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Incorporation of Site-Specific Attenuation Model using Kappa in Broadband Simulations

Swasti Saxena, John G. Anderson, & Ramin Motamed

Published June 25, 2017, SCEC Contribution #8936

This research aims to develop a physics-based, source-to-site simulation of ground motions for the site response matching both surface and downhole seismograms at the Wildlife Liquefaction Array (WLA) in Southern California. Since attenuation parameters are an essential part of the continuum model and greatly affect the response of an earthquake, this study is focused on determining a site-specific Q profile at WLA.

The exponential decay observed at high frequencies in the Fourier spectrum of a seismic record is characterized with the parameter kappa. The spatial variation of kappa, consistent with spatial variation of Q, estimated from ground motion records at different depths at the WLA site, allows us to estimate lateral and vertical Q profiles.

The final profiles, evaluated for Qp and Qs separately, are used in synthetic ground motion simulations based on Composite Source Model since this model retains a full wave propagation solution at high frequencies. Finally, we compare the simulation results obtained using site specific attenuation as well as a generic Q-model, with observed records, note the difference in responses, and discuss the results.

Saxena, S., Anderson, J. G., & Motamed, R. (2017, 06). Incorporation of Site-Specific Attenuation Model using Kappa in Broadband Simulations. Oral Presentation at 11th National Conference on Earthquake Engineering.