity. Our primary effort under this grant was devoted to developing an understanding of distributed deformation in the continental crust. An initial effort was carried out on the fractal clustering of earthquakes in time. It was shown that earthquakes do not obey random Poisson statistics, but can be approximated in many cases by coupled, scale-invariant fractal statistics. We applied our approach to the statistics of earthquakes in the New Hebrides region of the southwest Pacific because of the very high level of seismicity there. This work was written up and published in the Bulletin of the Seismological Society of America. This approach was also applied to the statistics of the seismicity on the San Andreas fault system.

A simulation of the Upper San Fernando dam using a synthesized approach

International Nuclear Information System (INIS)

Beaty, M.H.; Byrne, P.M.

1999-01-01

A mechanics-based approach to assessing post-liquefaction displacements in slopes is discussed. The approach, which involves approximation of soil behaviour by using numerical models, is derived from total stress procedures and is said to have two major advantages: (1) it combines the triggering and post-liquefaction response into one analysis, and (2) it improves the modeling of post-liquefaction element behaviour. Application of the approach is demonstrated through the simulation of the response of the Upper San Fernando dam to the 1971 San Fernando earthquake. Results were compared to the Bartlett and Youd empirical procedure and were found to agree with expectations reasonably well. Viscous damping, blowcount, and residual strength in simple shear were found to be the key variables. Some questions still remain to be answered regarding some of the input parameters, particularly the viscous damping coefficients. Research to further elucidate the mechanism is continuing. 21 refs., 19 figs

Constraints on Friction, Dilatancy, Diffusivity, and Effective Stress From Low-Frequency Earthquake Rates on the Deep San Andreas Fault

Science.gov (United States)

Beeler, N. M.; Thomas, Amanda; Bürgmann, Roland; Shelly, David

2018-01-01

Families of recurring low-frequency earthquakes (LFEs) within nonvolcanic tremor on the San Andreas Fault in central California are sensitive to tidal stresses. LFEs occur at all levels of the tides, are strongly correlated and in phase with the 200 Pa shear stresses, and weakly and not systematically correlated with the 2 kPa tidal normal stresses. We assume that LFEs are small sources that repeatedly fail during shear within a much larger scale, aseismically slipping fault zone and consider two different models of the fault slip: (1) modulation of the fault slip rate by the tidal stresses or (2) episodic slip, triggered by the tides. LFEs are strongly clustered with duration much shorter than the semidiurnal tide; they cannot be significantly modulated on that time scale. The recurrence times of clusters, however, are many times longer than the semidiurnal, leading to an appearance of tidal triggering. In this context we examine the predictions of laboratory-observed triggered frictional (dilatant) fault slip. The undrained end-member model produces no sensitivity to the tidal normal stress, and slip onsets are in phase with the tidal shear stress. The tidal correlation constrains the diffusivity to be less than 1 × 10-6/s and the product of the friction and dilatancy coefficients to be at most 5 × 10-7, orders of magnitude smaller than observed at room temperature. In the absence of dilatancy the effective normal stress at failure would be about 55 kPa. For this model the observations require intrinsic weakness, low dilatancy, and lithostatic pore fluid.

The HayWired Scenario - How Can the San Francisco Bay Region Bounce Back Better?

Science.gov (United States)

Hudnut, K. W.; Wein, A. M.; Cox, D. A.; Perry, S. C.; Porter, K.; Johnson, L. A.; Strauss, J. A.

2017-12-01

The HayWired scenario is a hypothetical yet scientifically realistic and quantitative depiction of a moment magnitude (Mw) 7.0 earthquake occurring on April 18, 2018, at 4:18 p.m. on the Hayward Fault in the east bay part of the San Francisco Bay area, California. The hypothetical earthquake has its epicenter in Oakland, and strong ground shaking from the scenario causes a wide range of severe impacts throughout the greater bay region. In the scenario, the Hayward Fault is ruptured along its length for 83 kilometers (about 52 miles). Building on a decades-long series of efforts to reduce earthquake risk in the SF Bay area, the hypothetical HayWired earthquake is used to examine the well-known earthquake hazard of the Hayward Fault, with a focus on newly emerging vulnerabilities. After a major earthquake disaster, reestablishing water services and food-supply chains are, of course, top priorities. However, problems associated with telecommunication outages or "network congestion" will increase and become more urgent as the bay region deepens its reliance on the "Internet of Things." Communications at all levels are crucial during incident response following an earthquake. Damage to critical facilities (such as power plants) from earthquake shaking and to electrical and telecommunications wires and fiber-optic cables that are severed where they cross a fault rupture can trigger cascading Internet and telecommunications outages, and restoring these services is crucially important for emergency-response coordination. Without good communications, emergency-response efficiency is reduced, and as a result, life-saving response functions can be compromised. For these reasons, the name HayWired was chosen for this scenario to emphasize the need to examine our interconnectedness and reliance on telecommunications and other lifelines (such as water and electricity). Earthquake risk in the SF Bay area has been greatly reduced as a result of previous concerted efforts; for

Correlation of pre-earthquake electromagnetic signals with laboratory and field rock experiments

Directory of Open Access Journals (Sweden)

T. Bleier

2010-09-01

Full Text Available Analysis of the 2007 M5.4 Alum Rock earthquake near San José California showed that magnetic pulsations were present in large numbers and with significant amplitudes during the 2 week period leading up the event. These pulsations were 1–30 s in duration, had unusual polarities (many with only positive or only negative polarities versus both polarities, and were different than other pulsations observed over 2 years of data in that the pulse sequence was sustained over a 2 week period prior to the quake, and then disappeared shortly after the quake. A search for the underlying physics process that might explain these pulses was was undertaken, and one theory (Freund, 2002 demonstrated that charge carriers were released when various types of rocks were stressed in a laboratory environment. It was also significant that the observed charge carrier generation was transient, and resulted in pulsating current patterns. In an attempt to determine if this phenomenon occurred outside of the laboratory environment, the authors scaled up the physics experiment from a relatively small rock sample in a dry laboratory setting, to a large 7 metric tonne boulder comprised of Yosemite granite. This boulder was located in a natural, humid (above ground setting at Bass Lake, Ca. The boulder was instrumented with two Zonge Engineering, Model ANT4 induction type magnetometers, two Trifield Air Ion Counters, a surface charge detector, a geophone, a Bruker Model EM27 Fourier Transform Infra Red (FTIR spectrometer with Sterling cycle cooler, and various temperature sensors. The boulder was stressed over about 8 h using expanding concrete (Bustar^tm, until it fractured into three major pieces. The recorded data showed surface charge build up, magnetic pulsations, impulsive air conductivity changes, and acoustical cues starting about 5 h before the boulder actually broke. These magnetic and air conductivity pulse signatures resembled both the laboratory

San Francisco folio, California, Tamalpais, San Francisco, Concord, San Mateo, and Haywards quadrangles

Science.gov (United States)

Lawson, Andrew Cowper

1914-01-01

The five sheets of the San Francisco folio the Tamalpais, Ban Francisco, Concord, Ban Mateo, and Haywards sheets map a territory lying between latitude 37° 30' and 38° and longitude 122° and 122° 45'. Large parts of four of these sheets cover the waters of the Bay of San Francisco or of the adjacent Pacific Ocean. (See fig. 1.) Within the area mapped are the cities of San Francisco, Oakland, Berkeley, Alameda, Ban Rafael, and San Mateo, and many smaller towns and villages. These cities, which have a population aggregating about 750,000, together form the largest and most important center of commercial and industrial activity on the west coast of the United States. The natural advantages afforded by a great harbor, where the railways from the east meet the ships from all ports of the world, have determined the site of a flourishing cosmopolitan, commercial city on the shores of San Francisco Bay. The bay is encircled by hilly and mountainous country diversified by fertile valley lands and divides the territory mapped into two rather contrasted parts, the western part being again divided by the Golden Gate. It will therefore be convenient to sketch the geographic features under four headings (1) the area east of San Francisco Bay; (2) the San Francisco Peninsula; (3) the Marin Peninsula; (4) San Francisco Bay. (See fig. 2.)

Earthquakes in El Salvador: a descriptive study of health concerns in a rural community and the clinical implications: Part III--Mental health and psychosocial effects.

Science.gov (United States)

Woersching, Joanna C; Snyder, Audrey E

2004-01-01

In 2001, the mountain town of San Sebastian, El Salvador experienced a series of earthquakes that affected the livelihood of its people. A convenience sample of 100 households of 594 inhabitants of San Sebastian and the surrounding rural farming areas was completed. One study participant for each household was evaluated for mental health and psychosocial changes after the earthquakes. The participant's questionnaire was used to investigate the relationship between physical health, access to health care, housing, food and water, and the occurrence of negative mental health markers six months after the disasters. Findings indicate that the majority (67%) of respondents experienced 6 or more mental health complaints. Risk factors associated with multiple negative mental health symptoms included change in household income and loss of job, a new illness or a new injury in the household, reliance on healthcare services since the earthquake, and managing a chronic illness. Findings indicate a need for rapid, acute mental health screening with at-risk groups and the need to educate the entire community regarding what medical and mental health treatments are available to reduce barriers to treatment and increase public awareness.

Potential Effects of a Scenario Earthquake on the Economy of Southern California: Labor Market 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 economic Super Sectors 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 Super Sector to each Instrumental Intensity level. The analysis concerns the direct effect of the scenario earthquake on economic sectors and provides a baseline for the indirect and interactive analysis of an input-output model of the regional economy. 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 the North American Industry Classification System. According to the analysis results, nearly 225,000 business

Impulsive radon emanation on a creeping segment of the San Andreas fault, California

International Nuclear Information System (INIS)

King, C.-Y.

1984-01-01

Radon emanation was continuously monitored for several months at two locations along a creeping segment of the San Andreas fault in central California. The recorded emanations showed several impulsive increases that lasted as much as five hours with amplitudes considerably larger than meteorologically induced diurnal variations. Some of the radon increases were accompanied or followed by earthquakes or fault-creep events. They were possibly the result of some sudden outbursts of relatively radon-rich ground gas, sometimes triggered by crustal deformation or vibration. (Auth.)

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

The Implications of Strike-Slip Earthquake Source Properties on the Transform Boundary Development Process

Science.gov (United States)

Neely, J. S.; Huang, Y.; Furlong, K.

2017-12-01

Subduction-Transform Edge Propagator (STEP) faults, produced by the tearing of a subducting plate, allow us to study the development of a transform plate boundary and improve our understanding of both long-term geologic processes and short-term seismic hazards. The 280 km long San Cristobal Trough (SCT), formed by the tearing of the Australia plate as it subducts under the Pacific plate near the Solomon and Vanuatu subduction zones, shows along-strike variations in earthquake behaviors. The segment of the SCT closest to the tear rarely hosts earthquakes > Mw 6, whereas the SCT sections more than 80 - 100 km from the tear experience Mw7 earthquakes with repeated rupture along the same segments. To understand the effect of cumulative displacement on SCT seismicity, we analyze b-values, centroid-time delays and corner frequencies of the SCT earthquakes. We use the spectral ratio method based on Empirical Green's Functions (eGfs) to isolate source effects from propagation and site effects. We find high b-values along the SCT closest to the tear with values decreasing with distance before finally increasing again towards the far end of the SCT. Centroid time-delays for the Mw 7 strike-slip earthquakes increase with distance from the tear, but corner frequency estimates for a recent sequence of Mw 7 earthquakes are approximately equal, indicating a growing complexity in earthquake behavior with distance from the tear due to a displacement-driven transform boundary development process (see figure). The increasing complexity possibly stems from the earthquakes along the eastern SCT rupturing through multiple asperities resulting in multiple moment pulses. If not for the bounding Vanuatu subduction zone at the far end of the SCT, the eastern SCT section, which has experienced the most displacement, might be capable of hosting larger earthquakes. When assessing the seismic hazard of other STEP faults, cumulative fault displacement should be considered a key input in

Long-Term Fault Memory: A New Time-Dependent Recurrence Model for Large Earthquake Clusters on Plate Boundaries

Science.gov (United States)

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

2017-12-01

A challenge for earthquake hazard assessment is that geologic records often show large earthquakes occurring in temporal clusters separated by periods of quiescence. For example, in Cascadia, a paleoseismic record going back 10,000 years shows four to five clusters separated by approximately 1,000 year gaps. If we are still in the cluster that began 1700 years ago, a large earthquake is likely to happen soon. If the cluster has ended, a great earthquake is less likely. For a Gaussian distribution of recurrence times, the probability of an earthquake in the next 50 years is six times larger if we are still in the most recent cluster. Earthquake hazard assessments typically employ one of two recurrence models, neither of which directly incorporate clustering. In one, earthquake probability is time-independent and modeled as Poissonian, so an earthquake is equally likely at any time. The fault has no "memory" because when a prior earthquake occurred has no bearing on when the next will occur. The other common model is a time-dependent earthquake cycle in which the probability of an earthquake increases with time until one happens, after which the probability resets to zero. Because the probability is reset after each earthquake, the fault "remembers" only the last earthquake. This approach can be used with any assumed probability density function for recurrence times. We propose an alternative, Long-Term Fault Memory (LTFM), a modified earthquake cycle model where the probability of an earthquake increases with time until one happens, after which it decreases, but not necessarily to zero. Hence the probability of the next earthquake depends on the fault's history over multiple cycles, giving "long-term memory". Physically, this reflects an earthquake releasing only part of the elastic strain stored on the fault. We use the LTFM to simulate earthquake clustering along the San Andreas Fault and Cascadia. In some portions of the simulated earthquake history, events would

San Andreas Fault, Southern California , Radar Image, Wrapped Color as Height

Science.gov (United States)

2000-01-01

This topographic radar image vividly displays California's famous San Andreas Fault along the southwestern edge of the Mojave Desert, 75 kilometers (46 miles) north of downtown Los Angeles. The entire segment of the fault shown in this image last ruptured during the Fort Tejon earthquake of 1857. This was one of the greatest earthquakes ever recorded in the U.S., and it left an amazing surface rupture scar over 350 kilometers in length along the San Andreas. Were the Fort Tejon shock to happen today, the damage would run into billions of dollars, and the loss of life would likely be substantial, as the communities of Wrightwood, Palmdale, and Lancaster (among others) all lie upon or near the 1857 rupture area. The Lancaster/Palmdale area appears as bright patches just below the center of the image and the San Gabriel Mountains fill the lower left half of the image. At the extreme lower left is Pasadena. High resolution topographic data such as these are used by geologists to study the role of active tectonics in shaping the landscape, and to produce earthquake hazard maps.This image combines two types of data from the Shuttle Radar Topography Mission. The image brightness corresponds to the strength of the radar signal reflected from the ground, while colors show the elevation as measured by SRTM. Each cycle of colors (from pink through blue back to pink) represents an equal amount of elevation difference (400 meters, or 1300 feet) similar to contour lines on a standard topographic map. This image contains about 2400 meters (8000 feet) of total relief.The Shuttle Radar Topography Mission (SRTM), launched on February 11,2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an

Surface-seismic imaging for nehrp soil profile classifications and earthquake hazards in urban areas

Science.gov (United States)

Williams, R.A.; Stephenson, W.J.; Odum, J.K.

1998-01-01

We acquired high-resolution seismic-refraction data on the ground surface in selected areas of the San Fernando Valley (SFV) to help explain the earthquake damage patterns and the variation in ground motion caused by the 17 January 1994 magnitude 6.7 Northridge earthquake. We used these data to determine the compressional- and shear-wave velocities (Vp and Vs) at 20 aftershock recording sites to 30-m depth ( V??s30, and V??p30). Two other sites, located next to boreholes with downhole Vp and Vs data, show that we imaged very similar seismic-vefocity structures in the upper 40 m. Overall, high site response appears to be associated with tow Vs in the near surface, but there can be a wide rangepf site amplifications for a given NEHRP soil type. The data suggest that for the SFV, if the V??s30 is known, we can determine whether the earthquake ground motion will be amplified above a factor of 2 relative to a local rock site.

Earthquakes

Science.gov (United States)

An earthquake happens when two blocks of the earth suddenly slip past one another. Earthquakes strike suddenly, violently, and without warning at any time of the day or night. If an earthquake occurs in a populated area, it may cause ...

Update of Earthquake Strong-Motion Instrumentation at Lawrence Livermore National Laboratory

Energy Technology Data Exchange (ETDEWEB)

Murray, Robert C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2013-09-01

Following the January 1980 earthquake that was felt at Lawrence Livermore National Laboratory (LLNL), a network of strong-motion accelerographs was installed at LLNL. Prior to the 1980 earthquake, there were no accelerographs installed. The ground motion from the 1980 earthquake was estimated from USGS instruments around the Laboratory to be between 0.2 – 0.3 g horizontal peak ground acceleration. These instruments were located at the Veterans Hospital, 5 miles southwest of LLNL, and in San Ramon, about 12 miles west of LLNL. In 2011, the Department of Energy (DOE) requested to know the status of our seismic instruments. We conducted a survey of our instrumentation systems and responded to DOE in a letter. During this survey, it was found that the recorders in Buildings 111 and 332 were not operational. The instruments on Nova had been removed, and only three of the 10 NIF instruments installed in 2005 were operational (two were damaged and five had been removed from operation at the request of the program). After the survey, it was clear that the site seismic instrumentation had degraded substantially and would benefit from an overhaul and more attention to ongoing maintenance. LLNL management decided to update the LLNL seismic instrumentation system. The updated system is documented in this report.

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

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.

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

Seismic Evidence for Conjugate Slip and Block Rotation Within the San Andreas Fault System, Southern California

Science.gov (United States)

Nicholson, Craig; Seeber, Leonardo; Williams, Patrick; Sykes, Lynn R.

1986-08-01

The pattern of seismicity in southern California indicates that much of the activity is presently occurring on secondary structures, several of which are oriented nearly orthogonal to the strikes of the major through-going faults. Slip along these secondary transverse features is predominantly left-lateral and is consistent with the reactivation of conjugate faults by the current regional stress field. Near the intersection of the San Jacinto and San Andreas faults, however, these active left-lateral faults appear to define a set of small crustal blocks, which in conjunction with both normal and reverse faulting earthquakes, suggests contemporary clockwise rotation as a result of regional right-lateral shear. Other left-lateral faults representing additional rotating block systems are identified in adjacent areas from geologic and seismologic data. Many of these structures predate the modern San Andreas system and may control the pattern of strain accumulation in southern California. Geodetic and paleomagnetic evidence confirm that block rotation by strike-slip faulting is nearly ubiquitous, particularly in areas where shear is distributed, and that it accommodates both short-term elastic and long-term nonelastic strain. A rotating block model accounts for a number of structural styles characteristic of strike-slip deformation in California, including: variable slip rates and alternating transtensional and transpressional features observed along strike of major wrench faults; domains of evenly-spaced antithetic faults that terminate against major fault boundaries; continued development of bends in faults with large lateral displacements; anomalous focal mechanisms; and differential uplift in areas otherwise expected to experience extension and subsidence. Since block rotation requires a detachment surface at depth to permit rotational movement, low-angle structures like detachments, of either local or regional extent, may be involved in the contemporary strike

Earthquake prediction

International Nuclear Information System (INIS)

Ward, P.L.

1978-01-01

The state of the art of earthquake prediction is summarized, the possible responses to such prediction are examined, and some needs in the present prediction program and in research related to use of this new technology are reviewed. Three basic aspects of earthquake prediction are discussed: location of the areas where large earthquakes are most likely to occur, observation within these areas of measurable changes (earthquake precursors) and determination of the area and time over which the earthquake will occur, and development of models of the earthquake source in order to interpret the precursors reliably. 6 figures

Episodic radon changes in subsurface soil gas along active faults and possible relation to earthquakes

International Nuclear Information System (INIS)

King, C.

1980-01-01

Subsurface soil gas along active faults in central California has been continuously monitored by the Track Etch method to test whether its radon-isotope content may show any premonitory changes useful for earthquake prediction. The monitoring network was installed in May 1975 and has since been gradually expanded to consist of more than 60 stations along a 380-km section of the San Andreas fault system between Santa Rosa and Cholame. This network has recorded several episodes, each lasting several weeks to several months, during which the radon concentration increased by a factor of approximately 2 above average along some long, but limited, fault segments (approx.100 km). These episodes occurred in different seasons and do not appear to be systematically related to changes in meteorological conditions. However, they coincided reasonably well in time and space with larger local earthquakes above a threshold magnitude of about 4.0. These episodic radon changes may be caused by a changing outgassing rate in the fault zones in response to some episodic strain changes, which incidentally caused the earthquakes

Triggered surface slips in the Salton Trough associated with the 1999 Hector Mine, California, earthquake

Science.gov (United States)

Rymer, M.J.; Boatwright, J.; Seekins, L.C.; Yule, J.D.; Liu, J.

2002-01-01

Surface fracturing occurred along the southern San Andreas, Superstition Hills, and Imperial faults in association with the 16 October 1999 (Mw 7.1) Hector Mine earthquake, making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the Salton Trough. Fractures associated with the event formed discontinuous breaks over a 39-km-long stretch of the San Andreas fault, from the Mecca Hills southeastward to Salt Creek and Durmid Hill, a distance from the epicenter of 107 to 139 km. Sense of slip was right lateral; only locally was there a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 13 mm. Maximum slip values in 1999 and earlier triggered slips are most common in the central Mecca Hills. Field evidence indicates a transient opening as the Hector Mine seismic waves passed the southern San Andreas fault. Comparison of nearby strong-motion records indicates several periods of relative opening with passage of the Hector Mine seismic wave-a similar process may have contributed to the field evidence of a transient opening. Slip on the Superstition Hills fault extended at least 9 km, at a distance from the Hector Mine epicenter of about 188 to 196 km. This length of slip is a minimum value, because we saw fresh surface breakage extending farther northwest than our measurement sites. Sense of slip was right lateral; locally there was a minor (~1 mm) vertical component of slip. Dextral slip ranged from 1 to 18 mm, with the largest amounts found distributed (or skewed) away from the Hector Mine earthquake source. Slip triggered on the Superstition Hills fault commonly is skewed away from the earthquake source, most notably in 1968, 1979, and 1999. Surface slip on the Imperial fault and within the Imperial Valley extended about 22 km, representing a distance from the Hector Mine epicenter of about 204 to 226 km. Sense of slip dominantly was right lateral; the right-lateral component of slip

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

Science.gov (United States)

2010-07-02

...-AA00 Safety Zone; San Diego POPS Fireworks, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary... waters of San Diego Bay in support of the San Diego POPS Fireworks. This safety zone is necessary to... San Diego POPS Fireworks, which will include fireworks presentations conducted from a barge in San...

Seismic trapped modes in the oroville and san andreas fault zones.

Science.gov (United States)

Li, Y G; Leary, P; Aki, K; Malin, P

1990-08-17

Three-component borehole seismic profiling of the recently active Oroville, California, normal fault and microearthquake event recording with a near-fault three-component borehole seismometer on the San Andreas fault at Parkfield, California, have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals. These wave trains are interpreted as fault zone-trapped seismic modes. Parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers, as shallow as 4 kilometers, and extend 12 kilometers along the fault on either side of the recording station. Selected Oroville and Parkfield wave forms are modeled as the fundamental and first higher trapped SH modes of a narrow low-velocity layer at the fault. Modeling results suggest that the Oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second, whereas at Parkfield, the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1.1 to 1.8 kilometers per second. These low-velocity layers are probably the rupture planes on which earthquakes occur.

Earthquakes in El Salvador: a descriptive study of health concerns in a rural community and the clinical implications, part I.

