Coseismic deformation of the 2002 Denali fault earthquake: Contributions from synthetic aperture radar range offsets

[1] We investigate coseismic deformation from the 2002 Denali fault earthquake using synthetic aperture radar (SAR) range offsets. Through a cross-correlation technique, we form a range offset map from two radar amplitude images. A profile across the fault at the Trans-Alaska Pipeline shows right-lateral strike-slip and displacement values that agree with predictions from a GPS-based slip model to within the uncertainty of the range offset data. Using a fixed strike-slip/dip-slip ratio taken from geologic measurements, we derive a lateral slip estimate from the range offsets. This slip estimate shows that the largest geologic offset measurement in a region most accurately represents the full slip value. We then invert a combination of the range offsets, GPS data, and geologic surface offset data to solve for the slip distribution on a three-dimensional fault model in an elastic half-space. The combined model displays highly variable slip, with values generally increasing from west to east along the Denali fault, as well as four major patches of high slip on that fault. As expected, the combined model is nearly identical to the GPS-based model outside the SAR coverage area. Within the coverage area, however, the combined model has better constraints and predicts slip values much closer to the geologic measurements. The offset map displays asymmetrical displacements across the fault. We show that a combination of a bending fault, variable slip, and the SAR line-of-sight geometry can explain this asymmetry. We also discuss how fault geometry influences slip and moment release along the rupture.

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