Application of Assessment Indicators of Active Tectonic in Estimating Tectonic Situation in Heble Roud Basin

The quantitative measurements allows the geo morphologists to compare different land forms and calculate the morphologic indices. The alluvial fans are among the common forms in the arid and semi arid regions which developed under tectonic and climatic elements. These forms are quite sensitive to tectonic changes and register their effects in themselves. Therefore, through studying these effects and evidences, we can realize the procedure of the tectonic effects and changes of alluvial fans. The purpose of this study is to investigate the role of tectonic factors in the development and morphological changes of the alluvial fans of Garmsar. In this study, the topographic maps, geology, satellite photos and the digital elevation model (DEM) were used as the main research data. In addition, the morphology of the alluvial fans of the region was studied closely and through the field study. Then, using the geomorphic indexes which includes the sinuosity of the mountain in-front (SMF) Ratio of valley floor width to valley height (VF), Drainage Asymmetry factor (AF), Stream Length-Gradient Index (SL), Transverse Topographic Symmetry Factor (T), Fan Comicality Index (FCI), the region in terms of tectonic activities were assessed. Through combination of these indexes, the index of active tectonic (Iat) can be obtained. The results show that according to the (Iat) amounts, Garmsar alluvial fans are placed at the medium level of neo tectonic activities. The obtained geomorphologic evidences such as elevated river terraces, sequence of alluvial fans, changing base surface of Heble Roud and existence of old terraces and deepened channels confirms the results of the study.