Abstract
Most current crustal deformation models do not account for topographic effects, crustal lateral variations, and complex fault geometries. To overcome these limitations, we apply finite element models constrained by interferometric Synthetic Aperture Radar (InSAR) images of co-seismic displacements to the 2008 Mw 6.3 Dangxiong earthquake that occurred in Yadong–Gulu rift, southern Tibet. For mountainous plateau environments, InSAR observations are advantageous for studying crustal deformation and crustal medium structure. We evaluate the effect of topography and variations in Poisson’s ratio and elastic moduli on estimation of coseismic deformation from InSAR observations. The results show that coseismic surface displacements are more sensitive to variations in Young’s modulus than to variations in topography and Poisson’s ratio. Therefore, with constant Poisson’s ratio and density, we change the Young’s modulus on each side of the fault to obtain the model that best fits the observations. This is attained when the Young’s moduli in the eastern and western sides of the fault were 2.6 × 1010 Pa and 7.8 × 1010 Pa, respectively. The result is consistent with previous field surveys that the medium on either side of the fault is different.
Highlights
The development of space-based geodetic techniques including Global Positioning System (GPS)and Interferometric Synthetic Aperture Radar (InSAR) has allowed the observation of the deformation that occurs during earthquakes with an accuracy of mm and spatial resolution of m [1,2]
In a study of the Sumatra subduction zone, Hsu et al [23] noted that the discrepancies between homogeneous and heterogeneous models are strongly dependent on the contrast of the elastic properties between the two sides of the fault; from the root mean square we can deduce whether the models match the true crustal structure
The coseismic deformation pattern revealed by the InSAR observations confirmed that the deformation is concentrated mainly in a small region across the fault
Summary
The development of space-based geodetic techniques including Global Positioning System (GPS)and Interferometric Synthetic Aperture Radar (InSAR) has allowed the observation of the deformation that occurs during earthquakes with an accuracy of mm and spatial resolution of m [1,2]. More advanced models which account for crustal heterogeneity in horizontally layered elastic half-space were subsequently developed [5,6]. These analytical or semi-analytical models can rapidly reproduce the surface deformation and stress–strain distribution generated by faulting, they generally do not allow for topographic effects, lateral variations in the mechanical properties of the crust, or complex fault geometries.
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