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

by Roland Bürgmann, M. Emin Ayhan, Eric J. Fielding, Tim J. Wright, Simon McClusky, Bahadir Aktug, Coskun Demir, Onur Lenk, and Ali Türkezer

Abstract

Only 87 days after the M_w 7.5, 17 August 1999 İzmit earthquake, the Düzce 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 Düzce earthquake and the preceding İzmit 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 inversions indicate maximum strike slip near the center of the Düzce 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 Düzce earthquake had the highest slip-to-rupture-length ratio of any historic earthquake along the NAF.

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