Modeling Long-term Changes of Low-frequency Earthquake Recurrence

Abstract:

Tectonic tremor and low-frequency earthquakes (LFE) are found in the deeper crust of various tectonic environments in the last decade. LFEs are presumed to be caused by failure of deep fault patches during a slow slip event, and the long-term variation in LFE recurrence could provide crucial insight into the deep fault zone processes that may lead to future large earthquakes. However, the physical mechanisms causing the temporal changes of LFE recurrence are still under debate. In this study, we combine observations of long-term changes in LFE recurrence near Parkfield, California (Wu et al. 2013) with a brittle and ductile friction (BDF) model (Daub et al. 2011), and use the model to constrain the possible physical mechanisms causing the observed long-term changes in LFE recurrence after the 2004 M6 Parkfield earthquake. The BDF model mimics the slipping of deep fault patches by a spring-drugged block slider with both brittle and ductile friction components. Our on-going work includes testing the BDF model by varying two sets of parameters: 1) time varying shear stress caused by the postseismic relaxation of the static stress imposed by the 2004 Parkfield earthquake, and 2) gradual recovery of brittle friction strength following the strong shaking of the Parkfield earthquake. Hopefully our modeling results can help to clarify the roles of the two mechanisms, and link seismic observations of LFE to the physics of deep fault deformation.