Filters: Tags: geophysics (X) > partyWithName: Natural Hazards (X) > partyWithName: Earthquake Hazards Program (X)
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New Zealand’s Alpine Fault (AF) ruptures quasi-periodically in large-magnitude earthquakes. Paleoseismological evidence suggests that about half of all recognized AF earthquakes terminated at the boundary between the Central and South Westland sections of the fault. There, fault geometry and the polarity of uplift change. The South Westland AF exhibits oblique-normal fault motion on a structure oriented 055/82SE that, for at least 35 km along strike, contains saponite-rich principal slip zone gouges. New hydrothermal friction experiments reveal that the saponite fault gouge is frictionally weak, exhibiting friction coefficients between =0.12 and =0.16 for a range of temperatures (T=25–210 C) and effective normal...
The database contains uniformly processed ground motion intensity measurements (peak horizontal ground motions and 5-percent-damped pseudospectral accelerations for oscillator periods 0.1–10 s). The earthquake event set includes more than 3,800 M≥3 earthquakes in Oklahoma and Kansas from January 2009 to December 2016. Ground motion time series were collected out to 500 km. We also relocated the majority of the earthquake hypocenters using a multiple-event relocation algorithm to produce a set of near-uniformly processed hypocentral locations. Details about data processing are reported in the accompanying article. First posted - October 11, 2017 Revised - December 18, 2017, ver. 1.1
Categories: Data,
Data Release - Revised;
Tags: EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
Kansas,
Near-surface site characteristics are critical for accurately modeling ground motion, which in turn influences seismic hazard analysis and design of critical infrastructure. Currently, there are many strong motion accelerometers within the Advanced National Seismic System (ANSS) that are missing this information. We use a Geographic Information Systems (GIS) based framework to intersect the site coordinates of approximately 5,500 ANSS accelerometers located throughout the United States and its territories with geology and velocity information. We consider: (1) surficial geology from digitized geologic maps (Horton, 2017; Wilson et al., 2015; Sherrod et al., 2007; Bawiec, 1999; Saucedo, 2005; Bedrossian et al., 2012;...
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: ANSS,
Alabama,
American Samoa,
Arizona,
Arkansas,
In October 2016, we acquired an approximately 15-km-long seismic profile along a linear transect across the East Bay region of the San Francisco Bay area. Our goal was to image previously unknown strands of the Hayward Fault zone and to better delineate the structure and geometry of the main trace of the Hayward Fault. Our profile started near the southern border of San Leandro, California at the San Francisco Bay shoreline, trended ENE through the northern edge of Castro Valley, California, and ended approximately 5 km WSW of San Ramon, California. The data were analyzed using refraction tomography modeling, reflection processing, and guided-wave analysis. The analyzed data are presented in separate reports by...
Categories: Data;
Tags: Geophysics,
Hayward,
San Francisco Bay Area,
Seismology,
USGS Science Data Catalog (SDC),
This data release contains field data for two P-wave seismic reflection profiles acquired across the Warm Springs Valley fault zone, part of the Northern Walker Lane, NV. The dataset consists of high-resolution seismic reflection field records in .segy format, shot coordinates in .csv format, and observers’ logs in .pdf format. The high-resolution seismic profiles are approximately 4 km long. The northern profile (Warm Springs Line 1) is oblique to a prominent fault bounded ridge. The southern profile (Warm Springs Line 2) crosses the northern end of Warm Springs Valley and is nearly co-located with COCORP profile NV-08. To obtain the seismic profiles, we used a 230 kg accelerated weight drop source and a nominal...
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Fault,
Geophysics,
Hazards,
Nevada,
Seismic,
This digital elevation model provides a tool for calibrating tsunami risk to observations of the 1945 Makran tsunami in Karachi Harbour. The DEM bathymetry is derived from soundings made mainly during the first eight years after the tsunami. Although deficient in portraying intertidal backwaters and upland topography, the DEM accurately depicts the sheltered setting of one of the two tide gauges that recorded the 1945 tsunami.
