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

Abstract

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 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 150years. A critical piece to understanding earthquake potential on the CSAF is determining whether slip deficit is occurring with stress accumulation on stick-slip regions or without stress accumulation 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 the area of the fault accumulating stress, if ruptured every 150years, would release slip equivalent to at most a Mw=6.75 earthquake, significantly less than the Mw=7.2-7.4, 150year equivalent total slip deficit rate. Key Points Only small areas of the creeping San Andreas fault is accumulating stress At most 40% of the total moment accumulation is on locked areas Locked areas would rupture in at most a M6.7 earthquake every 150 years ©2013. American Geophysical Union. All Rights Reserved.