Science.gov (United States)

Woersching, Joanna C; Snyder, Audrey E

2003-01-01

This is the first article in a series that evaluates the health concerns of people living in a Salvadoran rural community after major earthquakes. Part I reviews the background, methods, and results of post-earthquake conditions with regards to healthcare, access to healthcare, housing, food, water and sanitation. Part II reviews the implications of these results and recommendations for improvements within the community. Part III investigates the psychosocial and mental health consequences of the earthquakes and provides suggestions for improved mental health awareness, assessment, and intervention. El Salvador experienced 2 major earthquakes in January and February 2001. This study evaluates the effects of the earthquakes on the health practices in the rural town of San Sebastian. The research was conducted with use of a convenience sample survey of subjects affected by the earthquakes. The sample included 594 people within 100 households. The 32-question survey assessed post-earthquake conditions in the areas of health care and access to care, housing, food and water, and sanitation. Communicable diseases affected a number of family members. After the earthquakes, 38% of households reported new injuries, and 79% reported acute exacerbations of chronic illness. Rural inhabitants were 30% more likely to have an uninhabitable home than were urban inhabitants. Concerns included safe housing, water purification, and waste elimination. The findings indicate a need for greater public health awareness and community action to adapt living conditions after a disaster and prevent the spread of communicable disease.

Long Period Earthquakes Beneath California's Young and Restless Volcanoes

Science.gov (United States)

Pitt, A. M.; Dawson, P. B.; Shelly, D. R.; Hill, D. P.; Mangan, M.

2013-12-01

The newly established USGS California Volcano Observatory has the broad responsibility of monitoring and assessing hazards at California's potentially threatening volcanoes, most notably Mount Shasta, Medicine Lake, Clear Lake Volcanic Field, and Lassen Volcanic Center in northern California; and Long Valley Caldera, Mammoth Mountain, and Mono-Inyo Craters in east-central California. Volcanic eruptions occur in California about as frequently as the largest San Andreas Fault Zone earthquakes-more than ten eruptions have occurred in the last 1,000 years, most recently at Lassen Peak (1666 C.E. and 1914-1917 C.E.) and Mono-Inyo Craters (c. 1700 C.E.). The Long Valley region (Long Valley caldera and Mammoth Mountain) underwent several episodes of heightened unrest over the last three decades, including intense swarms of volcano-tectonic (VT) earthquakes, rapid caldera uplift, and hazardous CO2 emissions. Both Medicine Lake and Lassen are subsiding at appreciable rates, and along with Clear Lake, Long Valley Caldera, and Mammoth Mountain, sporadically experience long period (LP) earthquakes related to migration of magmatic or hydrothermal fluids. Worldwide, the last two decades have shown the importance of tracking LP earthquakes beneath young volcanic systems, as they often provide indication of impending unrest or eruption. Herein we document the occurrence of LP earthquakes at several of California's young volcanoes, updating a previous study published in Pitt et al., 2002, SRL. All events were detected and located using data from stations within the Northern California Seismic Network (NCSN). Event detection was spatially and temporally uneven across the NCSN in the 1980s and 1990s, but additional stations, adoption of the Earthworm processing system, and heightened vigilance by seismologists have improved the catalog over the last decade. LP earthquakes are now relatively well-recorded under Lassen (~150 events since 2000), Clear Lake (~60 events), Mammoth Mountain

Coulomb stress interactions among M≥5.9 earthquakes in the Gorda deformation zone and on the Mendocino Fracture Zone, Cascadia megathrust, and northern San Andreas fault

Science.gov (United States)

Rollins, John C.; Stein, Ross S.

2010-01-01

The Gorda deformation zone, a 50,000 km2 area of diffuse shear and rotation offshore northernmost California, has been the site of 20 M ≥ 5.9 earthquakes on four different fault orientations since 1976, including four M ≥ 7 shocks. This is the highest rate of large earthquakes in the contiguous United States. We calculate that the source faults of six recent M ≥ 5.9 earthquakes had experienced ≥0.6 bar Coulomb stress increases imparted by earthquakes that struck less than 9 months beforehand. Control tests indicate that ≥0.6 bar Coulomb stress interactions between M ≥ 5.9 earthquakes separated by Mw = 7.3 Trinidad earthquake are consistent with the locations of M ≥ 5.9 earthquakes in the Gorda zone until at least 1995, as well as earthquakes on the Mendocino Fault Zone in 1994 and 2000. Coulomb stress changes imparted by the 1980 earthquake are also consistent with its distinct elbow-shaped aftershock pattern. From these observations, we derive generalized static stress interactions among right-lateral, left-lateral and thrust faults near triple junctions.

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.

Preliminary Monitoring of Soil gas Radon in Potentially Active Faults, San Sai District, Chiang Mai Province, Thailand

Science.gov (United States)

Pondthai, P.; Udphuay, S.

2013-05-01

The magnitude of 5.1 Mw earthquake occurred in San Sai District, Chiang Mai Province, Thailand in December 2006 was considered an uncommon event due to the fact that there was no statistical record of such significant earthquake in the area. Therefore the earthquake might have been associated with a potentially active fault zone within the area. The objective of this study is to measure soil gas radon across this unknown fault zone within the Chiang Mai Basin, northern Thailand. Two profiles traversing the expected fault zone of soil gas radon measurements have been monitored, using TASTRAK solid state track nuclear detectors (SSNTDs). Radon signals from three periods of measurement show a distinctive consistent spatial distribution pattern. Anomalous radon areas along the profiles are connected to fault locations previously interpreted from other geophysical survey results. The increased radon signal changes from the radon background level with the signal-to-background ratio above 3 are considered anomalous. Such pattern of radon anomaly supports the existence of the faults. The radon measurement, therefore is a powerful technique in mapping active fault zone.

Status of Public Earthquake Early Warning in the U.S

Science.gov (United States)

Given, D. D.

2013-12-01

Earthquake Early Warning (EEW) is a proven use of seismological science that can give people and businesses outside the epicentral area of a large earthquake up to a minute to take protective actions before the most destructive shaking hits them. Since 2006 several organizations have been collaborating to create such a system in the United States. These groups include the US Geological Survey, Caltech, UC Berkeley, the University of Washington, the Southern California Earthquake Center, the Swiss Federal Institute of Technology, Zürich, the California Office of Emergency Services, and the California Geological Survey. A demonstration version of the system, called ShakeAlert, began sending test notifications to selected users in California in January 2012. In August 2012 San Francisco's Bay Area Rapid Transit district began slowing and stopping trains in response to strong ground shaking. The next step in the project is to progress to a production prototype for the west coast. The system is built on top of the considerable technical and organizational earthquake monitoring infrastructure of the Advanced National Seismic System (ANSS). While a fully functional, robust, public EEW system will require significant new investment and development in several major areas, modest progress is being made with current resources. First, high-quality sensors must be installed with sufficient density, particularly near source faults. Where possible, we are upgrading and augmenting the existing ANSS networks on the west coast. Second, data telemetry from those sensors must be engineered for speed and reliability. Next, robust central processing infrastructure is being designed and built. Also, computer algorithms to detect and characterize the evolving earthquake must be further developed and tested. Last year the Gordon and Betty Moore Foundation funded USGS, Caltech, UCB and UW to accelerate R&D efforts. Every available means of distributing alerts must be used to insure the

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

San Andreas Fault, Southern California, Shaded relief, wrapped color as height

Science.gov (United States)

2000-01-01

This topographic image vividly displays California's famous San Andreas Fault along the southwestern edge of the Mojave Desert, 75 kilometers (46 miles) north of downtown Los Angeles. The entire segment of the fault shown in this image last ruptured during the Fort Tejon earthquake of 1857. This was one of the greatest earthquakes ever recorded in the U.S., and it left an amazing surface rupture scar over 350 kilometers in length along the San Andreas. Were the Fort Tejon shock to happen today, the damage would run into billions of dollars, and the loss of life would likely be substantial, as the communities of Wrightwood, Palmdale, and Lancaster (among others) all lie upon or near the 1857 rupture area. The San Gabriel Mountains fill the lower left half of the image. At the extreme lower left is Pasadena. High resolution topographic data such as these are used by geologists to study the role of active tectonics in shaping the landscape, and to produce earthquake hazard maps.This image was generated using topographic data from the Shuttle Radar Topography Mission. Colors show the elevation as measured by SRTM. Each cycle of colors (from pink through blue back to pink) represents an equal amount of elevation difference (400 meters, or 1300 feet) similar to contour lines on a standard topographic map. This image contains about 2400 meters (8000 feet) of total relief. For the shading, a computer-generated artificial light source illuminates the elevation data to produce a pattern of light and shadows. Slopes facing the light appear bright, while those facing away are shaded. Shaded relief maps are commonly used in applications such as geologic mapping and land use planning.The Shuttle Radar Topography Mission (SRTM), launched on February 11,2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three

Geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the San Jacinto fault zone, southern California

Science.gov (United States)

Langenheim, V.E.; Jachens, R.C.; Morton, D.M.; Kistler, R.W.; Matti, J.C.

2004-01-01

We examine the role of preexisting crustal structure within the Peninsular Ranges batholith on determining the location of the San Jacinto fault zone by analysis of geophysical anomalies and initial strontium ratio data. A 1000-km-long boundary within the Peninsular Ranges batholith, separating relatively mafic, dense, and magnetic rocks of the western Peninsular Ranges batholith from the more felsic, less dense, and weakly magnetic rocks of the eastern Peninsular Ranges batholith, strikes north-northwest toward the San Jacinto fault zone. Modeling of the gravity and magnetic field anomalies caused by this boundary indicates that it extends to depths of at least 20 km. The anomalies do not cross the San Jacinto fault zone, but instead trend northwesterly and coincide with the fault zone. A 75-km-long gradient in initial strontium ratios (Sri) in the eastern Peninsular Ranges batholith coincides with the San Jacinto fault zone. Here rocks east of the fault are characterized by Sri greater than 0.706, indicating a source of largely continental crust, sedimentary materials, or different lithosphere. We argue that the physical property contrast produced by the Peninsular Ranges batholith boundary provided a mechanically favorable path for the San Jacinto fault zone, bypassing the San Gorgonio structural knot as slip was transferred from the San Andreas fault 1.0-1.5 Ma. Two historical M6.7 earthquakes may have nucleated along the Peninsular Ranges batholith discontinuity in San Jacinto Valley, suggesting that Peninsular Ranges batholith crustal structure may continue to affect how strain is accommodated along the San Jacinto fault zone. ?? 2004 Geological Society of America.

Overview of SAFOD Phases 1 and 2: Drilling, Sampling and Measurements in the San Andreas Fault Zone at Seismogenic Depth

Science.gov (United States)

Zoback, M. D.; Hickman, S.; Ellsworth, W.

2005-12-01

In this talk we provide an overview of on-site drilling, sampling and downhole measurement activities associated with the first two Phases of the San Andreas Fault Observatory at Depth. SAFOD is located at the transition between the creeping and locked sections of the fault, 9 km NW of Parkfield, CA. A 2.1 km deep vertical pilot hole was drilled at the site in 2002. The SAFOD main borehole was drilled vertically to a depth of 1.5 km and then deviated at an average angle of 55° to vertical, passing beneath the surface trace of the San Andreas fault, 1.8 km to the NW at a depth of 3.2 km. Repeating microearthquakes on the San Andreas define the main active fault trace at depth, as well as a secondary active fault about 250 m to the SW (i.e., closer to SAFOD). The hole was rotary drilled, comprehensive cuttings were obtained and a real-time analysis of gases in the drilling mud was carried out. Spot cores were obtained at three depths (at casing set points) in the shallow granite and deeper sedimentary rocks penetrated by the hole, augmented by over fifty side-wall cores. Continuous coring of the San Andreas Fault Zone will be carried out in Phase 3 of the project in the summer of 2007. In addition to sampling mud gas, discrete fluid and gas samples were obtained at several depths for geochemical analysis. Real-time geophysical measurements were made while drilling through most of the San Andreas Fault Zone. A suite of "open hole" geophysical measurements were also made over essentially the entire depth of the hole. Construction of the multi-component SAFOD observatory is well underway, with a seismometer and tiltmeter operating at 1 km depth in the pilot hole and a fiber-optic laser strainmeter cemented behind casing in the main hole. A seismometer deployed at depth in the hole between Phases 1 and 2 detected one of the target earthquakes. A number of surface-to-borehole seismic experiments have been carried out to characterize seismic velocities and structures at

Analysis of earthquake clustering and source spectra in the Salton Sea Geothermal Field

Science.gov (United States)

Cheng, Y.; Chen, X.

2015-12-01

The Salton Sea Geothermal field is located within the tectonic step-over between San Andreas Fault and Imperial Fault. Since the 1980s, geothermal energy exploration has resulted with step-like increase of microearthquake activities, which mirror the expansion of geothermal field. Distinguishing naturally occurred and induced seismicity, and their corresponding characteristics (e.g., energy release) is important for hazard assessment. Between 2008 and 2014, seismic data recorded by a local borehole array were provided public access from CalEnergy through SCEC data center; and the high quality local recording of over 7000 microearthquakes provides unique opportunity to sort out characteristics of induced versus natural activities. We obtain high-resolution earthquake location using improved S-wave picks, waveform cross-correlation and a new 3D velocity model. We then develop method to identify spatial-temporally isolated earthquake clusters. These clusters are classified into aftershock-type, swarm-type, and mixed-type (aftershock-like, with low skew, low magnitude and shorter duration), based on the relative timing of largest earthquakes and moment-release. The mixed-type clusters are mostly located at 3 - 4 km depth near injection well; while aftershock-type clusters and swarm-type clusters also occur further from injection well. By counting number of aftershocks within 1day following mainshock in each cluster, we find that the mixed-type clusters have much higher aftershock productivity compared with other types and historic M4 earthquakes. We analyze detailed spatial variation of 'b-value'. We find that the mixed-type clusters are mostly located within high b-value patches, while large (M>3) earthquakes and other types of clusters are located within low b-value patches. We are currently processing P and S-wave spectra to analyze the spatial-temporal correlation of earthquake stress parameter and seismicity characteristics. Preliminary results suggest that the

Spatial-temporal variation of low-frequency earthquake bursts near Parkfield, California

Science.gov (United States)

Wu, Chunquan; Guyer, Robert; Shelly, David R.; Trugman, D.; Frank, William; Gomberg, Joan S.; Johnson, P.

2015-01-01

Tectonic tremor (TT) and low-frequency earthquakes (LFEs) have been found in the deeper crust of various tectonic environments globally in the last decade. The spatial-temporal behaviour of LFEs provides insight into deep fault zone processes. In this study, we examine recurrence times from a 12-yr catalogue of 88 LFE families with ∼730 000 LFEs in the vicinity of the Parkfield section of the San Andreas Fault (SAF) in central California. We apply an automatic burst detection algorithm to the LFE recurrence times to identify the clustering behaviour of LFEs (LFE bursts) in each family. We find that the burst behaviours in the northern and southern LFE groups differ. Generally, the northern group has longer burst duration but fewer LFEs per burst, while the southern group has shorter burst duration but more LFEs per burst. The southern group LFE bursts are generally more correlated than the northern group, suggesting more coherent deep fault slip and relatively simpler deep fault structure beneath the locked section of SAF. We also found that the 2004 Parkfield earthquake clearly increased the number of LFEs per burst and average burst duration for both the northern and the southern groups, with a relatively larger effect on the northern group. This could be due to the weakness of northern part of the fault, or the northwesterly rupture direction of the Parkfield earthquake.

20 cool facts about the New Madrid Seismic Zone-Commemorating the bicentennial of the New Madrid earthquake sequence, December 1811-February 1812 [poster

Science.gov (United States)

Williams, R.A.; McCallister, N.S.; Dart, R.L.

2011-01-01

This poster summarizes a few of the more significant facts about the series of large earthquakes that struck the New Madrid seismic zone of southeastern Missouri, northeastern Arkansas, and adjacent parts of Tennessee and Kentucky from December 1811 to February 1812. Three earthquakes in this sequence had a magnitude (M) of 7.0 or greater. The first earthquake occurred on December 16, 1811, at 2:15 a.m.; the second on January 23, 1812, at 9 a.m.; and the third on February 7, 1812, at 3:45 a.m. These three earthquakes were among the largest to strike North America since European settlement. The mainshocks were followed by many hundreds of aftershocks that occurred over the next decade. Many of the aftershocks were major earthquakes themselves. The area that was strongly shaken by the three main shocks was 2-3 times as large as the strongly shaken area of the 1964 M9.2 Alaskan earthquake and 10 times as large as that of the 1906 M7.8 San Francisco earthquake. Geologic studies show that the 1811-1812 sequence was not an isolated event in the New Madrid region. The 1811-1812 New Madrid earthquake sequence was preceded by at least two other similar sequences in about A.D. 1450 and A.D. 900. Research also indicates that other large earthquakes have occurred in the region surrounding the main New Madrid seismicity trends in the past 5,000 years or so.

Research on groundwater radon as a fluid phase precursor to earthquakes

International Nuclear Information System (INIS)

Teng, T.; Sun, L.

1986-01-01

Groundwater radon monitoring work carried out in southern California by the University of Southern California since 1974 is summarized here. This effort began with a sampling network over a locked segment of the San Andreas fault from Tejon to Cajon and was later expanded to cover part of the southern Transverse Mountain ranges. Groundwater samples were brought back weekly to the laboratory for high precision scintillation counting. Needs for more frequent sampling and less labor prompted the development of an economical and field worthy instrument known as the continuous radon monitor. About 10 have been installed in the network since early 1980. The groundwater radon content was found to show anomalous increases (mostly at a single station) before a number of moderate and nearby earthquakes. Our work is hampered by a lack of large earthquakes that may have a regional impact on radon anomalies and by the complexity of the underground hydrological regime. To circumvent this difficulty, we have chosen to monitor only deep artesian wells or hot spring wells

Fiscal 2000 research report on the research on earthquake disaster prevention technology for industrial machinery systems; 2000 nendo sangyo kikai system no boshin bosai gijutsu no chosa kenkyu hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

Available technologies were extracted and technical problems were discussed in detail in connection with the above-named technology, and a technology development scenario was prepared. The study covered the subjects of an earthquake resistant disaster prevention system, ready for activation upon earthquake occurrence, with its structure designed to counter severe vibration; a real-time earthquake resistant disaster prevention system capable of ensuring system safety upon receiving earthquake occurrence information and of instantly collecting information on damage incurred; and an early restoration system to operate upon termination of earthquake. With the active utilization in mind of information technology now making a rapid progress, importance was stressed of a system under which earthquake information, disaster prevention networks, and information on the soil and geography would be linked to the database of the equipment involved. For research on the current state of earthquake disaster prevention technology, an on-site survey was conducted of the disaster prevention facilities now under construction in Hyogo Prefecture, and another survey was conducted of Shizuoka Prefecture's long-standing consideration of earthquake disaster prevention measures. Data were collected at the 5th Corporate Disaster Prevention Symposium held in San Jose, U.S. (NEDO)

Earthquake Culture: A Significant Element in Earthquake Disaster Risk Assessment and Earthquake Disaster Risk Management

OpenAIRE

Ibrion, Mihaela

2018-01-01

This book chapter brings to attention the dramatic impact of large earthquake disasters on local communities and society and highlights the necessity of building and enhancing the earthquake culture. Iran was considered as a research case study and fifteen large earthquake disasters in Iran were investigated and analyzed over more than a century-time period. It was found that the earthquake culture in Iran was and is still conditioned by many factors or parameters which are not integrated and...

Potential Effects of a Scenario Earthquake on the Economy of Southern California: Baseline County-Level Migration Characteristics and Trends 1995-2000 and 2001-2010

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. In support of the MHDP objectives, the ShakeOut Scenario was developed. It describes a magnitude 7.8 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 uses historical, estimated, and projected population data from several Federal and State data sources to estimate baseline characteristics and trends of the region's population migration (that is, changes in a person's place of residence over time). The analysis characterizes migration by various demographic, economic, family, and household variables for the period 1995-2000. It also uses existing estimates (beginning in 2001) of the three components of population change - births, deaths, and migration - to extrapolate near-term projections of county-level migration trends through 2010. The 2010 date was chosen to provide baseline projections corresponding to a two-year recovery period following the November 2008 date that was selected for the occurrence of the ShakeOut Scenario earthquake. The baseline characteristics and projections shall assist with evaluating the effects of inflow and outflow migration trends for alternative futures in which the simulated M7.8 earthquake either does or does not occur and the impact of the event on housing and jobs, as well as community composition and regional economy changes based on dispersion of intellectual, physical, economic, and cultural capital.

A geographical and multi-criteria vulnerability assessment of transportation networks against extreme earthquakes

International Nuclear Information System (INIS)

Kermanshah, A.; Derrible, S.

2016-01-01

The purpose of this study is to provide a geographical and multi-criteria vulnerability assessment method to quantify the impacts of extreme earthquakes on road networks. The method is applied to two US cities, Los Angeles and San Francisco, both of which are susceptible to severe seismic activities. Aided by the recent proliferation of data and the wide adoption of Geography Information Systems (GIS), we use a data-driven approach using USGS ShakeMaps to determine vulnerable locations in road networks. To simulate the extreme earthquake, we remove road sections within “very strong” intensities provided by USGS. Subsequently, we measure vulnerability as a percentage drop in four families of metrics: overall properties (length of remaining system); topological indicators (betweenness centrality); accessibility; and travel demand using Longitudinal Employment Household Dynamics (LEHD) data. The various metrics are then plotted on a Vulnerability Surface (VS), from which the area can be assimilated to an overall vulnerability indicator. This VS approach offers a simple and pertinent method to capture the impacts of extreme earthquake. It can also be useful to planners to assess the robustness of various alternative scenarios in their plans to ensure that cities located in seismic areas are better prepared to face severe earthquakes. - Highlights: • Developed geographical and multi-criteria vulnerability assessment method. • Quantify the impacts of extreme earthquakes on transportation networks. • Data-driven approach using USGS ShakeMaps to determine vulnerable locations. • Measure vulnerability as a percentage drop in four families of metrics: ○Overall properties. ○Topological indicators. ○Accessibility. ○Travel demand using Longitudinal Employment Household Dynamics (LEHD) data. • Developed Vulnerability Surface (VS), a new pragmatic vulnerability indicator.

Spontaneous non-volcanic tremor detected in the Anza Seismic Gap of San Jacinto Fault

Science.gov (United States)

Hutchison, A. A.; Ghosh, A.

2017-12-01

Non-volcanic tremor (NVT), a type of slow earthquake, is becoming more frequently detected along plate boundaries, particularly in subduction zones, and is also observed along the San Andreas Fault [e.g. Nadeau & Dolenc, 2005]. NVT is typically associated with transient deformation (i.e. slow slip) in the transition zone [e.g. Ide et al., 2007], and at times it is observed with deep creep along faults [e.g. Beroza & Ide, 2011]. Using several independent location and detection methods including multi-beam backprojection [Ghosh et al., 2009a; 2012], envelope cross correlation [Wech & Creager, 2008], spectral analyses and visual inspection of existing network stations and high-density mini seismic array data, we detect multiple discrete spontaneous tremor events in the Anza Gap of the San Jacinto Fault (SJF) in June, 2011. The events occur on the SJF where the Hot Springs Fault terminates, on the northwestern boundary of the Anza Gap, below the inferred seismogenic zone characterized by velocity weakening frictional behavior [e.g. Lindsay et al., 2014]. The location methods provide consistent locations for each event in our catalog. Low slowness values help rule-out surface noise that may result in false detections. Analyses of frequency spectra show these time windows are depleted in high frequency energy in the displacement amplitude spectrum compared to small local regular (fast) earthquakes. This spectral pattern is characteristic of tremor [Shelly et al., 2007]. We interpret this tremor to be a seismic manifestation of slow-slip events below the seismogenic zone. Recently, an independent geodetic study suggests that the 2010 El Mayor-Cucupah earthquake triggered a slow-slip event in the Anza Gap [Inbal et al., 2017]. In addition, multiple studies infer deep creep in the SJF [e.g. Meng & Peng et al., 2016; Jiang & Fialko, 2016] indicating that this fault is capable of producing slow slip events. Transient tectonic behavior like tremor and slow slip may be playing

Evidence of displacement-driven maturation along the San Cristobal Trough transform plate boundary

Science.gov (United States)

Neely, James S.; Furlong, Kevin P.

