Post-seismic and interseismic fault creep II: transient creep and interseismic stress shadows on megathrusts
We use idealized subduction megathrust models to examine aseismic, frictional fault creep throughout the interseismic period. We consider rate-dependent and rate- and state-dependent friction. When there is significant post-seismic creep surrounding locations of coseismic slip, the creep rates surrounding an asperity may be lower than the plate convergence rate late in the seismic cycle. This lowering of the creep rates is due to stress shadows forming around the interseismically locked asperities. The size of the stress shadows increases as there is more transient post-seismic creep. Larger asperities produce larger interseismic stress shadows, and multiple asperities can act together to produce a stress shadow larger than the sum of the effects of the individual asperities. For rate-state frictional megathrusts, there is a wide range of transient post-seismic creep that occurs: from pulses of post-seismic creep with decreasing creep rates through time, to delayed post-seismic creep. Delayed post-seismic creep may occur well into the interseismic period, with transient creep lasting over a significant portion of the seismic cycle. Delayed post-seismic creep is generally favoured in velocity strengthening regions with either a larger magnitude of the frictional direct effect or a larger effective normal stress. In addition, regions of the fault undergoing delayed post-seismic creep must be above steady state following coseismic slip.
Additional Information© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2009 December 12. Received 2009 October 8; in original form 2009 Marh 22. Article first published online: 19 Feb 2010. We thank the editor, M. Cocco, and two anonymous reviewer for insightful comments and suggestions. We also thank R. Kanda for discussions that improved this manuscript. All calculations were done using Matlab, The Mathworks Inc. This research was supported in part by the Gordon and Betty Moore Foundation. This is Caltech Tectonic Observatory contribution #117 and Caltech Seismological Laboratory contribution #10,032.
Published - Hetland_GJI2010_b.pdf