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Poster #203, Ground Motions

Toward development of physics-based coherency models using deterministic broad-band earthquake ground motion simulations

Elnaz Seylabi, Arben Pitarka, & David B. McCallen
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Poster Presentation

2020 SCEC Annual Meeting, Poster #203, SCEC Contribution #10424 VIEW PDF
We present a coherency analysis of synthetic earthquake ground motions and compare the computed lagged coherency to the existing empirical models. Our overarching goal is to study the effects of physical parameters -- such as subsurface heterogeneity, topography, seismic source type, and spatial distance -- on the coherency of simulated ground motions, and develop a three-dimensional physics-based model that can be used for the generation of spatially varying ground motion fields in earthquake engineering applications, e.g., performance-based engineering of distributed infrastructure. To this end, we perform a series of earthquake simulations in the San Francisco Bay Area using the SW4 finit...e difference code. We also use stochastic perturbations to model the small-scale geologic heterogeneity in the USGS 3D velocity model used in the simulations. We define a dense array with 0.1km spacing and compute the lagged coherency as a function of both distance and frequency. The analyses performed to-date suggest that: (1) the lagged coherency can decrease up to 60% in the frequency range of 0-4Hz and at a spatial distancing of less than 0.5km; (2) vertical components of the simulated ground motions show stronger incoherency compared to their horizontal counterparts; and (3) inclusion of small-scale stochastic perturbations in the velocity structure reduces the ground motion coherency.