Hollingsworth, James and Nazari, Hamid and Ritz, Jean‐François and Salamati, Reza and Talebian, Morteza and Bahroudi, Abbas and Walker, Richard T. and Rizza, Magali and Jackson, James (2010) Active tectonics of the east Alborz mountains, NE Iran: Rupture of the left-lateral Astaneh fault system during the great 856 A.D. Qumis earthquake. Journal of Geophysical Research B, 115 ( ). Art. No. B12313. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20110118-100537108
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The 856 A.D. Qumis earthquake (M7.9) is the most destructive earthquake to have occurred in Iran, killing more than 200,000 people and destroying the cities of Damghan and the old Parthian capital of Shahr-i Qumis (Hecatompylos). This study combines evidence of historical seismicity with observations of the geomorphology and paleoseismology to provide the first detailed description of active faulting in the Damghan region of the east Alborz mountains, Iran. Regional left-lateral shear is accommodated on the Astaneh, Damghan, and North Damghan faults. Quaternary alluvial fans have been displaced along the Astaneh fault, with 15–20 m stream offsets recording the cumulative displacement over the last two to five earthquakes. A paleoseismology study from a single trench along a 5–10 km segment of the Astaneh fault reveals a rupture prior to 1300 A.D. and significantly later than 600 B.C. Despite the limitations of a single trench in documenting the spatial and temporal evolution of the fault over the late Quaternary, we are nevertheless able to bracket the last event to a time period consistent with the 856 A.D. earthquake. Two older earthquakes were also identified during the Holocene occurring between 600 B.C. and 4600 B.C. and between 4600 B.C. and 9600 B.C. The location of our trench within a bend on the Astaneh fault, which could act as a barrier to rupture propagation, means the three earthquakes recovered from our trench over the Holocene may represent a minimum. Further trenching will reveal how the Astaneh fault ruptures over repeated earthquakes and, consequently, the magnitude and extent of slip during the 856 A.D. earthquake.
|Additional Information:||© 2010 American Geophysical Union. Received 3 December 2009; revised 6 August 2010; accepted 24 August 2010; published 9 December 2010. We thank the Geological Survey of Iran for organizing all aspects of the fieldwork and for their continued support of our work in Iran. M. Fattahi (Institute of Geophysics, Tehran, and Oxford University) also provided valuable field support for a tripto Damghan. J‐L Michelot and M. Massault (Orsay‐Paris XI) kindly provided radiocarbon ages, which were performed in the framework of the LMC14 Artemis INSU programme. We are also grateful to Shannon Mahan (USGS Denver), who performed the OSL dating of sample AT3.OS2.06. Quickbird and Corona satellite images were purchased using funds from a NERC Postdoctoral Fellowship awarded to R.T.W. Thanks go to the staff and students of Damghan University who helped with GPS work in the Astaneh valley. J.H. would like to acknowledge support from the NCO‐COMET research group during his time at Cambridge and the Gordon and Betty Moore Foundation during his time at Caltech. This work benefited from useful discussion with Manuchehr Ghorashi, Nicky White, Mahnaz Rezaeian, Keith Priestley, Barry Parsons, Conall Mac Niocaill, Bertrand Meyer, and Alex Copley. Quickbird satellite images were either purchased from DigiGlobe or obtained from Google Earth, Landsat7 images were obtained from the Global Land Cover Facility at the University of Maryland, and ASTER and SRTM data were obtained through the USGS and NASA. Stereo SPOT5 scenes used for the generation of a 5 m DEM of the Astaneh Valley were acquired by J.H. after a successful application to the ISIS program sponsored by CNES. This manuscript was greatly improved by the comments of three anonymous reviewers. Various images in this paper were created using the public domain Generic Mapping Tools (GMT) software [Wessel and Smith, 1998].|
|Subject Keywords:||Seismology: Seismicity and tectonics; Seismology: Paleoseismology; Tectonophysics: Tectonics and landscape evolution; Geochronology: Geomorphological geochronology|
|Official Citation:||Hollingsworth, J., H. Nazari, J.-F. Ritz, R. Salamati, M. Talebian, A. Bahroudi, R. T. Walker, M. Rizza, and J. Jackson (2010), Active tectonics of the east Alborz mountains, NE Iran: Rupture of the left-lateral Astaneh fault system during the great 856 A.D. Qumis earthquake, J. Geophys. Res., 115, B12313, doi:10.1029/2009JB007185|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||26 Jan 2011 22:39|
|Last Modified:||26 Dec 2012 12:51|
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