SASW Testing in the Salt Lake Valley, UT
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Abstract
Nickname: Deep Surface Wave Profiling in the Salt Lake Valley
NEES-2006-0173
The purpose of this study is to determine intermediate (250 ft (75 m) to 750 ft (230 m)) to deep (> 750 ft (230 m)) shear-wave velocity (Vs) profiles in the Salt Lake Valley. The Spectral-Analysis-of-Surface-Waves (SASW) method was used in the field to profile 11 locations. Vs profiles from this work have been provided to the Utah Ground Shaking Working Group and added to the community velocity model (CVM). The CVM is the first
research goal of a plan developed in 2004 by the Utah Ground Shaking Working Group to develop a ground-shaking map for the Salt Lake region.
For the 11 locations tested, six deep and five intermediate Vs profiles were evaluated. An unsuccessful attempt was made to test rock at Sites 5 and 8. All testing was performed using a low-frequency vibroseis called a??Liquidatora??. Liquidator is specially designed to excite energy in the low-frequency range of 0.5 to 4 Hz. SASW testing at low frequencies allows Vs profiling to greater depths than any other active source. The Vs
profiles at the sites were correlated with previous studies performed in the Salt Lake Valley. Most previous work involved Vs profiling at depths less than 150 ft (50 m). The primary focus of this study is to evaluate Vs profiles of the valley sediments at depths below 150 ft (50 m) and to determine the depth to the unconsolidated/semi-consolidated boundary in the Salt Lake Valley.