Three-dimensional, finite-difference simulations of a realistic finite-fault rupture on the southern Hayward fault are used to evaluate the effects of random, correlated velocity perturbations on predicted ground motions. Velocity perturbations are added to a three-dimensional (3D) regional seismic velocity model of the San Francisco BayArea using a 3D vonKarman random medium.Velocity correlation lengths of 5 and 10 km and standard deviations in the velocity of 5% and 10% are considered. The results showthat significant deviations in predicted ground velocities are seen in the calculated frequency range (???1 Hz) for standard deviations in velocity of 5% to 10%. These results have implications for the practical limits on the accuracy of scenario groundmotion calculations and on retrieval of source parameters using higher-frequency, strong-motion data.
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Effects of 3D random correlated velocity perturbations on predicted ground motions