Spatially variable fault friction derived from dynamic modeling of aseismic afterslip due to the 2004 Parkfield earthquake

Chang, S.-H.a b and Avouac, J.-P. and Barbot, S.a c and Lee, J.-C.b (2013) Spatially variable fault friction derived from dynamic modeling of aseismic afterslip due to the 2004 Parkfield earthquake. Journal of Geophysical Research: Solid Earth, 118 (7). pp. 3431-3447. ISSN 2156-2202 DOI https://doi.org/10.1002/jgrb.50231

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Abstract

We investigate fault friction from dynamic modeling of fault slip prior to and following the Mw 6.0 earthquake which ruptured the Parkfield segment of the San Andreas Fault in 2004. The dynamic modeling assumes a purely rate-strengthening friction law, with a logarithmic dependency on sliding rate: μ=μ *+a-blnvv*. The initial state of stress is explicitly taken into account, and afterslip is triggered by the stress change induced by the earthquake source model given a priori. We consider different initial stress states and two coseismic models, and invert for the other model parameters using a nonlinear inversion scheme. The model parameters include the reference friction μ*, the friction rate dependency characterized by the quantity a-b, assumed to be either uniform or depth dependent. The model parameters are determined from fitting the transient postseismic geodetic signal measured at continuous GPS stations. Our study provides a view of frictional properties at the kilometers scale over the 0-15 km depth illuminated by the coseismic stress change induced by the Parkfield earthquake. The reference friction is estimated to be between 0.1 and 0.5. With independent a priori constraints on the amplitude of differential stress, the range of possible values narrows down to 0.1-0.17. The friction rate coefficient a-b is estimated to be � 10- 3 - 10- 2 with a hint that it increases upward from about 1-3 � 10-3 at 3-7 km depth to about 4-7 � 10-3 at 0-1 km depth. It is remarkable that our results are consistent with frictional properties measured on rock samples recovered from the fault zone thanks to the San Andreas Fault Observatory at Depth experiment. ©2013. American Geophysical Union. All Rights Reserved.

Item Type:	Article
Uncontrolled Keywords:	NILAREP
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Journal of Geophysical Research: Solid Earth
Volume:	118
Page Range:	pp. 3431-3447
Identification Number:	https://doi.org/10.1002/jgrb.50231
Depositing User:	Sarah Humbert
Date Deposited:	22 Apr 2015 23:09
Last Modified:	22 Apr 2015 23:09
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3209

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