Exploring the Rheology of Tibet from Postseismic Deformation Following Recent Large Earthquakes
Abstract
The rheological structure of the crust beneath the Tibetan plateau is a big unknown in solid earth geophysics. During the last eleven years, there have been ten large earthquakes across the plateau with magnitudes between 6.0 and 7.9. The focal mechanisms are a mixture of normal, thrust and strike-slip. Together these earthquakes offer a good opportunity to explore the rheology of the crust beneath the plateau, through analysis of the postseismic transient deformation that occurs in the years following each event. We focus on three major earthquakes, all with M > 7, across the northern part of the plateau. These are the 1997 Manyi and the 2001 Kokoxili strike-slip events, and the 2008 Yutian normal faulting event. We present InSAR observations of postseismic motion for each case, using ERS, Envisat and ALOS data. The deep stress relaxation that is responsible for the observed surface transients is modeled in terms of different candidate rheologies for the mid to lower crust of Tibet, our aim being to determine the rheological model that best explains the geodetic measurements. Guided by earlier work by Ryder et al. (2007, Geophys. J. Int.) on the Manyi postseismic phase, we test linear viscoelastic models incorporating both univiscous and biviscous layers, and we also model localized afterslip. The modeling results are considered in the context of complementary geophysical data bearing on rheological properties. Additionally, we plan to look for postseismic signals following other, smaller earthquakes across the plateau, and run first order models to interpret the observations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.T11E..08R
- Keywords:
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- 8159 Rheology: crust and lithosphere (8031)