Estimating the effects of laterally heterogeneous elasticity on coseismic deformation –a rotationally symmetric case

Abstract:

The advancement of the Global Geodetic Observing System (GGOS) has provided us with information associated with mass transports and related deformation processes including surface loading and co- and post-seismic deformations. Coseismic deformation is theoretically modeled as an elastic response of the Earth to a given internal dislocation. For modeling regional to global scale coseismic deformation accurately, self-gravitating spherical Earth model can be employed. Recent seismic tomography and high-pressure/high-temperature experiments have suggested finer 3-D distributions of elasticity and density structures within the Earth, which motivate us to quantify the impact of 3-D elasticity and density structures on the deformation. Several approaches such as the Finite Element Method (FEM) have been proposed so far to consider lateral heterogeneities in those structures. In a previous study, we presented a spectral finite-element approach combined with an iterative, perturbation method in order to take into account lateral heterogeneities in the bulk and shear moduli for surface loading. The distinct feature of this method is that the deformation of the whole sphere is modeled in the spectral domain with finite elements dependent only on the radial coordinate. By this, self-gravitation can be treated naturally, which is often considered only approximately in an ordinary FEM. In this study, we modify the weak formulation for surface loading so that it can deal with internal dislocation. As the first step, we will apply this method to a rotational symmetric set up, where elasticity depends on radial distance and polar angle, and estimate the effects of lateral heterogeneities.