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Calibration Coefficients for the U.S. Geological Survey National Crustal Model and Depth to Water Table

March 9, 2020

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 database. In this data release, the calibration coefficients and depth to water table across the conterminous U.S. that are needed to calculate velocities and densities that can be extracted from the NCM are presented. Calibration coefficients are implemented in a porosity model using Biot-Gassmann theory and derived from analysis of over 2000 compressional- and /or shear-wave velocity profiles (less than 10 km deep) from across the conterminous United States and southwest Canada.

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