2018-03-01

The San Cristobal Trough (SCT), formed by the tearing of the Australia plate as it subducts under the Pacific plate near the Solomon Islands, provides an opportunity to study the transform boundary development process. Recent seismicity (2013-2016) along the 280 km long SCT, known as a Subduction-Transform Edge Propagator (STEP) fault, highlights the tearing process and ongoing development of the plate boundary. The region's earthquakes reveal two key characteristics. First, earthquakes at the western terminus of the SCT, which we interpret to indicate the Australia plate tearing, display disparate fault geometries. These events demonstrate that plate tearing is accommodated via multiple intersecting planes rather than a single through-going fault. Second, the SCT hosts sequences of Mw ∼7 strike-slip earthquakes that migrate westward through a rapid succession of events. Sequences in 1993 and 2015 both began along the eastern SCT and propagated west, but neither progression ruptured into or nucleated a large earthquake within the region near the tear. Utilizing b-value and Coulomb Failure Stress analyses, we examine these along-strike variations in the SCT's seismicity. b-Values are highest along the youngest, western end of the SCT and decrease with increasing distance from the tear. This trend may reflect increasing strain localization with increasing displacement. Coulomb Failure Stress analyses indicate that the stress conditions were conducive to continued western propagation of the 1993 and 2015 sequences suggesting that the unruptured western SCT may have fault geometries or properties that inhibit continued rupture. Our results indicate a displacement-driven fault maturation process. The multi-plane Australia plate tearing likely creates a western SCT with diffuse strain accommodated along a network of disorganized faults. After ∼90 km of cumulative displacement (∼900,000 yr of plate motion), strain localizes and faults align, allowing the SCT to host

78 FR 19103 - Safety Zone; Spanish Navy School Ship San Sebastian El Cano Escort; Bahia de San Juan; San Juan, PR

Science.gov (United States)

2013-03-29

...-AA00 Safety Zone; Spanish Navy School Ship San Sebastian El Cano Escort; Bahia de San Juan; San Juan... temporary moving safety zone on the waters of Bahia de San Juan during the transit of the Spanish Navy... Channel entrance, and to protect the high ranking officials on board the Spanish Navy School Ship San...

Deep Borehole Instrumentation Along San Francisco Bay Bridges: 1996 - 2003 and Strong Ground Motion Systhesis Along the San Francisco/Oakland Bay Bridge

Energy Technology Data Exchange (ETDEWEB)

Hutchings, L; Foxall, W; Kasameyer, P; larsen, S; Hayek, C; Tyler-Turpin, C; Aquilino, J; Long, L

2005-04-22

As a result of collaboration between the Berkeley Seismographic Station, Lawrence Livermore National Laboratory, and Caltrans, instrument packages have been placed in bedrock in six boreholes and two surface sites along the San Francisco/Oakland Bay Bridge. Since 1996 over 200 local earthquakes have been recorded. Prior to this study few seismic recording instruments existed in bed-rock in San Francisco Bay. We utilized the data to perform analysis of ground motion variability, wave passage, site response, and up-and down-hole wave propagation along the Bay Bridge. We also synthesized strong ground motion at nine locations along the Bay Bridge. Key to these studies is LLNL's effort to exploit the information available in weak ground motions (generally from earthquakes < M=4.0) to enhance predictions of seismic hazards. We found that Yerba Island has no apparent site response at the surface relative to a borehole site. The horizontal to vertical spectral ratio method best revealed no site response, while the complex signal spectral ratio method had the lowest variance for spectral ratios and best predicted surface recordings when the borehole recording was used as input. Both methods identified resonances at about the same frequencies. Regional attenuation results in a significant loss of high frequencies in both surface and borehole recordings. Records are band limited at near 3 Hz. Therefore a traditional rock outcrop site response, flat to high frequency in displacement, is not available. We applied a methodology to predict and synthesize strong ground motion along the San Francisco/Oakland Bay Bridge from a M=7.25 earthquake along the Hayward fault, about12 km distant. We synthesized for three-components and broad-band (0.0-25.0 Hz) ground motion accelerations, velocities, and displacements. We examined two different possible rupture scenarios, a ''mean'' and ''one standard deviation'' model. We combined the high

Earthquakes and Earthquake Engineering. LC Science Tracer Bullet.

Science.gov (United States)

Buydos, John F., Comp.

An earthquake is a shaking of the ground resulting from a disturbance in the earth's interior. Seismology is the (1) study of earthquakes; (2) origin, propagation, and energy of seismic phenomena; (3) prediction of these phenomena; and (4) investigation of the structure of the earth. Earthquake engineering or engineering seismology includes the…

Compact High Resolution SANS using very cold neutrons (VCN-SANS)

International Nuclear Information System (INIS)

Kennedy, S.; Yamada, M.; Iwashita, Y.; Geltenbort, P.; Bleuel, M.; Shimizu, H.

2011-01-01

SANS (Small Angle Neutron Scattering) is a popular method for elucidation of nano-scale structures. However science continually challenges SANS for higher performance, prompting exploration of ever-more exotic and expensive technologies. We propose a compact high resolution SANS, using very cold neutrons, magnetic focusing lens and a wide-angle spherical detector. This system will compete with modern 40 m pinhole SANS in one tenth of the length, matching minimum Q, Q-resolution and dynamic range. It will also probe dynamics using the MIEZE method. Our prototype lens (a rotating permanent-magnet sextupole), focuses a pulsed neutron beam over 3-5 nm wavelength and has measured SANS from micelles and polymer blends. (authors)

Analog earthquakes

International Nuclear Information System (INIS)

Hofmann, R.B.

1995-01-01

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

The Mw6.0 24 August 2014 South Napa earthquake

Science.gov (United States)

Brocher, Thomas M.; Baltay, Annemarie S.; Hardebeck, Jeanne L.; Pollitz, Fred F.; Murray, Jessica R.; Llenos, Andrea L.; Schwartz, David P.; Blair, James Luke; Ponti, Daniel J.; Lienkaemper, James J.; Langenheim, V.E.; Dawson, Timothy E.; Hudnut, Kenneth W.; Shelly, David R.; Dreger, Douglas S.; Boatwright, John; Aagaard, Brad T.; Wald, David J.; Allen, Richard M.; Barnhart, William D.; Knudsen, Keith L.; Brooks, Benjamin A.; Scharer, Katherine M.

2015-01-01

The Mw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right‐lateral earthquake propagated mostly unilaterally to the north and up‐dip, directing the strongest shaking toward the city of Napa, where peak ground accelerations (PGAs) between 45%g and 61%g were recorded and modified Mercalli intensities (MMIs) of VII–VIII were reported. Tectonic surface rupture with dextral slip of up to 46 cm was observed on a 12.5 km long segment, some of which was along a previously mapped strand of the West Napa fault system, although the rupture extended to the north of the mapped Quaternary strand. Modeling of seismic and geodetic data suggests an average coseismic slip of 50 cm, with a maximum slip of about 1 m at depths of 10–11 km. We observed up to 35 cm of afterslip along the surface trace in the week following the mainshock, primarily along the southern half of the surface rupture that experienced relatively little coseismic offset. Relocation of the sparse aftershock sequence suggests en echelon southwest‐ and northeast‐dipping fault planes, reflective of the complex fault geometry in this region. The Napa basin and historic and late Holocene alluvial flood deposits in downtown Napa amplified the ground motions there. Few ground failures were mapped, reflecting the dry season (as well as a persistent drought that had lowered the groundwater table) and the short duration of strong shaking in the epicentral area.

Finite element models of earthquake cycles in mature strike-slip fault zones

Science.gov (United States)

Lynch, John Charles

The research presented in this dissertation is on the subject of strike-slip earthquakes and the stresses that build and release in the Earth's crust during earthquake cycles. Numerical models of these cycles in a layered elastic/viscoelastic crust are produced using the finite element method. A fault that alternately sticks and slips poses a particularly challenging problem for numerical implementation, and a new contact element dubbed the "Velcro" element was developed to address this problem (Appendix A). Additionally, the finite element code used in this study was bench-marked against analytical solutions for some simplified problems (Chapter 2), and the resolving power was tested for the fault region of the models (Appendix B). With the modeling method thus developed, there are two main questions posed. First, in Chapter 3, the effect of a finite-width shear zone is considered. By defining a viscoelastic shear zone beneath a periodically slipping fault, it is found that shear stress concentrates at the edges of the shear zone and thus causes the stress tensor to rotate into non-Andersonian orientations. Several methods are used to examine the stress patterns, including the plunge angles of the principal stresses and a new method that plots the stress tensor in a manner analogous to seismic focal mechanism diagrams. In Chapter 4, a simple San Andreas-like model is constructed, consisting of two great earthquake producing faults separated by a freely-slipping shorter fault. The model inputs of lower crustal viscosity, fault separation distance, and relative breaking strengths are examined for their effect on fault communication. It is found that with a lower crustal viscosity of 1018 Pa s (in the lower range of estimates for California), the two faults tend to synchronize their earthquake cycles, even in the cases where the faults have asymmetric breaking strengths. These models imply that postseismic stress transfer over hundreds of kilometers may play a

Fractal properties and simulation of micro-seismicity for seismic hazard analysis: a comparison of North Anatolian and San Andreas Fault Zones

Directory of Open Access Journals (Sweden)

Naside Ozer

2012-02-01

Full Text Available We analyzed statistical properties of earthquakes in western Anatolia as well as the North Anatolian Fault Zone (NAFZ in terms of spatio-temporal variations of fractal dimensions, p- and b-values. During statistically homogeneous periods characterized by closer fractal dimension values, we propose that occurrence of relatively larger shocks (M >= 5.0 is unlikely. Decreases in seismic activity in such intervals result in spatial b-value distributions that are primarily stable. Fractal dimensions decrease with time in proportion to increasing seismicity. Conversely, no spatiotemporal patterns were observed for p-value changes. In order to evaluate failure probabilities and simulate earthquake occurrence in the western NAFZ, we applied a modified version of the renormalization group method. Assuming an increase in small earthquakes is indicative of larger shocks, we apply the mentioned model to micro-seismic (M<= 3.0 activity, and test our results using San Andreas Fault Zone (SAFZ data. We propose that fractal dimension is a direct indicator of material heterogeneity and strength. Results from a model suggest simulated and observed earthquake occurrences are coherent, and may be used for seismic hazard estimation on creeping strike-slip fault zones.

Broadband records of earthquakes in deep gold mines and a comparison with results from SAFOD, California

Science.gov (United States)

McGarr, Arthur F.; Boettcher, M.; Fletcher, Jon Peter B.; Sell, Russell; Johnston, Malcolm J.; 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 , where  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.

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

Science.gov (United States)

2011-08-01

...-AA00 Safety Zone; San Diego POPS Fireworks, San Diego, CA AGENCY: Coast Guard, DHS. ACTION: Temporary... San Diego Bay in support of the San Diego POPS Fireworks. This safety zone is necessary to provide for... of the waterway during scheduled fireworks events. Persons and vessels will be prohibited from...

Replegamiento de láminas de corrimiento epidérmicas mediante fallas inversas de basamento activas en la Precordillera Oriental del oeste de Argentina

OpenAIRE

Meigs, A.; Krugh, W. C.; Schiffman, C.; Vergés, Jaume; Ramos, V. A.

2006-01-01

Devastating earthquakes like the 1944 San Juan earthquake reflect active deformation in western Argentina. Although the earthquake caused considerable damage to San Juan, the source of the earthquake remains uncertain. Potential source faults occur in the thin-skinned fold-and-thrust belt Precordillera province and in the thick-skinned Sierras Pampeanas province, to the west and east, respectively of Sierra de Villicum, a thrust sheet in the eastern Precordillera northwest of San Juan. Sierra...

Turkish Compulsory Earthquake Insurance and "Istanbul Earthquake

Science.gov (United States)

Durukal, E.; Sesetyan, K.; Erdik, M.

2009-04-01

The city of Istanbul will likely experience substantial direct and indirect losses as a result of a future large (M=7+) earthquake with an annual probability of occurrence of about 2%. This paper dwells on the expected building losses in terms of probable maximum and average annualized losses and discusses the results from the perspective of the compulsory earthquake insurance scheme operational in the country. The TCIP system is essentially designed to operate in Turkey with sufficient penetration to enable the accumulation of funds in the pool. Today, with only 20% national penetration, and about approximately one-half of all policies in highly earthquake prone areas (one-third in Istanbul) the system exhibits signs of adverse selection, inadequate premium structure and insufficient funding. Our findings indicate that the national compulsory earthquake insurance pool in Turkey will face difficulties in covering incurring building losses in Istanbul in the occurrence of a large earthquake. The annualized earthquake losses in Istanbul are between 140-300 million. Even if we assume that the deductible is raised to 15%, the earthquake losses that need to be paid after a large earthquake in Istanbul will be at about 2.5 Billion, somewhat above the current capacity of the TCIP. Thus, a modification to the system for the insured in Istanbul (or Marmara region) is necessary. This may mean an increase in the premia and deductible rates, purchase of larger re-insurance covers and development of a claim processing system. Also, to avoid adverse selection, the penetration rates elsewhere in Turkey need to be increased substantially. A better model would be introduction of parametric insurance for Istanbul. By such a model the losses will not be indemnified, however will be directly calculated on the basis of indexed ground motion levels and damages. The immediate improvement of a parametric insurance model over the existing one will be the elimination of the claim processing

33 CFR 165.754 - Safety Zone: San Juan Harbor, San Juan, PR.

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Safety Zone: San Juan Harbor, San Juan, PR. 165.754 Section 165.754 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND... Zone: San Juan Harbor, San Juan, PR. (a) Regulated area. A moving safety zone is established in the...

Earthquake potential revealed by tidal influence on earthquake size-frequency statistics

Science.gov (United States)

Ide, Satoshi; Yabe, Suguru; Tanaka, Yoshiyuki

2016-11-01

The possibility that tidal stress can trigger earthquakes is long debated. In particular, a clear causal relationship between small earthquakes and the phase of tidal stress is elusive. However, tectonic tremors deep within subduction zones are highly sensitive to tidal stress levels, with tremor rate increasing at an exponential rate with rising tidal stress. Thus, slow deformation and the possibility of earthquakes at subduction plate boundaries may be enhanced during periods of large tidal stress. Here we calculate the tidal stress history, and specifically the amplitude of tidal stress, on a fault plane in the two weeks before large earthquakes globally, based on data from the global, Japanese, and Californian earthquake catalogues. We find that very large earthquakes, including the 2004 Sumatran, 2010 Maule earthquake in Chile and the 2011 Tohoku-Oki earthquake in Japan, tend to occur near the time of maximum tidal stress amplitude. This tendency is not obvious for small earthquakes. However, we also find that the fraction of large earthquakes increases (the b-value of the Gutenberg-Richter relation decreases) as the amplitude of tidal shear stress increases. The relationship is also reasonable, considering the well-known relationship between stress and the b-value. This suggests that the probability of a tiny rock failure expanding to a gigantic rupture increases with increasing tidal stress levels. We conclude that large earthquakes are more probable during periods of high tidal stress.

Using a modified time-reverse imaging technique to locate low-frequency earthquakes on the San Andreas Fault near Cholame, California

Science.gov (United States)

Horstmann, Tobias; Harrington, Rebecca M.; Cochran, Elizabeth S.

2015-01-01

We present a new method to locate low-frequency earthquakes (LFEs) within tectonic tremor episodes based on time-reverse imaging techniques. The modified time-reverse imaging technique presented here is the first method that locates individual LFEs within tremor episodes within 5 km uncertainty without relying on high-amplitude P-wave arrivals and that produces similar hypocentral locations to methods that locate events by stacking hundreds of LFEs without having to assume event co-location. In contrast to classic time-reverse imaging algorithms, we implement a modification to the method that searches for phase coherence over a short time period rather than identifying the maximum amplitude of a superpositioned wavefield. The method is independent of amplitude and can help constrain event origin time. The method uses individual LFE origin times, but does not rely on a priori information on LFE templates and families.We apply the method to locate 34 individual LFEs within tremor episodes that occur between 2010 and 2011 on the San Andreas Fault, near Cholame, California. Individual LFE location accuracies range from 2.6 to 5 km horizontally and 4.8 km vertically. Other methods that have been able to locate individual LFEs with accuracy of less than 5 km have mainly used large-amplitude events where a P-phase arrival can be identified. The method described here has the potential to locate a larger number of individual low-amplitude events with only the S-phase arrival. Location accuracy is controlled by the velocity model resolution and the wavelength of the dominant energy of the signal. Location results are also dependent on the number of stations used and are negligibly correlated with other factors such as the maximum gap in azimuthal coverage, source–station distance and signal-to-noise ratio.

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.

OMG Earthquake! Can Twitter improve earthquake response?

Science.gov (United States)

Earle, P. S.; Guy, M.; Ostrum, C.; Horvath, S.; Buckmaster, R. A.

2009-12-01

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 its earthquake response products and the delivery of hazard information. The goal is to gather near real-time, earthquake-related messages (tweets) and provide geo-located earthquake detections and rough maps of the corresponding felt areas. Twitter and other social Internet technologies are providing the general public with anecdotal earthquake hazard information before scientific information has been published from authoritative sources. People local to an event often publish information within seconds via these technologies. In contrast, depending on the location of the earthquake, scientific alerts take between 2 to 20 minutes. Examining the tweets following the March 30, 2009, M4.3 Morgan Hill earthquake shows it is possible (in some cases) to rapidly detect and map the felt area of an earthquake using Twitter responses. Within a minute of the earthquake, the frequency of “earthquake” tweets rose above the background level of less than 1 per hour to about 150 per minute. Using the tweets submitted in the first minute, a rough map of the felt area can be obtained by plotting the tweet locations. Mapping the tweets from the first six minutes shows observations extending from Monterey to Sacramento, similar to the perceived shaking region mapped by the USGS “Did You Feel It” system. The tweets submitted after the earthquake also provided (very) short first-impression narratives from people who experienced the shaking. Accurately assessing the potential and robustness of a Twitter-based system is difficult because only tweets spanning the previous seven days can be searched, making a historical study impossible. We have, however, been archiving tweets for several months, and it is clear that significant limitations do exist. The main drawback is the lack of quantitative information

Earthquake Early Warning Systems

OpenAIRE

Pei-Yang Lin

2011-01-01

Because of Taiwan’s unique geographical environment, earthquake disasters occur frequently in Taiwan. The Central Weather Bureau collated earthquake data from between 1901 and 2006 (Central Weather Bureau, 2007) and found that 97 earthquakes had occurred, of which, 52 resulted in casualties. The 921 Chichi Earthquake had the most profound impact. Because earthquakes have instant destructive power and current scientific technologies cannot provide precise early warnings in advance, earthquake ...

Steep-dip seismic imaging of the shallow San Andreas fault near Parkfield.

Science.gov (United States)

Hole, J A; Catchings, R D; St Clair, K C; Rymer, M J; Okaya, D A; Carney, B J

2001-11-16

Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70 degrees to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed locations of earthquakes and the surface fault trace. The seismic velocity cross section shows strong lateral variations. Relatively low velocity (10 to 30%), high electrical conductivity, and low density indicate a 1-kilometer-wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace.

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.

Ground water and earthquakes

Energy Technology Data Exchange (ETDEWEB)

Ts' ai, T H

1977-11-01

Chinese folk wisdom has long seen a relationship between ground water and earthquakes. Before an earthquake there is often an unusual change in the ground water level and volume of flow. Changes in the amount of particulate matter in ground water as well as changes in color, bubbling, gas emission, and noises and geysers are also often observed before earthquakes. Analysis of these features can help predict earthquakes. Other factors unrelated to earthquakes can cause some of these changes, too. As a first step it is necessary to find sites which are sensitive to changes in ground stress to be used as sensor points for predicting earthquakes. The necessary features are described. Recording of seismic waves of earthquake aftershocks is also an important part of earthquake predictions.

The 2014, MW6.9 North Aegean earthquake: seismic and geodetic evidence for coseismic slip on persistent asperities

Science.gov (United States)

Konca, Ali Ozgun; Cetin, Seda; Karabulut, Hayrullah; Reilinger, Robert; Dogan, Ugur; Ergintav, Semih; Cakir, Ziyadin; Tari, Ergin

2018-05-01

We report that asperities with the highest coseismic slip in the 2014 MW6.9 North Aegean earthquake persisted through the interseismic, coseismic and immediate post-seismic periods. We use GPS and seismic data to obtain the source model of the 2014 earthquake, which is located on the western extension of the North Anatolian Fault (NAF). The earthquake ruptured a bilateral, 90 km strike-slip fault with three slip patches: one asperity located west of the hypocentre and two to the east with a rupture duration of 40 s. Relocated pre-earthquake seismicity and aftershocks show that zones with significant coseismic slip were relatively quiet during both the 7 yr of interseismic and the 3-month aftershock periods, while the surrounding regions generated significant seismicity during both the interseismic and post-seismic periods. We interpret the unusually long fault length and source duration, and distribution of pre- and post-main-shock seismicity as evidence for a rupture of asperities that persisted through strain accumulation and coseismic strain release in a partially coupled fault zone. We further suggest that the association of seismicity with fault creep may characterize the adjacent Izmit, Marmara Sea and Saros segments of the NAF. Similar behaviour has been reported for sections of the San Andreas Fault, and some large subduction zones, suggesting that the association of seismicity with creeping fault segments and rapid relocking of asperities may characterize many large earthquake faults.

Photomosaics and event evidence from the Frazier Mountain paleoseismic site, trench 1, cuts 1–4, San Andreas Fault Zone, southern California (2007–2009)

Science.gov (United States)

Scharer, Katherine M.; Fumal, Tom E.; Weldon, Ray J.; Streig, Ashley R.

2014-01-01

The Frazier Mountain paleoseismic site is located at the northwest end of the Mojave section of the San Andreas Fault, in a small, closed depression at the base of Frazier Mountain near Tejon Pass, California (lat 34.8122° N., long 118.9034° W.). The site was known to contain a good record of earthquakes due to previous excavations by Lindvall and others (2002). This report provides data resulting from four nested excavations, or cuts, along trench 1 (T1) in 2007 and 2009 at the Frazier Mountain site. The four cuts were excavated progressively deeper and wider in an orientation perpendicular to the San Andreas Fault, exposing distal fan and marsh sediments deposited since ca. A.D. 1200. The results of the trenching show that earthquakes that ruptured the site have repeatedly produced a small depression or sag on the surface, which is subsequently infilled with sand and silt deposits. This report provides high-resolution photomosaics and logs for the T1 cuts, a detailed stratigraphic column for the deposits, and a table summarizing all of the evidence for ground rupturing paleoearthquakes logged in the trenches.

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.

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

Seismicity Precursors of the M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes

Energy Technology Data Exchange (ETDEWEB)

Korneev, Valeri A.

