Evaluation of the tectonic status of the sub-basins of Fars province (from evaz to Karmostaj) using geomorphic indicators and SBAS time series method

Introduction

Geological processes (tectonics) are formed by forces that originate from the earth's crust and change the shape of the earth's crust. These processes create external forms and landforms such as continents, mountains and oceans, and the set of these processes is called tectonic cycle, so tectonics refers to processes, buildings and landforms. Related are to changes in the shape of the earth. In order to check the tectonic status of a region or basin, there are various methods. In the meantime, geomorphic indicators are a useful and reliable tool in evaluating tectonic activities because they can be used to identify areas that have experienced fast or even slow tectonic activities in the past. Are easily identified. The amount of new land construction activities is different in different regions of the Iranian plateau, among which, Zagros is active in terms of new land construction activities and is associated with many movements. The studies of geostructural processes will be useful for the better management of geomorphological hazards, which are important for many human activities such as the design and construction of cities, power plants, airports, military and security facilities, dams and industrial centers. Also, identifying the features of the environment, the geomorphological forms of a region and being aware of them help us to better understand the environmental capabilities and by providing this information to the authorities, they can use them in the implementation of regional planning. And local, civil planning, land use plans and in general sustainable management of the environment suitable for that area. Considering the importance of the topic, in this research, the tectonic situation of Zagros in Fars province from evaz to Karmostaj has been evaluated.





Methodology

In this research, the Sentinel 1 radar images, SRTM 12.5 meter high digital model and satellite images are used as the most important research data. The most important tools used in the research were ArcGIS (to prepare the desired maps), GMT (to run the SBAS time series model) and SPSS (to perform the calculations related to the indicators). Also, 10 geomorphic indices and SBAS time series model were used in this research. This research has been done in two stages according to the desired goals. In the first stage, the tectonic status of the region has been evaluated using 10 geomorphic indicators. In the second stage, using Sentinel 1 radar images and the radar interferometry method and SBAS time series, the amount of vertical displacement in the study area has been evaluated. In order to implement the SBAS time series model, first, 21 Sentinel 1 radar images related to a 2-year period (2020 to 2022) have been prepared.



Results and Discussion

In this research, in order to investigate the tectonic status of the studied area, geomorphic indicators and also radar interferometry method have been used. The results of investigating the tectonic status of sub-basins in the region in terms of IAT index have shown that sub-basin 4 has the lowest average with an average coefficient of 1.5, and overall, in terms of the indicators used, it has a more active tectonic status than other sub-basins. After this sub-basin, sub-basins 6 and 9 have a more active tectonic situation with coefficients of 1.6 and 1.7, respectively. Also, sub-basins 10, 2 and 3 have the highest average with coefficients of 2.2, 1.2 and 1.2, respectively, and in terms of the indicators used, they are tectonically less active than other sub-basins. They have Also, the results of the radar interferometry method have shown that the study area during the studied time period (from 12/01/2020 to 01/01/2022) had 127 mm of elevation and 109 mm of subsidence. . Examining the spatial situation of the vertical movement that has occurred indicates that a large part of the southern anticlines of Lar and Gerash cities has faced subsidence and a large part of the plains of this region has faced uplift. According to these changes, it can be said that the tectonic factor played the main role in the displacement that occurred in the region.



Conclusion

The results of this research have shown that the studied area is tectonically active. Also, in this research, the relationship between the amount of vertical movement of the region and geomorphic indicators has been investigated. First of all, it should be said that the correctness of the geomorphic indicators is confirmed, because based on the radar images, the studied area is tectonically active. But the remarkable thing about the results obtained from the radar images is the type of displacement that occurred and the effect on the geomorphic indicators. In fact, as it was said, the plains of the region are elevated and this problem has caused the difference in the height of the basin to decrease. Based on this, the type of vertical displacement of the region has caused some indices such as Hi, Bs, SI, S and Gi to show the tectonic activity of the region less than it is. In total, the results obtained up to this stage have shown that some geomorphic indicators show the tectonic status of the region less than the actual value.