Coseismic Deformation of the 2002 Denali Fault (Alaska) earthquakes from InSAR: preliminary results and prospects

Since the launch of the European satellite ERS-1 in 1992, InSAR has been used to map the coseismic deformation of around 30 continental earthquakes, including several large events on strike-slip faults (1992, Landers earthquake; 1997 Manyi earthquake; 1999 Izmit earthquake; 1999 Hector Mine earthquake). Because InSAR does not require any equipment on the ground, it is ideally suited to mapping deformation from quakes in remote areas, where conventional geodesy is more challenging. InSAR may be the only way of capturing the coseismic deformation caused by the recent earthquakes on the Denali Fault. At 63 degrees north, the ground tracks of polar-orbiting satellites are closely spaced - the ~300 km extent of the November 3 event is covered by around 18 ERS ground tracks (9 ascending, 9 descending). New ERS-2 images covering part of the rupture can therefore be obtained every 2 days on average. In addition, data from the Canadian Radarsat satellite are also being actively acquired. These data are being added to an extensive archive for this area at the Alaska SAR Facility. We hope to present interferograms showing the surface deformation that occurred during the Denali Fault earthquake sequence. If recent acquisitions prove useable, we will present source models for the earthquakes based on these data. Several ERS-2 images were acquired in the 10-day period between the M6.7 "foreshock" and the M7.9 event, so it may be possible to isolate the deformation from the first event. This would enable us to determine whether, as appears likely, stress changes induced by the M6.7 event encouraged the later M7.9 event. In our experience, the onset of winter snow and ice may mean we fail to produce a useful interferogram using recent images. However, it is likely that summer-to-summer interferograms will be coherent. We will present results of the analysis of images from the ERS catalogue to test the coherence in this area over intervals of 1 to 3 years.