A global hybrid <i> V <sub>S</sub> </i> <sub>30</sub> map with a topographic slope–based default and regional map insets
David C. Heath, David J. Wald, C. Bruce Worden, Eric M. Thompson, Gregory M. Smoczyk
Abstract
Time‐averaged shear wave velocity over the upper 30 m of the earth’s surface ( V S 30 ) is a key parameter for estimating ground motion amplification as both a predictive and a diagnostic tool for earthquake hazards. The first‐order approximation of V S 30 is commonly obtained through a topographic slope–based or terrain proxy due to the widely available nature of digital elevation models. However, better‐constrained V S 30 maps have been developed in many regions. Such maps preferentially employ various combinations of V S 30 measurements, higher‐resolution elevation models, lithologic, geologic, geomorphic, and other proxies and often utilize refined interpolation schemes. We develop a new hybrid global V S 30 map database that defaults to the global slope‐based V S 30 map, but smoothly inserts regional V S 30 maps where available. In addition, we present comparisons of the default slope‐based proxy maps against the new hybrid version in terms of V S 30 and amplification ratio maps, and uncertainties in assigned V S 30 values.