2008 Articles

Coseismic sediment deformation during the 1989 Loma Prieta earthquake

Borja, Ronaldo I.; Sun, WaiChing

Inelastic horizontal sediment deformation from the MS 7.1, 17 October 1989 Loma Prieta earthquake has been estimated to be on the order of 20 cm at a site in Gilroy, California, about 32 km east of the epicenter. This estimate was based on combined deterministic-stochastic simulations using ground motion data and sediment properties measured from in situ seismic tests and laboratory tests on cored sediment samples of up to 170 m deep. The calculated deformation is comparable to measured horizontal coseismic displacements at various stations in the Santa Cruz network, suggesting that previously back-figured fault rupture mechanisms may have been influenced by the coseismic sediment deformation.