TIME-DEPENDENT RESIDUAL DEFORMATIONS ASSOCIATED WITH THE JUNE 9, 1994BOLIVIA EARTHQUAKE

By means of a spherical Earth model with Maxwell theology we compute t he coseismic and the postseismic displacements associated with the Jun e 9, 1994 Bolivia earthquake. Our results are compared with the coseis mic uplift detected by an of broadband seismic stations in Southern Bo livia with previous theoretical predictions. Our solution method has b een recently employed to study the global deformations due to large li thospheric earthquakes. In contrast to purely elastic Earth models, ou r method includes the time-dependent effects associated with mantle re laxation. The results presented here show that the surface deformation due to a deep-focus earthquake are sensibly magnified by the delayed viscoelastic mantle relaxation. The time-scales which characterize man tle relaxation and the time evolution of surface observables depend on the rheological profile of the upper mantle, and particularly on the thickness of the viscoelastic asthenosphere.