Homogeneous vs heterogeneous subduction zone models: Coseismic and postseismic deformation

A finite-element model (FEM) incorporating geologic properties characterist ic of a subduction zone is compared with FEMs approximating homogeneous ela stic half-spaces (HEHS)s to investigate the effect of heterogeneity on cose ismic and postseismic deformation predictions for the 1995 Colima-Jalisco M -w=8.0 earthquake. The FEMs are used to compute a coefficient matrix relati ng displacements at observation points due to unit dislocations of contact- node pairs on the fault surface. The Green's function responses are used to solve the inverse problem of estimating dislocation distributions from cos eismic GPS displacements. Predictions from the FEM with heterogeneous mater ial properties, loaded with either of the HEHS dislocation distributions, s ignificantly overestimate coseismic displacements. Postseismic deformation predictions are also sensitive to the coseismic dislocation distribution, w hich drives poroelastic and viscoelastic relaxation. FEM-generated Green's functions, which allow for spatial variations in material properties, are t hus preferable to those that assume a simple HEHS because the latter leads to dislocation distributions unsuitable for predicting the postseismic resp onse.