Assessing Processes of Post-Seismic Deformation from Geodetic Observations Following the 1999 M7.1 Hector Mine Earthquake

The occurrence of the 1999 Hector Mine earthquake (M7.1) in the Mojave Desert has provided the scientific comunity with a wealth of data for analyzing time dependent deformation. A combination of survey mode GPS observations spanning from the time immediately following the earthquake up to July 2001, as well as continuous GPS stations from within the SCIGN network, provide us with a good spatial data density to observe patterns in post-seismic deformation. Inclusion of the SCIGN stations provides critical spatial and temporal data coverage for determining both horizontal and vertical deformation. Data were analyzed using the GIPSY processing software and the resulting deformation field is compared to post-seismic afterslip models. Modeled fault slip rates are estimated from GPS velocities from both the continuous and campaign mode GPS stations. It has been demonstrated that the horizontal data alone is not sufficient at distinguishing between afterslip and visco-elastic processes (Pollitz 2000). Comparisons of the GPS data, in particular the vertical, to afterslip models provide useful insight as to whether the post-seismic deformation field is the result of afterslip on the rupture plane or other time dependent processes in the lower crust.