Kinematics of the November 12, 1999 (Mw = 7.2) Düzce earthquake deduced from SAR interferometry

On November 12 1999, a destructive earthquake struck the Düzce area, following the 17 August 1999 Izmit earthquake that had occurred to the west about 3 months earlier. The Mw=7.2 Düzce earthquake was somewhat interesting in several ways. The most surprising feature of this earthquake is related to its rupture geometry, which appears to contradict what is commonly observed in strike-slip earthquakes. First, compared to its magnitude, the length of the surface rupture mapped in the field was rather short (∼35 km). Second, according to seismic and some geodetic observations, the fault plane dips to the north at a very low angle ranging from 53° to 73° despite its predominant strike-slip motion, which is also inconsistent with tectonic field observations. In this study, the coseismic surface deformation caused by the November 12 1999 Düzce earthquake is mapped using Synthetic Aperture Radar interferometry (InSAR), and to constrain the rupture geometry, the InSAR data is modelled together with the coseismic GPS measurements using an elastic dislocation method. Modelling the geodetic observations with a linear inversion technique shows that the Düzce earthquake might have been associated with multiple fault breaks involving a near-vertical Düzce Fault and a reactivated old thrust fault that dips to the north.