Late cenozoic stress evolution along the Karasu Valley, SE Turkey

Abstract

This study defines the Mio-Pliocene to present-day stress regime acting at the northeastern comer of the eastern Mediterranean region along the Karasu Valley (i.e., the Amanos Range), taking in the Antakya, Osmaniye and Kahramanmaras provinces. The inversion slip vectors measured on fault planes and chronologies between striations indicate that the stress regime varied from transpressional initially to transtensional, having consistent NW- and NE-trending sigma(Hmax)(sigma(1)) and sigma(Hmin)(sigma(3)) axes, respectively; there are significantly different mean stress-ratio (R-m) values however. The older mean stress state is characterized by N151 +/- 11degreesE-trending sigma(1) and N59 +/- 12degreesE-trending sigma(3) axes, and by a mean arithmetic R. value of 0.76, indicating that the regional stress regime is transpressional. The younger stress regime is characterized by N154 +/- 8degreesE-trending sigma(1) and N243 +/- 8degreesE-trending sigma(3) axes, and by a mean arithmetic R-m value of 0.17, indicating a transtensional character for this regional stress regime. The low R values of the stress deviators related to the recent stress state reflect normal-component slips. The earthquake focal mechanism inversions confirm that the younger stress regime continues into the Recent. The inversion identifies a transtensional stress regime representing strike-slip and an extensional stress state with a consistent NE-trending sigma(Hmin)(sigma(3)) axis. These stress states are characterized by N66degreesE and N249degreesE-trending sigma(3) axes, respectively. Both significant regional stress regimes induce left-lateral displacement along the southern part of the East Anatolian Fault (EAF, or Amanos Fault). The temporal change, probably in Quaternary time, within the regional stress regime-from transpression to transtension-resulted from the coeval influences of subduction processes in the west-southwest (i.e., along the Cyprus arc), continental collision in the east, and westward escape of the Anatolian block. (C) 2004 Elsevier B.V. All rights reserved.