Site-response characterization for implementing SHAKEMAP in northern Utah (RI-248)

By: F. X. Ashland

As part of the effort to implement “ShakeMap” in northern Utah, this publication used surface geology and available shear-wave velocity data to characterize and map the site response of geologic units during earthquake ground shaking. Site-response mapping was performed at two scales: (1) 1:500,000, using a simple geology-based site-response classification for generalized geologic units of northern Utah, and (2) 1:250,000, using a more detailed classification for the Quaternary units of the Wasatch Front urban corridor. Calculated or estimated average shear-wave velocities in the upper 30 meters range from 199 to 2,197 meters/second for the site-response units.

Adequate predictions of the average shear-wave velocity in the upper 30 meters (100 ft) (Vs30) are necessary to obtain site amplification factors for geologic units in northern Utah. This report summarizes the results of the site-response characterization of the surface geology in northern Utah. The scope of work included: 1.) evaluation of the available shear-wave velocity data for Quaternary deposits in northern Utah to determine statistically distinct site-response units, 2.) literature review and analysis of shear-wave velocity data for geologic units for which shear-wave velocities are lacking in northern Utah, and 3.) calculation of site amplification factors.

Other Information:
Published: 2001
Pages: 10 p.
Plates: 2 pl.
Scale: 1:500,000
Location: Box Elder, Cache, Davis, Morgan, Rich, Summit, Tooele, Utah, Wasatch, and Weber Counties
Media Type: Paper Publication