Categories: Data;
Types: Downloadable,
GeoTIFF,
Map Service,
Raster;
Tags: Geography,
Geomorphology,
Geophysics,
Marine Geology,
Seismology,
VS30, the time-averaged shear-wave velocity (VS) to a depth of 30 meters, is a key index adopted by the earthquake engineering community to account for seismic site conditions. VS30 is typically based on geophysical measurements of VS derived from invasive and noninvasive techniques at sites of interest. Owing to cost considerations, as well as logistical and environmental concerns, VS30 data are sparse or not readily available for most areas. Where data are available, VS30 values are often assembled in assorted formats that are accessible from disparate and (or) impermanent Websites. To help remedy this situation, we compiled VS30 measurements obtained by studies funded by the U.S. Geological Survey (USGS) and...
Categories: Data;
Tags: Geophysics,
Seismology,
USGS Science Data Catalog (SDC),
United States,
earthquake seismology,
I use template matching and precise relative relocation techniques to develop a high-resolution earthquake catalog for the initial portion of the 2019 Ridgecrest earthquake sequence, from July 4-16, encompassing the foreshock sequence and the first 10+ days of aftershocks following the Mw 7.1 mainshock. Using 13,525 routinely cataloged events as waveform templates, I detect and precisely locate a total of 34,091 events. Precisely located earthquakes reveal numerous cross-cutting fault structures with dominantly perpendicular SW- and NW-strikes. Foreshocks of the Mw 6.4 event appear to align on a NW-striking fault. Aftershocks of the Mw 6.4 event suggest that it further ruptured this NW-striking fault, as well as...
Seismicity catalogs, GIS shapefiles, gridded seismic hazard curve data, gridded ground motion data, and mapped gridded ground motion values are available for the 2014 National Seismic Hazard Model for the Conterminous U.S. Probabilistic seismic hazard data and maps of the conterminous U.S. for peak ground acceleration (PGA) and 0.2 and 1.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404) and 10 percent in 50 years (annual probability of 0.0021), assuming firm rock soil conditions at 760 m/s, are available. Hazard was calculated on a 0.05 degree by 0.05 degree grid, defined by a bounding box encompassing the conterminous U.S. (-125 to -65 degrees longitude...
Subduction zones are home to the most seismically active faults on the planet. The shallow megathrust interface of subduction zones host our largest earthquakes, and are the only faults capable of M9+ ruptures. Despite these facts, our knowledge of subduction zone geometry - which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone earthquakes - is incomplete. Here we calculate the three- dimensional geometries of all active global subduction zones. The resulting model - Slab2 - provides for the first time a comprehensive geometrical analysis of all known slabs in unprecedented detail. ##### This distribution includes models of three-dimensional slab geometry under...
Seismicity catalogs, gridded seismic hazard curve data, gridded ground motion data, and mapped gridded ground motion values are available for the 2002 National Seismic Hazard Model for the Conterminous U.S. Seismicity catalogs are available for the western U.S. (in Mw) and central and eastern U.S. (in mb). Probabilistic seismic hazard data and maps of the conterminous U.S. for peak ground acceleration (PGA) and 0.1, 0.2, 0.3, 0.5, 1.0 and 2.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404) and 10 percent in 50 years (annual probability of 0.0021), assuming firm rock soil conditions at 760 m/s, are available. Hazard was calculated on a 0.1 degree by 0.1...
The 2018 Kīlauea eruption and caldera collapse generated intense cycles of seismicity tied to repeated large seismic (Mw ~5) collapse events associated with magma withdrawal from beneath the summit. To gain insight into the underlying dynamics and aid eruption response, we applied waveform-based earthquake detection and double-difference location as the eruption unfolded. Here, we augment these rapid results by grouping events based on patterns of correlation-derived phase polarities across the network. From April 29 to August 6, bracketing the eruption, we used ~2800 events cataloged by the Hawaiian Volcano Observatory to detect and precisely locate 44,000+ earthquakes. Resulting hypocentroids resolve complex,...
Gridded ground motion data and mapped gridded ground motion values are available for the 1999 Alaska Seismic Hazard Model. Probabilistic seismic hazard data and maps of Alaska and the Aleutians for peak ground acceleration (PGA) and 0.2, 0.3, and 1.0 second spectral acceleration at probability levels of 2 percent in 50 years (annual probability of 0.000404) and 10 percent in 50 years (annual probably of 0.0021), assuming firm rock soil conditions at 760 m/s, are available. Development of the 1999 Alaska Seismic Hazard Model is documented in the USGS Open-File Report 99-36 (https://doi.org/10.3133/ofr9936). This dataset is considered a legacy dataset. The original dataset was released at the time of publication...
