Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

Fault coupling and potential for earthquakes on the creeping section of the Central San Andreas Fault

Jeremy L. Maurer, & Kaj M. Johnson

Published May 2014, SCEC Contribution #1804

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 of the SAF 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 (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data with elastic block models to estimate the degree of locking on the CSAF and place bounds on moment accumulation rate on the fault. We find 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 3.28x104 to 5.85x107 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. 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.

Maurer, J. L., & Johnson, K. M. (2014). Fault coupling and potential for earthquakes on the creeping section of the Central San Andreas Fault. Journal of Geophysical Research, 119(5), 4414–4428. doi: 10.1002/2013JB010741.