ShakeOut-D: Ground Motion Estimates Using an Ensemble of Large Earthquakes on the Southern San Andreas Fault With Spontaneous Rupture Propagation

Kim B. Olsen, Steven M. Day, Luis A. Dalguer, John E. Mayhew, Yifeng Cui, Jing Zhu, Victor M. Cruz-Atienza, Daniel Roten, Philip J. Maechling, Thomas H. Jordan, David A. Okaya, & Amit Chourasia

Published 2009, SCEC Contribution #1255

We simulate ground motion in southern California from an ensemble of 7 spontaneous rupture models of large (Mw7.8) northwest-propagating earthquakes on the southern San Andreas fault (ShakeOut-D). Compared to long-period spectral accelerations from the Next Generation Attenuation (NGA) empirical relations, ShakeOut-D predicts similar average rock-site values (i.e., within roughly their epistemic uncertainty), but significantly larger values in Los Angeles and Ventura basins due to wave-guide focusing effects. The ShakeOut-D ground motion predictions differ from those of a kinematically parameterized, geometrically similar, scenario rupture: (1) the kinematic rock-site predictions depart significantly from the common distance-attenuation trend of the NGA and ShakeOut-D results, and (2) ShakeOut-D predictions of long-period spectral acceleration within the basins of the greater Los Angeles area are lower by factors of 2-3 than the corresponding kinematic predictions. We attribute these differences to a the less coherent wavefield excited by the complex rupture paths of the ShakeOut-D sources.

Citation
Olsen, K. B., Day, S. M., Dalguer, L. A., Mayhew, J. E., Cui, Y., Zhu, J., Cruz-Atienza, V. M., Roten, D., Maechling, P. J., Jordan, T. H., Okaya, D. A., & Chourasia, A. (2009). ShakeOut-D: Ground Motion Estimates Using an Ensemble of Large Earthquakes on the Southern San Andreas Fault With Spontaneous Rupture Propagation . Geophysical Research Letters, 36, L04304 1-6. doi: 10.1029/2008GL036832.