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Conductivity structure of the San Andreas fault, Parkfield, revisited
Author(s) -
Park Stephen K.,
Roberts Jeffery J.
Publication year - 2003
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2003gl017689
Subject(s) - geology , san andreas fault , magnetotellurics , sedimentary rock , syncline , seismology , induced seismicity , fault (geology) , geophysics , petrology , tectonics , electrical resistivity and conductivity , geochemistry , engineering , electrical engineering
A previous interpretation of a high resolution magnetotelluric profile across the San Andreas fault at Parkfield attributed an anomalously conductive region just west of the fault and extending to depths of 3 km to fractured rock saturated with brines. Laboratory measured electrical resistivities of samples of sedimentary rocks known to border the fault to the east are comparable to resistivities of the anomalous zone. We suggest that the anomalous region results from conductive sedimentary rocks in a plunging syncline that is adjacent to the fault, rather than caused by fractured rock. If correct, the current surface trace of the San Andreas fault at Middle Mountain does not form the boundary between the Salinian block and the North American plate. Instead, that boundary is ∼1 km west and collocated with current seismicity.