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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 4. (April)

First Page: 781

Last Page: 782

Title: Faults and Earthquakes in Monterey Bay Region, California: ABSTRACT

Author(s): H. Gary Greene, William H. K. Lee, David S. McCulloch, Earl E. Brabb

Article Type: Meeting abstract

Abstract:

The structure of the continental margin, between Monterey Bay on the south and Point Reyes on the north, is dominated by a northwest-trending belt of rocks composed of continental crust (Salinian block) that is separated from oceanic crust on the east by the active San Andreas Previous HitfaultNext Hit system, and on the west by the Sur-Nacimiento Previous HitfaultNext Hit zone. Recent marine geophysical

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investigation have shown extensive faulting within this crustal block--some of which appears to have locally offset Holocene deposits. Most of the faults within the Salinian block in the Monterey Bay region occur in two major intersecting Previous HitfaultNext Hit zones; the northward-trending Carmel Canyon Previous HitfaultNext Hit zone, extending offshore from Point Sur (oriented N25°W), and the northwest-trending Monterey Bay Previous HitfaultNext Hit zone, extending offshore from the town of Monterey (oriented N50°W). The Carmel Canyon Previous HitfaultNext Hit zone appears to connect the Palo Colorado Previous HitfaultNext Hit in the south with the San Gregorio Previous HitfaultNext Hit in the north. The Monterey Bay Previous HitfaultNext Hit zone appears to be the offshore continuation of the Sur-Nacimiento Previous HitfaultNext Hit zone.

Epicenters of many recent earthquakes are concentrated at the intersection of the Carmel Canyon and Monterey Bay Previous HitfaultNext Hit zones, in the central part of Monterey Bay. First-motion studies of 8 earthquakes indicate right-lateral strike-slip displacement on these offshore faults. The cessation of a 10-day period of rapid tectonic creep along the adjacent San Andreas Previous HitfaultNext Hit in 1970 coincided with a 4.3-magnitude earthquake in the Monterey Bay Previous HitfaultNext Hit zone. This, as well as first-motion studies of the earthquakes and mapping of the offshore faults and seismicity, suggests a direct coupling between the San Andreas Previous HitfaultNext Hit and the adjacent Previous HitfaultTop zones.

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