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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...
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 New Madrid Seismic Zone presents significant seismic hazard to the central and eastern United States. We mapped newly-identified coseismic ridge-spreading features, or sackungen, in the bluffs east of the Mississippi River in western Tennessee. We use this mapping dataset in an accompanying manuscript to show that sackungen form during earthquakes on the Reelfoot fault and may fail in preferred orientations. Ultimately, these data can be used to infer fault source and mechanism and improve the paleoseismic record used in hazard models.
We present high-resolution (10-cm pixel) digital surface models (DSMs) generated for the northern 16 km of the surface rupture associated with the 1983 Mw 6.9 Borah Peak earthquake. These DSMs were generated using Agisoft Photoscan (and Metashape) image-based modeling software and low-altitude aerial photographs acquired from unmanned aircraft systems and a tethered balloon. DSM files consist of GeoTIFFs with georeferencing information stored in the file headers.
A 3D temperature model is constructed in order to support the estimation of physical parameters within the USGS National Crustal Model. The crustal model is defined by a geological framework consisting of various lithologies with distinct mineral compositions. A temperature model is needed to calculate mineral density and bulk and shear modulus as a function of position within the crust. These properties control seismic velocity and impedance, which are needed to accurately estimate earthquake travel times and seismic amplitudes in earthquake hazard analyses. The temperature model is constrained by observations of surface temperature, temperature gradient, and conductivity, inferred Moho temperature and depth, and...
The 2014 update of the U.S. Geological Survey (USGS) National Seismic Hazard Model (NSHM) for the conterminous United States (2014 NSHM; Petersen and others, 2014; https://pubs.usgs.gov/of/2008/1128/) included probabilistic ground motion maps for 2 percent and 10 percent probabilities of exceedance in 50 years, derived from seismic hazard curves for peak ground acceleration (PGA) and 0.2 and 1.0 second spectral accelerations (SAs) with 5 percent damping for the National Earthquake Hazards Reduction Program (NEHRP) site class boundary B/C (time-averaged shear wave velocity in the upper 30 meters [VS30]=760 meters per second [m/s]). This data release provides 0.1 degree by 0.1 degree gridded seismic hazard curves,...
Categories: Data Release - Revised;
Tags: Conterminous U.S.,
EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
The U.S. Geological Survey National Crustal Model (NCM) is being developed to include spatially varying estimates of site response in seismic hazard assessments. Primary outputs of the NCM are continuous velocity and density profiles from the Earth’s surface to the mantle transition zone at 410 km depth for each location on a 1-kilometer grid across the conterminous United States. Datasets used to produce the NCM may have a resolution of better than 1 km near the Earth’s surface in some regions, but, with increasing depth, NCM resolution decreases to 10’s to 100’s of km in the mantle. Basic subsurface information is provided by the NCM geologic framework (NCMGF), thermal model, and petrologic and mineral physics...
We present a petrologic and mineral physics database as part of the USGS National Crustal Model (NCM) for the western United States. Each of 209 geologic units, 134 of which are currently part of the geologic framework within the NCM, is assigned a mineralogical composition according to generalized classifications with some refinement for specific geologic formations. The mineral physics database builds off of previous work to include several minerals specific to continental rock types. We explore the impact of this database on zero-porosity anharmonic P- and S-wave rock velocities and density relative to a well-used empirical study by Brocher (2005) and find that empirical relations between P-wave velocity and...
Categories: Data;
Tags: Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
NCM,
USGS,
A 3D geologic framework is presented here as part of the U.S. Geological Survey National Crustal Model for the western United States, which will be used to improve seismic hazard assessment. The framework is based on 1:250,000 to 1:1,000,000-scale state geologic maps and depths of multiple subsurface unit boundaries. The geology at or near the Earth’s surface is based on published maps with modifications to remove discontinuities across state borders. Extrapolation of rock type and age in the subsurface is achieved by iterative stripping of units of a given age, nearest neighbor interpolation of the remaining units, and constraints on basement geology. The subsurface depth of the interfaces between units is determined...
Significant uncertainty remains in how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using lidar imagery, we identified a ~5 km long lineament in Swakane canyon near Wenatchee, roughly coincident with a strand of the Entiat fault. Topographic profiles across the lineament reveal a southwest-side-up break in slope with an average of ~3 m of vertical separation of the hillslope surface. We consider a range of possible origins for this feature, including differential erosion across a fault-line scarp, slope failure (sackung or landslide), and surface deformation across an active fault strand. Based on trenching, radiocarbon and luminescence dating, and ground penetrating...
Categories: Data;
Types: Citation,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Cascades, Washington,
EHP,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
This data release provides a map of the time-averaged shear-wave velocity in the upper 30 m (Vs30) for California using the method described by Thompson and others (2014). There are two adjustments to the algorithm described by Thompson and others (2014), which is built on the geology-based Vs30 map by Wills and Clahan (2006). In this data release, we use the Wills and others (2015) updated geology-based Vs30 map. The second change is that we have adjusted the kriging procedure so that measured Vs30 values do not affect the predictions across distinctly different geologic units. July 2022 Update (ver. 2.0) Resolution is now 3 arcseconds instead of 7.5 arcseconds Fixed a code error that prevented some of the Vs30...
Categories: Data,
Data Release - Revised;
Types: Downloadable,
GeoTIFF,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service,
Raster;
Tags: California,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
USGS,
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