San Francisco Bay Area Kappa Model
Session: Advances in Understanding Near-Field Ground Motions: Observation, Prediction and Application II
Type: Oral
Date: 4/22/2021
Presentation Time: 02:30 PM Pacific
Description:
Understanding local site attenuation is important for removing site effects for regional seismological source and path studies, as well as for designing ground-motion models, a critical component of seismic hazard estimation. Kappa (k), the high frequency attenuation at a site, is representative of high frequency site conditions. It is widely used in earthquake simulations and has recently been considered as a site parameter in certain ground-motion models. In particular, this parameter may be of use for fully non-ergodic ground-motion models, which require spatially varying parameters, such as anelastic attenuation or site conditions. The San Francisco Bay Area is a seismically active region, yet no such k models currently exist, so we produce a k model for this area. Following the method of Klimasewski et al. (2019), we obtain site spectra for Bay Area seismic stations via spectral decomposition. However, we improve on this method by first removing crustal attenuation (Q) from the records with the model of Eberhart-Phillips (2016) to remove path effects from the site term, as our stations are located farther away from our events than those used in Klimasewski et al. (2019). We compute k on the resulting site spectra. Our dataset is composed of ~3000 events from the NCEDC database, ranging from M2.5-6, and 30 stations. Thus far, we see strong regional variations in k in the Bay Area. We specifically see higher k values in the Sacramento San Joaquin River Delta and along the Hayward fault, which corroborate the expected attenuation effects for such geologic features. We present the resulting k values in the San Francisco Bay Area and discuss the applicability of these values to represent local site effects to accurately predict ground motion for seismological and hazards studies.
Presenting Author: Tara Nye
Student Presenter: Yes
Authors
Tara Nye Presenting Author Corresponding Author tnye@uoregon.edu University of Oregon |
Elias King eliask@uoregon.edu University of Oregon |
Alexis Klimasewski aklimase@uoregon.edu University of Oregon |
Valerie Sahakian vjs@uoregon.edu University of Oregon |
Annemarie Baltay abaltay@usgs.gov U.S. Geological Survey |
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San Francisco Bay Area Kappa Model
Session
Advances in Understanding Near-Field Ground Motions: Observation, Prediction and Application