Document Type : Research Article
Authors
1
PhD Student of Geomorphology, Faculty of Geographical Sciences, Shahid Beheshti University, Tehran
2
Associate Professor of Geomorphology, Faculty of Geographical Sciences, Shahid Beheshti University, Tehran, Iran
3
Professor of Geomorphology, Faculty of Geographical Sciences, Shahid Beheshti University, Tehran, Iran
4
Associate Professor of the Sedimentary Basins and Petroleum Department., Faculty of Geology Sciences, Shahid Beheshti University, Tehran, Iran
10.22059/jhsci.2025.400930.892
Abstract
Landslides, as one of the unstable slope processes, play an important role in transforming mountainous landscapes and are a serious challenge in environmental management by causing changes in topography and destroying infrastructure. In this study, in order to evaluate the distribution of landslides and their relationship with morphotectonics, two basins of Tang Hamam and Alvand (Sarpol Zahab) in the Zagros zone were investigated. Using field studies and satellite images, a total of 65 landslide events were identified, and the ratio of landslide area to basin area (LA) and landslide density (LD) in the basins were obtained. Then, using geomorphological and tectonic indices, such as hypsometric integral (Hi), the valley height-width ratio (Vf), the basin asymmetry factor (Af), basin shape (Bs), the stream gradient-length ratio (SL), the mountain-front sinuosity (Smf), and Relative Tectonic Activity Index (Iat), the tectonic status of the basins was evaluated. Also, factors affecting the occurrence of landslides, including faults, earthquake focus, slope, and litology, and their quantitative relationship with the extent and frequency of landslides, were investigated. Spatial analyses of morphometric indices and relative tectonic activity index showed that tectonically, both the Tang Hamam and Alvand basins have moderate activity with values of 2.33 and 2, respectively. The ratio of landslide area to the basin area is 23.69% in the Tang Hamam basin whereas this ratio is 0.45% in the Alvand basin. Investigating the distribution of landslides relative to active faults and earthquake epicenters also showed that more than 97 percent of landslides are located less than 2 kilometers from active faults and more than 95 percent of them are located near earthquake epicenters. The findings also show that slope gradient is one of the effective factors in the occurrence of landslides, and the highest density of landslides was observed in slope angle class of 15-30 degrees. Geologically, most landslides have occurred in loose, low-resistance formations such as Amiran, Pabdeh, and Young alluvial deposits. Also, the presence of alternating hard layers of Asmari formation over loose and soft layers such as Pabdeh, especially in the Alvand basin and the slopes of the Shahneshin Mountain in the Tang Hamam basin, has led to increased instability and the occurrence of landslides. Overall, the study area has moderate tectonic activity with significant structural heterogeneity. These conditions, especially in areas that are simultaneously affected by geology, faults, earthquakes, slope, and morphometric features, increase the occurrence of landslides.
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