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 VS30 measurements. 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 existing VS30 maps.

Online Material: California statewide VS30 and ShakeMaps for Loma Prieta.

You do not currently have access to this article.