The 150 km long central section of the San Andreas Fault (CSAF) in central California creeps at the surface and has not produced a large earthquake historically. However, sections of the San Andreas Fault to the north and south are known to have ruptured repeatedly in M~7-8 earthquakes. It is currently unclear whether the creeping CSAF could rupture in large earthquakes, either individually or along with earthquakes on the locked sections to the north and south. We invert Global Positioning System and interferometric synthetic aperture radar data with elastic block models to estimate the degree of locking on the CSAF and place bounds on the moment accumulation rate on the fault. We find that the inferred moment accumulation rate is highly dependent on the long-term fault slip rate, which is poorly constrained along the CSAF. The inferred moment accumulation rate, normalized by shear modulus, ranges from 3.28 x 104 to 5.85 x 107 m3/yr, which is equivalent to a Mw = 5.5-7.2 earthquake every 150 years for a long-term slip rate of 26 mm/yr and Mw = 7.3-7.65 for a long-term slip rate of 34 mm/yr. The comparisons of slip distributions with microseismicity and repeating earthquakes indicate a possible locked patch between 10 and 20 km depth on the CSAF that could potentially rupture with Mw = 6.5.


Geosciences and Geological and Petroleum Engineering


This research was supported by the Southern California Earthquake Center. SCEC is funded by the NSF Cooperative Agreement EAR-0529922 and the USGS Cooperative Agreement 07HQAG0008.

Keywords and Phrases

Block Models; GPS; InSAR; Moment; San Andreas Fault

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

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© 2014 American Geophysical Union, All rights reserved.

Publication Date

01 May 2014