2006-03-09

The M6.0 2004 Parkfield and M7.0 1989 Loma Prietastrike-slip earthquakes on the San Andreas Fault (SAF) were preceded byseismicity peaks occurring several months prior to the main events.Earthquakes directly within the SAF zone were intentionally excluded fromthe analysis because they manifest stress-release processes rather thanstress accumulation. The observed increase in seismicity is interpretedas a signature of the increasing stress level in the surrounding crust,whereas the peaks and the subsequent decrease in seismicity areattributed to damage-induced softening processes. Furthermore, in bothcases there is a distinctive zone of low seismic activity that surroundsthe epicentral region in the pre-event period. The increase of seismicityin the crust surrounding a potential future event and the development ofa low-seismicity epicentral zone can be regarded as promising precursoryinformation that could help signal the arrival of large earthquakes. TheGutenberg-Richter relationship (GRR) should allow extrapolation ofseismicity changes down to seismic noise level magnitudes. Thishypothesis is verified by comparison of seismic noise at 80 Hz with theParkfield M4 1993-1994 series, where noise peaks 5 months before theseries to about twice the background level.

Foreshocks, aftershocks, and earthquake probabilities: Accounting for the landers earthquake

Science.gov (United States)

Jones, Lucile M.

1994-01-01

The equation to determine the probability that an earthquake occurring near a major fault will be a foreshock to a mainshock on that fault is modified to include the case of aftershocks to a previous earthquake occurring near the fault. The addition of aftershocks to the background seismicity makes its less probable that an earthquake will be a foreshock, because nonforeshocks have become more common. As the aftershocks decay with time, the probability that an earthquake will be a foreshock increases. However, fault interactions between the first mainshock and the major fault can increase the long-term probability of a characteristic earthquake on that fault, which will, in turn, increase the probability that an event is a foreshock, compensating for the decrease caused by the aftershocks.

Earthquake forecasting and warning

Energy Technology Data Exchange (ETDEWEB)

Rikitake, T.

1983-01-01

This review briefly describes two other books on the same subject either written or partially written by Rikitake. In this book, the status of earthquake prediction efforts in Japan, China, the Soviet Union, and the United States are updated. An overview of some of the organizational, legal, and societal aspects of earthquake prediction in these countries is presented, and scientific findings of precursory phenomena are included. A summary of circumstances surrounding the 1975 Haicheng earthquake, the 1978 Tangshan earthquake, and the 1976 Songpan-Pingwu earthquake (all magnitudes = 7.0) in China and the 1978 Izu-Oshima earthquake in Japan is presented. This book fails to comprehensively summarize recent advances in earthquake prediction research.

Acoustic Emission Precursors of M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes

Energy Technology Data Exchange (ETDEWEB)

Korneev, Valeri

2005-02-01

Two recent strike-slip earthquakes on the San Andreas Fault(SAF) in California, the M6.0 2004 Parkfield and M7.0 1989 Loma Prietaevents, revealed peaks in the acoustic emission (AE) activity in thesurrounding crust several months prior to the main events. Earthquakesdirectly within the SAF zone were intentionally excluded from theanalysis. The observed increase in AE is assumed to be a signature of theincreasing stress level in the surrounding crust, while the peak andsubsequent decrease in AE starting several months prior to the mainevents is attributed to damage-induced softening processes as discussedherein. Further, distinctive zones of low seismic activity surroundingthe epicentral regions in the pre-event time period are present for thetwo studied events. Both AE increases in the crust surrounding apotential future event and the development of a low-seismicity epicentralzone can be regarded as promising precursory information that could helpsignal the arrival of large earthquakes.

Ionospheric earthquake precursors

International Nuclear Information System (INIS)

Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

1996-01-01

Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

SU-E-T-152: Building An Ultrafast, Earthquake Proof Treatment Planning System

Energy Technology Data Exchange (ETDEWEB)

Bush, K [Stanford University, Stanford, CA (United States); Freeman, J; Zavalkovskiy, B [Stanford Health Care, Palo Alto, CA (United States)

2015-06-15

Purpose: Situated 20 miles from 5 major fault lines in California’s Bay Area, Stanford Universityhas a critical need for IT infrastructure planning to handle the high probability devastating earthquakes. Recently, a multi-million dollar project has been underway to overhaul Stanford’s radiation oncology information systems, maximizing planning system performance and providing true disaster recovery abilities. An overview of the project will be given with particular focus on lessons learned throughout the build. Methods: In this implementation, two isolated external datacenters provide geographical redundancy to Stanford’s main campus datacenter. Real-time mirroring is made of all data stored to our serial attached network (SAN) storage. In each datacenter, hardware/software virtualization was heavily implemented to maximize server efficiency and provide a robust mechanism to seamlessly migrate users in the event of an earthquake. System performance is routinely assessed through the use of virtualized data robots, able to log in to the system at scheduled times, perform routine planning tasks and report timing results to a performance dashboard. A substantial dose calculation framework (608 CPU cores) has been constructed as part of the implementation. Results: Migration to a virtualized server environment with a high performance SAN has resulted in up to a 45% speed up of common treatment planning tasks. Switching to a 608 core DCF has resulted in a 280% speed increase in dose calculations. Server tuning was found to further improved read/write performance by 20%. Disaster recovery tests are carried out quarterly and, although successful, remain time consuming to perform and verify functionality. Conclusion: Achieving true disaster recovery capabilities is possible through server virtualization, support from skilled IT staff and leadership. Substantial performance improvements are also achievable through careful tuning of server resources and disk read

SU-E-T-152: Building An Ultrafast, Earthquake Proof Treatment Planning System

International Nuclear Information System (INIS)

Bush, K; Freeman, J; Zavalkovskiy, B

2015-01-01

Purpose: Situated 20 miles from 5 major fault lines in California’s Bay Area, Stanford Universityhas a critical need for IT infrastructure planning to handle the high probability devastating earthquakes. Recently, a multi-million dollar project has been underway to overhaul Stanford’s radiation oncology information systems, maximizing planning system performance and providing true disaster recovery abilities. An overview of the project will be given with particular focus on lessons learned throughout the build. Methods: In this implementation, two isolated external datacenters provide geographical redundancy to Stanford’s main campus datacenter. Real-time mirroring is made of all data stored to our serial attached network (SAN) storage. In each datacenter, hardware/software virtualization was heavily implemented to maximize server efficiency and provide a robust mechanism to seamlessly migrate users in the event of an earthquake. System performance is routinely assessed through the use of virtualized data robots, able to log in to the system at scheduled times, perform routine planning tasks and report timing results to a performance dashboard. A substantial dose calculation framework (608 CPU cores) has been constructed as part of the implementation. Results: Migration to a virtualized server environment with a high performance SAN has resulted in up to a 45% speed up of common treatment planning tasks. Switching to a 608 core DCF has resulted in a 280% speed increase in dose calculations. Server tuning was found to further improved read/write performance by 20%. Disaster recovery tests are carried out quarterly and, although successful, remain time consuming to perform and verify functionality. Conclusion: Achieving true disaster recovery capabilities is possible through server virtualization, support from skilled IT staff and leadership. Substantial performance improvements are also achievable through careful tuning of server resources and disk read

Evaluation of earthquake vibration on aseismic design of nuclear power plant judging from recent earthquakes

International Nuclear Information System (INIS)

Dan, Kazuo

2006-01-01

The Regulatory Guide for Aseismic Design of Nuclear Reactor Facilities was revised on 19 th September, 2006. Six factors for evaluation of earthquake vibration are considered on the basis of the recent earthquakes. They are 1) evaluation of earthquake vibration by method using fault model, 2) investigation and approval of active fault, 3) direct hit earthquake, 4) assumption of the short active fault as the hypocentral fault, 5) locality of the earthquake and the earthquake vibration and 6) remaining risk. A guiding principle of revision required new evaluation method of earthquake vibration using fault model, and evaluation of probability of earthquake vibration. The remaining risk means the facilities and people get into danger when stronger earthquake than the design occurred, accordingly, the scattering has to be considered at evaluation of earthquake vibration. The earthquake belt of Hyogo-Nanbu earthquake and strong vibration pulse in 1995, relation between length of surface earthquake fault and hypocentral fault, and distribution of seismic intensity of off Kushiro in 1993 are shown. (S.Y.)

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.

A rheologically layered three-dimensional model of the San Andreas fault in central and southern California

Science.gov (United States)

Williams, Charles A.; Richardson, Randall M.

1991-01-01

The effects of rheological parameters and the fault slip distribution on the horizontal and vertical deformation in the vicinity of the fault are investigated using 3D kinematic finite element models of the San Andreas fault in central and southern California. It is shown that fault models with different rheological stratification schemes and slip distributions predict characteristic deformation patterns. Models that do not include aseismic slip below the fault locking depth predict deformation patterns that are strongly dependent on time since the last earthquake, while models that incorporate the aseismic slip below the locking depth depend on time to a significantly lesser degree.

Preparing a population for an earthquake like Chi-Chi: The Great Southern California ShakeOut

Science.gov (United States)

Jones, Lucile M.; ,

2009-01-01

The Great Southern California ShakeOut was a week of special events featuring the largest earthquake drill in United States history. On November 13, 2008, over 5 million southern Californians pretended that a magnitude-7.8 earthquake had occurred and practiced actions that could reduce its impact on their lives. 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 drill was based on a scenario of the impacts and consequences of such an earthquake on the Southern San Andreas Fault, developed by over 300 experts led by the U.S. Geological Survey in partnership with the California Geological Survey, the Southern California Earthquake Center, Earthquake Engineering Research Institute, lifeline operators, emergency services and many other organizations. The ShakeOut campaign was designed and implemented by earthquake scientists, emergency managers, sociologists, art designers and community participants. The means of communication were developed using results from sociological research on what encouraged people to take action. This was structured around four objectives: 1) consistent messages – people are more inclined to believe something when they hear the same thing from multiple sources; 2) visual reinforcement – people are more inclined to do something they see other people doing; 3) encourage “milling” or discussing contemplated action – people need to discuss an action with others they care about before committing to undertaking it; and 4) focus on concrete actions – people are more likely to prepare for a set of concrete consequences of a particular hazard than for an abstract concept of risk. The goals of the ShakeOut were established in Spring 2008 and were: 1) to register 5 million people to participate in the drill; 2) to change the culture of earthquake preparedness in southern California; and 3) to reduce earthquake losses in southern California. All of these

Proceedings of the Regional Seminar on Earthquake Engineering (13th) Held in Istanbul, Turkey on 14-24 September 1987.

Science.gov (United States)

1987-09-01

Earthquake Engineering Conference held in San Francisco in July 198 . It is an international collaboration programme disigned to mitigate the damage...i0 25 30 days Fig. Field data showing restoring Processes of life line os ystems. :j50 0i i i . . rH l o? 50- f- Kitchen fire sources J-0 Kerosene...and another, intermediate, narrow, lobby, serving as entrance, kitchen , a.s.o. As a matter of fact, statistics indicate that the ra- tio of 3 room

Strong Earthquake Motion Estimates for Three Sites on the U.C. Riverside Campus; TOPICAL

International Nuclear Information System (INIS)

Archuleta, R.; Elgamal, A.; Heuze, F.; Lai, T.; Lavalle, D.; Lawrence, B.; Liu, P.C.; Matesic, L.; Park, S.; Riemar, M.; Steidl, J.; Vucetic, M.; Wagoner, J.; Yang, Z.

2000-01-01

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 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, geophysical logging

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.

Minería, conflicto y mediadores locales: Minera San Xavier en Cerro de San Pedro, México Mineira, conflito e mediadores locais: Minera San Xavier em Cerro de San Pedro Mining, conflict and local brokers: Minera San Xavier in Cerro de San Pedro

Directory of Open Access Journals (Sweden)

Hernán Horacio Schiaffini

2011-12-01

Full Text Available Este trabajo indaga en las instancias de mediación que intervienen en la articulación de procesos económicos de gran escala y su puesta en práctica local. Basándonos en el conflicto que se produjo en el Municipio de Cerro de San Pedro (San Luis Potosí, México entre la empresa Minera San Xavier y el Frente Amplio Opositor (FAO a la misma, aplicamos el método etnográfico con el objetivo de describir las estructuras locales de mediación política y analizar sus prácticas y racionalidad. Intentamos demostrar así la importancia de los factores políticos locales en las vinculaciones entre estado, empresa y población.Este trabalho indaga nas instâncias de mediação que intervêm em processos econômicos de grande escala e sua posta em prática local. Baseando-nos no conflito no Cerro de San Pedro (San Luis Potosí, México entre a empresa Minera San Xavier e a Frente Amplio Opositor (FAO aplicamos o método etnográfico pra descrever as estruturas de mediação política locais e analisar suas práticas e racionalidade. Tenta-se demonstrar assim a importância dos fatores políticos locais nas vinculações entre estado, empresa e população.This paper investigates in instances of mediation involved in large-scale economic processes and local implementation. Analyzing the conflict in Cerro de San Pedro (San Luis Potosí, México among San Xavier mining company and the Frente Amplio Opositor (FAO, it applies an ethnographic approach to describe the local structures of political mediation and its practices and rationality. The work shows the relevance of local factors in the relationships between State, company and people.

Anomalous hydrogen emissions from the San Andreas fault observed at the Cienega Winery, central California

Science.gov (United States)

Sato, Motoaki; Sutton, A. J.; McGee, K. A.

1984-03-01

We began continuous monitoring of H2 concentration in soil along the San Andreas and Calaveras faults in central California in December 1980, using small H2/O2 fuel-cell sensors. Ten monitoring stations deployed to date have shown that anomalous H2 emissions take place occasionally in addition to diurnal changes. Among the ten sites, the Cienega Winery site has produced data that are characterized by very small diurnal changes, a stable baseline, and remarkably distinct spike-like H2 anomalies since its installation in July 1982. A major peak appeared on 1 10 November 1982, and another on 3 April 1983, and a medium peak on 1 November 1983. The occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site. In order to methodically assess how these peaks are related to earthquakes, three H2 degassing models were examined. A plausible correlational pattern was obtained by using a model that (1) adopts a hemicircular spreading pattern of H2 along an incipient fracture plane from the hypocenter of an earthquake, (2) relies on the FeO-H2O reaction for H2 generation, and (3) relates the accumulated amount of H2 to the mass of serpentinization of underlying ophiolitic rocks; the mass was tentatively assumed to be proportional to the seismic energy of the earthquake.

Results of the Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California.

Science.gov (United States)

Lee, Ya-Ting; Turcotte, Donald L; Holliday, James R; Sachs, Michael K; Rundle, John B; Chen, Chien-Chih; Tiampo, Kristy F

2011-10-04

The Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California was the first competitive evaluation of forecasts of future earthquake occurrence. Participants submitted expected probabilities of occurrence of M ≥ 4.95 earthquakes in 0.1° × 0.1° cells for the period 1 January 1, 2006, to December 31, 2010. Probabilities were submitted for 7,682 cells in California and adjacent regions. During this period, 31 M ≥ 4.95 earthquakes occurred in the test region. These earthquakes occurred in 22 test cells. This seismic activity was dominated by earthquakes associated with the M = 7.2, April 4, 2010, El Mayor-Cucapah earthquake in northern Mexico. This earthquake occurred in the test region, and 16 of the other 30 earthquakes in the test region could be associated with it. Nine complete forecasts were submitted by six participants. In this paper, we present the forecasts in a way that allows the reader to evaluate which forecast is the most "successful" in terms of the locations of future earthquakes. We conclude that the RELM test was a success and suggest ways in which the results can be used to improve future forecasts.

Earthquakes, September-October 1986

Science.gov (United States)

Person, W.J.

1987-01-01

There was one great earthquake (8.0 and above) during this reporting period in the South Pacific in the Kermadec Islands. There were no major earthquakes (7.0-7.9) but earthquake-related deaths were reported in Greece and in El Salvador. There were no destrcutive earthquakes in the United States.

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.

Importance of weak minerals on earthquake mechanics

Science.gov (United States)

Kaneki, S.; Hirono, T.

2017-12-01

The role of weak minerals such as smectite and talc on earthquake mechanics is one of the important issues, and has been debated for recent several decades. Traditionally weak minerals in fault have been reported to weaken fault strength causing from its low frictional resistance. Furthermore, velocity-strengthening behavior of such weak mineral (talc) is considered to responsible for fault creep (aseismic slip) in the San Andreas fault. In contrast, recent studies reported that large amount of weak smectite in the Japan Trench could facilitate gigantic seismic slip during the 2011 Tohoku-oki earthquake. To investigate the role of weak minerals on rupture propagation process and magnitude of slip, we focus on the frictional properties of carbonaceous materials (CMs), which is the representative weak materials widely distributed in and around the convergent boundaries. Field observation and geochemical analyses revealed that graphitized CMs-layer is distributed along the slip surface of a fossil plate-subduction fault. Laboratory friction experiments demonstrated that pure quartz, bulk mixtures with bituminous coal (1 wt.%), and quartz with layered coal samples exhibited almost similar frictional properties (initial, yield, and dynamic friction). However, mixtures of quartz (99 wt.%) and layered graphite (1 wt.%) showed significantly lower initial and yield friction coefficient (0.31 and 0.50, respectively). Furthermore, the stress ratio S, defined as (yield stress-initial stress)/(initial stress-dynamic stress), increased in layered graphite samples (1.97) compared to quartz samples (0.14). Similar trend was observed in smectite-rich fault gouge. By referring the reported results of dynamic rupture propagation simulation using S ratio of 1.4 (typical value for the Japan Trench) and 2.0 (this study), we confirmed that higher S ratio results in smaller slip distance by approximately 20 %. On the basis of these results, we could conclude that weak minerals have lower

Megathrust earthquakes in Central Chile: What is next after the Maule 2010 earthquake?

Science.gov (United States)

Madariaga, R.

2013-05-01

The 27 February 2010 Maule earthquake occurred in a well identified gap in the Chilean subduction zone. The event has now been studied in detail using both far-field, near field seismic and geodetic data, we will review this information gathered so far. The event broke a region that was much longer along strike than the gap left over from the 1835 Concepcion earthquake, sometimes called the Darwin earthquake because he was in the area when the earthquake occurred and made many observations. Recent studies of contemporary documents by Udias et al indicate that the area broken by the Maule earthquake in 2010 had previously broken by a similar earthquake in 1751, but several events in the magnitude 8 range occurred in the area principally in 1835 already mentioned and, more recently on 1 December 1928 to the North and on 21 May 1960 (1 1/2 days before the big Chilean earthquake of 1960). Currently the area of the 2010 earthquake and the region immediately to the North is undergoing a very large increase in seismicity with numerous clusters of seismicity that move along the plate interface. Examination of the seismicity of Chile of the 18th and 19th century show that the region immediately to the North of the 2010 earthquake broke in a very large megathrust event in July 1730. this is the largest known earthquake in central Chile. The region where this event occurred has broken in many occasions with M 8 range earthquakes in 1822, 1880, 1906, 1971 and 1985. Is it preparing for a new very large megathrust event? The 1906 earthquake of Mw 8.3 filled the central part of the gap but it has broken again on several occasions in 1971, 1973 and 1985. The main question is whether the 1906 earthquake relieved enough stresses from the 1730 rupture zone. Geodetic data shows that most of the region that broke in 1730 is currently almost fully locked from the northern end of the Maule earthquake at 34.5°S to 30°S, near the southern end of the of the Mw 8.5 Atacama earthquake of 11

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.

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

Science.gov (United States)

Gao, Meng-Tan; Jin, Xue-Shen; An, Wei-Ping; Lü, Xiao-Jian

2004-07-01

The geography information system of the 1303 Hongton 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 studies. 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.

Earthquake Triggering in the September 2017 Mexican Earthquake Sequence

Science.gov (United States)

Fielding, E. J.; Gombert, B.; Duputel, Z.; Huang, M. H.; Liang, C.; Bekaert, D. P.; Moore, A. W.; Liu, Z.; Ampuero, J. P.

2017-12-01

Southern Mexico was struck by four earthquakes with Mw > 6 and numerous smaller earthquakes in September 2017, starting with the 8 September Mw 8.2 Tehuantepec earthquake beneath the Gulf of Tehuantepec offshore Chiapas and Oaxaca. We study whether this M8.2 earthquake triggered the three subsequent large M>6 quakes in southern Mexico to improve understanding of earthquake interactions and time-dependent risk. All four large earthquakes were extensional despite the the subduction of the Cocos plate. The traditional definition of aftershocks: likely an aftershock if it occurs within two rupture lengths of the main shock soon afterwards. Two Mw 6.1 earthquakes, one half an hour after the M8.2 beneath the Tehuantepec gulf and one on 23 September near Ixtepec in Oaxaca, both fit as traditional aftershocks, within 200 km of the main rupture. The 19 September Mw 7.1 Puebla earthquake was 600 km away from the M8.2 shock, outside the standard aftershock zone. Geodetic measurements from interferometric analysis of synthetic aperture radar (InSAR) and time-series analysis of GPS station data constrain finite fault total slip models for the M8.2, M7.1, and M6.1 Ixtepec earthquakes. The early M6.1 aftershock was too close in time and space to the M8.2 to measure with InSAR or GPS. We analyzed InSAR data from Copernicus Sentinel-1A and -1B satellites and JAXA ALOS-2 satellite. Our preliminary geodetic slip model for the M8.2 quake shows significant slip extended > 150 km NW from the hypocenter, longer than slip in the v1 finite-fault model (FFM) from teleseismic waveforms posted by G. Hayes at USGS NEIC. Our slip model for the M7.1 earthquake is similar to the v2 NEIC FFM. Interferograms for the M6.1 Ixtepec quake confirm the shallow depth in the upper-plate crust and show centroid is about 30 km SW of the NEIC epicenter, a significant NEIC location bias, but consistent with cluster relocations (E. Bergman, pers. comm.) and with Mexican SSN location. Coulomb static stress

Effects of local geology on ground motion in the San Francisco Bay region, California—A continued study

Science.gov (United States)

Gibbs, James F.; Borcherdt, Roger D.

1974-01-01

Measurements of ground motion generated by nuclear explosions in Nevada have been completed for 99 locations in the San Francisco Bay region, California. The seismograms, Fourier amplitude spectra, spectral amplification curves for the signal, and the Fourier amplitude spectra of the seismic noise are presented for 60 locations. Analog amplifications, based on the maximum signal amplitude, are computed for an additional 39 locations. The recordings of the nuclear explosions show marked amplitude variations which are consistently related to the local geologic conditions of the recording site. The average spectral amplifications observed for vertical and horizontal ground motions are, respectively: (1, 1) for granite, (1.5, 1.6) for the Franciscan Formation, (2.3, 2.3), for other pre-Tertiary and Tertiary rocks, (3.0, 2.7) for the Santa Clara Formation, (3.3, 4.4) for older bay sediments, and (3.7, 11.3) for younger bay mud. Spectral amplification curves define predominant ground frequencies for younger bay mud sites and for some older bay sediment sites. The predominant frequencies for most sites were not clearly defined by the amplitude spectra computed from the seismic background noise. The intensities ascribed to various sites in the San Francisco Bay region for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the intensities for 917 sites on Franciscan rocks generally decrease with the logarithm of distance as Intensity = 2.69 - 1.90 log (Distance Km). For sites on other geologic units, intensity increments, derived from this empirical rela.tion, correlate strongly with the Average Horizontal Spectral Amplifications (MISA) according to the empirical relation Intensity Increment= 0.27 + 2.70 log(AHSA). Average

Evidence for strong Holocene earthquake(s) in the Wabash Valley seismic zone

International Nuclear Information System (INIS)

Obermeier, S.

