Post-seismic deformation following the M7.1 Hector Mine earthquake: An integrated approach utilizing InSAR and seismic data

The post-seismic period is a critical stage of the earthquake cycle, indicating how a fault regains strength following a large magnitude earthquake. Additionally, regions of large post-seismic deformation may reflect the variable stress field created during rupture. Interferometric images provide excellent spatial and temporal coverage of deformation in areas of high coherence such as the Mojave Desert, where the Hector Mine earthquake occurred. We analyze high quality interferometric pairs covering days to years after the Hector Mine mainshock. The InSAR data reveal a complex deformation field with patterns of small (0.1 km) to medium (10 km) spatial scales. We see large deformation to the north, where the fault bifurcates into two strands and significant deformation concentrated along the majority of the surface rupture. We assume a diffusive process is governing the deformation and find a diffusion time constant for each image pixel. The resulting map suggests a spatially variable recovery time around the Hector Mine rupture zone. We compare deformation patterns highlighted by InSAR with seismic array data. Following the Hector Mine mainshock portable seismic array deployments took place in 1999, 2000, and 2001, recording thousands of aftershocks as well as active source detonations within the fault zone. Seismic data were used to probe the main rupture plane of deformation via fault zone trapped waves. These data delimit a 75-100 m wide low velocity zone that experienced some velocity recovery in the years subsequent to rupture [Vidale and Li, 2003; Li et al., 2003]. In addition, a study of shear-wave anisotropy along the Hector Mine rupture zone determined orientation of microcracks in the region around the surface rupture [Cochran et al., 2003]. Preliminary results suggest a good correlation between the InSAR results and seismic data, with areas of high surface deformation corresponding to zones of anomalous seismic velocity and/or large anisotropy. However, each process suggests post-seismic relaxation occurs over different time scales and we investigate different models to explain the observations.