Slip partitioning of the Calaveras fault, California, and prospects for future earthquakes

Journal Article · Sun Jun 10 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB06p08483· OSTI ID:5014615

Oppenheimer, D H; Bakun, W H; Lindh, A G ^[1]

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1. Geological Survey, Menlo Park, CA (United States)

Examination of main shock and microearthquake data from the Calaveras fault during the last 20 years reveals that main shock hypocenters occur at depths of 8-9 km near the base of the zone of microearthquakes. The spatial pattern of pre-main shock microseismicity surrounding the Coyote Lake and Morgan Hill hypocenters is similar to the pattern of the post-main shock microseismicity. Microseismicity extends between depths of 4 and 10 km and defines zones of concentrated microseismicity and aseismic zones. Estimates of the fault regions which slipped during the Coyote Lake Morgan Hill earthquakes as derived from seismic radiation coincide with zones which are otherwise aseismic. The authors propose that these persistent aseismic zones represent stuck patches which slip only during moderate earthquakes. From the pattern of microearthquake locations they recognize six aseismic zones where they expect future main shocks will rupture the Calaveras fault. From an analysis of historic seismic data they establish the main shock rupture history for each aseismic zone and identify two zones that are the most likely sites for the next M > 5 earthquakes. The first zone is located near Gilroy and was last ruptured by a M5.2 earthquake in 1949. The second zone is located south of Calaveras Reservoir and north of the 1988 M5.1 Alum Rock earthquake. It has not slipped seismically since at least 1903, and the size of the aseismic region is sufficiently large to sustain a M5.5 earthquake.

• OSTI ID: 5014615
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
DATA ANALYSIS
DEPTH
DEVELOPED COUNTRIES
DIMENSIONS
DISTRIBUTION
EARTHQUAKE MAGNITUDE
EARTHQUAKES
FEDERAL REGION IX
FORECASTING
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
HISTORICAL ASPECTS
HYPOCENTERS
MICROEARTHQUAKES
NORTH AMERICA
SEISMIC EVENTS
SEISMICITY
SLIP
SPATIAL DISTRIBUTION
USA