Constraining the slip distribution and fault geometry of the M w 7.9, 3 November 2002, Denali fault earthquake with Interferometric Synthetic Aperture Radar and Global Positioning System data

Abstract

The M w 7.9, Denali fault earthquake ( DFE ) is the largest continental strike-slip earthquake to occur since the development of Interferometric Synthetic Aperture Radar (In SAR ). We use five interferograms, constructed using radar images from the Canadian Radarsat-1 satellite, to map the surface deformation at the western end of the fault rupture. Additional geodetic data are provided by displacements observed at 40 campaign and continuous Global Positioning System ( GPS ) sites. We use the data to determine the geometry of the Susitna Glacier fault, thrusting on which initiated the DFE , and to determine a slip model for the entire event that is consistent with both the In SAR and GPS data. We find there was an average of 7.3 ± 0.4 m slip on the Susitna Glacier fault, between 1 and 9.5 km depth on a 29 km long fault that dips north at 41 ± 0.7° and has a surface projection close to the mapped rupture. On the Denali fault, a simple model with large slip patches finds a maximum of 8.7 ± 0.7 m of slip between the surface and 14.3 ± 0.2 km depth. A more complex distributed slip model finds a peak of 12.5 ± 0.8 m in the upper 4 km, significantly higher than the observed surface slip. We estimate a geodetic moment of 670 ± 10 × 10 18 N m ( M w 7.9), consistent with seismic estimates. Lack of preseismic data resulted in an absence of In SAR coverage for the eastern half of the DFE rupture. A dedicated geodetic In SAR mission could obviate coverage problems in the future.