Regional terrain-based VS30 prediction models for China

Abstract Time-averaged shear-wave velocity to 30 m (VS30) is commonly used in ground motion models as a parameter for evaluating site effects. This study used a collection of boreholes in Beijing, Tianjin, Guangxi, Guangdong, and three other municipalities and provinces, which were divided into three regions with reference to the seismic ground motion parameter zonation map of China, to establish VS30 prediction models based on terrain categories. Regional effects were verified by comparing morphometric parameters (topographic slope, surface texture, and local convexity) thresholds and terrain classification maps obtained from the global digital elevation model (DEM) data and the regional DEM data of the three regions. Additionally, VS30 prediction models for the three regions using both types of terrain classification maps were established and analyzed comparatively to provide credible regional VS30 models for China. Through analysis of the correlations between the measured VS30 values and the predicted VS30 values, and with consideration of the geological characteristics of the boreholes, the VS30 prediction models based on terrain classification maps from regional data were finally applied in developing regional VS30 models for China. Intercomparison of the VS30 prediction models for the three regions indicated that subregional consideration is necessary in terrain classification. Finally, a spatial analysis method adopting inverse distance weighting of the residuals was used to update the initial VS30 models. The developed VS30 models could be used both in developing regional ground motion models and in the construction of earthquake disaster scenarios.