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From VS30 to near-surface velocity profiles: Integrating soft sediments in SCEC's UCVM

Domniki Asimaki, Jian Shi, & Ricardo Taborda

Published August 15, 2016, SCEC Contribution #6919, 2016 SCEC Annual Meeting Poster #266

The near-surface soil layers of sedimentary basins play a critical role in modifying the amplitude, frequency and duration of earthquake ground shaking. These phenomena, referred to as site effects, play a very important role in ground-motion simulations, in the development of site amplification factors, and more generally in earthquake hazard and risk predictions on a regional scale. In this study, we develop a model that translates Vs30, the only proxy available to describe the stiffness of the near surface sediments in Southern California, into a generic velocity profile suitable for use in wave propagation-based ground motion models. We specifically develop a Vs30-dependent shear wave velocity model (previously referred to as Geotechnical Layer or GTL), based on the statistics of a few hundred measured velocity profiles with VS30 ranging from 150 m/s to 800 m/s. We validate the model by comparing the site amplification of the measured and the developed VS30-dependent velocity profiles. We lastly develop and demonstrate the implementation of a spatially correlated random realization algorithm, intended to populate the near surface of the 3D UCVM domain with our VS30-dependent velocity profiles. The next step of this work is to use the profiles to improve high-frequency predictions of 3D physics-based ground motion simulations; and to develop VS30-dependent amplification factors for implementation in the SCEC broadband platform.

Key Words
VS30, GTL, soil, site response

Asimaki, D., Shi, J., & Taborda, R. (2016, 08). From VS30 to near-surface velocity profiles: Integrating soft sediments in SCEC's UCVM. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motion Prediction (GMP)