A VS30 map for California with geologic and topographic constraints

Bulletin of the Seismological Society of America
By: , and 



For many earthquake engineering applications, site response is estimated through empirical correlations with the time‐averaged shear‐wave velocity to 30 m depth (VS30). These applications therefore depend on the availability of either site‐specific VS30 measurements or VS30 maps at local, regional, and global scales. Because VS30 measurements are sparse, a proxy frequently is needed to estimate VS30 at unsampled locations. We present a new VS30 map for California, which accounts for observational constraints from multiple sources and spatial scales, such as geology, topography, and site‐specific VS30measurements. We apply the geostatistical approach of regression kriging (RK) to combine these constraints for predicting VS30. For the VS30 trend, we start with geology‐based VS30 values and identify two distinct trends between topographic gradient and the residuals from the geology VS30 model. One trend applies to deep and fine Quaternary alluvium, whereas the second trend is slightly stronger and applies to Pleistocene sedimentary units. The RK framework ensures that the resulting map of California is locally refined to reflect the rapidly expanding database of VS30 measurements throughout California. We compare the accuracy of the new mapping method to a previously developed map of VS30 for California. We also illustrate the sensitivity of ground motions to the new VS30 map by comparing real and scenario ShakeMaps with VS30 values from our new map to those for existingVS30 maps.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A VS30 map for California with geologic and topographic constraints
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120130312
Volume 104
Issue 5
Year Published 2014
Language English
Publisher Seismological Society of America
Contributing office(s) Geologic Hazards Science Center
Description 9 p.
First page 2313
Last page 2321
Country United States
State California
Online Only (Y/N) N
Additional Online Files (Y/N) N
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