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The 2002 U.S. Geological Survey (USGS) National Seismic Hazard Maps display earthquake ground motions for various probability levels across the United States and are applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy. This update of the maps incorporates new findings on earthquake ground shaking, faults, seismicity, and geodesy. The resulting maps are derived from seismic hazard curves calculated on a grid of sites across the United States that describe the frequency of exceeding a set of ground motions.
Types: Citation;
Tags: B/C site class boundary,
EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
A comparison of the 2017 USGS South America seismic hazard model with the Global Seismic Hazard Assessment Program (GSHAP) model and the 2010 USGS preliminary model was made to see how the models differ. The comparisons were made as ratios of PGA at 10% probability of exceedance in 50 years. Ratio maps of each comparison are included as a geo-referenced tiff (GeoTIFF).
For background, please see the Parent Item. The Maximum Considered Earthquake Geometric Mean (MCEG) peak ground acceleration (PGA) values of the 2009 NEHRP Recommended Seismic Provisions and the 2010 ASCE/SEI 7 Standard are calculated from the data in the downloadable files below, via the following equations: PGA = min[ PGAUH , max( PGAD84th , 0.6 ) ] for the 2009 NEHRP Recommended Seismic Provisions; PGA = min[ PGAUH , max( PGAD84th , 0.5 ) ] for the 2010 ASCE/SEI 7 Standard; where PGAUH = uniform-hazard peak ground acceleration; PGAD84th = 84th-percentile peak ground acceleration; and 0.6 or 0.5 = deterministic lower limit peak ground acceleration. These peak ground...
Categories: Data
The U.S. Geological Survey (USGS) national seismic hazard models (NSHM) consider two kinds of earthquake sources. Specific faults are modeled where possible. Where faults cannot be identified or characterized, alternative sources can be developed from seismicity catalogs. In a paper submitted to Seismological Research Letters ("Related External Resources", below), we describe a methodology that has been developed at the USGS for making earthquake catalogs for seismic hazard analysis. In this data release we provide the catalogs for the conterminous U.S. that accompany the SRL article. A new catalog is assembled from several preexisting catalogs. Moment magnitudes and related parameters for modeling seismicity...
5. Declustered seismicity catalogs used in the 2018 update of the U.S. National Seismic Hazard Model
An updated, declustered seismicity catalog is assembled from several preexisting catalogs. The methodology developed by Mueller (2019) was used to convert original magnitudes to uniform moment magnitudes, delete duplicate events, delete non-tectonic events, and finally decluster the catalog.
A comparison of the 2017 USGS South America seismic hazard model and the 2010 USGS preliminary model was made to see how the models differ. The comparison was made as the ratio of PGA at 10% probability of exceedance in 50 years. The ratio map is included here as a geo-referenced tiff (GeoTIFF). The gridded data for the 2017 PGA at 10% probability can be found here, while the gridded data for the 2010 PGA at 10% probability can be found in the zip archive that can be downloaded using a link on this page.
Categories: Data;
Types: Citation,
Downloadable,
GeoTIFF,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Raster,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
Maximum considered earthquake geometric mean peak ground acceleration maps (MCEG) are for assessment of the potential for liquefaction and soil strength loss, as well as for determination of lateral earth pressures in the design of basement and retaining walls. The maps are derived from the USGS seismic hazard maps in accordance with the site-specific ground-motion procedures of the NEHRP Recommended Seismic Provisions for New Building and Other Structures and the ASCE Minimum Design Loads for Buildings and Other Structures (also known as the ASCE 7 Standard; ASCE, 2016). The MCEG ground motions are taken as the lesser of probabilistic and deterministic values, as explained in the Provisions. The gridded probabilistic...
Categories: Data;
Types: Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
A comparison of the 2017 USGS South America seismic hazard model and the Global Seismic Hazard Assessment Program (GSHAP) model was made to see how the models differ. The comparison was made as the ratio of PGA at 10% probability of exceedance in 50 years. The ratio map is included here as a geo-referenced tiff (GeoTIFF). The gridded data for the 2017 PGA at 10% probability can be found here, while the GSHAP data can be found here. Shedlock, K.M., Giardini, Domenico, Grünthal, Gottfried, and Zhang, Peizhan, 2000, The GSHAP Global Seismic Hazar Map, Sesimological Research Letters, 71, 679-686. https://doi.org/10.1785/gssrl.71.6.679
Categories: Data;
Types: Citation,
Downloadable,
GeoTIFF,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Raster,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
The crustal fault model accounts for earthquakes that occur on faults that have not ruptured recently, but have have been active in historic and prehistoric periods. Although hundreds of Quaternary faults have been mapped, only a few of these faults have been studied sufficiently to reach a consensus regarding rate of deformation that can be applied in this hazard assessment. Information regarding the seismogenic source geometry and seismogenic source behavior that is necessary to model each fault is included for each fault. Files that can be used as input to computer hazard code are included.
For background, please see the Parent Item. The attached files below for 8 site classes each provide risk-targeted spectral accelerations (in units of g) for a grid of latitudes and longitudes and 22 spectral periods, including 0.0 seconds for peak ground acceleration (denoted SA0P0). The spectral accelerations for Site Class BC and spectral periods of 0.0, 0.2, and 1.0 seconds were directly derived from the USGS seismic hazard curves released in the "Associated Item"; from these three values, the spectral accelerations for the other site classes and spectral periods were derived indirectly via the FEMA P-2078 procedures cited below, because corresponding USGS hazard curves were not yet available for Guam and the...
