Quantitative Relationships between the Volume of Alluvial Fans and ‎its Relation to Active Tectonics ‎(Case study: Alluvial Fans of Southern Slopes of Joghatay Mountains)‎

The purpose of this study is to assess the quantitative relationship between the volume of alluvial fans and its relation to active tectonics in the southern slopes of Joghatay Mountains. To achieve this objective, first, the range of alluvial fans, Angle Broom (S) and alluvial fans radius (R) in the software Arc / Gis using digital maps and digital elevation model (DEM) were determined. Then, the difference between the height between the top and base of the alluvial fans (h) was calculated and, based on the above parameters. In order to evaluate the effects of other variables such as tectonic and geomorphic characteristics like lithology using some integral index over the facade (Hi), the index of mountain front sinuosity (Smf), index basin asymmetry (Af), transverse topographic symmetry (T), index ( SL), (BS) and the ratio of valley floor width to depth Valley (Vf). The results of the mean of all indices indicate that 61.55% of the region is located in the active to semi-active tectonic state, which reveals the role of tectonic factors in providing sediment and increasing the volume of alluvial fans in the region. In addition, the common role of lithological factors and tectonic forces can be pointed out. Due to the nature of some of the faults in the region, the soft and loose deposits including Flysch and neogen marls on hard Conglomerate formation have caused the sediment load more to the regional currents and contributes to the development of alluvial fans in the region. Also, the elevation of alluvial fans sediments and the change in the surface of the local area as a result of the faults activity has resulted in the deep excavation of the base of the rivers. This, in turn, contributes to the development of the alluvial fans as a result of base digging and solid loading, leading to the formation of multi-part and fragmented alluvial fans. In order to homogenize the basins in terms of area, they were divided into three groups and these relationships were analyzed in each group. The results indicate that there is a direct and significant relationship between the feeding basin and the volume of alluvial fans, while there is no such relationship between the slope of the basin and the volume of alluvial fans.