Homogeneous vs heterogeneous subduction zone models: Coseismic and postseismic deformation

Abstract. A nite-element model (FEM) incorporating ge-ologic properties characteristic of a subduction zone is com-pared with FEMs approximating homogeneous elastic half-spaces (HEHS)s to investigate the eect of heterogeneity on coseismic and postseismic deformation predictions for the 1995 Colima-Jalisco Mw=8.0 earthquake. The FEMs are used to compute a coecient matrix relating displacements at observation points due to unit dislocations of contact-node pairs on the fault surface. The Green's function re-sponses are used to solve the inverse problem of estimat-ing dislocation distributions from coseismic GPS displace-ments. Predictions from the FEM with heterogeneous ma-terial properties, loaded with either of the HEHS dislocation distributions, signicantly overestimate coseismic displace-ments. Postseismic deformation predictions are also sensi-tive to the coseismic dislocation distribution, which drives poroelastic and viscoelastic relaxation. FEM-generated Green's functions, which allow for spatial variations in ma-terial properties, are thus preferable to those that assume a simple HEHS because the latter leads to dislocation distri-butions unsuitable for predicting the postseismic response