Categories: Data
The subduction model accounts for large earthquakes (M 7–9.5) that occur on the subduction interface. The subduction zones along the northern and western coast of South America, the Panama deformation zones, and the Lesser Antilles subduction zone of the Caribbean are considered in the subduction model of this hazard assessment. The subduction interface of the Nazca plate beneath the western coast of South America has been separated into five zones, down to a depth of 50 km. The five zones are based on the locations of impinging subduction ridges, dimensions of large earthquakes, and fault complications. An alternative model for Chile (Medina et al., 2017) is applied to the Nazca subduction zones 3–5. This...
A seismic hazard model for South America, based on a smoothed (gridded) seismicity model, a subduction model, a crustal fault model, and a ground motion model, has been produced by the U.S. Geological Survey. These models are combined to account for ground shaking from earthquakes on known faults as well as earthquakes on un-modeled faults. This data set represents the hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. It represents the annual rate of exceedance versus 0.2-second spectral response acceleration.
A seismic hazard model for South America, based on a smoothed (gridded) seismicity model, a subduction model, a crustal fault model, and a ground motion model, has been produced by the U.S. Geological Survey. These models are combined to account for ground shaking from earthquakes on known faults as well as earthquakes on un-modeled faults. This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. This particular data set is for peak ground acceleration with a 2 percent probability of exceedance in 50 years.
Categories: Data;
Types: Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
Based on the USGS probabilistic seismic hazard model for South America, earthquake ground motion "design" maps were prepared, using the same procedures used to prepare seismic design maps for the U.S. and its territorries. The design maps for the U.S. and its territories have been adopted by U.S. building codes and consist of two parts: 1) Risk-targeted maximum considered earthquake (MCER) spectral acceleration maps at periods of 0.2 and 1.0 seconds, and 2) maximum considered earthquake geometric mean (MCEG) PGA maps. Both types of maps are derived in accordance with the site_specific ground motion procedures of the NEHRP Recommended Seismic Provisions for New Buildings and Other Structures (BSSC, 2015) and...
A seismic hazard model for South America, based on a smoothed (gridded) seismicity model, a subduction model, a crustal fault model, and a ground motion model, has been produced by the U.S. Geological Survey. These models are combined to account for ground shaking from earthquakes on known faults as well as earthquakes on un-modeled faults. This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. This particular data set is for Modified Mercalli Intensity with a 50 percent probability of exceedance in 50 years. The maps and data were derived from PGA ground-motion conversions of Worden et al. (2012), and include soil amplification...
Categories: Data;
Types: Citation,
Downloadable,
GeoTIFF,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Raster,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
A seismic hazard model for South America, based on a smoothed (gridded) seismicity model, a subduction model, a crustal fault model, and a ground motion model, has been produced by the U.S. Geological Survey. These models are combined to account for ground shaking from earthquakes on known faults as well as earthquakes on un-modeled faults. This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. This particular data set is for horizontal spectral response acceleration for 0.2-second period with a 2 percent probability of exceedance in 50 years.
Categories: Data;
Types: Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: Argentina,
Bolivia,
Brazil,
Chile,
Colombia,
Disaggregation of the seismic hazard for peak ground acceleration having a 2 percent probability of exceedance in 50 years is given for several major cities in South America. These disaggregation plots and reports show the relative contribution of individual sources to the seismic hazard (aggregated by magnitude and distance).
The datasets for this investigation consist of microtremor array data collected at: 1) 18 sites in Salt Lake and Utah valleys, Utah, and 2) two sites as part of the Frontier Observatory for Research in Geothermal Energy (FORGE) near Milford, Utah. Each of the 18 sites in the Salt Lake and Utah valleys were acquired with four-sensor arrays with three-component (3C) sensors having flat response from 0.033 Hz to 50 Hz. The data acquired as part of the FORGE investigation used both 3C broadband and 5-Hz geophone sensors. Additional information on these datasets can be found in the supporting documentation provided in this data release as well as in the paper by Zhang and others (2019) that utilized these data.
The “Database of Central and Eastern North American Seismic Velocity Structure” involves the compilation of one-dimensional (1D) seismic velocity-depth functions for central and eastern North America (CENA). The present database is an update of the report by Chulick and Mooney (2002) who present a compilation and statistical analysis of 1D seismic velocity-depth functions for North America and its margins. All seismic velocity-depth functions are extracted from peer-reviewed journal articles, with 86% derived from active-source seismic refraction profiles and the remaining 14% from receiver functions or local earthquake tomography models. No reanalysis of the original seismic field data was undertaken. The database...
Categories: Data;
Tags: EHP,
ESC,
Earthquake Hazards Program,
Earthquake Science Center,
Geophysics,
The updated 2018 National Seismic Hazard Model includes new ground motion models, aleatory uncertainty, and soil amplification factors for the central and eastern U.S. and incorporates basin depths from local seismic velocity models in four western U.S. (WUS) urban areas. These additions allow us, for the first time, to calculate probabilistic seismic hazard curves for an expanded set of spectral periods (0.01 s to 10 s) and site classes (VS30 = 150 m/s to 1,500 m/s) for the conterminous U.S. (CONUS), as well as account for amplification of long-period ground motions in deep sedimentary basins in the Los Angeles, San Francisco Bay, Salt Lake City, and Seattle regions. Ground motion data for 2, 5, and 10 percent...
Categories: Data,
Data Release - Revised;
Tags: Conterminous U.S.,
EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
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