Geomorphologic and structural assessment of active tectonics in NE Shiraz (Fars, SW Iran)

The study area is the Rahmat Anticline. This is located in Fars Province (SW Fold Simple Zagros Belt). The aims of this study are morphotectonic studies and structural analysis in several parts of area. For this purpose: 1) morphotectonic indices, drainage basin shape index (Bs), Mountain front Sinuosity Index (Smf) and valley floor width – height ratio (Vf) were measured by digital elevation model (DEM) and stream order method; 2) the pattern of stress was determined by inversion method. The results obtained from morphotectonics indices indicate that the study area has a higher level of active tectonics in the north part of the anticline. Based on the results derived from the diagrams, it is suggested that there are three stress directions NE-SW, N-S and NW-SE compressional stress directions in the north anticline, which is obvious in the study area. Fault slip analysis reveals two successive late Cenozoic regional compressional trends, NE-SW and N-S. The latter is in good agreement with the present-day stress. The significance of the NE-SW compression is discussed alternatively in terms of stress deviations or block rotations in relation to the strike-slip fault system. As a result, the study area was divided into two classes of relative tectonic activities. Class 1 is indicative of the most active tectonics, occuring mainly in the north part of the anticline. Class 2, corresponding to lowly active tectonics, occurred mainly along south part of the anticline.