Imaging and ground motion in urban sedimentary basins: The Santa Clara and San Bernardino Valleys

Hartzell, Stephen H.; Jachens, Robert C.; Brocher, Thomas M.; Frankel, Arthur

doi:10.3133/ofr98244

Cited by 1 publication

(1 citation statement)

References 25 publications

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“…In 1998 the U.S. Geological Survey held a workshop (Hartzell, Jachens et al, 1998) to select an urban sedimentary basin on which to focus 3D wave propagation and ground-motion studies. The impetus for this workshop was the 1994 Northridge, California, earthquake and the 1995 Hyogo-ken Nanbu earthquake in Kobe, Japan, and the realization of the significant seismic hazard posed by urban sedimentary basins.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Validation of a 3D Velocity Structure for the Santa Clara Valley, California, for Seismic-Wave Simulations

Hartzell¹,

Harmsen²,

Williams³

et al. 2006

Bulletin of the Seismological Society of America

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A 3D seismic velocity and attenuation model is developed for Santa Clara Valley, California, and its surrounding uplands to predict ground motions from scenario earthquakes. The model is developed using a variety of geologic and geophysical data. Our starting point is a 3D geologic model developed primarily from geologic mapping and gravity and magnetic surveys. An initial velocity model is constructed by using seismic velocities from boreholes, reflection/refraction lines, and spatial autocorrelation microtremor surveys. This model is further refined and the seismic attenuation is estimated through waveform modeling of weak motions from small local events and strong-ground motion from the 1989 Loma Prieta earthquake. Waveforms are calculated to an upper frequency of 1 Hz using a parallelized finite-difference code that utilizes two regions with a factor of 3 difference in grid spacing to reduce memory requirements. Cenozoic basins trap and strongly amplify ground motions. This effect is particularly strong in the Evergreen Basin on the northeastern side of the Santa Clara Valley, where the steeply dipping Silver Creek fault forms the southwestern boundary of the basin. In comparison, the Cupertino Basin on the southwestern side of the valley has a more moderate response, which is attributed to a greater age and velocity of the Cenozoic fill. Surface waves play a major role in the ground motion of sedimentary basins, and they are seen to strongly develop along the western margins of the Santa Clara Valley for our simulation of the Loma Prieta earthquake.

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Section: Introductionmentioning

confidence: 99%