Strike-slip faulting, rotation, and along-strike elongation in the Kopeh Dagh mountains, NE Iran |
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| Authors: | James Hollingsworth James Jackson Richard Walker Mohammad Reza Gheitanchi Mohammad Javad Bolourchi |
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| Institution: | Bullard Laboratories, Madingley Road, Cambridge, CB3 0EZ, UK.;E-mail: Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR;, UK Institute of Geophysics, Tehran University, Tehran, PO Box 13145–1137,;Iran Geological Survey of Iran, Azadi Sq., Meraj Avenue, PO Box 13185–1494,;Tehran, Iran |
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| Abstract: | The Kopeh Dagh is a linear mountain range separating the shortening in Iran from the stable, flat Turkmenistan platform. In its central part is an array of active right-lateral strike-slip faults that obliquely cut the range and produce offsets of several kilometres in the geomorphology and geological structure. They are responsible for major destructive earthquakes in the 19th and 20th centuries and represent an important seismic hazard for this now-populous region of NE Iran. These strike-slip faults all end in thrusts, revealed by the uplift and incision of Late Quaternary river terraces, and do not continue beyond the Atrak river valley, which forms the southern margin of the Kopeh Dagh. The cumulative offset on these strike-slip faults, and their associated rotation about vertical axes, can account for ～60 km of N–S shortening. This value is similar to estimates of the Late Quaternary N–S right-lateral shear between central Iran and Afghanistan, which must be accommodated in NE Iran. The strike-slip faults also require ～30 km of along-strike extension of the Kopeh Dagh, which is taken up by the westward component of motion between the South Caspian Basin and both Eurasia and Central Iran. It is probable that these motions occurred over the last ～10 Ma. |
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| Keywords: | Baghan fault earthquake location geomorphology Kopeh Dagh NE Iran Quchan earthquake seismology |
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