Document Type : Original Research Paper
Authors
1 Research Institute for Earth Sciences, Geological Survey of Iran, Tehran-Iran.
2 Laboratoire Géosciences Montpellier, Université Montpellier 2, Montpellier, France.
Abstract
The Taleghan Fault is located at the southern side of Taleghan valley in Central Alborz, 50 km north west of the Tehran mega city. Usually described as a south-dipping reverse fault, it could be the source of some of the strongest historical earthquakes recorded in the Tehran region, notably the 958 AD (estimated magnitude M 7.7). The fault stands out as one of the major active structure menacing the cities of Tehran and Karadj, representing together 12 millions inhabitants. In order to analyze the recent activity of the fault, a morphological study was carried out along the fault combining satellite imagery, aerial photographs and Digital Elevation Model. We found out an active branch that had never been described whereas the fault classically mapped appears inactive. Detailed field work along the branch allows us to show that the fault had its vertical component recently reverted from reverse movement to normal movement. One of the measured ratios of accumulated horizontal / vertical displacements associated to the left lateral and normal movement is 2.5-5. The strike, estimated dip and rake in the eastern part are 105°, 60° and 40° respectinely making it a left lateral- normal strike slip fault in this part of the Central Alborz.
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