Subsurface map and seismic risk analysis of the Salt Lake Valley (OFR-152)

By: H. Radkins, M. Murphy, and G. T. Schuster

This report is divided into two sections: 1) a compilation and integration of existing geophysical data pertaining to the sub-surface structure of Salt Lake Basin, and 2) a suite of synthetic seismograms which attempt to simulate the site amplification in Salt Lake Valley due to low frequency incident P-SV waves.

The central portion of the valley is found to be less well determined than the northern and southern portions due to lack of seismic data. Work at the University of Utah is continuing, with this compilation of data being used to constrain 2 1/2-D gravity inversion along cross sections of the Salt Lake Valley. The purpose of this inversion is to determine in more detail the sub-surface structure in the central portion of the valley.

The 2-D P-SV synthetic seismograms have shown that the deep basin structure is responsible for much of the low frequency site amplification, and that site response in Salt Lake Valley is sensitive to the incidence angle of the source. Most of the low frequency energy collects over the deeper part of the basin, with surface waves as a dominant waveform. Steeply dipping basin walls enhance the formation of surface waves, and convert more energy into the horizontal direction than do shallowly dipping walls.

Other Information:
Published: 1989
Pages: 82 p.
Plates: 4 pl.
Location: Salt Lake County
Media Type: Paper Publication