Internal structure of the San Andreas Fault at Parkfield, California

Magnetotelluric and seismic reflection surveys at Parkfield, California, show that the San Andreas fault zone is characterized by a vertical zone of low electrical resistivity. This zone is ≈500 m wide and extends to a depth of ≈4000 m. The low electrical resistivity is attributed to high porosity o...

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Bibliographic Details
Published in:Geology (Boulder) 1997-04, Vol.25 (4), p.359-362
Main Authors: Unsworth, Martyn J, Malin, Peter E, Egbert, Gary D, Booker, John R
Format: Article
Language:English
Subjects:
active faults
apparent resistivity
applied (geophysical surveys & methods)
California
Central California
creep
earthquakes
electrical properties
fault zones
faults
fluid phase
fractured materials
geologic hazards
geophysical methods
geophysical surveys
Geophysics
high-resolution methods
magnetotelluric methods
microearthquakes
Monterey County California
Parkfield California
resistivity
San Andreas Fault
seismic methods
seismicity
Seismology
Structural geology
surveys
United States
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Summary:Magnetotelluric and seismic reflection surveys at Parkfield, California, show that the San Andreas fault zone is characterized by a vertical zone of low electrical resistivity. This zone is ≈500 m wide and extends to a depth of ≈4000 m. The low electrical resistivity is attributed to high porosity of saline fluids present in the highly fractured fault zone. The occurrence of microearthquakes and creep in the low resistivity zone is consistent with suggestions that seismicity at Parkfield is fluid driven.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1997)025<0359:ISOTSA>2.3.CO;2