1991-01-01

Many small and slightly damaging earthquakes have taken place in the region of the lower Wabash River Valley of Indiana and Illinois during the 200 years of historic record. Seismologists have long suspected the Wabash Valley seismic zone to be capable of producing earthquakes much stronger than the largest of record (m b 5.8). The seismic zone contains the poorly defined Wabash Valley fault zone and also appears to contain other vaguely defined faults at depths from which the strongest earthquakes presently originate. Faults near the surface are generally covered with thick alluvium in lowlands and a veneer of loess in uplands, which make direct observations of faults difficult. Partly because of this difficulty, a search for paleoliquefaction features was begun in 1990. Conclusions of the study are as follows: (1) an earthquake much stronger than any historic earthquake struck the lower Wabash Valley between 1,500 and 7,500 years ago; (2) the epicentral region of the prehistoric strong earthquake was the Wabash Valley seismic zone; (3) apparent sites have been located where 1811-12 earthquake accelerations can be bracketed

76 FR 1386 - Safety Zone; Centennial of Naval Aviation Kickoff, San Diego Bay, San Diego, CA

Science.gov (United States)

2011-01-10

...-AA00 Safety Zone; Centennial of Naval Aviation Kickoff, San Diego Bay, San Diego, CA AGENCY: Coast... zone on the navigable waters of San Diego Bay in San Diego, CA in support of the Centennial of Naval... February 12, 2010, the Centennial of Naval Aviation Kickoff will take place in San Diego Bay. In support of...

The 1985 central chile earthquake: a repeat of previous great earthquakes in the region?

Science.gov (United States)

Comte, D; Eisenberg, A; Lorca, E; Pardo, M; Ponce, L; Saragoni, R; Singh, S K; Suárez, G

1986-07-25

A great earthquake (surface-wave magnitude, 7.8) occurred along the coast of central Chile on 3 March 1985, causing heavy damage to coastal towns. Intense foreshock activity near the epicenter of the main shock occurred for 11 days before the earthquake. The aftershocks of the 1985 earthquake define a rupture area of 170 by 110 square kilometers. The earthquake was forecast on the basis of the nearly constant repeat time (83 +/- 9 years) of great earthquakes in this region. An analysis of previous earthquakes suggests that the rupture lengths of great shocks in the region vary by a factor of about 3. The nearly constant repeat time and variable rupture lengths cannot be reconciled with time- or slip-predictable models of earthquake recurrence. The great earthquakes in the region seem to involve a variable rupture mode and yet, for unknown reasons, remain periodic. Historical data suggest that the region south of the 1985 rupture zone should now be considered a gap of high seismic potential that may rupture in a great earthquake in the next few tens of years.

Correlation of data on strain accumulation adjacent to the San Andreas Fault with available models

Science.gov (United States)

Turcotte, Donald L.

1986-01-01

Theoretical and numerical studies of deformation on strike slip faults were performed and the results applied to geodetic observations performed in the vicinity of the San Andreas Fault in California. The initial efforts were devoted to an extensive series of finite element calculations of the deformation associated with cyclic displacements on a strike-slip fault. Measurements of strain accumulation adjacent to the San Andreas Fault indicate that the zone of strain accumulation extends only a few tens of kilometers away from the fault. There is a concern about the tendency to make geodetic observations along the line to the source. This technique has serious problems for strike slip faults since the vector velocity is also along the fault. Use of a series of stations lying perpendicular to the fault whose positions are measured relative to a reference station are suggested to correct the problem. The complexity of faulting adjacent to the San Andreas Fault indicated that the homogeneous elastic and viscoelastic approach to deformation had serious limitations. These limitation led to the proposal of an approach that assumes a fault is composed of a distribution of asperities and barriers on all scales. Thus, an earthquake on a fault is treated as a failure of a fractal tree. Work continued on the development of a fractal based model for deformation in the western United States. In order to better understand the distribution of seismicity on the San Andreas Fault system a fractal analog was developed. The fractal concept also provides a means of testing whether clustering in time or space is a scale-invariant process.

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

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...

Locating non-volcanic tremor along the San Andreas Fault using a multiple array source imaging technique

Science.gov (United States)

Ryberg, T.; Haberland, C.H.; Fuis, G.S.; Ellsworth, W.L.; Shelly, D.R.

2010-01-01

Non-volcanic tremor (NVT) has been observed at several subduction zones and at the San Andreas Fault (SAF). Tremor locations are commonly derived by cross-correlating envelope-transformed seismic traces in combination with source-scanning techniques. Recently, they have also been located by using relative relocations with master events, that is low-frequency earthquakes that are part of the tremor; locations are derived by conventional traveltime-based methods. Here we present a method to locate the sources of NVT using an imaging approach for multiple array data. The performance of the method is checked with synthetic tests and the relocation of earthquakes. We also applied the method to tremor occurring near Cholame, California. A set of small-aperture arrays (i.e. an array consisting of arrays) installed around Cholame provided the data set for this study. We observed several tremor episodes and located tremor sources in the vicinity of SAF. During individual tremor episodes, we observed a systematic change of source location, indicating rapid migration of the tremor source along SAF. ?? 2010 The Authors Geophysical Journal International ?? 2010 RAS.

The relationship between earthquake exposure and posttraumatic stress disorder in 2013 Lushan earthquake

Science.gov (United States)

Wang, Yan; Lu, Yi

2018-01-01

The objective of this study is to explore the relationship between earthquake exposure and the incidence of PTSD. A stratification random sample survey was conducted to collect data in the Longmenshan thrust fault after Lushan earthquake three years. We used the Children's Revised Impact of Event Scale (CRIES-13) and the Earthquake Experience Scale. Subjects in this study included 3944 school student survivors in local eleven schools. The prevalence of probable PTSD is relatively higher, when the people was trapped in the earthquake, was injured in the earthquake or have relatives who died in the earthquake. It concluded that researchers need to pay more attention to the children and adolescents. The government should pay more attention to these people and provide more economic support.

Fault Creep along the Southern San Andreas from Interferometric Synthetic Aperture Radar, Permanent Scatterers, and Stacking

Science.gov (United States)

Lyons, Suzanne; Sandwell, David

2003-01-01

Interferometric synthetic aperture radar (InSAR) provides a practical means of mapping creep along major strike-slip faults. The small amplitude of the creep signal (less than 10 mm/yr), combined with its short wavelength, makes it difficult to extract from long time span interferograms, especially in agricultural or heavily vegetated areas. We utilize two approaches to extract the fault creep signal from 37 ERS SAR images along the southem San Andreas Fault. First, amplitude stacking is utilized to identify permanent scatterers, which are then used to weight the interferogram prior to spatial filtering. This weighting improves correlation and also provides a mask for poorly correlated areas. Second, the unwrapped phase is stacked to reduce tropospheric and other short-wavelength noise. This combined processing enables us to recover the near-field (approximately 200 m) slip signal across the fault due to shallow creep. Displacement maps fiom 60 interferograms reveal a diffuse secular strain buildup, punctuated by localized interseismic creep of 4-6 mm/yr line of sight (LOS, 12-18 mm/yr horizontal). With the exception of Durmid Hill, this entire segment of the southern San Andreas experienced right-lateral triggered slip of up to 10 cm during the 3.5-year period spanning the 1992 Landers earthquake. The deformation change following the 1999 Hector Mine earthquake was much smaller (4 cm) and broader than for the Landers event. Profiles across the fault during the interseismic phase show peak-to-trough amplitude ranging from 15 to 25 mm/yr (horizontal component) and the minimum misfit models show a range of creeping/locking depth values that fit the data.

Crowdsourced earthquake early warning

Science.gov (United States)

Minson, Sarah E.; Brooks, Benjamin A.; Glennie, Craig L.; Murray, Jessica R.; Langbein, John O.; Owen, Susan E.; Heaton, Thomas H.; Iannucci, Robert A.; Hauser, Darren L.

2015-01-01

Earthquake early warning (EEW) can reduce harm to people and infrastructure from earthquakes and tsunamis, but it has not been implemented in most high earthquake-risk regions because of prohibitive cost. Common consumer devices such as smartphones contain low-cost versions of the sensors used in EEW. Although less accurate than scientific-grade instruments, these sensors are globally ubiquitous. Through controlled tests of consumer devices, simulation of an Mw (moment magnitude) 7 earthquake on California’s Hayward fault, and real data from the Mw 9 Tohoku-oki earthquake, we demonstrate that EEW could be achieved via crowdsourcing.

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...

Earthquake hazard evaluation for Switzerland

International Nuclear Information System (INIS)

Ruettener, E.

1995-01-01

Earthquake hazard analysis is of considerable importance for Switzerland, a country with moderate seismic activity but high economic values at risk. The evaluation of earthquake hazard, i.e. the determination of return periods versus ground motion parameters, requires a description of earthquake occurrences in space and time. In this study the seismic hazard for major cities in Switzerland is determined. The seismic hazard analysis is based on historic earthquake records as well as instrumental data. The historic earthquake data show considerable uncertainties concerning epicenter location and epicentral intensity. A specific concept is required, therefore, which permits the description of the uncertainties of each individual earthquake. This is achieved by probability distributions for earthquake size and location. Historical considerations, which indicate changes in public earthquake awareness at various times (mainly due to large historical earthquakes), as well as statistical tests have been used to identify time periods of complete earthquake reporting as a function of intensity. As a result, the catalog is judged to be complete since 1878 for all earthquakes with epicentral intensities greater than IV, since 1750 for intensities greater than VI, since 1600 for intensities greater than VIII, and since 1300 for intensities greater than IX. Instrumental data provide accurate information about the depth distribution of earthquakes in Switzerland. In the Alps, focal depths are restricted to the uppermost 15 km of the crust, whereas below the northern Alpine foreland earthquakes are distributed throughout the entire crust (30 km). This depth distribution is considered in the final hazard analysis by probability distributions. (author) figs., tabs., refs

Earthquake Clusters and Spatio-temporal Migration of earthquakes in Northeastern Tibetan Plateau: a Finite Element Modeling

Science.gov (United States)

Sun, Y.; Luo, G.

2017-12-01

Seismicity in a region is usually characterized by earthquake clusters and earthquake migration along its major fault zones. However, we do not fully understand why and how earthquake clusters and spatio-temporal migration of earthquakes occur. The northeastern Tibetan Plateau is a good example for us to investigate these problems. In this study, we construct and use a three-dimensional viscoelastoplastic finite-element model to simulate earthquake cycles and spatio-temporal migration of earthquakes along major fault zones in northeastern Tibetan Plateau. We calculate stress evolution and fault interactions, and explore effects of topographic loading and viscosity of middle-lower crust and upper mantle on model results. Model results show that earthquakes and fault interactions increase Coulomb stress on the neighboring faults or segments, accelerating the future earthquakes in this region. Thus, earthquakes occur sequentially in a short time, leading to regional earthquake clusters. Through long-term evolution, stresses on some seismogenic faults, which are far apart, may almost simultaneously reach the critical state of fault failure, probably also leading to regional earthquake clusters and earthquake migration. Based on our model synthetic seismic catalog and paleoseismic data, we analyze probability of earthquake migration between major faults in northeastern Tibetan Plateau. We find that following the 1920 M 8.5 Haiyuan earthquake and the 1927 M 8.0 Gulang earthquake, the next big event (M≥7) in northeastern Tibetan Plateau would be most likely to occur on the Haiyuan fault.

Relating seismicity to the velocity structure of the San Andreas Fault near Parkfield, CA

Science.gov (United States)

Lippoldt, Rachel; Porritt, Robert W.; Sammis, Charles G.

2017-06-01

The central section of the San Andreas Fault (SAF) displays a range of seismic phenomena including normal earthquakes, low-frequency earthquakes (LFE), repeating microearthquakes (REQ) and aseismic creep. Although many lines of evidence suggest that LFEs are tied to the presence of fluids, their geological setting is still poorly understood. Here, we map the seismic velocity structures associated with LFEs beneath the central SAF using surface wave tomography from ambient seismic noise to provide constraints on the physical conditions that control LFE occurrence. Fault perpendicular sections show that the SAF, as revealed by lateral contrasts in relative velocities, is contiguous to depths of 50 km and appears to be relatively localized at depths between about 15 and 30 km. This is consistent with the hypothesis that LFEs are shear-slip events on a deep extension of the SAF. We find that along strike variations in seismic behaviour correspond to changes in the seismic structure, which support proposed connections between fluids and seismicity. LFEs and REQs occur within low-velocity structures, suggesting that the presence of fluids, weaker minerals, or hydrous phase minerals may play an important role in the generation of slow-slip phenomena.

Perception of earthquake risk in Taiwan: effects of gender and past earthquake experience.

Science.gov (United States)

Kung, Yi-Wen; Chen, Sue-Huei

2012-09-01

This study explored how individuals in Taiwan perceive the risk of earthquake and the relationship of past earthquake experience and gender to risk perception. Participants (n= 1,405), including earthquake survivors and those in the general population without prior direct earthquake exposure, were selected and interviewed through a computer-assisted telephone interviewing procedure using a random sampling and stratification method covering all 24 regions of Taiwan. A factor analysis of the interview data yielded a two-factor structure of risk perception in regard to earthquake. The first factor, "personal impact," encompassed perception of threat and fear related to earthquakes. The second factor, "controllability," encompassed a sense of efficacy of self-protection in regard to earthquakes. The findings indicated prior earthquake survivors and females reported higher scores on the personal impact factor than males and those with no prior direct earthquake experience, although there were no group differences on the controllability factor. The findings support that risk perception has multiple components, and suggest that past experience (survivor status) and gender (female) affect the perception of risk. Exploration of potential contributions of other demographic factors such as age, education, and marital status to personal impact, especially for females and survivors, is discussed. Future research on and intervention program with regard to risk perception are suggested accordingly. © 2012 Society for Risk Analysis.

The earthquake problem in engineering design: generating earthquake design basis information

International Nuclear Information System (INIS)

Sharma, R.D.

1987-01-01

Designing earthquake resistant structures requires certain design inputs specific to the seismotectonic status of the region, in which a critical facility is to be located. Generating these inputs requires collection of earthquake related information using present day techniques in seismology and geology, and processing the collected information to integrate it to arrive at a consolidated picture of the seismotectonics of the region. The earthquake problem in engineering design has been outlined in the context of a seismic design of nuclear power plants vis a vis current state of the art techniques. The extent to which the accepted procedures of assessing seismic risk in the region and generating the design inputs have been adherred to determine to a great extent the safety of the structures against future earthquakes. The document is a step towards developing an aproach for generating these inputs, which form the earthquake design basis. (author)

76 FR 9709 - Water Quality Challenges in the San Francisco Bay/Sacramento-San Joaquin Delta Estuary

Science.gov (United States)

2011-02-22

... Water Quality Challenges in the San Francisco Bay/Sacramento-San Joaquin Delta Estuary AGENCY... the San Francisco Bay/ Sacramento-San Joaquin Delta Estuary (Bay Delta Estuary) in California. EPA is... programs to address recent significant declines in multiple aquatic species in the Bay Delta Estuary. EPA...

Limitation of the Predominant-Period Estimator for Earthquake Early Warning and the Initial Rupture of Earthquakes

Science.gov (United States)

Yamada, T.; Ide, S.

2007-12-01

Earthquake early warning is an important and challenging issue for the reduction of the seismic damage, especially for the mitigation of human suffering. One of the most important problems in earthquake early warning systems is how immediately we can estimate the final size of an earthquake after we observe the ground motion. It is relevant to the problem whether the initial rupture of an earthquake has some information associated with its final size. Nakamura (1988) developed the Urgent Earthquake Detection and Alarm System (UrEDAS). It calculates the predominant period of the P wave (τp) and estimates the magnitude of an earthquake immediately after the P wave arrival from the value of τpmax, or the maximum value of τp. The similar approach has been adapted by other earthquake alarm systems (e.g., Allen and Kanamori (2003)). To investigate the characteristic of the parameter τp and the effect of the length of the time window (TW) in the τpmax calculation, we analyze the high-frequency recordings of earthquakes at very close distances in the Mponeng mine in South Africa. We find that values of τpmax have upper and lower limits. For larger earthquakes whose source durations are longer than TW, the values of τpmax have an upper limit which depends on TW. On the other hand, the values for smaller earthquakes have a lower limit which is proportional to the sampling interval. For intermediate earthquakes, the values of τpmax are close to their typical source durations. These two limits and the slope for intermediate earthquakes yield an artificial final size dependence of τpmax in a wide size range. The parameter τpmax is useful for detecting large earthquakes and broadcasting earthquake early warnings. However, its dependence on the final size of earthquakes does not suggest that the earthquake rupture is deterministic. This is because τpmax does not always have a direct relation to the physical quantities of an earthquake.

Sun, Moon and Earthquakes

Science.gov (United States)

Kolvankar, V. G.

2013-12-01

During a study conducted to find the effect of Earth tides on the occurrence of earthquakes, for small areas [typically 1000km X1000km] of high-seismicity regions, it was noticed that the Sun's position in terms of universal time [GMT] shows links to the sum of EMD [longitude of earthquake location - longitude of Moon's foot print on earth] and SEM [Sun-Earth-Moon angle]. This paper provides the details of this relationship after studying earthquake data for over forty high-seismicity regions of the world. It was found that over 98% of the earthquakes for these different regions, examined for the period 1973-2008, show a direct relationship between the Sun's position [GMT] and [EMD+SEM]. As the time changes from 00-24 hours, the factor [EMD+SEM] changes through 360 degree, and plotting these two variables for earthquakes from different small regions reveals a simple 45 degree straight-line relationship between them. This relationship was tested for all earthquakes and earthquake sequences for magnitude 2.0 and above. This study conclusively proves how Sun and the Moon govern all earthquakes. Fig. 12 [A+B]. The left-hand figure provides a 24-hour plot for forty consecutive days including the main event (00:58:23 on 26.12.2004, Lat.+3.30, Long+95.980, Mb 9.0, EQ count 376). The right-hand figure provides an earthquake plot for (EMD+SEM) vs GMT timings for the same data. All the 376 events including the main event faithfully follow the straight-line curve.

Fault healing and earthquake spectra from stick slip sequences in the laboratory and on active faults

Science.gov (United States)

McLaskey, G. C.; Glaser, S. D.; Thomas, A.; Burgmann, R.

2011-12-01

Repeating earthquake sequences (RES) are thought to occur on isolated patches of a fault that fail in repeated stick-slip fashion. RES enable researchers to study the effect of variations in earthquake recurrence time and the relationship between fault healing and earthquake generation. Fault healing is thought to be the physical process responsible for the 'state' variable in widely used rate- and state-dependent friction equations. We analyze RES created in laboratory stick slip experiments on a direct shear apparatus instrumented with an array of very high frequency (1KHz - 1MHz) displacement sensors. Tests are conducted on the model material polymethylmethacrylate (PMMA). While frictional properties of this glassy polymer can be characterized with the rate- and state- dependent friction laws, the rate of healing in PMMA is higher than room temperature rock. Our experiments show that in addition to a modest increase in fault strength and stress drop with increasing healing time, there are distinct spectral changes in the recorded laboratory earthquakes. Using the impact of a tiny sphere on the surface of the test specimen as a known source calibration function, we are able to remove the instrument and apparatus response from recorded signals so that the source spectrum of the laboratory earthquakes can be accurately estimated. The rupture of a fault that was allowed to heal produces a laboratory earthquake with increased high frequency content compared to one produced by a fault which has had less time to heal. These laboratory results are supported by observations of RES on the Calaveras and San Andreas faults, which show similar spectral changes when recurrence time is perturbed by a nearby large earthquake. Healing is typically attributed to a creep-like relaxation of the material which causes the true area of contact of interacting asperity populations to increase with time in a quasi-logarithmic way. The increase in high frequency seismicity shown here

In-situ measurements of seismic velocities in the San Francisco Bay Region; part III

Science.gov (United States)

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

1977-01-01

Seismic wave velocities (compressional and shear) are important parameters for estimating 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. In the current program seismic velocities have been measured at 59 locations 1n the San Francisco Bay Region. This report is the third in a series of Open-File Reports and describes the in-situ velocity measurements at locations 35-59. At each location 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 cuttings, undisturbed (cored) 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 sites. 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. There is a variety of geologic and seismic data available in the San Francisco Bay Region for use 1n developing the general zoning techniques which can then be applied to other areas. Shear wave velocities 1n near-surface geologic materials are of especial interest for engineering seismology and seismic zonation studies, yet in general, they are difficult to measure because of contamination by compressional waves. A comparison of various in-situ techniques by Warrick (1974) establishes the reliability of the method utilizing a "horizontal traction" source for sites underlain by bay mud and alluvium. Gibbs, and others (1975a) present data from 12 holes and establishes the reliability of the method for sites underlain by a variety of different rock units and suggest extending the measurements to

Earthquake engineering development before and after the March 4, 1977, Vrancea, Romania earthquake

International Nuclear Information System (INIS)

Georgescu, E.-S.

2002-01-01

At 25 years since the of the Vrancea earthquake of March, 4th 1977, we can analyze in an open and critical way its impact on the evolution of earthquake engineering codes and protection policies in Romania. The earthquake (M G-R = 7.2; M w = 7.5), produced 1,570 casualties and more than 11,300 injured persons (90% of the victims in Bucharest), seismic losses were estimated at more then USD 2 billions. The 1977 earthquake represented a significant episode of XXth century in seismic zones of Romania and neighboring countries. The INCERC seismic record of March 4, 1977 put, for the first time, in evidence the spectral content of long period seismic motions of Vrancea earthquakes, the duration, the number of cycles and values of actual accelerations, with important effects of overloading upon flexible structures. The seismic coefficients k s , the spectral curve (the dynamic coefficient β r ) and the seismic zonation map, the requirements in the antiseismic design norms were drastically, changed while the microzonation maps of the time ceased to be used, and the specific Vrancea earthquake recurrence was reconsidered based on hazard studies Thus, the paper emphasises: - the existing engineering knowledge, earthquake code and zoning maps requirements until 1977 as well as seismology and structural lessons since 1977; - recent aspects of implementing of the Earthquake Code P.100/1992 and harmonization with Eurocodes, in conjunction with the specific of urban and rural seismic risk and enforcing policies on strengthening of existing buildings; - a strategic view of disaster prevention, using earthquake scenarios and loss assessments, insurance, earthquake education and training; - the need of a closer transfer of knowledge between seismologists, engineers and officials in charge with disaster prevention public policies. (author)

Influence of Vegetation on the Avifauna in Two Urban Parks in Plovdiv, Bulgaria

Directory of Open Access Journals (Sweden)

Yanitsa Petrova

2012-12-01

Full Text Available This study is related to the investigation of the impact that vegetation caused on the avifauna of the parks “Lauta” and “Tsar Simeon Garden” located in the city of Plovdiv, Bulgaria. As a result of the study, we found that the biodiversity of the vegetation in park “Tsar Simeon Garden” is highly significant in comparison with the same in park “Lauta”. In the park “Tsar Simeon Garden” introduced plant species dominate over indigenous species, as compared with the park “Lauta”. The differences in the vegetation are caused by different management approaches carried out in the both parks. The degree of similarity between trees and bushes in both parks is low. The vegetation also had a significant influence on the avifauna living within the parks. The avian biodiversity in park “Lauta” is two times higher in comparison with the avian biodiversity in park “Tsar Simeon Garden”. The degree of similarity in the avifauna between both parks is significant, due the fact that all of the species, except one documented in “Tsar Simeon Garden” being documented in park “Lauta” as well. Eighteen new species of birds were recorded and described for the first time in the city of Plovdiv. The conservation status of the avifauna in park “Lauta” is quite significant in comparison with the same in park “Tsar Simeon Garden”.

33 CFR 165.776 - Security Zone; Coast Guard Base San Juan, San Juan Harbor, Puerto Rico

Science.gov (United States)

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Security Zone; Coast Guard Base San Juan, San Juan Harbor, Puerto Rico 165.776 Section 165.776 Navigation and Navigable Waters COAST... Guard District § 165.776 Security Zone; Coast Guard Base San Juan, San Juan Harbor, Puerto Rico (a...

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.

Toward real-time regional earthquake simulation of Taiwan earthquakes

Science.gov (United States)

Lee, S.; Liu, Q.; Tromp, J.; Komatitsch, D.; Liang, W.; Huang, B.

