Regional Path Effects for Ground Motion Analysis in Sacramento-San Joaquin River Delta, California
Session: Probabilistic Seismic Hazard Assessment: Where Do We Go from Here? II
Type: Oral
Date: 4/20/2021
Presentation Time: 02:45 PM Pacific
Description:
As part of a long-term project to develop semi-empirical site amplification models for application to the peaty organic soil sites in the Sacramento-San Joaquin Delta region of California, we have investigated regional variations in source-to-site path effects. In these assessments, the “sites” are located in the Delta region and the source regions are geographically diverse, including (1) the north coast region north and west of the San Francisco Bay area; (2) the Bay Area region, extending from the Pacific coast to the western edge of the Delta; (3) the central coast region south and east of Hollister; and (4) the eastern Sierra region (approximately from Tahoe to Mammoth). We investigate differences in path effects, particularly with regard to anelastic attenuation, for earthquakes in these regions. These path assessments are important for non-ergodic site response evaluations at Delta sites, so that systematic errors in source-to-site path effects are not mapped into empirical estimates of elastic site response.
We use a data set consisting of 77 northern California and Nevada events that has produced 11,027 recordings. Mixed-effects residuals analyses are performed using the Boore et al. (2014; hereafter BSSA) ground motion model. We find no evidence of path bias for Bay Area and central coast events, whereas north coast and eastern Sierra events have attenuation rates faster and slower, respectively (i.e., lower and higher Q), than the standard BSSA model for California at high frequencies (> approximately 0.6 Hz). We propose an iterative approach to investigate these path effects in which systematic site response effects are removed. The result of this work is period-dependent path adjustment models applicable to the north coast and eastern Sierra regions.
Presenting Author: Tristan E. Buckreis
Student Presenter: Yes
Authors
Tristan Buckreis Presenting Author Corresponding Author tristanbuckreis@ucla.edu University of California, Los Angeles |
Scott Brandenberg sjbrandenberg@g.ucla.edu University of California, Los Angeles |
Jonathan Stewart jstewart@seas.ucla.edu University of California, Los Angeles |
|
|
|
|
|
|
Regional Path Effects for Ground Motion Analysis in Sacramento-San Joaquin River Delta, California
Category
Probabilistic Seismic Hazard Assessment: Where Do We Go from Here?