Observations of Time-Dependent Fault Creep Using InSAR

Authors: Schmidt, D. A., Bürgmann, R.

We compile InSAR images of varying time windows from 1992 to 1999 to produce a timeline of crustal movement along the southern segment of the Hayward Fault in California. This portion of the fault extending from Niles Canyon to Fremont is monitored using creepmeters, leveling lines, theodolites, and GPS. These instruments have recorded a detailed history of fault creep along the Hayward fault, which appears strongly influenced by the Loma Prieta earthquake in 1989. Unfortunately, these measurements are unable to address the full spatial distribution of crustal movements both along the surface trace and away from the fault. Observations using a greater spatial distribution are necessary for discriminating between surface creep originating from tectonic versus non-tectonic processes, such as aquifer rehydration. We analyze data collected by ERS1 and ERS2 satellites along both ascending and descending orbital trajectories. Incorporating data from both trajectories, in addition to GPS data, allows us to potentially discriminate between horizontal and vertical movements. A timeline of crustal movement is compiled from as many as 35 differential interferograms that focus on a creep event observed in 1996.