2013-12-01

We developed a Real-time Online earthquake Simulation system (ROS) to simulate regional earthquakes in Taiwan. The ROS uses a centroid moment tensor solution of seismic events from a Real-time Moment Tensor monitoring system (RMT), which provides all the point source parameters including the event origin time, hypocentral location, moment magnitude and focal mechanism within 2 minutes after the occurrence of an earthquake. Then, all of the source parameters are automatically forwarded to the ROS to perform an earthquake simulation, which is based on a spectral-element method (SEM). We have improved SEM mesh quality by introducing a thin high-resolution mesh layer near the surface to accommodate steep and rapidly varying topography. The mesh for the shallow sedimentary basin is adjusted to reflect its complex geometry and sharp lateral velocity contrasts. The grid resolution at the surface is about 545 m, which is sufficient to resolve topography and tomography data for simulations accurate up to 1.0 Hz. The ROS is also an infrastructural service, making online earthquake simulation feasible. Users can conduct their own earthquake simulation by providing a set of source parameters through the ROS webpage. For visualization, a ShakeMovie and ShakeMap are produced during the simulation. The time needed for one event is roughly 3 minutes for a 70 sec ground motion simulation. The ROS is operated online at the Institute of Earth Sciences, Academia Sinica (http://ros.earth.sinica.edu.tw/). Our long-term goal for the ROS system is to contribute to public earth science outreach and to realize seismic ground motion prediction in real-time.

Geophysical Anomalies and Earthquake Prediction

Science.gov (United States)

Jackson, D. D.

2008-12-01

Finding anomalies is easy. Predicting earthquakes convincingly from such anomalies is far from easy. Why? Why have so many beautiful geophysical abnormalities not led to successful prediction strategies? What is earthquake prediction? By my definition it is convincing information that an earthquake of specified size is temporarily much more likely than usual in a specific region for a specified time interval. We know a lot about normal earthquake behavior, including locations where earthquake rates are higher than elsewhere, with estimable rates and size distributions. We know that earthquakes have power law size distributions over large areas, that they cluster in time and space, and that aftershocks follow with power-law dependence on time. These relationships justify prudent protective measures and scientific investigation. Earthquake prediction would justify exceptional temporary measures well beyond those normal prudent actions. Convincing earthquake prediction would result from methods that have demonstrated many successes with few false alarms. Predicting earthquakes convincingly is difficult for several profound reasons. First, earthquakes start in tiny volumes at inaccessible depth. The power law size dependence means that tiny unobservable ones are frequent almost everywhere and occasionally grow to larger size. Thus prediction of important earthquakes is not about nucleation, but about identifying the conditions for growth. Second, earthquakes are complex. They derive their energy from stress, which is perniciously hard to estimate or model because it is nearly singular at the margins of cracks and faults. Physical properties vary from place to place, so the preparatory processes certainly vary as well. Thus establishing the needed track record for validation is very difficult, especially for large events with immense interval times in any one location. Third, the anomalies are generally complex as well. Electromagnetic anomalies in particular require

Historical earthquake research in Austria

Science.gov (United States)

Hammerl, Christa

2017-12-01

Austria has a moderate seismicity, and on average the population feels 40 earthquakes per year or approximately three earthquakes per month. A severe earthquake with light building damage is expected roughly every 2 to 3 years in Austria. Severe damage to buildings ( I 0 > 8° EMS) occurs significantly less frequently, the average period of recurrence is about 75 years. For this reason the historical earthquake research has been of special importance in Austria. The interest in historical earthquakes in the past in the Austro-Hungarian Empire is outlined, beginning with an initiative of the Austrian Academy of Sciences and the development of historical earthquake research as an independent research field after the 1978 "Zwentendorf plebiscite" on whether the nuclear power plant will start up. The applied methods are introduced briefly along with the most important studies and last but not least as an example of a recently carried out case study, one of the strongest past earthquakes in Austria, the earthquake of 17 July 1670, is presented. The research into historical earthquakes in Austria concentrates on seismic events of the pre-instrumental period. The investigations are not only of historical interest, but also contribute to the completeness and correctness of the Austrian earthquake catalogue, which is the basis for seismic hazard analysis and as such benefits the public, communities, civil engineers, architects, civil protection, and many others.

Three-Dimensional Finite Difference Simulation of Ground Motions from the August 24, 2014 South Napa Earthquake

Energy Technology Data Exchange (ETDEWEB)

Rodgers, Arthur J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Berkeley, CA (United States); Dreger, Douglas S. [Univ. of California, Berkeley, CA (United States); Pitarka, Arben [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-06-15

We performed three-dimensional (3D) anelastic ground motion simulations of the South Napa earthquake to investigate the performance of different finite rupture models and the effects of 3D structure on the observed wavefield. We considered rupture models reported by Dreger et al. (2015), Ji et al., (2015), Wei et al. (2015) and Melgar et al. (2015). We used the SW4 anelastic finite difference code developed at Lawrence Livermore National Laboratory (Petersson and Sjogreen, 2013) and distributed by the Computational Infrastructure for Geodynamics. This code can compute the seismic response for fully 3D sub-surface models, including surface topography and linear anelasticity. We use the 3D geologic/seismic model of the San Francisco Bay Area developed by the United States Geological Survey (Aagaard et al., 2008, 2010). Evaluation of earlier versions of this model indicated that the structure can reproduce main features of observed waveforms from moderate earthquakes (Rodgers et al., 2008; Kim et al., 2010). Simulations were performed for a domain covering local distances (< 25 km) and resolution providing simulated ground motions valid to 1 Hz.

Time-lapse imaging of fault properties at seismogenic depth using repeating earthquakes, active sources and seismic ambient noise

Science.gov (United States)

Cheng, Xin

2009-12-01

The time-varying stress field of fault systems at seismogenic depths plays the mort important role in controlling the sequencing and nucleation of seismic events. Using seismic observations from repeating earthquakes, controlled active sources and seismic ambient noise, five studies at four different fault systems across North America, Central Japan, North and mid-West China are presented to describe our efforts to measure such time dependent structural properties. Repeating and similar earthquakes are hunted and analyzed to study the post-seismic fault relaxation at the aftershock zone of the 1984 M 6.8 western Nagano and the 1976 M 7.8 Tangshan earthquakes. The lack of observed repeating earthquakes at western Nagano is attributed to the absence of a well developed weak fault zone, suggesting that the fault damage zone has been almost completely healed. In contrast, the high percentage of similar and repeating events found at Tangshan suggest the existence of mature fault zones characterized by stable creep under steady tectonic loading. At the Parkfield region of the San Andreas Fault, repeating earthquake clusters and chemical explosions are used to construct a scatterer migration image based on the observation of systematic temporal variations in the seismic waveforms across the occurrence time of the 2004 M 6 Parkfield earthquake. Coseismic fluid charge or discharge in fractures caused by the Parkfield earthquake is used to explain the observed seismic scattering properties change at depth. In the same region, a controlled source cross-well experiment conducted at SAFOD pilot and main holes documents two large excursions in the travel time required for a shear wave to travel through the rock along a fixed pathway shortly before two rupture events, suggesting that they may be related to pre-rupture stress induced changes in crack properties. At central China, a tomographic inversion based on the theory of seismic ambient noise and coda wave interferometry

The Elizabeth Lake paleoseismic site: Rupture pattern constraints for the past ~800 years for the Mojave section of the south-central San Andreas Fault

Science.gov (United States)

Bemis, Sean; Scharer, Katherine M.; Dolan, James F.; Rhodes, Ed

2016-01-01

The southern San Andreas Fault in California has hosted two historic surface-rupturing earthquakes, the ~M7 1812 Wrightwood earthquake and the ~M7.9 1857 Fort Tejon earthquake (e.g., Sieh, 1978; Jacoby et al., 1988). Numerous paleoseismic studies have established chronologies of historic and prehistoric earthquakes at sites along the full length of the 1857 rupture (e.g., Sieh, 1978; Scharer et al., 2014). These studies provide an unparalleled opportunity to examine patterns of recent ruptures; however, at least two significant spatial gaps in high-quality paleoseismic sites remain. At ~100 km long each, these gaps contribute up to 100 km of uncertainty to paleo-rupture lengths and could also permit a surface rupture from an earthquake up to ~M7.2 to go undetected [using scaling relationships of Wells and Coppersmith (1994)]. Given the known occurrence of an ~M7 earthquake on this portion of the SAF (1812), it is critical to fill these gaps in order to better constrain paleo-rupture lengths and to increase the probability of capturing the full spatial record of surface rupturing earthquakes.   In this study, we target a new site within the 100 km long stretch of the San Andreas Fault between the Frazier Mountain and Pallett Creek paleoseismic sites (Figure 1), near Elizabeth Lake, California. Prior excavations at the site during 1998-1999 encountered promising stratigraphy but these studies were hindered by shallow groundwater throughout the site. We began our current phase of investigations in 2012, targeting the northwestern end of a 40 x 350 m fault-parallel depression that defines the site (Figure 2). Subsequent investigations in 2013 and 2014 focused on the southeastern end of the depression where the fault trace is constrained between topographic highs and is proximal to an active drainage. In total, our paleoseismic investigations consist of 10 fault-perpendicular trenches that cross the depression (Figure 2) and expose a >2000 year depositional record

Enhanced Preliminary Assessment Report: Presidio of San Francisco Military Reservation, San Francisco, California

Science.gov (United States)

1989-11-01

CAD981415656 Filmore Steiner Bay San Francisco 24 PG&E Gas Plant SanFran 502-IG CAD981415714 Bay North Point Buchanan Laguna 25 PG&E Gas Plant SanFran 502-1H...76-ioV /5,JO /0.7 /,230 PSF Water PSF, Main U.N. Lagunda Honda Analvte Plant Clearwell Reservoir Plaza Reservoi- Chlordane inetab. ə.2 ə.2 (1.2 ə.2

Where was the 1898 Mare Island Earthquake? Insights from the 2014 South Napa Earthquake

Science.gov (United States)

Hough, S. E.

2014-12-01

The 2014 South Napa earthquake provides an opportunity to reconsider the Mare Island earthquake of 31 March 1898, which caused severe damage to buildings at a Navy yard on the island. Revising archival accounts of the 1898 earthquake, I estimate a lower intensity magnitude, 5.8, than the value in the current Uniform California Earthquake Rupture Forecast (UCERF) catalog (6.4). However, I note that intensity magnitude can differ from Mw by upwards of half a unit depending on stress drop, which for a historical earthquake is unknowable. In the aftermath of the 2014 earthquake, there has been speculation that apparently severe effects on Mare Island in 1898 were due to the vulnerability of local structures. No surface rupture has ever been identified from the 1898 event, which is commonly associated with the Hayward-Rodgers Creek fault system, some 10 km west of Mare Island (e.g., Parsons et al., 2003). Reconsideration of detailed archival accounts of the 1898 earthquake, together with a comparison of the intensity distributions for the two earthquakes, points to genuinely severe, likely near-field ground motions on Mare Island. The 2014 earthquake did cause significant damage to older brick buildings on Mare Island, but the level of damage does not match the severity of documented damage in 1898. The high intensity files for the two earthquakes are more over spatially shifted, with the centroid of the 2014 distribution near the town of Napa and that of the 1898 distribution near Mare Island, east of the Hayward-Rodgers Creek system. I conclude that the 1898 Mare Island earthquake was centered on or near Mare Island, possibly involving rupture of one or both strands of the Franklin fault, a low-slip-rate fault sub-parallel to the Rodgers Creek fault to the west and the West Napa fault to the east. I estimate Mw5.8 assuming an average stress drop; data are also consistent with Mw6.4 if stress drop was a factor of ≈3 lower than average for California earthquakes. I

Earthquakes, May-June 1991

Science.gov (United States)

Person, W.J.

1992-01-01

One major earthquake occurred during this reporting period. This was a magntidue 7.1 in Indonesia (Minahassa Peninsula) on June 20. Earthquake-related deaths were reported in the Western Caucasus (Georgia, USSR) on May 3 and June 15. One earthquake-related death was also reported El Salvador on June 21. 

Modeling, Forecasting and Mitigating Extreme Earthquakes

Science.gov (United States)

Ismail-Zadeh, A.; Le Mouel, J.; Soloviev, A.

2012-12-01

Recent earthquake disasters highlighted the importance of multi- and trans-disciplinary studies of earthquake risk. A major component of earthquake disaster risk analysis is hazards research, which should cover not only a traditional assessment of ground shaking, but also studies of geodetic, paleoseismic, geomagnetic, hydrological, deep drilling and other geophysical and geological observations together with comprehensive modeling of earthquakes and forecasting extreme events. Extreme earthquakes (large magnitude and rare events) are manifestations of complex behavior of the lithosphere structured as a hierarchical system of blocks of different sizes. Understanding of physics and dynamics of the extreme events comes from observations, measurements and modeling. A quantitative approach to simulate earthquakes in models of fault dynamics will be presented. The models reproduce basic features of the observed seismicity (e.g., the frequency-magnitude relationship, clustering of earthquakes, occurrence of extreme seismic events). They provide a link between geodynamic processes and seismicity, allow studying extreme events, influence of fault network properties on seismic patterns and seismic cycles, and assist, in a broader sense, in earthquake forecast modeling. Some aspects of predictability of large earthquakes (how well can large earthquakes be predicted today?) will be also discussed along with possibilities in mitigation of earthquake disasters (e.g., on 'inverse' forensic investigations of earthquake disasters).

Earthquake Catalogue of the Caucasus

Science.gov (United States)

Godoladze, T.; Gok, R.; Tvaradze, N.; Tumanova, N.; Gunia, I.; Onur, T.

2016-12-01

The Caucasus has a documented historical catalog stretching back to the beginning of the Christian era. Most of the largest historical earthquakes prior to the 19th century are assumed to have occurred on active faults of the Greater Caucasus. Important earthquakes include the Samtskhe earthquake of 1283 (Ms˜7.0, Io=9); Lechkhumi-Svaneti earthquake of 1350 (Ms˜7.0, Io=9); and the Alaverdi earthquake of 1742 (Ms˜6.8, Io=9). Two significant historical earthquakes that may have occurred within the Javakheti plateau in the Lesser Caucasus are the Tmogvi earthquake of 1088 (Ms˜6.5, Io=9) and the Akhalkalaki earthquake of 1899 (Ms˜6.3, Io =8-9). Large earthquakes that occurred in the Caucasus within the period of instrumental observation are: Gori 1920; Tabatskuri 1940; Chkhalta 1963; Racha earthquake of 1991 (Ms=7.0), is the largest event ever recorded in the region; Barisakho earthquake of 1992 (M=6.5); Spitak earthquake of 1988 (Ms=6.9, 100 km south of Tbilisi), which killed over 50,000 people in Armenia. Recently, permanent broadband stations have been deployed across the region as part of the various national networks (Georgia (˜25 stations), Azerbaijan (˜35 stations), Armenia (˜14 stations)). The data from the last 10 years of observation provides an opportunity to perform modern, fundamental scientific investigations. In order to improve seismic data quality a catalog of all instrumentally recorded earthquakes has been compiled by the IES (Institute of Earth Sciences/NSMC, Ilia State University) in the framework of regional joint project (Armenia, Azerbaijan, Georgia, Turkey, USA) "Probabilistic Seismic Hazard Assessment (PSHA) in the Caucasus. The catalogue consists of more then 80,000 events. First arrivals of each earthquake of Mw>=4.0 have been carefully examined. To reduce calculation errors, we corrected arrivals from the seismic records. We improved locations of the events and recalculate Moment magnitudes in order to obtain unified magnitude

Earthquakes in El Salvador: a descriptive study of health concerns in a rural community and the clinical implications--part II.

Science.gov (United States)

Woersching, Joanna C; Snyder, Audrey E

2004-01-01

Results reported in Part I of the Earthquakes in El Salvador series (see Disaster Management & Response 2003;1:105-9) indicated clinically relevant findings. The findings indicated a need for greater public health action within all five categories reviewed: healthcare, access to healthcare, housing, food, water and sanitation. Significant results between urban and rural communities indicated a need for broader community aid, public health and sanitation services to rural areas. Faster and more efficient disaster management and care services throughout the San Sebastian community were also necessary modifications.

Natural Time and Nowcasting Earthquakes: Are Large Global Earthquakes Temporally Clustered?

Science.gov (United States)

Luginbuhl, Molly; Rundle, John B.; Turcotte, Donald L.

2018-02-01

The objective of this paper is to analyze the temporal clustering of large global earthquakes with respect to natural time, or interevent count, as opposed to regular clock time. To do this, we use two techniques: (1) nowcasting, a new method of statistically classifying seismicity and seismic risk, and (2) time series analysis of interevent counts. We chose the sequences of M_{λ } ≥ 7.0 and M_{λ } ≥ 8.0 earthquakes from the global centroid moment tensor (CMT) catalog from 2004 to 2016 for analysis. A significant number of these earthquakes will be aftershocks of the largest events, but no satisfactory method of declustering the aftershocks in clock time is available. A major advantage of using natural time is that it eliminates the need for declustering aftershocks. The event count we utilize is the number of small earthquakes that occur between large earthquakes. The small earthquake magnitude is chosen to be as small as possible, such that the catalog is still complete based on the Gutenberg-Richter statistics. For the CMT catalog, starting in 2004, we found the completeness magnitude to be M_{σ } ≥ 5.1. For the nowcasting method, the cumulative probability distribution of these interevent counts is obtained. We quantify the distribution using the exponent, β, of the best fitting Weibull distribution; β = 1 for a random (exponential) distribution. We considered 197 earthquakes with M_{λ } ≥ 7.0 and found β = 0.83 ± 0.08. We considered 15 earthquakes with M_{λ } ≥ 8.0, but this number was considered too small to generate a meaningful distribution. For comparison, we generated synthetic catalogs of earthquakes that occur randomly with the Gutenberg-Richter frequency-magnitude statistics. We considered a synthetic catalog of 1.97 × 10^5 M_{λ } ≥ 7.0 earthquakes and found β = 0.99 ± 0.01. The random catalog converted to natural time was also random. We then generated 1.5 × 10^4 synthetic catalogs with 197 M_{λ } ≥ 7.0 in each catalog and

Earthquake hazard assessment and small earthquakes

International Nuclear Information System (INIS)

Reiter, L.

1987-01-01

The significance of small earthquakes and their treatment in nuclear power plant seismic hazard assessment is an issue which has received increased attention over the past few years. In probabilistic studies, sensitivity studies showed that the choice of the lower bound magnitude used in hazard calculations can have a larger than expected effect on the calculated hazard. Of particular interest is the fact that some of the difference in seismic hazard calculations between the Lawrence Livermore National Laboratory (LLNL) and Electric Power Research Institute (EPRI) studies can be attributed to this choice. The LLNL study assumed a lower bound magnitude of 3.75 while the EPRI study assumed a lower bound magnitude of 5.0. The magnitudes used were assumed to be body wave magnitudes or their equivalents. In deterministic studies recent ground motion recordings of small to moderate earthquakes at or near nuclear power plants have shown that the high frequencies of design response spectra may be exceeded. These exceedances became important issues in the licensing of the Summer and Perry nuclear power plants. At various times in the past particular concerns have been raised with respect to the hazard and damage potential of small to moderate earthquakes occurring at very shallow depths. In this paper a closer look is taken at these issues. Emphasis is given to the impact of lower bound magnitude on probabilistic hazard calculations and the historical record of damage from small to moderate earthquakes. Limited recommendations are made as to how these issues should be viewed

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.

Historic Eastern Canadian earthquakes

International Nuclear Information System (INIS)

Asmis, G.J.K.; Atchinson, R.J.

1981-01-01

Nuclear power plants licensed in Canada have been designed to resist earthquakes: not all plants, however, have been explicitly designed to the same level of earthquake induced forces. Understanding the nature of strong ground motion near the source of the earthquake is still very tentative. This paper reviews historical and scientific accounts of the three strongest earthquakes - St. Lawrence (1925), Temiskaming (1935), Cornwall (1944) - that have occurred in Canada in 'modern' times, field studies of near-field strong ground motion records and their resultant damage or non-damage to industrial facilities, and numerical modelling of earthquake sources and resultant wave propagation to produce accelerograms consistent with the above historical record and field studies. It is concluded that for future construction of NPP's near-field strong motion must be explicitly considered in design

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...

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.

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…

Excel, Earthquakes, and Moneyball: exploring Cascadia earthquake probabilities using spreadsheets and baseball analogies

Science.gov (United States)

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

2017-12-01

Much recent media attention focuses on Cascadia's earthquake hazard. A widely cited magazine article starts "An earthquake will destroy a sizable portion of the coastal Northwest. The question is when." Stories include statements like "a massive earthquake is overdue", "in the next 50 years, there is a 1-in-10 chance a "really big one" will erupt," or "the odds of the big Cascadia earthquake happening in the next fifty years are roughly one in three." These lead students to ask where the quoted probabilities come from and what they mean. These probability estimates involve two primary choices: what data are used to describe when past earthquakes happened and what models are used to forecast when future earthquakes will happen. The data come from a 10,000-year record of large paleoearthquakes compiled from subsidence data on land and turbidites, offshore deposits recording submarine slope failure. Earthquakes seem to have happened in clusters of four or five events, separated by gaps. Earthquakes within a cluster occur more frequently and regularly than in the full record. Hence the next earthquake is more likely if we assume that we are in the recent cluster that started about 1700 years ago, than if we assume the cluster is over. Students can explore how changing assumptions drastically changes probability estimates using easy-to-write and display spreadsheets, like those shown below. Insight can also come from baseball analogies. The cluster issue is like deciding whether to assume that a hitter's performance in the next game is better described by his lifetime record, or by the past few games, since he may be hitting unusually well or in a slump. The other big choice is whether to assume that the probability of an earthquake is constant with time, or is small immediately after one occurs and then grows with time. This is like whether to assume that a player's performance is the same from year to year, or changes over their career. Thus saying "the chance of

76 FR 10945 - San Luis Trust Bank, FSB, San Luis Obispo, CA; Notice of Appointment of Receiver

Science.gov (United States)

2011-02-28

... DEPARTMENT OF THE TREASURY Office of Thrift Supervision San Luis Trust Bank, FSB, San Luis Obispo, CA; Notice of Appointment of Receiver Notice is hereby given that, pursuant to the authority... appointed the Federal Deposit Insurance Corporation as sole Receiver for San Luis Trust Bank, FSB, San Luis...

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.

Toward real-time regional earthquake simulation II: Real-time Online earthquake Simulation (ROS) of Taiwan earthquakes

Science.gov (United States)

Lee, Shiann-Jong; Liu, Qinya; Tromp, Jeroen; Komatitsch, Dimitri; Liang, Wen-Tzong; Huang, Bor-Shouh

2014-06-01

We developed a Real-time Online earthquake Simulation system (ROS) to simulate regional earthquakes in Taiwan. The ROS uses a centroid moment tensor solution of seismic events from a Real-time Moment Tensor monitoring system (RMT), which provides all the point source parameters including the event origin time, hypocentral location, moment magnitude and focal mechanism within 2 min after the occurrence of an earthquake. Then, all of the source parameters are automatically forwarded to the ROS to perform an earthquake simulation, which is based on a spectral-element method (SEM). A new island-wide, high resolution SEM mesh model is developed for the whole Taiwan in this study. We have improved SEM mesh quality by introducing a thin high-resolution mesh layer near the surface to accommodate steep and rapidly varying topography. The mesh for the shallow sedimentary basin is adjusted to reflect its complex geometry and sharp lateral velocity contrasts. The grid resolution at the surface is about 545 m, which is sufficient to resolve topography and tomography data for simulations accurate up to 1.0 Hz. The ROS is also an infrastructural service, making online earthquake simulation feasible. Users can conduct their own earthquake simulation by providing a set of source parameters through the ROS webpage. For visualization, a ShakeMovie and ShakeMap are produced during the simulation. The time needed for one event is roughly 3 min for a 70 s ground motion simulation. The ROS is operated online at the Institute of Earth Sciences, Academia Sinica (http://ros.earth.sinica.edu.tw/). Our long-term goal for the ROS system is to contribute to public earth science outreach and to realize seismic ground motion prediction in real-time.

