Deformation during the 12 November 1999 Duzce, Turkey, Earthquake, from GPS and InSAR Data

Only 87 days after the Mw 7.5, 17 August 1999 Izmit earthquake, the Duzce earthquake ruptured a ca. 40-km-long adjoining strand of the North Anatolian fault (NAF) system to the east. We used displacements of 50 Global Positioning System (GPS) sites together with interferometric synthetic aperture radar (InSAR) range-change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture. Postseismic deformation transients from the Duzce earth- quake and the preceding I zmit event that are included in some of the measurements are corrected for using dislocation models fit to GPS data spanning the various time periods. Nonlinear inversions for fault geometry indicate that the rupture occurred on a ca. 54� north-dipping oblique normal, right-lateral fault. Distributed-slip inver- sions indicate maximum strike slip near the center of the Duzce fault close to the earthquake hypocenter. Slip magnitude and depth of faulting decrease to the west and east of the hypocenter. Both GPS and InSAR data suggest that normal slip is restricted to the shallow portion of the rupture. The Duzce earthquake had the highest slip-to-rupture-length ratio of any historic earthquake along the NAF.