We generated digital elevation models (DEMs) using pre- and post-event in-track stereo 0.5 m resolution panchromatic Worldview 1 and 2 images (©2019, DigitalGlobe) using the Surface Extraction from TIN-based Searchspace Minimization (SETSM) software [Noh and Howat, 2015] running on the University of Iowa Argon supercomputer (Table S1). The post-event DEMs exhibit along-track striping artifacts common to the Worldview 2 sensor. While de-striping tools, for example within NASAs Ames Stereo Pipeline [Shean et al., 2016], are commonly applied to resolve this issue, a de-striping correction has not been developed for this latitude. Noh, M.-J., and I. M. Howat (2015), Automated stereo-photogrammetric DEM generation...
Gridded seismic hazard curve data, gridded ground motion data, and mapped gridded ground motion values are available for the 2010 Haiti Seismic Hazard Model. Probabilistic seismic hazard data and maps are available for peak ground acceleration (PGA) and 0.2, and 1.0 second spectral acceleration at probability levels of 2 percent in 50 years and 10 percent in 50 years, assuming firm rock soil conditions at 760 m/s. Development of the 2010 Haiti Seismic Hazard Model is documented at https://pubs.usgs.gov/of/2010/1067/ and https://doi.org/10.1193/1.3631016. This dataset is considered a legacy dataset. The original dataset was uploaded to the USGS website at the time of publication of the seismic hazard model (2010)...
This dataset presents where, why, and how much probabilistic ground motions have changed with the 2018 update of the National Seismic Hazard Model (NSHM) for the conterminous U.S. (CONUS) vs. the 2014 NSHM. In the central and eastern U.S., hazard changes are the result of updated ground motion models (further broken down by median and epistemic uncertainty, aleatory variability, and site effects models) and gridded seismicity models. In the western U.S., hazard changes are the result of updated ground motion models in four urban areas with deep sedimentary basins and gridded seismicity models. Probabilistic ground motion changes (2% in 50 years probability of exceedance for a firm rock site, VS30 = 760 m/s, NEHRP...
Categories: Data;
Tags: Conterminous U.S.,
EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
The U.S. Geological Survey acquired high-resolution P- and S-wave seismic data across the Frijoles Fault strand of the San Gregorio Fault Zone (SGFZ) at northern Año Nuevo, California in 2012. SGFZ is a right-lateral fault system that is mainly offshore, and prior studies provide highly variable slip estimates, which indicates uncertainty about the seismic hazard it poses. Therefore, the primary goal of the seismic survey was to better understand the structure and geometry of the onshore section of the Frijoles Fault strand of the SGFZ. We deployed 118 geophones (channels) at 5-m spacing along a linear profile centered on the mapped surface trace of the Frijoles Fault and co-located active P- and S-wave sources...
Categories: Data;
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Ano Nuevo,
California,
Central California Coastal,
Geophysics,
Seismology,
Peak ground velocity (PGV) gridded probabilistic seismic hazard data for the updated 2018 National Seismic Hazard Model (NSHM) for the Conterminous United States (CONUS). PGV hazard curves and ground motions have been calculated on a 0.05 by 0.05 degree grid using the NSHM CONUS 2018 earthquake source model. PGV support has been incorporated into the NSHM using a newly developed PGV model conditioned on pseudo-spectral acceleration (Abrahamson and Bhasin, 2020, PEER Report No. 2020/05). See Powers et al. (in press) for implementation details. This dataset complements the "Data Release for Additional Period and Site Class Data for the 2018 National Seismic Hazard Model for the Conterminous United States (ver. 1.2,...
This item contains a single text file containing the station information for each station in the dataset that contains a peak ground displacement observation about the GNSS noise floor. The text file is organized in the following format: EventYear, Event Magnitude (Mw), Station ID, Station Longitude, Station Latitude, Station Elevation, Station Hypocentral Distance, PGD (meters)
Laboratory slide-hold-slide tests, combined with flow through tests, conducted on Westerly granite with 30 degree sawcut. Tests were conducted with a constant confining pressure of 30 MPa with an average pore pressure of 10 MPa at temperatures of 23 and 200 degC. Three fluid flow conditions were examined (1) no flow, (2) cycled flow, and (3) continuous flow.
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