Slow-moving deformation pulses along tectonic faults |
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| Authors: | Yoshiaki Ida |
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| Institution: | Institute for Solid State Physics, University of Tokyo, Tokyo Japan |
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| Abstract: | A model of slow-moving disturbances of deformation is proposed to interpret the observed propagations of earthquake foci and nonseismic creep. The analysis is based on the assumption that thin fault gouge participates in the viscous slip. Nonuniform deformation diffusses at the rate of ν = μw/2η for the gouge of viscosity η and thickness w that is enclosed by the elastic rocks of rigidity μ. A crack-like solution propagates uniformly, involving the discontinuity that bounds the faulted area by an unfractured part, or by another gouge with different viscosity. The unit of the propagation velocity of such cracks is also given by the above-defined ν. Comparing the expression of ν with the various field observations, most of which yield the propagation speeds of 10–104 km/year, the effective viscosity of the gouge is estimated as 1011–1014 poises. The nonseismic fault creep in central California is analysed, and a little higher value of acting stress is obtained than the result of Nason and Weertman (1973). |
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