1-Introduction
Mass movements include all movements that occur under the influence of mass weight. The effect of fault zones and tectonic activity on landslides and the relationship between them can be evaluated by examining the density of landslides in the fault zone and their boundaries and the impact of tectonic activity on landslides. The impact of tectonic activity by the occurrence of an earthquake and the creation of a driving force, tectonic uplifts, the creation of conditions and materials prone to landslides through the creation and development of fractures and cracks caused by faulting, the creation of cracks and fissures in rocks and acceleration The process of mechanical and chemical weathering, creating gouges and cutting faults; Increasing the permeability of rocks is a change in the amount and direction of the slope of the geological and topographical layers.
2-Materials and methods
The study scope includes the entire country. The location of all the landslides detected in Iran and the known faults of Iran, the slope of the landslides and field observations and technical investigations of three cases of landslides near the faults have been investigated. The research method in the present study is based on library studies and field observations. In this regard, the information related to the state of geology, tectonics and landslides that occurred in Iran is examined in a library form, and then the information of previous landslides has been collected and compared to Field investigation of old and new landslides is discussed. After completing the geological information, faults, landslides and their location, he analyzed the data and analyzed and compared the location of landslides with faults using Arc Gis software. And the slope of their place of occurrence is done. Also, as an example, several cases of landslides that have occurred in the area of ​​active faults have also been investigated and the effect of the fault zone on the occurrence of landslides will be analyzed. Finally, by analyzing the results of comparing the occurrence of landslides with the location of the faults, the evaluation of the active tectonics is carried out.
3-Results and discussion
The relationship between tectonic activities and the occurrence of landslides has been investigated by different researchers and confirmed in different regions. Therefore, considering that tectonic activity is caused by the occurrence of earthquakes and the creation of a driving force, tectonic uplifts, fractures and crushings caused by faulting, the creation of cracks and fissures in rocks and the acceleration of the process of mechanical and chemical weathering, the creation of fault gouges and cutting A fault as a material prone to landslides, increasing the permeability of rocks, changes in the direction and slope of geological layers, etc., cause landslides, the relationship between tectonic activity and landslides was investigated. Therefore, by comparing the location of the landslides detected in the country with the active faults of the country, it was found that the density of landslides is higher in the area near the active faults. As it was determined in the observations and field investigations of three selected landslide samples in Zagros, Azerbaijan and Alborz region (including the landslides of Qala Rostam, Kafcherin and Qafe Bala Qala), the activity of faults causes fractures, crushing, increased permeability, Changes in the slope and layering of rocks, and most importantly, have caused landslide-prone materials. However, it was not possible to convert this impact into quantitative data due to geological conditions and lack of data, and it was enough to interpret and describe this impact qualitatively. Also, by examining the location of the landslides that occurred in the country and the slope of the landslides, it was found that a high percentage of landslides occurred at slopes higher than 15 degrees, and qualitatively, it can be related to the slope and elevation of the mountain. established with tectonic activity and described the effect of tectonic activity on the occurrence of landslides.
4- Conclusion
By comparing the location of landslides detected in the country with active faults in the country, it was found that the density of landslides is higher in the vicinity of active faults. So that in the range of 500 meters and 2000 meters of active faults, the number of detected landslides is 65% more than the areas far from the fault, and a high percentage of landslides occurred at slopes higher than 15 degrees, which is due to It is influenced by tectonic activity due to the increase in the slope and elevation of the mountains. According to the field investigation of three landslide samples, the effect of fault activity on the creation of landslide-prone materials was determined. Therefore, one of the main factors of the occurrence of landslides and the frequency of their occurrence in the fault areas and close to the faults can be considered as the effect of tectonic activity and faults, which through the occurrence of earthquakes and the creation of a driving force, tectonic uplifts, fractures and crushing caused by faulting, creation of joints and cracks in rocks and accelerating the process of mechanical and chemical weathering, creation of fault gouges and fault cuts as materials prone to sliding, increasing the permeability of rocks, changes in the direction and degree of slope of geological layers, etc. In other words, it can be said that tectonic activities have increased the occurrence of landslides in the country. In terms of the vulnerability of residential areas and other important facilities located near active and quaternary faults, in addition to seismic waves and surface rupture during an earthquake, they are also threatened by the risk of landslides. Therefore, it is necessary and necessary to adopt engineering measures in the construction of houses located in fault zones to prevent damage caused by landslides, as well as not to build on sloping land and away from the boundaries of fault ruptures.