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Seismotectonics and fault structure of the California central coast

Jeanne L. Hardebeck
Seismotectonics and fault structure of the California central coast
Bulletin of the Seismological Society of America (June 2010) 100 (3): 1031-1050

Abstract

I present and interpret new earthquake relocations and focal mechanisms for the California Central Coast. The relocations improve upon catalog locations by using 3D seismic velocity models to account for lateral variations in structure and by using relative arrival times from waveform cross-correlation and double-difference methods to image seismicity features more sharply. Focal mechanisms are computed using ray tracing in the 3D velocity models. Seismicity alignments on the Hosgri fault confirm that it is vertical down to at least 12 km depth, and the focal mechanisms are consistent with right-lateral strike-slip motion on a vertical fault. A prominent, newly observed feature is an approximately 25 km long linear trend of seismicity running just offshore and parallel to the coastline in the region of Point Buchon, informally named the Shoreline fault. This seismicity trend is accompanied by a linear magnetic anomaly, and both the seismicity and the magnetic anomaly end where they obliquely meet the Hosgri fault. Focal mechanisms indicate that the Shoreline fault is a vertical strike-slip fault. Several seismicity lineations with vertical strike-slip mechanisms are observed in Estero Bay. Events greater than about 10 km depth in Estero Bay, however, exhibit reverse-faulting mechanisms, perhaps reflecting slip at the top of the remnant subducted slab. Strike-slip mechanisms are observed offshore along the Hosgri-San Simeon fault system and onshore along the West Huasna and Rinconada faults, while reverse mechanisms are generally confined to the region between these two systems. This suggests a model in which the reverse faulting is primarily due to restraining left-transfer of right-lateral slip.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 100
Serial Issue: 3
Title: Seismotectonics and fault structure of the California central coast
Affiliation: U. S. Geological Survey, Menlo Park, CA, United States
Pages: 1031-1050
Published: 201006
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 42
Accession Number: 2010-059072
Categories: SeismologyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N34°30'00" - N36°00'00", W121°30'00" - W120°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201032
Program Name: USGSOPNon-USGS publications with USGS authors
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