Sedimentary Signatures of Submarine Earthquakes: Deciphering the Extent of Sediment Remobilization from the 2011 Tohoku Earthquake and Tsunami and 2010 Haiti Earthquake

Science.gov (United States)

McHugh, C. M.; Seeber, L.; Moernaut, J.; Strasser, M.; Kanamatsu, T.; Ikehara, K.; Bopp, R.; Mustaque, S.; Usami, K.; Schwestermann, T.; Kioka, A.; Moore, L. M.

2017-12-01

The 2004 Sumatra-Andaman Mw9.3 and the 2011 Tohoku (Japan) Mw9.0 earthquakes and tsunamis were huge geological events with major societal consequences. Both were along subduction boundaries and ruptured portions of these boundaries that had been deemed incapable of such events. Submarine strike-slip earthquakes, such as the 2010 Mw7.0 in Haiti, are smaller but may be closer to population centers and can be similarly catastrophic. Both classes of earthquakes remobilize sediment and leave distinct signatures in the geologic record by a wide range of processes that depends on both environment and earthquake characteristics. Understanding them has the potential of greatly expanding the record of past earthquakes, which is critical for geohazard analysis. Recent events offer precious ground truth about the earthquakes and short-lived radioisotopes offer invaluable tools to identify sediments they remobilized. In the 2011 Mw9 Japan earthquake they document the spatial extent of remobilized sediment from water depths of 626m in the forearc slope to trench depths of 8000m. Subbottom profiles, multibeam bathymetry and 40 piston cores collected by the R/V Natsushima and R/V Sonne expeditions to the Japan Trench document multiple turbidites and high-density flows. Core tops enriched in xs210Pb,137Cs and 134Cs reveal sediment deposited by the 2011 Tohoku earthquake and tsunami. The thickest deposits (2m) were documented on a mid-slope terrace and trench (4000-8000m). Sediment was deposited on some terraces (600-3000m), but shed from the steep forearc slope (3000-4000m). The 2010 Haiti mainshock ruptured along the southern flank of Canal du Sud and triggered multiple nearshore sediment failures, generated turbidity currents and stirred fine sediment into suspension throughout this basin. A tsunami was modeled to stem from both sediment failures and tectonics. Remobilized sediment was tracked with short-lived radioisotopes from the nearshore, slope, in fault basins including the

Analysis of pre-earthquake ionospheric anomalies before the global M = 7.0+ earthquakes in 2010

Directory of Open Access Journals (Sweden)

W. F. Peng

2012-03-01

Full Text Available The pre-earthquake ionospheric anomalies that occurred before the global M = 7.0+ earthquakes in 2010 are investigated using the total electron content (TEC from the global ionosphere map (GIM. We analyze the possible causes of the ionospheric anomalies based on the space environment and magnetic field status. Results show that some anomalies are related to the earthquakes. By analyzing the time of occurrence, duration, and spatial distribution of these ionospheric anomalies, a number of new conclusions are drawn, as follows: earthquake-related ionospheric anomalies are not bound to appear; both positive and negative anomalies are likely to occur; and the earthquake-related ionospheric anomalies discussed in the current study occurred 0–2 days before the associated earthquakes and in the afternoon to sunset (i.e. between 12:00 and 20:00 local time. Pre-earthquake ionospheric anomalies occur mainly in areas near the epicenter. However, the maximum affected area in the ionosphere does not coincide with the vertical projection of the epicenter of the subsequent earthquake. The directions deviating from the epicenters do not follow a fixed rule. The corresponding ionospheric effects can also be observed in the magnetically conjugated region. However, the probability of the anomalies appearance and extent of the anomalies in the magnetically conjugated region are smaller than the anomalies near the epicenter. Deep-focus earthquakes may also exhibit very significant pre-earthquake ionospheric anomalies.

76 FR 22809 - Safety Zone; Bay Ferry II Maritime Security Exercise; San Francisco Bay, San Francisco, CA

Science.gov (United States)

2011-04-25

... DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 165 [Docket No. USCG-2011-0196] RIN 1625-AA00 Safety Zone; Bay Ferry II Maritime Security Exercise; San Francisco Bay, San Francisco, CA AGENCY... Security Exercise; San Francisco Bay, San Francisco, CA. (a) Location. The limits of this safety zone...

Scientific drilling into the San Andreas fault and site characterization research: Planning and coordination efforts. Final technical report

Energy Technology Data Exchange (ETDEWEB)

Zoback, M.D.

1998-08-30

The fundamental scientific issue addressed in this proposal, obtaining an improved understanding of the physical and chemical processes responsible for earthquakes along major fault zones, is clearly of global scientific interest. By sampling the San Andreas fault zone and making direct measurements of fault zone properties to 4.0 km at Parkfield they will be studying an active plate-boundary fault at a depth where aseismic creep and small earthquakes occur and where a number of the scientific questions associated with deeper fault zone drilling can begin to be addressed. Also, the technological challenges associated with drilling, coring, downhole measurements and borehole instrumentation that may eventually have to be faced in deeper drilling can first be addressed at moderate depth and temperature in the Parkfield hole. Throughout the planning process leading to the development of this proposal they have invited participation by scientists from around the world. As a result, the workshops and meetings they have held for this project have involved about 350 scientists and engineers from about a dozen countries.

The 2008 Wenchuan Earthquake and the Rise and Fall of Earthquake Prediction in China

Science.gov (United States)

Chen, Q.; Wang, K.

2009-12-01

Regardless of the future potential of earthquake prediction, it is presently impractical to rely on it to mitigate earthquake disasters. The practical approach is to strengthen the resilience of our built environment to earthquakes based on hazard assessment. But this was not common understanding in China when the M 7.9 Wenchuan earthquake struck the Sichuan Province on 12 May 2008, claiming over 80,000 lives. In China, earthquake prediction is a government-sanctioned and law-regulated measure of disaster prevention. A sudden boom of the earthquake prediction program in 1966-1976 coincided with a succession of nine M > 7 damaging earthquakes in the densely populated region of the country and the political chaos of the Cultural Revolution. It climaxed with the prediction of the 1975 Haicheng earthquake, which was due mainly to an unusually pronounced foreshock sequence and the extraordinary readiness of some local officials to issue imminent warning and evacuation order. The Haicheng prediction was a success in practice and yielded useful lessons, but the experience cannot be applied to most other earthquakes and cultural environments. Since the disastrous Tangshan earthquake in 1976 that killed over 240,000 people, there have been two opposite trends in China: decreasing confidence in prediction and increasing emphasis on regulating construction design for earthquake resilience. In 1976, most of the seismic intensity XI areas of Tangshan were literally razed to the ground, but in 2008, many buildings in the intensity XI areas of Wenchuan did not collapse. Prediction did not save life in either of these events; the difference was made by construction standards. For regular buildings, there was no seismic design in Tangshan to resist any earthquake shaking in 1976, but limited seismic design was required for the Wenchuan area in 2008. Although the construction standards were later recognized to be too low, those buildings that met the standards suffered much less

1/f and the Earthquake Problem: Scaling constraints that facilitate operational earthquake forecasting

Science.gov (United States)

yoder, M. R.; Rundle, J. B.; Turcotte, D. L.

2012-12-01

The difficulty of forecasting earthquakes can fundamentally be attributed to the self-similar, or "1/f", nature of seismic sequences. Specifically, the rate of occurrence of earthquakes is inversely proportional to their magnitude m, or more accurately to their scalar moment M. With respect to this "1/f problem," it can be argued that catalog selection (or equivalently, determining catalog constraints) constitutes the most significant challenge to seismicity based earthquake forecasting. Here, we address and introduce a potential solution to this most daunting problem. Specifically, we introduce a framework to constrain, or partition, an earthquake catalog (a study region) in order to resolve local seismicity. In particular, we combine Gutenberg-Richter (GR), rupture length, and Omori scaling with various empirical measurements to relate the size (spatial and temporal extents) of a study area (or bins within a study area) to the local earthquake magnitude potential - the magnitude of earthquake the region is expected to experience. From this, we introduce a new type of time dependent hazard map for which the tuning parameter space is nearly fully constrained. In a similar fashion, by combining various scaling relations and also by incorporating finite extents (rupture length, area, and duration) as constraints, we develop a method to estimate the Omori (temporal) and spatial aftershock decay parameters as a function of the parent earthquake's magnitude m. From this formulation, we develop an ETAS type model that overcomes many point-source limitations of contemporary ETAS. These models demonstrate promise with respect to earthquake forecasting applications. Moreover, the methods employed suggest a general framework whereby earthquake and other complex-system, 1/f type, problems can be constrained from scaling relations and finite extents.; Record-breaking hazard map of southern California, 2012-08-06. "Warm" colors indicate local acceleration (elevated hazard

Post-earthquake building safety inspection: Lessons from the Canterbury, New Zealand, earthquakes

Science.gov (United States)

Marshall, J.; Jaiswal, Kishor; Gould, N.; Turner, F.; Lizundia, B.; Barnes, J.

2013-01-01

The authors discuss some of the unique aspects and lessons of the New Zealand post-earthquake building safety inspection program that was implemented following the Canterbury earthquake sequence of 2010–2011. The post-event safety assessment program was one of the largest and longest programs undertaken in recent times anywhere in the world. The effort engaged hundreds of engineering professionals throughout the country, and also sought expertise from outside, to perform post-earthquake structural safety inspections of more than 100,000 buildings in the city of Christchurch and the surrounding suburbs. While the building safety inspection procedure implemented was analogous to the ATC 20 program in the United States, many modifications were proposed and implemented in order to assess the large number of buildings that were subjected to strong and variable shaking during a period of two years. This note discusses some of the key aspects of the post-earthquake building safety inspection program and summarizes important lessons that can improve future earthquake response.

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.

Observations of basin ground motions from a dense seismic array in San Jose, California

Science.gov (United States)

Frankel, A.; Carver, D.; Cranswick, E.; Bice, T.; Sell, R.; Hanson, S.

2001-01-01

We installed a dense array of 41 digital seismographs in San Jose, California, to evaluate in detail the effects of a deep sedimentary basin and shallow sedimentary deposits on earthquake ground motions. This urban array is located near the eastern edge of the Santa Clara Valley and spans the Evergreen sedimentary basin identified by gravity data. Average station spacing is 1 km, with three stations initially spaced 110 m apart. Despite the high-noise urban environment, the stations of the array successfully triggered on and recorded small local earthquakes (M 2.5-2.8 at 10-25 km distance) and larger regional events such as the M 5.0 Bolinas earthquake (90 km distance), M 4.6-5.6 earthquakes near Mammoth Lakes (270 km distance), M 4.9-5.6 events in western Nevada (420 km distance) and the M 7.1 Hector Mine earthquake (590 km distance). Maps of spectral ratios across the array show that the highest amplitudes in all frequency bands studied (0.125-8 Hz) are generally observed at stations farther from the eastern edge of the Santa Clara Valley. Larger spectral amplitudes are often observed above the western edge of the Evergreen Basin. Snapshots of the recorded wavefield crossing the array for regional events to the east reveal that large, low-frequency (0.125-0.5 Hz) arrivals after the S-wave travel from south to north across the array. A moving-window, cross-correlation analysis finds that these later arrivals are surface waves traveling from the south. The timing and propagation direction of these arrivals indicates that they were likely produced by scattering of incident S waves at the border of the Santa Clara Valley to the south of the array. It is remarkable that the largest low-frequency phases at many of the valley sites for regional events to the east are basin surface waves coming from a direction about 70 degrees different from that of the epicenters. Basin surface waves emanating from the eastern edge of the valley are also identified by the cross

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.

Countermeasures to earthquakes in nuclear plants

International Nuclear Information System (INIS)

Sato, Kazuhide

1979-01-01

The contribution of atomic energy to mankind is unmeasured, but the danger of radioactivity is a special thing. Therefore in the design of nuclear power plants, the safety has been regarded as important, and in Japan where earthquakes occur frequently, the countermeasures to earthquakes have been incorporated in the examination of safety naturally. The radioactive substances handled in nuclear power stations and spent fuel reprocessing plants are briefly explained. The occurrence of earthquakes cannot be predicted effectively, and the disaster due to earthquakes is apt to be remarkably large. In nuclear plants, the prevention of damage in the facilities and the maintenance of the functions are required at the time of earthquakes. Regarding the location of nuclear plants, the history of earthquakes, the possible magnitude of earthquakes, the properties of ground and the position of nuclear plants should be examined. After the place of installation has been decided, the earthquake used for design is selected, evaluating live faults and determining the standard earthquakes. As the fundamentals of aseismatic design, the classification according to importance, the earthquakes for design corresponding to the classes of importance, the combination of loads and allowable stress are explained. (Kako, I.)

San Andreas Fault in the Carrizo Plain

Science.gov (United States)

2000-01-01

The 1,200-kilometer (800-mile)San Andreas is the longest fault in California and one of the longest in North America. This perspective view of a portion of the fault was generated using data from the Shuttle Radar Topography Mission (SRTM), which flew on NASA's Space Shuttle last February, and an enhanced, true-color Landsat satellite image. The view shown looks southeast along the San Andreas where it cuts along the base of the mountains in the Temblor Range near Bakersfield. The fault is the distinctively linear feature to the right of the mountains. To the left of the range is a portion of the agriculturally rich San Joaquin Valley. In the background is the snow-capped peak of Mt. Pinos at an elevation of 2,692 meters (8,831 feet). The complex topography in the area is some of the most spectacular along the course of the fault. To the right of the fault is the famous Carrizo Plain. Dry conditions on the plain have helped preserve the surface trace of the fault, which is scrutinized by both amateur and professional geologists. In 1857, one of the largest earthquakes ever recorded in the United States occurred just north of the Carrizo Plain. With an estimated magnitude of 8.0, the quake severely shook buildings in Los Angeles, caused significant surface rupture along a 350-kilometer (220-mile) segment of the fault, and was felt as far away as Las Vegas, Nev. This portion of the San Andreas is an important area of study for seismologists. For visualization purposes, topographic heights displayed in this image are exaggerated two times.The elevation data used in this image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of Earth's land surface. To collect the 3-D SRTM data, engineers added a mast 60

Do earthquakes exhibit self-organized criticality?

International Nuclear Information System (INIS)

Yang Xiaosong; Ma Jin; Du Shuming

2004-01-01

If earthquakes are phenomena of self-organized criticality (SOC), statistical characteristics of the earthquake time series should be invariant after the sequence of events in an earthquake catalog are randomly rearranged. In this Letter we argue that earthquakes are unlikely phenomena of SOC because our analysis of the Southern California Earthquake Catalog shows that the first-return-time probability P M (T) is apparently changed after the time series is rearranged. This suggests that the SOC theory should not be used to oppose the efforts of earthquake prediction

Earthquake precursors: spatial-temporal gravity changes before the great earthquakes in the Sichuan-Yunnan area

Science.gov (United States)

Zhu, Yi-Qing; Liang, Wei-Feng; Zhang, Song

2018-01-01

Using multiple-scale mobile gravity data in the Sichuan-Yunnan area, we systematically analyzed the relationships between spatial-temporal gravity changes and the 2014 Ludian, Yunnan Province Ms6.5 earthquake and the 2014 Kangding Ms6.3, 2013 Lushan Ms7.0, and 2008 Wenchuan Ms8.0 earthquakes in Sichuan Province. Our main results are as follows. (1) Before the occurrence of large earthquakes, gravity anomalies occur in a large area around the epicenters. The directions of gravity change gradient belts usually agree roughly with the directions of the main fault zones of the study area. Such gravity changes might reflect the increase of crustal stress, as well as the significant active tectonic movements and surface deformations along fault zones, during the period of gestation of great earthquakes. (2) Continuous significant changes of the multiple-scale gravity fields, as well as greater gravity changes with larger time scales, can be regarded as medium-range precursors of large earthquakes. The subsequent large earthquakes always occur in the area where the gravity changes greatly. (3) The spatial-temporal gravity changes are very useful in determining the epicenter of coming large earthquakes. The large gravity networks are useful to determine the general areas of coming large earthquakes. However, the local gravity networks with high spatial-temporal resolution are suitable for determining the location of epicenters. Therefore, denser gravity observation networks are necessary for better forecasts of the epicenters of large earthquakes. (4) Using gravity changes from mobile observation data, we made medium-range forecasts of the Kangding, Ludian, Lushan, and Wenchuan earthquakes, with especially successful forecasts of the location of their epicenters. Based on the above discussions, we emphasize that medium-/long-term potential for large earthquakes might exist nowadays in some areas with significant gravity anomalies in the study region. Thus, the monitoring

Tremor-tide correlations and near-lithostatic pore pressure on the deep San Andreas fault.

Science.gov (United States)

Thomas, Amanda M; Nadeau, Robert M; Bürgmann, Roland

2009-12-24

Since its initial discovery nearly a decade ago, non-volcanic tremor has provided information about a region of the Earth that was previously thought incapable of generating seismic radiation. A thorough explanation of the geologic process responsible for tremor generation has, however, yet to be determined. Owing to their location at the plate interface, temporal correlation with geodetically measured slow-slip events and dominant shear wave energy, tremor observations in southwest Japan have been interpreted as a superposition of many low-frequency earthquakes that represent slip on a fault surface. Fluids may also be fundamental to the failure process in subduction zone environments, as teleseismic and tidal modulation of tremor in Cascadia and Japan and high Poisson ratios in both source regions are indicative of pressurized pore fluids. Here we identify a robust correlation between extremely small, tidally induced shear stress parallel to the San Andreas fault and non-volcanic tremor activity near Parkfield, California. We suggest that this tremor represents shear failure on a critically stressed fault in the presence of near-lithostatic pore pressure. There are a number of similarities between tremor in subduction zone environments, such as Cascadia and Japan, and tremor on the deep San Andreas transform, suggesting that the results presented here may also be applicable in other tectonic settings.

3D Constraints On Fault Architecture and Strain Distribution of the Newport-Inglewood Rose Canyon and San Onofre Trend Fault Systems

Science.gov (United States)

Holmes, J. J.; Driscoll, N. W.; Kent, G. M.

2017-12-01

The Inner California Borderlands (ICB) is situated off the coast of southern California and northern Baja. The structural and geomorphic characteristics of the area record a middle Oligocene transition from subduction to microplate capture along the California coast. Marine stratigraphic evidence shows large-scale extension and rotation overprinted by modern strike-slip deformation. Geodetic and geologic observations indicate that approximately 6-8 mm/yr of Pacific-North American relative plate motion is accommodated by offshore strike-slip faulting in the ICB. The farthest inshore fault system, the Newport-Inglewood Rose Canyon (NIRC) Fault is a dextral strike-slip system that is primarily offshore for approximately 120 km from San Diego to the San Joaquin Hills near Newport Beach, California. Based on trenching and well data, the NIRC Fault Holocene slip rate is 1.5-2.0 mm/yr to the south and 0.5-1.0 mm/yr along its northern extent. An earthquake rupturing the entire length of the system could produce an Mw 7.0 earthquake or larger. West of the main segments of the NIRC Fault is the San Onofre Trend (SOT) along the continental slope. Previous work concluded that this is part of a strike-slip system that eventually merges with the NIRC Fault. Others have interpreted this system as deformation associated with the Oceanside Blind Thrust Fault purported to underlie most of the region. In late 2013, we acquired the first high-resolution 3D Parallel Cable (P-Cable) seismic surveys of the NIRC and SOT faults as part of the Southern California Regional Fault Mapping project. Analysis of stratigraphy and 3D mapping of this new data has yielded a new kinematic fault model of the area that provides new insight on deformation caused by interactions in both compressional and extensional regimes. For the first time, we can reconstruct fault interaction and investigate how strain is distributed through time along a typical strike-slip margin using 3D constraints on fault

Overestimation of the earthquake hazard along the Himalaya: constraints in bracketing of medieval earthquakes from paleoseismic studies

Science.gov (United States)

Arora, Shreya; Malik, Javed N.

2017-12-01

The Himalaya is one of the most seismically active regions of the world. The occurrence of several large magnitude earthquakes viz. 1905 Kangra earthquake (Mw 7.8), 1934 Bihar-Nepal earthquake (Mw 8.2), 1950 Assam earthquake (Mw 8.4), 2005 Kashmir (Mw 7.6), and 2015 Gorkha (Mw 7.8) are the testimony to ongoing tectonic activity. In the last few decades, tremendous efforts have been made along the Himalayan arc to understand the patterns of earthquake occurrences, size, extent, and return periods. Some of the large magnitude earthquakes produced surface rupture, while some remained blind. Furthermore, due to the incompleteness of the earthquake catalogue, a very few events can be correlated with medieval earthquakes. Based on the existing paleoseismic data certainly, there exists a complexity to precisely determine the extent of surface rupture of these earthquakes and also for those events, which occurred during historic times. In this paper, we have compiled the paleo-seismological data and recalibrated the radiocarbon ages from the trenches excavated by previous workers along the entire Himalaya and compared earthquake scenario with the past. Our studies suggest that there were multiple earthquake events with overlapping surface ruptures in small patches with an average rupture length of 300 km limiting Mw 7.8-8.0 for the Himalayan arc, rather than two or three giant earthquakes rupturing the whole front. It has been identified that the large magnitude Himalayan earthquakes, such as 1905 Kangra, 1934 Bihar-Nepal, and 1950 Assam, that have occurred within a time frame of 45 years. Now, if these events are dated, there is a high possibility that within the range of ±50 years, they may be considered as the remnant of one giant earthquake rupturing the entire Himalayan arc. Therefore, leading to an overestimation of seismic hazard scenario in Himalaya.

Stress triggering of the Lushan M7. 0 earthquake by the Wenchuan Ms8. 0 earthquake

Directory of Open Access Journals (Sweden)

Wu Jianchao

2013-08-01

Full Text Available The Wenchuan Ms8. 0 earthquake and the Lushan M7. 0 earthquake occurred in the north and south segments of the Longmenshan nappe tectonic belt, respectively. Based on the focal mechanism and finite fault model of the Wenchuan Ms8. 0 earthquake, we calculated the coulomb failure stress change. The inverted coulomb stress changes based on the Nishimura and Chenji models both show that the Lushan M7. 0 earthquake occurred in the increased area of coulomb failure stress induced by the Wenchuan Ms8. 0 earthquake. The coulomb failure stress increased by approximately 0. 135 – 0. 152 bar in the source of the Lushan M7. 0 earthquake, which is far more than the stress triggering threshold. Therefore, the Lushan M7. 0 earthquake was most likely triggered by the coulomb failure stress change.

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...

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

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.

