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Linking Subsurface and Surface Processes: Insights on Vs30 Distribution in Southern California

Jessica C. Lin, Seulgi Moon, Alan Yong, Lingsen Meng, Antony Martin, & Paul M. Davis

Published August 7, 2017, SCEC Contribution #7420, 2017 SCEC Annual Meeting Poster #273

Earth’s surface and subsurface processes such as bedrock weathering, soil production, and river incision can influence and be influenced by spatial variations in the mechanical strength of surface material. Mechanically weakened rocks tend to have reduced seismic velocity, which can result in larger ground-motion amplification and greater potential for earthquake-induced damages. However, the influence and extent of surface and subsurface processes on the mechanical strength of surface material and seismic site conditions in southern California remain unclear. In this study, we examine whether physics-based models of surface and subsurface processes can explain the spatial variability and non-linearity of near-surface seismic velocity in southern California. We use geophysical measurements (Yong et al., 2013; Ancheta et al., 2014), consisting of shear-wave velocity (Vs) tomography data, Vs profiles, and the time-averaged Vs in the upper 30 m of the crust (Vs30) to infer lateral and vertical variations of surface material properties. Then, we compare Vs30 values with geologic and topographic attributes such as rock type, slope, elevation, and local relief, as well as metrics for surface processes such as soil production and bedrock weathering from topographic stress, frost cracking, chemical reactions, and vegetation presence. Results from this study will improve our understanding of physical processes that control subsurface material properties and their influences on local variability in seismic site conditions.

Lin, J. C., Moon, S., Yong, A., Meng, L., Martin, A., & Davis, P. M. (2017, 08). Linking Subsurface and Surface Processes: Insights on Vs30 Distribution in Southern California. Poster Presentation at 2017 SCEC Annual Meeting.

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