Document Type : Seismology and Engineering Seismology
Geological Survey of Japan/AIST
Department of Geography, Hiroshima University
Department of Earth Planet Science, Graduate School of Science, University of Tokyo
The Bam fault zone is a major active fault zone in southeastern Iran. Geomorphic evidence indicates that it has been responsible for repeated faulting events since late Pleistocene. The December 26, 2003 Bam earthquake was associated with two fresh surface ruptures 5 km apart trending north-south and a 2 km wide zone of hairline fractures developed between the two main ruptures in north Bam. The amount of slip along the surface ruptures ranges between 0.5-5.5 cm across the zone. The whole system of fresh ruptures associated with the Bam earthquake is not direct manifestations of the earthquake fault but are secondary structures such as synthetic shears (Reidel shears), mole tracks and oblique grabens which are strongly indicative of right-lateral motion along principal displacement zone in the earthquake source. This is compatible with the focal mechanism solutions of the Bam earthquake and fault displacements during the late Pleistocene.