عنوان مقاله [English]
Due to Iran's location in the Alpine-Himalayan orogeny , Iran is one of the most active areas in terms of infrastructure, of which the Sanandaj-Sirjan is a part. Sanandaj-Sirjan zone is the busiest structural zone in Iran, which has been formed as a part of Zagros orogeny and Alp-Himalayan orogeny system due to the convergence of the northern part of Gondwana and southern Eurasia at the end of the Mesozoic. Studying and recognizing active tectonics is very important in risk assessment, especially in areas with relatively high tectonic activity in the Holocene and Pleistocene, given that most active tectonic processes can damage human structures and be associated with sudden events. , Recognizing active tectonics in an area can reduce the risks of these events. Morphotectonics represents the relationship between tectonics and surface effects, and morphotectonic indicators are basic tools for rapid measurement and detection of areas with tectonic deformation.
Geomorphology represents the relationship between tectonics and surface features, and geomorphology indicators are preliminary and basic tools for rapid measurement and diagnosis of areas with tectonic deformation.
In this research, the active tectonics of a part of Sanandaj-Sirjan zone in the north of Kermanshah has been investigated, for this purpose, the indicators of the longitudinal gradient of the river (SL), hierarchical anomaly (Hi), branches (R), the shape of the drainage basin (Bs) and sinusitis mountain front (Smf) was measured in 54 watersheds in the region by By geographic information system (GIS(. Finally, the results of quantitative calculations were compared and analyzed with field observations in the region.
Results and Discussion
The values of five morphometric indices, including river longitudinal gradient (SL), hierarchical anomaly (Hi), branches (R), drainage basin shape (Bs) and sinusitis mountain front (Smf), were calculated separately for 54 basins in the study area. and finally a zoning map of the level of tectonic activity was prepared by combining the values obtained from the morphometric indices, the longitudinal gradient index (SL) of the river has high values in the eastern and southern parts of the studied area. In the east of the studied area, the northern basins of the Sahne fault and the southern basin of the Mianrehan fault show high and very high values of this activity index, which indicates the effect of the activity of the Sahne fault in this part of the region on the river slope. In the south of the studied area in the area of Biston-Taqbestan fault zone, basins 37, 43, 44, 48 have relatively high values of river longitudinal gradient index (SL).
Hierarchical anomaly index (Hi) and branching index (R) have high values in the western and eastern basins of the study area. Basins 22 and 25 in the north of the Sahne fault and the basins including the Morvarid fault have high activity based on these indicators. Also, the basins in the south of the region in the range of Koh-Safid fault and Qarasu fault, Biston-Taqbestan fault zone, as well as the southern basins of Qeshlaq fault in the west of the studied area show high values of these indicators. The drainage basin shape index (Bs) has the highest values in basins 49 and 47 in the south of the study area in the range of Koh Safid and Qaresu faults, basin 26 in the north of the Sahne fault, basin 12 in the north of the Marwarid fault and basin 37 in the north of the Biston fault zone. It has a vault. The elevations formed due to the activity of Sahne, Mianrahan, Morvarid and Biston-Taqbestan fault zone with a straight mountain front have the highest values of mountain front meandering index (Smf). Based on the results of calculating the mentioned indicators and preparing a map of tectonic activity by combining the values of these indicators, in general, the southern and eastern half of the study area have higher relative tectonic activity than the western and northern half. Biston-Taqbestan fault zone in the southern half of the study area and Sahne-Marwarid fault zone in the east of the study area have the most tectonic activity. All the basins north of the Sahne fault have high relative tectonic activity based on the indicators of longitudinal gradient (SL) and branches (R). Also, basins 17 and 26 have high values of basin shape index (Bs) and basins 22 and 26 have high values of index (Hi).
According to the studies, the current tectonic activity is very high in the Sahne-Morvarid fault zone as part of the main Zagros fault (MRF) and the Biston-Taqbestan thrust zone, and the moderate and relatively high activity in the Mianrahan fault and the Koh Safid fault zone. The title of a branch of the Zagros Thrust Fault (ZTF) in the study area can be inferred based on the results of the morphometric indices, as well as the high compliance of the earthquakes with the relative tectonic activity level zoning map based on the morphometric indices (Iat) in the study area. The importance of using (Iat) as primary studies to identify seismic areas and long-term earthquake prediction in areas with high tectonic activity.