Estimates of kappa in the San Francisco Bay area
Site characterization is a critical component of seismic hazards studies, especially in the development and use of ground motion models (GMMs). One such parameter, kappa ( Κ 0 ), represents local site attenuation and effectively describes regional variations in ground motion [1]. However, estimates of Κ 0 are limited. We estimate the site parameter Κ 0 for 296 broadband and accelerometer stations in the San Francisco Bay area using 225 local events with M>3.5. We first invert for kappa on the high-frequency slope of every record at a station, which represents full attenuation effects [2]. We then perform weighted regression of kappa versus distance to obtain expected kappa at the site ( Κ 0 ). We find that Κ 0 varies extensively in the San Francisco Bay area, with values ranging from 0.004-0.113 s, thus representing the heterogeneous geologic conditions in the region. Κ 0 estimates from this study will be useful to consider in future seismic hazard analyses and ground motion studies in the Bay Area.