Formulation of coseismic changes in Earth rotation and low-degree gravity field based on the spherical Earth dislocation theory

Abstract

In this paper we present analytical formulas to compute the coseismic Earth rotation change (polar motion and length of day) and low-degree gravity field change based on a spherical dislocation theory. Using the preliminary reference Earth model and our formulas, we calculate coseismic changes in Earth's rotation and low-degree Stokes coefficients caused by the four largest earthquakes since 1960. The results verify that the present method is consistent with previous studies, but the method cannot be verified by the observations. A case study on the 2011 Tohoku-Oki earthquake (Mw 9.0) indicates that the coseismic Earth rotation change depends on the magnitude and source parameters, and results show a difference between a point source and finite fault model. We also investigate the effect of seawater redistribution on coseismic Earth rotation change, but the effect is small and can be neglected.