Professor Howard Zebker

Fall 2001-2002

Date: Wednesday, October 3, 2001
Time: 4:15 PM; Refreshments at 4:00 PM
Location: 460-334

Earthquakes Observed with Satellite Radar Interferometry

Sjonni Jonsson
Dept. of Geophysics, Stanford University


Earthquakes do not only cause ground shaking when seismic waves propagate through the earth, they also cause permanent ground deformation close to the earthquake source. It is important to measure this deformation to find out what happened in the earthquake, e.g., about what fault ruptured, how much fault slip occurred, and about if the earthquake likely to trigger other earthquakes.

We use Synthetic Aperture Radar Interferometry (InSAR) from satellites to measure earthquake deformation. InSAR earthquake deformation maps (interferograms) are obtained from the phase difference of two radar images, acquired before and after an earthquake. The maps show how the ground permanently moved towards or away from the satellite. We simulate the observations using a simple earthquake model consisting of dislocation surfaces embedded in elastic half-space. The optimal dislocation parameters tell us where the fault is located and how much slip occurred.

Two examples of earthquake deformation studies will be presented. In the former study we analyzed observations of the Hector Mine earthquake (magnitude 7.2) that occurred in Mojave Desert, Southern California, in October 1999. In the second study we looked at two earthquakes (magnitude 6.5) that occurred only 4 days apart in South Iceland in June 2000.