Analysis of SPOT, GPS, InSAR, Strong-Motion, and Teleseismic Data: A Supershear Rupture with Variable Rupture Velocity

using seismological, remote sensing, and geodetic data. Ground deformation mea-sured 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 Mw 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 prob-ably 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. Online Material: Tables of best-fitting dip angles and rupture velocities, and fig-ures showing mutual consistency of derived displacements fields, additional slip and rise-time models, and teleseismic waveform fit