Using Two-station Microtremor Array Measurements to Estimate Shear-wave Velocity Profiles in the San Francisco Bay Area

2013 ◽  
Author(s):  
Koichi Hayashi ◽  
Deborah Underwood
Keyword(s):  
Shear Wave ◽  
San Francisco ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
San Francisco Bay ◽  
San Francisco Bay Area ◽  
Velocity Profiles ◽  
Bay Area ◽  
Array Measurements

Shear-Wave Velocity of Surficial Geologic Sediments in Northern California: Statistical Distributions and Depth Dependence

2005 ◽  
Vol 21 (1) ◽  
pp. 161-177 ◽  
Author(s):  
Thomas L. Holzer ◽  
Michael J. Bennett ◽  
Thomas E. Noce ◽  
John C. Tinsley
Keyword(s):  
Shear Wave ◽  
San Francisco ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
San Francisco Bay ◽  
Geometric Mean ◽  
Depth Dependence ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Coefficients Of Variation

Shear-wave velocities of shallow surficial geologic units were measured at 210 sites in a 140-km2 area in the greater Oakland, California, area near the margin of San Francisco Bay. Differences between average values of shear-wave velocity for each geologic unit computed by alternative approaches were in general smaller than the observed variability. Averages estimated by arithmetic mean, geometric mean, and slowness differed by 1 to 8%, while coefficients of variation ranged from 14 to 25%. With the exception of the younger Bay mud that underlies San Francisco Bay, velocities of the geologic units are approximately constant with depth. This suggests that shear-wave velocities measured at different depths in these surficial geologic units do not need to be normalized to account for overburden stress in order to compute average values. The depth dependence of the velocity of the younger Bay mud most likely is caused by consolidation. Velocities of each geologic unit are consistent with a normal statistical distribution. Average values increase with geologic age, as has been previously reported. Velocities below the water table are about 7% less than those above it.

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