The NGA-West2 site database (SDB) contains information on site condition and instrument housing for 4,147 strong-motion stations with recordings in the project flatfile. The stations are from active tectonic regions, mainly in California, Japan, Taiwan, China, and the Mediterranean area. The principal site parameter is the time-averaged shear wave velocity in the upper 30 m (VS30), which we characterize using measurements where available (2,013 stations) and proxy-based relationships otherwise. We also provide basin depths from published models for 2,761 sites mostly in California and Japan. We improved the documentation and consistency of site descriptors used as proxies for VS30 estimation (surface geology, ground slope, and geotechnical or geomorphic categories) and analyzed proxy performance relative to VS30 values from measurements. We present protocols for VS30 estimation from proxies that emphasize methods minimizing bias and dispersion relative to data. For each site, we provide the preferred VS30 and its dispersion.
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