The interpretation of BAM fault kinematics using Envisat SAR interferometric data

Abstract

The surface ruptures caused by the 26 December 2003 earthquake which affected the city of Bam (Kerman province, southeast Iran) have already been mapped using interferometric coherence images from Envisat SAR images. The clearly visible traces of these structures in the coherence images allow to prove that the Bam earthquake has been caused by the displacement along a previously unknown fault. Besides the coherence, the SAR interferograms of the ascending and descending orbits present a very complex deformation pattern especially north of Bam. Similar patterns have been observed in two independent datasets (ascending and descending) avoiding misinterpretation as atmospheric errors. Interferograms and derived deformation maps allow to interpret such structures in detail as a system of possible fractures and small faults accompanying the main rupture. Geocoded interferograms allow to trace in detail the direction of these structures, while deformation maps of ascending and descending passes allow the interpretation of their relative movement. The obtained pattern together with the structures mapped from the coherence images gives an opportunity to reconstruct the kinematics of the entire "Bam structure" and find its relation to the kinematics of the major intra-continental strike-slip system of the Gowk fault.