Broadband (0–4 Hz) Ground Motions for a Magnitude 7.0 Hayward Fault Earthquake With Three-Dimensional Structure and Topography

Abstract

We performed fully deterministic broadband (0–4 Hz) high-performance computing ground motion simulations of a magnitude 7.0 scenario earthquake on the Hayward Fault (HF) in the San Francisco Bay Area of Northern California. Simulations consider average one-dimensional (1-D) and three-dimensional (3-D) anelastic structure with flat and topographic free surfaces. Ground motion intensity measures (GMIMs) for the 3-D model display dramatic differences across the HF due to geologic heterogeneity, with low wave speeds east of the HF amplifying motions. The median GMIMs agree well with Ground Motion Prediction Equations (GMPEs); however, the 3-D model generates more scatter than the 1-D model. Ratios of 3-D/1-D GMIMs from the same source allow isolation of path and site effects for the 3-D model. These ratios show remarkably similar trends as site-specific factors for the GMPE predictions, suggesting that wave propagation effects in our 3-D simulations are on average consistent with empirical data.