A RHEOLOGICAL MODEL OF POST-SEISMIC DEFORMATION FOR THE 2001 KUNLUN, CHINA EARTHQUAKE, MW 7.8

Abstract

The Mw7.8 Kunlun earthquake of 14 November, 2001, in the northern Tibetan Plateau of China, was the largest event in the Chinese continental area in the latest 50 years. In this paper, layered visco-elastic models are calculated using the PSGRN/PSCMP code, and the results are fitted to the observed post-seismic deformation. We show that a model of a surface anelastic layer of 10km thickness over an elastic lower crust cannot explain the observed amplitude of deformation. A relaxation model featuring 30km of elastic upper crust over 40km of a ductile lower crust will account for the main features of exponential attenuation of post-seismic deformation. Combination of the two models, however, provides an even better fit including the fact that the deformation rate was higher in the first few weeks and slower thereafter. The viscous layer in the lower crust provides good control of the post-seismic deformation, including the long term decay of deformation over a period of months. The upper anelastic layer may contribute to the observed high deformation rate in the initial few weeks after the main earthquake. The results suggest that rheological differences may exist between the materials on either side of the Kunlun fault.