Taiwan-Specific Model for VS30 Prediction Considering Between-Proxy Correlations

Abstract

Ergodic site response models are generally conditional on the time-averaged shear wave velocity in the upper 30 m (V-S30). Ground motion databases contain many recordings from Taiwan, and because of site characterization efforts, 56% of recording sites have V-S30 derived from measurements. We develop proxy-based V-S30 prediction models, one application of which is for the remaining 44% of Taiwan sites. Our approach, which can be suitable for other regions, differs from previous studies in which proxies are based on detailed geologic categories and possible within-category topographic gradient effects. Instead, we use three broad, age-based geologic categories, and for the youngest category of Holocene and Quaternary undivided sediments, we propose models conditioned on gradient and elevation. We also adapt a geomorphic terrain-based method, thus providing two V-S30-predictionmodels. We describe a model weighting scheme that combines the models in consideration of their relative dispersions and correlation, producing a weighted mean and standard deviation natural-log V-S30. Included as an electronic supplement is a profile database file and a site database with site parameters for Taiwan ground motion stations.