Constraining the Slip Distribution and Fault Geometry of the Mw 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 (Insar). 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 Insar 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 Insar coverage for the eastern half of the dfe rupture. A dedicated geodetic Insar mission could obviate coverage problems in the future.