Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran

Talebian, M. and Copley, A. C. and Fattahi, M. and Ghorashi, M. and Jackson, J. A. and Nazari, H. and Sloan, R. A. and Walker, R. T. (2016) Active faulting within a megacity: the geometry and slip rate of the Pardisan thrust in central Tehran, Iran. Geophysical journal international, 207 (3). pp. 1688-1699. ISSN Online ISSN 1365-246X Print ISSN 0956-540X DOI 10.1093/gji/ggw347

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Abstract

Tehran, the capital city of Iran with a population of over 12 million, is one of the largest urban centres within the seismically active Alpine–Himalayan orogenic belt. Although several historic earthquakes have affected Tehran, their relation to individual faults is ambiguous for most. This ambiguity is partly due to a lack of knowledge about the locations, geometries and seismic potential of structures that have been obscured by dramatic urban growth over the past three decades, and which have covered most of the young geomorphic markers and natural exposures. Here we use aerial photographs from 1956, combined with an ∼1 m DEM derived from stereo Pleiades satellite imagery to investigate the geomorphology of a growing anticline above a thrust fault—the Pardisan thrust—within central Tehran. The topography across the ridge is consistent with a steep ramp extending from close to the surface to a depth of ∼2 km, where it presumably connects with a shallow-dipping detachment. No primary fault is visible at the surface, and it is possible that the faulting dissipates in the near surface as distributed shearing. We use optically stimulated luminescence to date remnants of uplifted and warped alluvial deposits that are offset vertically across the Pardisan fault, providing minimum uplift and slip-rates of at least 1 mm yr−1. Our study shows that the faults within the Tehran urban region have relatively rapid rates of slip, are important in the regional tectonics, and have a great impact on earthquake hazard assessment of the city and surrounding region.

Item Type: Article
Uncontrolled Keywords: 2016AREP; IA72;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
08 - Green Open Access
Journal or Publication Title: Geophysical journal international
Volume: 207
Page Range: pp. 1688-1699
Identification Number: 10.1093/gji/ggw347
Depositing User: Sarah Humbert
Date Deposited: 30 Jan 2017 10:36
Last Modified: 30 Jan 2017 10:37
URI: http://eprints.esc.cam.ac.uk/id/eprint/3806

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