Spectral element modeling of three dimensional wave propagation in a self-gravitating Earthwith an arbitrarily stratified outer core

Sent to Geophysical Journal International on July 29, 2003.This paper deals with the spectral element modeling of seismic wave propagation at the global scale.Two aspects relevant to low-frequency studies are particularly emphasized.First, the method is generalized beyond the Cowling approximation in order to fully account forthe effects of self-gravitation.In particular, the perturbation of the gravity field outside the Earth is handled by a projection of thespectral element solution onto the basis of spherical harmonics.Second, we propose a new formulation inside the fluid which allows to account for anarbitrary density stratification.It is based upon a decomposition of the displacement into two scalar potentials, and results ina fully explicit fluid-solid coupling strategy.The implementation of the method is carefully detailed and its accuracy is demonstrated through a seriesof benchmark tests