3D Green's functions for coseismic and postseismic deformation

Finite fault slip inversions are constrained by observational data of surface displacement and Green's functions calculated via a forward model of surface deformation. Although observational techniques in space geodesy have improved greatly in recent years, models of earthquake deformation generally do not include realistic Earth structure. Many finite fault slip inversions use Green's functions that are calculated in a homogeneous box model, even in settings where Earth elastic structure and topography can be expected to affect the inferred surface deformation. We present an efficient technique for calculating three-dimensional (3D) Green's functions in an elastic or viscoelastic domain with a spectral-element method that can accommodate topography and heterogeneous material properties. We calculate 3D surface displacements for the April 2015 Gorkha, Nepal and the 2010 Maule, Chile earthquakes to illustrate our technique. Both calculations use realistic topography and bathymetry provided by ETOPO1. We find that the inclusion of topography can significantly affect the calculated Green's functions. 3D Green's functions of the Gorkha earthquake are then used to evaluate the influence of that change on finite fault slip models.