Get access
Journal of Geophysical Research: Solid Earth

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

Authors

  • Shu-Hao Chang,

    Corresponding author
    1. Tectonics Observatory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
    • Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
    Search for more papers by this author
  • Jean-Philippe Avouac,

    1. Tectonics Observatory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
    Search for more papers by this author
  • Sylvain Barbot,

    1. Tectonics Observatory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
    2. Division of Earth Sciences, Nanyang Technological University, Singapore
    Current affiliation:
    1. Division of Earth Sciences, Nanyang Technological University, Singapore
    Search for more papers by this author
  • Jian-Cheng Lee

    1. Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
    Search for more papers by this author

Corresponding author: S.-H. Chang, Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan. (hao9702@earth.sinica.edu.tw)

Abstract

[1] 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: inline image. 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.

Get access to the full text of this article

Ancillary