Calculating coseismic deformation and stress changes in a heterogeneous ellipsoid earth model

Abstract

SUMMARY Coseismic deformation and stress change are important for geodetic interpretation and seismic hazard assessment. Most existing coseismic deformation models are based on the simplified geometry, such as the homogeneous half-space model or symmetric spherical earth model. In this work, taking the advantage of high-resolution parallel finite element methods, we construct a realistic full 3-D ellipsoidal earth model to properly account for the effects of topography, lateral heterogeneity, the curvature of the Earth and geometry variations at discontinuities (Moho/410 km/660 km) that are often ignored in the existing models. Our results show that, when calculating coseismic deformation and stress change induced by dislocations of large earthquakes, the relative error due to the Earth's curvature can be as high as 60 per cent, while the combined effects of topography and heterogeneity resulted in a 40 per cent discrepancy when the model is applied to, for example, the 2011 Tohoku Mw 9.0 earthquake, with the effect of the topography accounting for ∼10 per cent. The effect of the Earth's heterogeneity is more than 30 per cent in the case of the coseismic strain changes produced in northern China by the Tohoku earthquake. The effect of the Earth's ellipticity is relatively small, but should not be overlooked.