Estimates of kappa in the San Francisco Bay area

Tara A. Nye; Valerie J. Sahakian; E.L. King; Annemarie S. Baltay; Alexis Klimasewski

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USGS · 70247518

Estimates of kappa in the San Francisco Bay area

Tara A. Nye·Valerie J. Sahakian·E.L. King·Annemarie S. Baltay·Alexis Klimasewski

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Abstract

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.

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Source-reported bounding extent: 37.02839058004079° to 38.47318654986222° latitude; -123.09855510328197° to -121.42077907357066° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Tara A. Nye, Valerie J. Sahakian, E.L. King, Annemarie S. Baltay, Alexis Klimasewski. 2022. Estimates of kappa in the San Francisco Bay area. https://pubs.usgs.gov/publication/70247518

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