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Is stress accumulating on the creeping section of the San Andreas fault?

Kaj M. Johnson

Published December 12, 2013, SCEC Contribution #1808

The creeping section of the San Andreas fault (CSAF) in central California is a proposed barrier to propagation of large earthquakes. Yet, recent studies show that that the creeping section is not entirely uncoupled but is accumulating slip deficit at a rate equivalent to a Mw=7.2-7.4 earthquake every 150 years. A critical piece to understanding earthquake potential on the CSAF is determining whether slip deficit is occurring on stick-slip regions with stress build up or on stable-sliding regions shadowed by surrounding locked areas. We use a physical model to estimate the spatial distribution of locked, stress-accumulating areas of the fault constrained by surface creep rate measurements and GPS-derived velocities. We find that area of the fault accumulating stress, if ruptured every 150 years, would release slip equivalent to at most a Mw = 6.75 earthquake, significantly less than the Mw=7.2-7.4 150-year-equivalent total slip deficit rate.

Johnson, K. M. (2013). Is stress accumulating on the creeping section of the San Andreas fault?. Geophysical Research Letters, 40(23), 6101-6105. doi: 10.1002/2013GL058184.