Coseismic deformation associated with the November 1995, M-w=7.1 Nuweiba earthquake, Gulf of Elat (Aqaba), detected by synthetic aperture radar interferometry

The November 22, 1995, M-w=7.1 Nuweiba earthquake occurred along one of the left-stepping segments of the Dead Sea Transform in the Gulf of flat (Aqab a). Although it was the largest earthquake along this fault in the last few centuries, little is yet known about the geometry of the rupture, the slip distribution along it, and the nature of postseismic deformation following the main shock. In this study we examine the surface deformation pattern d uring the coseismic phase of the earthquake in an attempt to better elucida te the earthquake rupture process. As the entire rupture zone was beneath t he waters of the Gulf, and there is very little Global Positioning System ( GPS) data available in the region for the period spanning the earthquake, i nterferometric synthetic aperture radar (INSAR) provides the only source of information of surface deformation associated with this earthquake. We cho se four synthetic aperture radar (SAR) scenes of about 90x90 km each spanni ng the rupture area, imaged by the ERS-1 and ERS-2 satellites. The coseismi c interferograms show contours of equal satellite-to-ground range changes t hat correspond to surface displacements due to the earthquake rupture. Inte rferograms that span the earthquake by 1 week show similar fringe patterns' as those that span the earthquake by 6 months, suggesting that postseismic deformation is minor or confined to the first week after the earthquake. A high displacement gradient is seen on the western side of the Gulf, 20-40 km south of flat and Aqaba, where the total satellite-to-ground range chang es are at least 15 cm. The displacement gradient is relatively uniform on t he eastern side of the Gulf and the range changes are less than 10 cm. To i nterpret these results, we compare them to synthetic interferograms generat ed by elastic dislocation models with a variety of fault parameters. Althou gh selecting the best fit fault parameters is nonunique, we are able to gen erate a group of simplified model interferograms that provide a reasonable fit to the coseismic interferogram and serve to constrain the location of t he fault. The present analysis shows that if the rupture reached the Gulf-b ottom surface, the mean sinistral slip along the fault is constrained to ab out 1.4 m. If surface rupture did not occur, the average sinistral slip is constrained to the range of 1.4-3 m for a fault patch buried 0-4 km below t he Gulf-bottom Surface, respectively, with a minor normal component.