Thoracic Injuries in earthquake-related versus non-earthquake-related trauma patients: differentiation via Multi-detector Computed Tomography

Science.gov (United States)

Dong, Zhi-hui; Yang, Zhi-gang; Chen, Tian-wu; Chu, Zhi-gang; Deng, Wen; Shao, Heng

2011-01-01

PURPOSE: Massive earthquakes are harmful to humankind. This study of a historical cohort aimed to investigate the difference between earthquake-related crush thoracic traumas and thoracic traumas unrelated to earthquakes using a multi-detector Computed Tomography (CT). METHODS: We retrospectively compared an earthquake-exposed cohort of 215 thoracic trauma crush victims of the Sichuan earthquake to a cohort of 215 non-earthquake-related thoracic trauma patients, focusing on the lesions and coexisting injuries to the thoracic cage and the pulmonary parenchyma and pleura using a multi-detector CT. RESULTS: The incidence of rib fracture was elevated in the earthquake-exposed cohort (143 vs. 66 patients in the non-earthquake-exposed cohort, Risk Ratio (RR) = 2.2; pchest (45/143 vs. 11/66 patients, RR = 1.9; ptraumas resulting from the earthquake were life threatening with a high incidence of bony thoracic fractures. The ribs were frequently involved in bilateral and severe types of fractures, which were accompanied by non-rib fractures, pulmonary parenchymal and pleural injuries. PMID:21789386

Basic data features and results from a spatially dense seismic array on the San Jacinto fault zone

Science.gov (United States)

Ben-Zion, Yehuda; Vernon, Frank L.; Ozakin, Yaman; Zigone, Dimitri; Ross, Zachary E.; Meng, Haoran; White, Malcolm; Reyes, Juan; Hollis, Dan; Barklage, Mitchell

2015-07-01

We discuss several outstanding aspects of seismograms recorded during >4 weeks by a spatially dense Nodal array, straddling the damage zone of the San Jacinto fault in southern California, and some example results. The waveforms contain numerous spikes and bursts of high-frequency waves (up to the recorded 200 Hz) produced in part by minute failure events in the shallow crust. The high spatial density of the array facilitates the detection of 120 small local earthquakes in a single day, most of which not detected by the surrounding ANZA and regional southern California networks. Beamforming results identify likely ongoing cultural noise sources dominant in the frequency range 1-10 Hz and likely ongoing earthquake sources dominant in the frequency range 20-40 Hz. Matched-field processing and back-projection of seismograms provide alternate event location. The median noise levels during the experiment at different stations, waves generated by Betsy gunshots, and wavefields from nearby earthquakes point consistently to several structural units across the fault. Seismic trapping structure and local sedimentary basin produce localized motion amplification and stronger attenuation than adjacent regions. Cross correlations of high-frequency noise recorded at closely spaced stations provide a structural image of the subsurface material across the fault zone. The high spatial density and broad frequency range of the data can be used for additional high resolution studies of structure and source properties in the shallow crust.

Consideration for standard earthquake vibration (1). The Niigataken Chuetsu-oki Earthquake in 2007

International Nuclear Information System (INIS)

Ishibashi, Katsuhiko

2007-01-01

Outline of new guideline of quakeproof design standard of nuclear power plant and the standard earthquake vibration are explained. The improvement points of new guideline are discussed on the basis of Kashiwazaki-Kariwa Nuclear Power Plant incidents. The fundamental limits of new guideline are pointed. Placement of the quakeproof design standard of nuclear power plant, JEAG4601 of Japan Electric Association, new guideline, standard earthquake vibration of new guideline, the Niigataken Chuetsu-oki Earthquake in 2007 and damage of Kashiwazaki-Kariwa Nuclear Power Plant are discussed. The safety criteria of safety review system, organization, standard and guideline should be improved on the basis of this earthquake and nuclear plant accident. The general knowledge, 'a nuclear power plant is not constructed in the area expected large earthquake', has to be realized. Preconditions of all nuclear power plants should not cause damage to anything. (S.Y.)

Earthquake Emergency Education in Dushanbe, Tajikistan

Science.gov (United States)

Mohadjer, Solmaz; Bendick, Rebecca; Halvorson, Sarah J.; Saydullaev, Umed; Hojiboev, Orifjon; Stickler, Christine; Adam, Zachary R.

2010-01-01

We developed a middle school earthquake science and hazards curriculum to promote earthquake awareness to students in the Central Asian country of Tajikistan. These materials include pre- and post-assessment activities, six science activities describing physical processes related to earthquakes, five activities on earthquake hazards and mitigation…

Intensity earthquake scenario (scenario event - a damaging earthquake with higher probability of occurrence) for the city of Sofia

Science.gov (United States)

Aleksandrova, Irena; Simeonova, Stela; Solakov, Dimcho; Popova, Maria

2014-05-01

Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic risk to earthquakes are increasing steadily as urbanization and development occupy more areas that a prone to effects of strong earthquakes. Additionally, the uncontrolled growth of mega cities in highly seismic areas around the world is often associated with the construction of seismically unsafe buildings and infrastructures, and undertaken with an insufficient knowledge of the regional seismicity peculiarities and seismic hazard. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. The earthquake scenarios are intended as a basic input for developing detailed earthquake damage scenarios for the cities and can be used in earthquake-safe town and infrastructure planning. The city of Sofia is the capital of Bulgaria. It is situated in the centre of the Sofia area that is the most populated (the population is of more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria that faces considerable earthquake risk. The available historical documents prove the occurrence of destructive earthquakes during the 15th-18th centuries in the Sofia zone. In 19th century the city of Sofia has experienced two strong earthquakes: the 1818 earthquake with epicentral intensity I0=8-9 MSK and the 1858 earthquake with I0=9-10 MSK. During the 20th century the strongest event occurred in the vicinity of the city of Sofia is the 1917 earthquake with MS=5.3 (I0=7-8 MSK). Almost a century later (95 years) an earthquake of moment magnitude 5.6 (I0=7-8 MSK) hit the city of Sofia, on May 22nd, 2012. In the present study as a deterministic scenario event is considered a damaging earthquake with higher probability of occurrence that could affect the city with intensity less than or equal to VIII

Identifying Fault Connections of the Southern Pacific-North American Plate Boundary Using Triggered Slip and Crustal Velocities

Science.gov (United States)

Donnellan, A.; Grant Ludwig, L.; Rundle, J. B.; Parker, J. W.; Granat, R.; Heflin, M. B.; Pierce, M. E.; Wang, J.; Gunson, M.; Lyzenga, G. A.

2017-12-01

The 2010 M7.2 El Mayor - Cucapah earthquake caused extensive triggering of slip on faults proximal to the Salton Trough in southern California. Triggered slip and postseismic motions that have continued for over five years following the earthquake highlight connections between the El Mayor - Cucapah rupture and the network of faults that branch out along the southern Pacific - North American Plate Boundary. Coseismic triggering follows a network of conjugate faults from the northern end of the rupture to the Coachella segment of the southernmost San Andreas fault. Larger aftershocks and postseismic motions favor connections to the San Jacinto and Elsinore faults further west. The 2012 Brawley Swarm can be considered part of the branching on the Imperial Valley or east side of the plate boundary. Cluster analysis of long-term GPS velocities using Lloyds Algorithm, identifies bifurcation of the Pacific - North American plate boundary; The San Jacinto fault joins with the southern San Andreas fault, and the Salton Trough and Coachella segment of the San Andreas fault join with the Eastern California Shear Zone. The clustering analysis does not identify throughgoing deformation connecting the Coachella segment of the San Andreas fault with the rest of the San Andreas fault system through the San Gorgonio Pass. This observation is consistent with triggered slip from both the 1992 Landers and 2010 El Mayor - Cucapah earthquakes that follows the plate boundary bifurcation and with paleoseismic evidence of smaller earthquakes in the San Gorgonio Pass.

Earthquake recurrence models fail when earthquakes fail to reset the stress field

Science.gov (United States)

Tormann, Thessa; Wiemer, Stefan; Hardebeck, Jeanne L.

2012-01-01

Parkfield's regularly occurring M6 mainshocks, about every 25 years, have over two decades stoked seismologists' hopes to successfully predict an earthquake of significant size. However, with the longest known inter-event time of 38 years, the latest M6 in the series (28 Sep 2004) did not conform to any of the applied forecast models, questioning once more the predictability of earthquakes in general. Our study investigates the spatial pattern of b-values along the Parkfield segment through the seismic cycle and documents a stably stressed structure. The forecasted rate of M6 earthquakes based on Parkfield's microseismicity b-values corresponds well to observed rates. We interpret the observed b-value stability in terms of the evolution of the stress field in that area: the M6 Parkfield earthquakes do not fully unload the stress on the fault, explaining why time recurrent models fail. We present the 1989 M6.9 Loma Prieta earthquake as counter example, which did release a significant portion of the stress along its fault segment and yields a substantial change in b-values.

Earthquake Damage Assessment Using Objective Image Segmentation: A Case Study of 2010 Haiti Earthquake

Science.gov (United States)

Oommen, Thomas; Rebbapragada, Umaa; Cerminaro, Daniel

2012-01-01

In this study, we perform a case study on imagery from the Haiti earthquake that evaluates a novel object-based approach for characterizing earthquake induced surface effects of liquefaction against a traditional pixel based change technique. Our technique, which combines object-oriented change detection with discriminant/categorical functions, shows the power of distinguishing earthquake-induced surface effects from changes in buildings using the object properties concavity, convexity, orthogonality and rectangularity. Our results suggest that object-based analysis holds promise in automatically extracting earthquake-induced damages from high-resolution aerial/satellite imagery.

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.

The CATDAT damaging earthquakes database

Science.gov (United States)

Daniell, J. E.; Khazai, B.; Wenzel, F.; Vervaeck, A.

2011-08-01

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 reinsurance field.

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

Comparison of aftershock sequences between 1975 Haicheng earthquake and 1976 Tangshan earthquake

Science.gov (United States)

Liu, B.

2017-12-01

The 1975 ML 7.3 Haicheng earthquake and the 1976 ML 7.8 Tangshan earthquake occurred in the same tectonic unit. There are significant differences in spatial-temporal distribution, number of aftershocks and time duration for the aftershock sequence followed by these two main shocks. As we all know, aftershocks could be triggered by the regional seismicity change derived from the main shock, which was caused by the Coulomb stress perturbation. Based on the rate- and state- dependent friction law, we quantitative estimated the possible aftershock time duration with a combination of seismicity data, and compared the results from different approaches. The results indicate that, aftershock time durations from the Tangshan main shock is several times of that form the Haicheng main shock. This can be explained by the significant relationship between aftershock time duration and earthquake nucleation history, normal stressand shear stress loading rateon the fault. In fact the obvious difference of earthquake nucleation history from these two main shocks is the foreshocks. 1975 Haicheng earthquake has clear and long foreshocks, while 1976 Tangshan earthquake did not have clear foreshocks. In that case, abundant foreshocks may mean a long and active nucleation process that may have changed (weakened) the rocks in the source regions, so they should have a shorter aftershock sequences for the reason that stress in weak rocks decay faster.

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 A.; 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.

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.

Tradable Earthquake Certificates

NARCIS (Netherlands)

Woerdman, Edwin; Dulleman, Minne

2018-01-01

This article presents a market-based idea to compensate for earthquake damage caused by the extraction of natural gas and applies it to the case of Groningen in the Netherlands. Earthquake certificates give homeowners a right to yearly compensation for both property damage and degradation of living

78 FR 34123 - Notice of Inventory Completion: San Francisco State University NAGPRA Program, San Francisco, CA

Science.gov (United States)

2013-06-06

... completion of an inventory of human remains and associated funerary objects under the control of the San....R50000] Notice of Inventory Completion: San Francisco State University NAGPRA Program, San Francisco, CA... NAGPRA Program has completed an inventory of human remains and associated funerary objects, in...

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

Science.gov (United States)

2013-04-10

... completion of an inventory of human remains and associated funerary objects under the control of the San....R50000] Notice of Inventory Completion: San Francisco State University NAGPRA Program, San Francisco, CA... NAGPRA Program has completed an inventory of human remains and associated funerary objects, in...

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

Nowcasting Earthquakes and Tsunamis

Science.gov (United States)

Rundle, J. B.; Turcotte, D. L.

2017-12-01

The term "nowcasting" refers to the estimation of the current uncertain state of a dynamical system, whereas "forecasting" is a calculation of probabilities of future state(s). Nowcasting is a term that originated in economics and finance, referring to the process of determining the uncertain state of the economy or market indicators such as GDP at the current time by indirect means. We have applied this idea to seismically active regions, where the goal is to determine the current state of a system of faults, and its current level of progress through the earthquake cycle (http://onlinelibrary.wiley.com/doi/10.1002/2016EA000185/full). Advantages of our nowcasting method over forecasting models include: 1) Nowcasting is simply data analysis and does not involve a model having parameters that must be fit to data; 2) We use only earthquake catalog data which generally has known errors and characteristics; and 3) We use area-based analysis rather than fault-based analysis, meaning that the methods work equally well on land and in subduction zones. To use the nowcast method to estimate how far the fault system has progressed through the "cycle" of large recurring earthquakes, we use the global catalog of earthquakes, using "small" earthquakes to determine the level of hazard from "large" earthquakes in the region. We select a "small" region in which the nowcast is to be made, and compute the statistics of a much larger region around the small region. The statistics of the large region are then applied to the small region. For an application, we can define a small region around major global cities, for example a "small" circle of radius 150 km and a depth of 100 km, as well as a "large" earthquake magnitude, for example M6.0. The region of influence of such earthquakes is roughly 150 km radius x 100 km depth, which is the reason these values were selected. We can then compute and rank the seismic risk of the world's major cities in terms of their relative seismic risk

Levee Seepage Detection in the Sacramento-San Joaquin Delta Using Polarimetric SAR

Science.gov (United States)

An, K.; Jones, C. E.; Bekaert, D. P.

2017-12-01

The Sacramento-San Joaquin Delta's extensive levee system protects over 2,800 km2 of reclaimed lands and serves as the main irrigation and domestic water supply for the state of California. However, ongoing subsidence and disaster threats from floods and earthquakes make the Delta levee system highly vulnerable, endangering water supplies for 23 million California residents and 2.5 million acres of agricultural land. Levee failure in the Delta can cause saltwater intrusion from San Francisco Bay, reducing water quality and curtailing water exports to residents, commercial users, and farmers. To protect the Delta levee system, it is essential to search for signs of seepage in which water is piping through or beneath levees, which can be associated with deformation of the levees themselves. Until now, in-situ monitoring has largely been applied, however, this is a time-consuming and expensive approach. We use data acquired with NASA's UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar) airborne radar instrument to identify and characterize levee seepages and associated land subsidence through advanced remote sensing technologies. The high spatial resolution of UAVSAR can help to direct surveys to areas that are likely to be experiencing damage. UAVSAR is an L-band airborne sensor with high signal-to-noise ratio, repeat flight track accuracy, and spatial resolution of 7x7 m2 (for multi-looked products) that is necessary for detailed levee monitoring. The adaptability of radar instruments in their ability to see through smoke, haze, and clouds during the day or night, is especially relevant during disaster events, when cloud cover or lack of solar illumination inhibits traditional visual surveys of damage. We demonstrate the advantages of combining polarimetric radar imagery with geographic information systems (GIS) datasets in locating seepage features along critical levee infrastructure in the Delta for 2009-2016. The ability to efficiently locate potential

Seismicity map tools for earthquake studies

Science.gov (United States)

Boucouvalas, Anthony; Kaskebes, Athanasios; Tselikas, Nikos

2014-05-01

We report on the development of new and online set of tools for use within Google Maps, for earthquake research. We demonstrate this server based and online platform (developped with PHP, Javascript, MySQL) with the new tools using a database system with earthquake data. The platform allows us to carry out statistical and deterministic analysis on earthquake data use of Google Maps and plot various seismicity graphs. The tool box has been extended to draw on the map line segments, multiple straight lines horizontally and vertically as well as multiple circles, including geodesic lines. The application is demonstrated using localized seismic data from the geographic region of Greece as well as other global earthquake data. The application also offers regional segmentation (NxN) which allows the studying earthquake clustering, and earthquake cluster shift within the segments in space. The platform offers many filters such for plotting selected magnitude ranges or time periods. The plotting facility allows statistically based plots such as cumulative earthquake magnitude plots and earthquake magnitude histograms, calculation of 'b' etc. What is novel for the platform is the additional deterministic tools. Using the newly developed horizontal and vertical line and circle tools we have studied the spatial distribution trends of many earthquakes and we here show for the first time the link between Fibonacci Numbers and spatiotemporal location of some earthquakes. The new tools are valuable for examining visualizing trends in earthquake research as it allows calculation of statistics as well as deterministic precursors. We plan to show many new results based on our newly developed platform.

Earthquake at 40 feet

Science.gov (United States)

Miller, G. J.

1976-01-01

The earthquake that struck the island of Guam on November 1, 1975, at 11:17 a.m had many unique aspects-not the least of which was the experience of an earthquake of 6.25 Richter magnitude while at 40 feet. My wife Bonnie, a fellow diver, Greg Guzman, and I were diving at Gabgab Beach in teh outer harbor of Apra Harbor, engaged in underwater phoyography when the earthquake struck. 

Earthquakes and economic growth

OpenAIRE

Fisker, Peter Simonsen

2012-01-01

This study explores the economic consequences of earthquakes. In particular, it is investigated how exposure to earthquakes affects economic growth both across and within countries. The key result of the empirical analysis is that while there are no observable effects at the country level, earthquake exposure significantly decreases 5-year economic growth at the local level. Areas at lower stages of economic development suffer harder in terms of economic growth than richer areas. In addition,...

Radon anomalies prior to earthquakes (2). Atmospheric radon anomaly observed before the Hyogoken-Nanbu earthquake

International Nuclear Information System (INIS)

Ishikawa, Tetsuo; Tokonami, Shinji; Yasuoka, Yumi; Shinogi, Masaki; Nagahama, Hiroyuki; Omori, Yasutaka; Kawada, Yusuke

2008-01-01

Before the 1995 Hyogoken-Nanbu earthquake, various geochemical precursors were observed in the aftershock area: chloride ion concentration, groundwater discharge rate, groundwater radon concentration and so on. Kobe Pharmaceutical University (KPU) is located about 25 km northeast from the epicenter and within the aftershock area. Atmospheric radon concentration had been continuously measured from 1984 at KPU, using a flow-type ionization chamber. The radon concentration data were analyzed using the smoothed residual values which represent the daily minimum of radon concentration with the exclusion of normalized seasonal variation. The radon concentration (smoothed residual values) demonstrated an upward trend about two months before the Hyogoken-Nanbu earthquake. The trend can be well fitted to a log-periodic model related to earthquake fault dynamics. As a result of model fitting, a critical point was calculated to be between 13 and 27 January 1995, which was in good agreement with the occurrence date of earthquake (17 January 1995). The mechanism of radon anomaly before earthquakes is not fully understood. However, it might be possible to detect atmospheric radon anomaly as a precursor before a large earthquake, if (1) the measurement is conducted near the earthquake fault, (2) the monitoring station is located on granite (radon-rich) areas, and (3) the measurement is conducted for more than several years before the earthquake to obtain background data. (author)

Retrospective stress-forecasting of earthquakes

Science.gov (United States)

Gao, Yuan; Crampin, Stuart

2015-04-01

Observations of changes in azimuthally varying shear-wave splitting (SWS) above swarms of small earthquakes monitor stress-induced changes to the stress-aligned vertical microcracks pervading the upper crust, lower crust, and uppermost ~400km of the mantle. (The microcracks are intergranular films of hydrolysed melt in the mantle.) Earthquakes release stress, and an appropriate amount of stress for the relevant magnitude must accumulate before each event. Iceland is on an extension of the Mid-Atlantic Ridge, where two transform zones, uniquely run onshore. These onshore transform zones provide semi-continuous swarms of small earthquakes, which are the only place worldwide where SWS can be routinely monitored. Elsewhere SWS must be monitored above temporally-active occasional swarms of small earthquakes, or in infrequent SKS and other teleseismic reflections from the mantle. Observations of changes in SWS time-delays are attributed to stress-induced changes in crack aspect-ratios allowing stress-accumulation and stress-relaxation to be identified. Monitoring SWS in SW Iceland in 1988, stress-accumulation before an impending earthquake was recognised and emails were exchanged between the University of Edinburgh (EU) and the Iceland Meteorological Office (IMO). On 10th November 1988, EU emailed IMO that a M5 earthquake could occur soon on a seismically-active fault plane where seismicity was still continuing following a M5.1 earthquake six-months earlier. Three-days later, IMO emailed EU that a M5 earthquake had just occurred on the specified fault-plane. We suggest this is a successful earthquake stress-forecast, where we refer to the procedure as stress-forecasting earthquakes as opposed to predicting or forecasting to emphasise the different formalism. Lack of funds has prevented us monitoring SWS on Iceland seismograms, however, we have identified similar characteristic behaviour of SWS time-delays above swarms of small earthquakes which have enabled us to

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

75 FR 15611 - Safety Zone; United Portuguese SES Centennial Festa, San Diego Bay, San Diego, CA

Science.gov (United States)

2010-03-30

...-AA00 Safety Zone; United Portuguese SES Centennial Festa, San Diego Bay, San Diego, CA AGENCY: Coast... navigable waters of the San Diego Bay in support of the United Portuguese SES Centennial Festa. This... Centennial Festa, which will include a fireworks presentation originating from a tug and barge combination in...

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).

Earthquake effect on the geological environment

International Nuclear Information System (INIS)

Kawamura, Makoto

1999-01-01

Acceleration caused by the earthquake, changes in the water pressure, and the rock-mass strain were monitored for a series of 344 earthquakes from 1990 to 1998 at Kamaishi In Situ Test Site. The largest acceleration was registered to be 57.14 gal with the earthquake named 'North coast of Iwate Earthquake' (M4.4) occurred in June, 1996. Changes of the water pressure were recorded with 27 earthquakes; the largest change was -0.35 Kgt/cm 2 . The water-pressure change by earthquake was, however, usually smaller than that caused by rainfall in this area. No change in the electric conductivity or pH of ground water was detected before and after the earthquake throughout the entire period of monitoring. The rock-mass strain was measured with a extensometer whose detection limit was of the order of 10 -8 to 10 -9 degrees and the remaining strain of about 2.5x10 -9 degrees was detected following the 'Offshore Miyagi Earthquake' (M5.1) in October, 1997. (H. Baba)

Earthquake predictions using seismic velocity ratios

Science.gov (United States)

Sherburne, R. W.

1979-01-01

Since the beginning of modern seismology, seismologists have contemplated predicting earthquakes. The usefulness of earthquake predictions to the reduction of human and economic losses and the value of long-range earthquake prediction to planning is obvious. Not as clear are the long-range economic and social impacts of earthquake prediction to a speicifc area. The general consensus of opinion among scientists and government officials, however, is that the quest of earthquake prediction is a worthwhile goal and should be prusued with a sense of urgency. 

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.…

Smoking prevalence increases following Canterbury earthquakes.

Science.gov (United States)

Erskine, Nick; Daley, Vivien; Stevenson, Sue; Rhodes, Bronwen; Beckert, Lutz

2013-01-01

A magnitude 7.1 earthquake hit Canterbury in September 2010. This earthquake and associated aftershocks took the lives of 185 people and drastically changed residents' living, working, and social conditions. To explore the impact of the earthquakes on smoking status and levels of tobacco consumption in the residents of Christchurch. Semistructured interviews were carried out in two city malls and the central bus exchange 15 months after the first earthquake. A total of 1001 people were interviewed. In August 2010, prior to any earthquake, 409 (41%) participants had never smoked, 273 (27%) were currently smoking, and 316 (32%) were ex-smokers. Since the September 2010 earthquake, 76 (24%) of the 316 ex-smokers had smoked at least one cigarette and 29 (38.2%) had smoked more than 100 cigarettes. Of the 273 participants who were current smokers in August 2010, 93 (34.1%) had increased consumption following the earthquake, 94 (34.4%) had not changed, and 86 (31.5%) had decreased their consumption. 53 (57%) of the 93 people whose consumption increased reported that the earthquake and subsequent lifestyle changes as a reason to increase smoking. 24% of ex-smokers resumed smoking following the earthquake, resulting in increased smoking prevalence. Tobacco consumption levels increased in around one-third of current smokers.