Kinematic Evaluation of the Kazerum Fault System within the Zagros Fold-and-Thrust Belt, Iran

Abstract

The Kazerun fault system as an active transverse fault has affected the structures and sedimentation of the Zagros belt from Cambrian to the present. On the basis of published geological maps this fault system has divided into four segments: the Sisakht, Yasuj, Kamarij and Borazjan segments. The fault slip data in the seven sites close the Kamarij segment within this fault system; we have studied using the Direct Inversion and Right Dihedra methods. The results demonstrate that the reverse faulting and the strike-slip faulting on this fault system. This suggested that the discrepant stress axes direction on this fault system is that it takes up shortening perpendicular to the strike of the Zagros by a component of extension parallel to the strike of the belt, rather than by crustal thickening. In addition to analysis of the stress axes, fault-slip data were analyzed using the graphical kinematic method. The purpose of this analysis was to test the homogeneity of the data sets and to determine the geometric relationships that are represented by kinematic axes. Analysis indicates remarkably homogeneous kinematic axes as defined by the near-horizontal NE–SW shortening and near-horizontal NW–SE extension. In fact, the Kazerun fault system accommodates some of the shortening between Arabia and Central Iran by an elongation of the Zagros belt parallel to strike. It is not easy to assess the likely rate of elongation parallel to the strike of the Zagros. It is clear from the anticlines and reverse faulting earthquakes near the Kazerun fault system that it does not accommodate all the shortening at its position within the belt. These observations combined with the regional elevations and historical seismicity suggests to us that the rate of motion on the Kazerun fault system is relatively slow.