Mechanics of V-shaped conjugate strike-slip faults and the corresponding continuum mode of continental deformation

Research Article| September 01, 2011 Mechanics of V-shaped conjugate strike-slip faults and the corresponding continuum mode of continental deformation An Yin; An Yin † 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA2Structural Geology Group, China University of Geosciences (Beijing), Beijing 100085, China †E-mail: yin@ess.ucla.edu; ayin54@gmail.com. Search for other works by this author on: GSW Google Scholar Michael H. Taylor Michael H. Taylor 3Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA Search for other works by this author on: GSW Google Scholar Author and Article Information An Yin † 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA2Structural Geology Group, China University of Geosciences (Beijing), Beijing 100085, China Michael H. Taylor 3Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA †E-mail: yin@ess.ucla.edu; ayin54@gmail.com. Publisher: Geological Society of America Received: 22 Aug 2009 Revision Received: 15 Jul 2010 Accepted: 19 Jul 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (9-10): 1798–1821. https://doi.org/10.1130/B30159.1 Article history Received: 22 Aug 2009 Revision Received: 15 Jul 2010 Accepted: 19 Jul 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation An Yin, Michael H. Taylor; Mechanics of V-shaped conjugate strike-slip faults and the corresponding continuum mode of continental deformation. GSA Bulletin 2011;; 123 (9-10): 1798–1821. doi: https://doi.org/10.1130/B30159.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract V-shaped conjugate strike-slip faults occur widely on Earth, Venus, and Mars in the solar system. They commonly lie at 60°–75° in map view from the maximum compressive stress (σ1) direction. This fault pattern cannot be explained directly by the Coulomb fracture criterion, which predicts the formation of X-shaped shear fractures at 30° from the σ1 direction. Possible explanations of this odd fault geometry include rotation of early formed Coulomb fractures or reactivation of preexisting weakness. Here, we show that none of these mechanisms is feasible for the formation of a late Cenozoic conjugate strike-slip fault system in central Tibet. Instead, its initiation can be best explained by distributed deformation during the formation of two parallel and adjoining shear zones that have opposing senses of shear. Our suggestion is based on the current global positioning system (GPS) velocity field in Tibet, which can be divided into two east-trending shear zones: a northern left-slip zone consisting of active ENE-striking left-slip faults, and a southern right-slip zone consisting of active WNW-striking right-slip faults. The correlation between the GPS strain field and the fault pattern suggests that the central Tibet conjugate faults may have initiated as two sets of Riedel shears in the two parallel but separate shear zones. Because the two east-trending shear zones also experience north-south contraction, we refer to this mechanism of conjugate-fault formation as paired general-shear (PGS) deformation. Assuming a Newtonian fluid, the observed Tibetan GPS velocity field requires the paired shear zones to have formed either by gravitational spreading of the Tibetan lithosphere or a horizontal shear at the base of the upper crust or mantle lithosphere. We demonstrate the feasibility of the two inferred mechanisms for the formation of V-shaped conjugate faults using simple sandbox experiments. Our paired general-shear (PGS) model implies that the combined effect of the state of strain and the state of stress favors only one set (i.e., Riedel shear) of Coulomb conjugate shear fractures under general shear flow. It also requires continuum deformation rather than discrete extrusion tectonics as the most dominant mode of deformation during the late Cenozoic development of the central Tibetan Plateau. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.