Pure and Applied Geophysics

, Volume 166, Issue 10, pp 1853-1884

First online:

Spatio-temporal Slip, and Stress Level on the Faults within the Western Foothills of Taiwan: Implications for Fault Frictional Properties

  • Ya-Ju HsuAffiliated withInstitute of Earth SciencesDivision of Geological and Planetary Sciences, California Institute of Technology Email author 
  • , Jean-Philippe AvouacAffiliated withDivision of Geological and Planetary Sciences, California Institute of Technology
  • , Shui-Beih YuAffiliated withInstitute of Earth Sciences
  • , Chien-Hsin ChangAffiliated withCentral Weather Bureau
  • , Yih-Min WuAffiliated withDepartment of Geosciences, National Taiwan University
  • , Jochen WoessnerAffiliated withDivision of Geological and Planetary Sciences, California Institute of TechnologySwiss Seismological Service, ETH Zürich

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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 \({{\partial \mu }/{\partial \, {\rm ln}\, V}} = 8 \times 10^{ - 3}\). 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.


The Chi-Chi earthquake fault friction fault rheology stress fault slip distribution