Active tectonics within the NW and SE extensions of the Pambak-Sevan-Syunik fault: Implications for the present geodynamics of Armenia

Quaternary International
Geosciences Montpellier, UMR CNRS 5243, University of Montpellier II, France; Institute of Geological Sciences, National Academy of Sciences of Armenia, Armenia; Research Institute for Earth Sciences, Geological Survey of Iran, Iran; CRPG, UMR 7358, CNRS, Université de Lorraine, Vandoeuvre-lès-Nancy, France; Laboratoire Préhistoire et Quaternaire, Université de Lille 1, France; US Geological Survey, Denver Federal Center, Denver, Colorado, USA; Department of Earth and Atmospheric Sciences, University of Québec, Montréal, Canada
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Abstract

This study analyzes the active tectonics within the northwestern and southeastern extensions of the Pambak-Sevan-Syunik fault (PSSF), a major right-lateral strike-slip fault cutting through Armenia. Quantifying the deformations in terms of geometry, kinematics, slip rates and earthquake activity, using cosmogenic 3He, OSL/IRSL and radiocarbon dating techniques, reveal different behaviors between the two regions. Within the northwestern extension, in the region of Amasia, the PSSF bends to the west and splits into two main WNW–ESE trending reverse faults defining a compressional pop-up structure. We estimate an uplift rate and a shortening rate of 0.5 ± 0.1 mm/y and 1.4 ± 0.6 mm/y, respectively. This suggests that most of the ∼2 mm/y right lateral movement of the PSSF seems to be absorbed within the Amasia pop-structure. Within the southeastern extension, the PSSF shows signs of dying out within the Tsghuk Volcano region at the southernmost tip of the Syunik graben. There, the tectonic activity is characterized by a very slow NS trending normal faulting associated with a slight right-lateral movement. Slip rates analyses (i.e. vertical slip rate, EW stretching rate at 90° to the fault, and right-lateral slip rate of ∼0.2 mm/y, ∼0.1 mm/y and ∼0.05 mm/y, respectively) lead to the conclusion that the right lateral movement observed further north along the PSSF is mainly transferred within other active faults further west within the Karabagh (Hagari fault or other structures further northwestwards). Comparing our slip rates with those estimated from GPS data suggests that most of the deformation is localized and seismic, at least within the Tsghuk region. The geometrical and kinematic pattern observed within the two terminations of the PSSF suggests that the fault and its surrounding crustal blocks are presently rotating anticlockwise, as also observed within the GPS velocity field. This is consistent with the recent kinematic models proposed for the Caucasus-Kura-South Caspian region and brings a new insight into the present geodynamics of Armenia.

 

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Active tectonics within the NW and SE extensions of the Pambak-Sevan-Syunik fault: Implications for the present geodynamics of Armenia
Series title Quaternary International
DOI 10.1016/j.quaint.2015.05.021
Volume 395
Year Published 2016
Language English
Publisher Pergamon
Publisher location Oxford
Contributing office(s) Geosciences and Environmental Change Science Center
Description 18 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Quaternary International
First page 61
Last page 78
Country Armenia
Online Only (Y/N) N
Additional Online Files (Y/N) N
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