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1 Civil and Environmental Engineering
Department
5731 Boelter Hall
University of California
Los Angeles,
California
90095
jstewart{at}seas.ucla.edu
(J.P.S.)
2 GeoPentech
601 N. Parkcenter
Drive, Suite 210
Santa Ana, California
92705
yoojoong_choi{at}geopentech.com
(Y.C.)
3 URS Corporation
566 El Dorado
Street, 2nd Floor
Pasadena, California
91101-2560
Robert_Graves{at}URScorp.com
(R.W.G.)
4 Department of Earth and Planetary
Science
Harvard University
20 Oxford Street
Cambridge, Massachusetts
02138
shaw{at}eps.harvard.edu
(J.H.S.)
We validate a model for the velocity structure of basin sediments in southern California against sonic log data and evaluate the bias and uncertainty of basin depth terms. Basin depth, as measured by depth to the 1.5 km/sec shear-wave isosurface, is underpredicted near the basin margins where the basin is relatively shallow and overpredicted near the middle of the basin. The standard deviation of the residuals is approximately 410 m when the bias trends are not considered and approximately 240 m when they are considered. The effects of the bias on estimated ground motions are likely small because the available empirical models utilized this same velocity model, and hence inherently incorporate the bias effects. The effect of uncertainty in basin depths can introduce uncertainty in ground motions of up to 0.1 (in natural log units), which is small compared to typical error terms in attenuation relations.
This article has been cited by other articles:
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J. Pujol, K. Mueller, P. Shen, and V. Chitupolu High-Resolution 3D P-Wave Velocity Model for the East Ventura-San Fernando Basin, California, and Relocation of Events in the Northridge and San Fernando Aftershock Sequences Bulletin of the Seismological Society of America, December 1, 2006; 96(6): 2269 - 2280. [Abstract] [Full Text] [PDF] |
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