3D Simulations of M 7 Earthquakes on the Wasatch Fault, Utah, Part II: Broadband (0-10 Hz) Ground Motions and Nonlinear Soil Behavior

Abstract

Abstract We predict broadband (BB, 0–10 Hz) ground motions for M 7 earthquakes on the Salt Lake City segment of the Wasatch fault (WFSLC), Utah, which include the effects of nonlinear site response. The predictions are based on low‐frequency (LF, 0–1 Hz) finite‐difference (FD) simulations for six different rupture models generated during a previous study (Roten et al. , 2011), which we combine with high‐frequency (HF, 1–10 Hz) shear‐to‐shear (S‐to‐S) back‐scattering operators to generate BB synthetics. Average horizontal spectral accelerations at 5 and 10 Hz (0.2‐s SAs and 0.1‐s SAs, respectively) calculated from the linear BB synthetics exceed estimates from four recent ground‐motion prediction equations (GMPEs) at near‐fault ( g on the hanging‐wall side of the fault. Geometric mean 0.2‐s SAs exceed 1 g on the hanging‐wall and on the footwall sediments in the central Salt Lake basin, and peak horizontal ground accelerations range from 0.45 to >0.60 g in the same general locations. Online Material: Table of coefficients and amplitude‐dependent correction functions for nonlinear soil effects, and figures showing maps of SAs at various frequencies, PGA and PGV, with and without correction for nonlinear soil effects, results of 1D nonlinear simulations, and comparison to ground motion prediction equations.