A velocity model for basin sediments in Southern California based on field measurements

Domniki Asimaki, Jian Shi, & Ricardo Taborda

Published August 15, 2017, SCEC Contribution #7883, 2017 SCEC Annual Meeting Poster #271 (PDF)

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Geotechnical data from soils and weathered rocks on regional scales are sparse and discontinuous. On the same time, these shallow crustal formations can have a significant effect on the amplitude, frequency and duration strong ground motions, especially in the high frequency regime that is relevant to engineering studies. Therefore, modeling the soft sedimentary deposits is an essential and challenging step in the development of regional crustal velocity models, and has been gaining traction as the capabilities of physics-based simulations have targeted broadband ground motions with increasingly higher frequency content. We here present our newly developed velocity model for basin structures in Southern California. The so-called sediment velocity model (SVM) translates Vs30, the only proxy available to describe the stiffness of the near surface sediments, into a generic velocity profile suitable for use in wave propagation-based ground motion models. We base this model on the statistics of nearly a thousand measured velocity profiles with Vs30 ranging from 150 m/s to 1000 m/s. We validate the model by comparing the site amplification factors of the measured profiles and the SVM. We also develop the implementation of a spatially correlated random realization algorithm, namely "RandSVM", intended to populate the near surface of 3D regional velocity models with our SVM. The next step of this work is to use stochastic 3D realizations of RandSVM3D to improve high-frequency predictions of physics-based ground motion simulations, and 1D realizations to develop Vs30-dependent amplification factors for implementation in the SCEC broadband platform.

Key Words
shallow crust, velocity model, amplification, site response, nonlinear

Asimaki, D., Shi, J., & Taborda, R. (2017, 08). A velocity model for basin sediments in Southern California based on field measurements. Poster Presentation at 2017 SCEC Annual Meeting.

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