Analysies of the Bam Earthquake,SE Iran,on 26 December 2003

Abstract eng:
On 26 December 2003 at 1:26 utc a large earthquake Mw 6.6, (seismic moment 6-9×10 18 Nm) struck the city of Bam in the Kerman province, southeast Iran. USGS reported that its hypocenter was located at 29.004°N, 58.337°E (IIEES was located at 29.08°N, 58.38°E) and depth 10 km. Teleseismic focal mechanism from several groups show a steeply – dipping right lateral strike-slip fault. This earthquake caused catastrophic damage to Bam city and neighboring villages about 40000 people were killed and about 30000 people injured .The historical citadel “Arg-e-Bam” which is the biggest adobe complex in the world and the world heritage site by UNESCO, was damaged by this earthquake. We investigate the hypocenter of aftershocks of the Bam earthquake by using a temporal seismic network around the city of Bam. A seismic network consisting of 7 temporal stations was installed on 12/28/2003 by a team of geophysics institute of the University of Tehran, and continued until 2/26/2004. Each station was equipped with digital PDAS seismometer. In this study, we obtained the distributions of aftershocks by Hypo71 software. The hypocenters have distributed linearly over about 18-20 Km in parallel with a line 3- 4 km west of the geological Bam fault and extend from the south of Bam city(southeast railway station) to the heavily damaged area in the eastern part of the city including the historical mud brick citadel “Arg-e-Bam”. The aftershocks show that the Bam earthquake occurred not in the Bam fault, but in the new fault parallel geological Bam fault with distance 3- 4 km at west. The relation of the active fault plane to the surface features is still a matter of debate. Some authors suggest the Bam-Baravat scarp is the only active fault. Other authors suggest the co-seismic slip occurred on 2 different faults, a vertical strike-slip fault located west, beneath the co-seismic surface breaks, and a reverse fault dipping 60° westward that reaches the surface 4 km to the east, beneath the Bam-Baravat escarpment. In this study the aftershocks distribution don't confirm the evidence of two distinct faults.

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