A Texas-specific V S 30 map incorporating geology and V S 30 observations

Abstract

A Texas-specific $V_{\mathrm{S}30}$ map that uses geostatistical kriging integrated with a region-specific geologic proxy, field measurements of $V_{\mathrm{S}30}$ , and P-wave seismogram estimates of $V_{\mathrm{S}30}$ is developed. The region-specific geologic proxy is used first to predict $V_{\mathrm{S}30}$ from the surface geologic conditions across the state, and then geostatistical kriging with an external drift is used to incorporate the local $V_{\mathrm{S}30}$ measurements/estimates into the map. Compared with the $V_{\mathrm{S}30}$ map of Texas developed from a topographic slope proxy, the Texas-specific $V_{\mathrm{S}30}$ map predicts larger $V_{\mathrm{S}30}$ values across much of Texas, except for the Gulf Coast region where the values are similar. The utilization of kriging brings the Texas-specific $V_{\mathrm{S}30}$ map into better agreement with the in situ measurements and estimates of $V_{\mathrm{S}30}$ . The sensitivity of predicted ground motions by ShakeMap to changes in $V_{\mathrm{S}30}$ values is evaluated with a scenario earthquake in the Dallas–Fort Worth area. The results suggest smaller predicted ground motions due to the generally larger values of $V_{\mathrm{S}30}$ in the Texas-specific $V_{\mathrm{S}30}$ map as compared to the $V_{\mathrm{S}30}$ from the topographic proxy.