Simulated ground motion in Santa Clara Valley, California, and vicinity from M≥6.7 scenario earthquakes

Stephen C. Harmsen; Stephen H. Hartzell

doi:10.1785/0120060230

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Simulated ground motion in Santa Clara Valley, California, and vicinity from M≥6.7 scenario earthquakes

Stephen C. Harmsen·Stephen H. Hartzell

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Abstract

Models of the Santa Clara Valley (SCV) 3D velocity structure and 3D finite-difference software are used to predict ground motions from scenario earthquakes on the San Andreas (SAF), Monte Vista/Shannon, South Hayward, and Calaveras faults. Twenty different scenario ruptures are considered that explore different source models with alternative hypocenters, fault dimensions, and rupture velocities and three different velocity models. Ground motion from the full wave field up to 1 Hz is exhibited as maps of peak horizontal velocity and pseudospectral acceleration at periods of 1, 3, and 5 sec. Basin edge effects and amplification in sedimentary basins of the SCV are observed that exhibit effects from shallow sediments with relatively low shear-wave velocity (330 m/sec). Scenario earthquakes have been simulated for events with the following magnitudes: (1) M 6.8–7.4 Calaveras sources, (2) M 6.7–6.9 South Hayward sources, (3) M 6.7 Monte Vista/Shannon sources, and (4) M 7.1–7.2 Peninsula segment of the SAF sources. Ground motions are strongly influenced by source parameters such as rupture velocity, rise time, maximum depth of rupture, hypocenter, and source directivity. Cenozoic basins also exert a strong influence on ground motion. For example, the Evergreen Basin on the northeastern side of the SCV is especially responsive to 3–5-sec energy from most scenario earthquakes. The Cupertino Basin on the southwestern edge of the SCV tends to be highly excited by many Peninsula and Monte Vista fault scenarios. Sites over the interior of the Evergreen Basin can have long-duration coda that reflect the trapping of seismic energy within this basin. Plausible scenarios produce predominantly 5-sec wave trains with greater than 30 cm/sec sustained ground-motion amplitude with greater than 30 sec duration within the Evergreen Basin.

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Bulletin of the Seismological Society of America Article

Source-reported bounding extent: 36.76529191711624° to 38.02213147353745° latitude; -122.8216552734375° to -120.99243164062501° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Stephen C. Harmsen, Stephen H. Hartzell. 2008. Simulated ground motion in Santa Clara Valley, California, and vicinity from M≥6.7 scenario earthquakes. https://doi.org/10.1785/0120060230

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