Rupture Process of the 1999 Mw 7.1 Duzce Earthquake from Joint Analysis of SPOT, GPS, InSAR, Strong-Motion, and Teleseismic Data: A Supershear Rupture with Variable Rupture Velocity

We analyze the rupture process of the 1999 M-w 7.1 Duzce earthquake using seismological, remote sensing, and geodetic data. Ground deformation measured from the subpixel cross correlation of Satellite Pour l'Observation de la Terre (SPOT) images reveals a 55 km long fault trace and smooth surface-slip distribution peaking at 3.5-4 m. The westernmost segment overlaps for over 10 km with ruptures from the M-w 7.4 Izmit earthquake. The 15 km long easternmost segment, which cuts across mountainous topography, had not been reported previously. We determine a well-constrained source model using a four-segment fault geometry using constraints on surface fault slip and inverting Global Positioning System and Interferometric Synthetic Aperture Radar data along with strong-motion records. Our results show that some variability of the rupture velocity and an eastward supershear velocity are required to fit the strong-motion data. The rise time, up to 6 sec, correlates with cumulative slip, suggesting a sliding velocity of about 1 m/sec. The source model predicts teleseismic waveforms well, although early by 2 sec. This time shift is probably due to the weak beginning of the earthquake that is not observable at teleseismic distances. Strong-motion records are relatively well predicted from a source model derived from the teleseismic data using the fault geometry derived from the satellite images. This study demonstrates the benefit of using accurate fault geometries to determine finite-fault source models.