Structural Characteristics, Paleoseismology and Slip Rate of the Qoshadagh Fault, Northwest of Iran


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Abstract

Geometric and seismic parameters of the Qoshadagh Fault (QDF) were investigated to evaluate seismic hazard along this fault, which consists of three segments. The central E–W striking, dextral-reverse segment is the longest and terminates at both ends into NW–SE striking splay arrays. Both eastern and western splay arrays form locally transtensional bends. Paleoseismic data obtained from three excavated trenches across the fault combined with dated offset geomorphic features revealed that the central segment experienced at least 5 surface rupturing earthquakes during the past 2.5 ka, with maximum moment magnitude of Mw = 6.8 ± 0.2. The mean recurrence interval for the identified paleoearthquakes is 452 ± 143 years (±2σ) and the calculated amount of slip per event is ca. ≈0.85 m. These results imply that the QDF slips at an average rate of 1.9 ± 0.1 mm yr–1 for over the past 2.5 ka. The obtained values define the seismic behavior of the fault and are essential to remediate ensuing seismic risks.

About the authors

M. Faridi

Research Institute for Earth Sciences; Geological Survey of Iran

Author for correspondence.
Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tehran, PO Box 13185-1494; Tabriz, PO Box 5167733551

H. Nazari

Research Institute for Earth Sciences

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tehran, PO Box 13185-1494

J.-P. Burg

Department of Earth Sciences—Ion Beam Physics

Email: mfaridi@gsi.ir
Switzerland, Zürich, 8093

N. Haghipour

Department of Earth Sciences—Ion Beam Physics

Email: mfaridi@gsi.ir
Switzerland, Zürich, 8093

M. Talebian

Research Institute for Earth Sciences

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tehran, PO Box 13185-1494

M. Ghorashi

Research Institute for Earth Sciences

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tehran, PO Box 13185-1494

M. A. Shokri

Geological Survey of Iran

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Rasht, PO Box 4188957981

E. Ahmadzadeh

Research Institute for Earth Sciences

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tehran, PO Box 13185-1494

S. S. Sahebari

Roshdiyeh High Education Center

Email: mfaridi@gsi.ir
Iran, Islamic Republic of, Tabriz, PO Box 5158464918

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