Hsu, Ya-Ju and Avouac, Jean-Philippe and Yu, Shui-Beih and Chang, Chien-Hsin and Wu, Yih-Min and Woessner, Jochen (2009) Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties. Pure and Applied Geophysics, 166 (10-11). pp. 1853-1884. ISSN 0033-4553 http://resolver.caltech.edu/CaltechAUTHORS:20091020-152813715
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We use preseismic, coseismic, and postseismic GPS data of the 1999 Chi-Chi earthquake to infer spatio-temporal variation of fault slip and frictional behavior on the Chelungpu fault. The geodetic data shows that coseismic slip during the Chi-Chi earthquake occurred within a patch that was locked in the period preceding the earthquake, and that afterslip occurred dominantly downdip from the ruptured area. To first-order, the observed pattern and the temporal evolution of afterslip is consistent with models of the seismic cycle based on rate-and-state friction. Comparison with the distribution of temperature on the fault derived from thermo-kinematic modeling shows that aseismic slip becomes dominant where temperature is estimated to exceed 200° at depth. This inference is consistent with the temperature induced transition from velocity-weakening to velocity-strengthening friction that is observed in laboratory experiments on quartzo-feldspathic rocks. The time evolution of afterslip is consistent with afterslip being governed by velocity-strengthening frictional sliding. The dependency of friction, μ, on the sliding velocity, V, is estimated to be ∂μ/∂ln V = 8 × 10^(-3). We report an azimuthal difference of about 10–20° between preseismic and postseismic GPS velocities, which we interpret to reflect the very low shear stress on the creeping portion of the décollement beneath the Central Range, of the order of 1–3 MPa, implying a very low friction of about 0.01. This study highlights the importance of temperature and pore pressure in determining fault frictional sliding.
|Additional Information:||© 2009 Springer. Received: 15 September 2008; accepted: 3 March 2009; published online: 29 July 2009. We thank the editor, Dr. Y. Ben-Zion, Dr. J. C. Savage, and an anonymous reviewer for their constructive comments. We are grateful to many colleagues at the Institute of Earth Sciences, Academia Sinica, as well as the Central Weather Bureau for kindly provide geodetic and earthquake focal mechanism data. We have benefited from stimulating discussions with Mark Simons. This work was supported by the National Science Foundation grant EAR-0537625 to Caltech, the Gordon and Betty Moore Foundation, and the National Science Council of the Republic of China grant NSC 95-2119-M-001-064 –MY3. This is a contribution of Caltech Tectonics Observatory number 113 and the Institute of Earth Sciences, Academia Sinica, IESAS1335.|
|Group:||Caltech Tectonics Observatory, Caltech Tectonics Observatory. Taiwan Tectonics and Seismicity|
|Subject Keywords:||The Chi-Chi earthquake; fault friction; fault rheology; stress; fault slip distribution|
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|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||20 Oct 2009 23:00|
|Last Modified:||26 Dec 2012 11:29|
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