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Abstract
The U.S. Geological Survey is developing the National Crustal Model (NCM) for seismic hazard studies to facilitate modeling site, path, and source components of seismic hazard across the conterminous United States. The NCM is composed of a 1km grid of geophysical profiles, extending from the Earth’s surface into the upper mantle. It is constructed from a threedimensional (3D) geologic framework and geophysical rules that use (1) a petrologic and mineral physics database; (2) a 3D temperature model; and (3) a calibrated rock type- and age-dependent porosity model. Parameters needed to estimate site response for existing ground motion models (GMMs), including the time-averaged velocity in the upper 30 meters (VS30), the depths to 1.0 and 2.5 km/s shear-wave velocity (Z1.0 and Z2.5), and sediment thickness, can be computed from the NCM. As GMMs continue to improve in the future, other metrics could also be extracted or derived from the NCM, such as fundamental period, site attenuation (ko), a fully frequency-dependent site response function, or 3D geophysical volumes for wavefield simulations. Application of the NCM may also benefit other aspects of seismic hazard analysis, including better accounting for path-dependent attenuation and geometric spreading, more accurate estimation of earthquake source properties such as hypocentral location and stress drop, and calculation of crustal strength profiles that inform estimates of the base of seismicity.
Study Area
Publication type | Conference Paper |
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Publication Subtype | Conference Paper |
Title | Recent applications of the USGS National Crustal Model for Seismic Hazard Studies |
Year Published | 2024 |
Language | English |
Publisher | Minnesota Geological Survey |
Contributing office(s) | Earthquake Science Center, Geologic Hazards Science Center - Seismology / Geomagnetism |
Description | 2 p. |
Larger Work Type | Book |
Larger Work Subtype | Conference publication |
Larger Work Title | Geologic mapping forum 23/24 abstracts |
First page | 60 |
Last page | 61 |
Country | United States |
Other Geospatial | conterminous United States |
Google Analytic Metrics | Metrics page |