Location

San Diego, California

Session Start Date

3-26-2001

Session End Date

3-31-2001

Abstract

For a given seismic source, ground motions at soil sites can be estimated using either soil attenuation relationships, or ground response analyses with input motions scaled to match spectral ordinates from rock attenuation relationships. Ground response analyses are performed with the expectation that accounting for nonlinear sediment response improves the accuracy and reduces the uncertainty in estimated motions. Discussed here are the benefits of ground response analyses as a function of site condition. This is accomplished by preparing statistical predictions of ground motions at 36 strong motion recording sites on soil. Two predictions are made, one using a modified soil attenuation relationship, the other using ground response analyses with a large suite of carefully selected and scaled input motions. Predictions from both methods are compiled as 5% damped spectral ordinates, and are expressed as medians and standard errors. These quantities can then be compared to the spectra of the recorded motion to evaluate the residuals of the estimates. For periods, T< 1 s, ground response analyses are found to improve the accuracy of ground motion predictions relative to soil attenuation. However, a positive bias in median ground response estimates is found that indicates a systematic underprediction of ground motion.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fourth Conference

Publisher

University of Missouri--Rolla

Publication Date

3-26-2001

Document Version

Final Version

Rights

© 2001 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Mar 26th, 12:00 AM Mar 31st, 12:00 AM

Uncertainties and Residuals in Ground Motion Estimates at Soil Sites

San Diego, California

For a given seismic source, ground motions at soil sites can be estimated using either soil attenuation relationships, or ground response analyses with input motions scaled to match spectral ordinates from rock attenuation relationships. Ground response analyses are performed with the expectation that accounting for nonlinear sediment response improves the accuracy and reduces the uncertainty in estimated motions. Discussed here are the benefits of ground response analyses as a function of site condition. This is accomplished by preparing statistical predictions of ground motions at 36 strong motion recording sites on soil. Two predictions are made, one using a modified soil attenuation relationship, the other using ground response analyses with a large suite of carefully selected and scaled input motions. Predictions from both methods are compiled as 5% damped spectral ordinates, and are expressed as medians and standard errors. These quantities can then be compared to the spectra of the recorded motion to evaluate the residuals of the estimates. For periods, T< 1 s, ground response analyses are found to improve the accuracy of ground motion predictions relative to soil attenuation. However, a positive bias in median ground response estimates is found that indicates a systematic underprediction of ground motion.