Frictional parameters on the creeping San Andreas Fault inferred from the 1983 Coalinga-Nuñez and 2004 Parkfield earthquakes
Abstract
We use the creep meter and GPS time series data to infer frictional parameters on the creeping section of the San Andreas Fault (SAF) near the Parkfield, California. The creep meter data show that surface creep rate was abruptly retarded at five creep meter locations for 1-6 years following the 1983 Coalinga-Nuñez earthquakes just northwest of Parkfield. From Monte Carlo inversions of the data using spring-slider models with rate and state friction, we find that the retarded creep episode is explained with near-neutral-strengthening with friction parameter, σ(a - b) of 3×10^-6 - 3×10^-2, MPa. This is at least an order of magnitude lower than previous inferences from afterslip studies at Parkfield and other locations around the world (Hearn et al., 2002; Perfettini and Avouac, 2004, 2007; Miyazaki et al., 2004; Perfettini et al., 2005; Hsu et al., 2006; Barbot et al., 2009). We show, through forward models and spring-slider inversions GPS measurement of the 2004 Parkfield afterslip episode, that the friction parameters inferred from the 1983 Coalinga-Nuñez transient and Parkfield afterslip are entirely inconsistent. Spring-slider and finite-fault afterslip models of the 2004 afterslip event using friction parameters inferred from the 1983 transient predict excessive amounts of rapid afterslip in the days following the 2004 earthquake. Our preliminary analyses of models of fluid-infiltrated shear zones suggest that dilatancy-induced strengthening of the fault following the 2004 earthquake may be one plausible explanation for the apparent discrepancy.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.T31C2606C
- Keywords:
-
- 7223 SEISMOLOGY / Earthquake interaction;
- forecasting;
- and prediction;
- 8118 TECTONOPHYSICS / Dynamics and mechanics of faulting;
- 8163 TECTONOPHYSICS / Rheology and friction of fault zones