Inclusion of Frequency-Dependent Spatial Correlation into the SDSU Broadband Ground-Motion Generation Method

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

Seismic losses (such as disruption of distributed infrastructure and losses to portfolios of structures) are typically dependent upon the regional distribution of ground-motion intensities, rather than the intensity at only a single site. Ground motion time series recorded at stations separated by up to a few tens of kilometers show a frequency-dependent spatial coherency structure, and measures such as PGVs, PGAs, and peak spectral accelerations are found to be correlated. Quantifying ground motion over a spatially-distributed region is therefore important and requires information on the correlation between the ground motion intensities at different sites during a single event, where the spatial correlation can be significant within 50 km. The significance of excluding spatial correlation in ground motion simulations can result in an under-estimation of the seismic risk. The San Diego State University (SDSU) module on the Southern California Earthquake Center (SCEC) Broadband Platform (BBP) is a hybrid method that merges low-frequency deterministic synthetics and high-frequency stochastic scattering functions. We have implemented frequency-dependent spatial correlation into the SDSU method on the SCEC BBP using a post-processing method. This method makes use of a two-dimensional Gaussian random variable that has covariance corresponding to the spatial cross-correlation model developed by Loth and Baker (2013) for spectral accelerations. Our results for the Loma Prieta, CA, event show that the frequency-dependent spatial correlation in our broadband synthetics compares well to that estimated from seismic observations.

Presenting Author: Nan Wang

Authors