HR: 0800h
AN: G21A-0120    [Abstracts]
TI: Coseismic Deformation From the 2002 Mw 7.9 Denali Fault Earthquake: Insights From SAR Speckle Tracking
AU: * Elliott, J
EM: julie@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 United States
AU: Freymueller, J T
EM: jeff@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775 United States
AU: Rabus, B T
EM: brabus@mda.ca
AF: MacDonald Dettwiler, 13800 Commerce Pkwy, Richmond, BC V6V 2J3 Canada
AB: The 3 November 2002 Mw 7.9 Denali fault earthquake in central Alaska presents both unique opportunities and challenges for crustal deformation studies using synthetic aperture radar. While synthetic aperture radar interferometry (InSAR) can produce accuracies similar to those of GPS data, it has an inherent limitation: if the deformation gradient is too large, image coherence is destroyed. The displacements of the Denali fault earthquake greatly exceeded the limit. In addition, the fault passes beneath glaciers and rugged topography exists to the south. These factors combined to create many areas of incoherence around the fault. By exploiting offsets in correlation between images rather than phase differences, the technique of speckle tracking can overcome coherence problems. While not as accurate, speckle tracking can provide data where InSAR cannot. Here we present the results of a speckle tracking study of the Denali fault earthquake for an area surrounding the intersection of the fault with the Trans-Alaska Pipeline. We were able to use data as close as 1.2 km from the rupture. A fault-normal profile near the junction of the fault and pipeline shows a maximum of about 4 m of displacement across the fault in the radarˆs line-of-sight (LOS). Values along the profile agree well with those predicted by a GPS-derived model except in an area north of the fault where no GPS data was available. A series of along-strike profiles reveals an increase in displacement across the fault from about 3.5 m in LOS at the western end of the image to about 5 m in LOS at the eastern end. These values show general agreement with the GPS model except for a region to the north of the fault and in the eastern portion of the image where GPS data did not exist. Image displacements and the measured geologic offsets are similar until the eastern end of the image, where the image values are larger. This area corresponds to the section of the fault covered by the Canwell and Gakona Glaciers.
DE: 7209 Earthquake dynamics and mechanics
DE: 1242 Seismic deformations (7205)
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting