Width and dip of the southern San Andreas Fault at Salt Creek from modeling of geophysical data

By: , and 
Edited by: Robert E. Reynolds

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Abstract

We investigate the geometry and width of the southernmost stretch of the San Andreas Fault zone using new gravity and magnetic data along line 7 of the Salton Seismic Imaging Project. In the Salt Creek area of Durmid Hill, the San Andreas Fault coincides with a complex magnetic signature, with high-amplitude, short-wavelength magnetic anomalies superposed on a broader magnetic anomaly that is at least 5 km wide centered 2–3 km northeast of the fault. Marine magnetic data show that high-frequency magnetic anomalies extend more than 1 km west of the mapped trace of the San Andreas Fault. Modeling of magnetic data is consistent with a moderate to steep (> 50 degrees) northeast dip of the San Andreas Fault, but also suggests that the sedimentary sequence is folded west of the fault, causing the short wavelength of the anomalies west of the fault. Gravity anomalies are consistent with the previously modeled seismic velocity structure across the San Andreas Fault. Modeling of gravity data indicates a steep dip for the San Andreas Fault, but does not resolve unequivocally the direction of dip. Gravity data define a deeper basin, bounded by the Powerline and Hot Springs Faults, than imaged by the seismic experiment. This basin extends southeast of Line 7 for nearly 20 km, with linear margins parallel to the San Andreas Fault. These data suggest that the San Andreas Fault zone is wider than indicated by its mapped surface trace.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Width and dip of the southern San Andreas Fault at Salt Creek from modeling of geophysical data
Year Published 2014
Language English
Publisher California State University Desert Studies Center
Publisher location Fullerton, CA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 11 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Not a drop left to drink
First page 83
Last page 93
Conference Title 2014 Desert Symposium
Conference Date April 2014
Country United States
State California
Other Geospatial San Andreas Fault