Estimation of land surface displacement in Kermanshah plain and effect of earthquake Ezgele on displacement process using SBAS method

The shape of the earth changes over time and these changes can be periodic or non-periodic. Land deformation may be related to tectonic processes such as earthquakes, faults, volcanoes, landslides, and anthropogenic processes such as mine activity and groundwater exploitation. Subsidence and uplift is one of the most important changes in the shape of the earth. Which is directly related to the tectonic status of the areas. Which is directly related to the tectonic status of the areas. The land of Iran as part of the active alpine-Himalayan tectonic zone has been affected by numerous tectonic activities over time, with the emergence of the Zagros-Makran and Alborz-Kope-Dagh mountains in the Iranian plateau due to the Arabian-Indian Plateau drifting from the landforms resulting from this convergence. Kermanshah plain is also active in tectonic terms due to its location in folded Zagros, therefore it has a lot of potential for the displacement of the Earth's surface. Today, the calculation of ground-level displacements using radar interference technology includes unique capabilities in terms of dimensions, cost, time and accuracy compared to other measurement techniques. Accordingly, in the present study, radar interferometry method was used to assess the amount of subsidence and uplift of Kermanshah Plain and the correlation of this displacement with the earthquake in Kermanshah on 21/08/1396.

Nowadays, calculation of displacements occurring on the surface using radar interferometry technology has unique capabilities in terms of size, cost, time and accuracy compared to other measurement techniques. Therefore, in the present study, using radar interferometry method and SBAS time series, the vertical displacement rate of Kermanshah plain and its relationship with 7.3 earthquake of Kermanshah Ezgele have been investigated. In this study, the displacement rate was calculated for three periods:-the first time in the history of 11.24.2016 to 11.07.2017 and includes 13 image Sentinel 1.Second period is from the date of 07/11/2017 to 11/19/2017 (before and after the earthquake). The third time frame selected to assess the impact of the earthquake on the process of changes and calculations for different purposes is from 24/11/2016 to 19/11/2017 (including 2 images).

The results show that the Kermanshah herd earthquake has a direct role in the vertical displacement of Kermanshah plain. The result of calculating the vertical displacement in the first period indicates that the northwest and southeast areas of Kermanshah urban area have subsided and the northeast and southwest elevations have been elevated, but this trend has changed due to the earthquake of the Ezgele, So that the earthquake of the Ezgele has increased many parts of the study area, especially its southern regions, and has also subsided in the northeast areas of the study area, so the results in the third time period have been very variable, It is concluded that the Kermanshah northeast highlands, which had been uplifted during the first period, were associated with a subsidence due to the Kermanshah herd earthquake. Also the southeastern areas of Kermanshah urban area which had subsided in the first period, Due to the direct impact of the earthquake from the Ezgele, it has been experiencing an uplift in the third period. Therefore, it can be said that the earthquake of the Ezgele, while changing the vertical displacement process of Kermanshah plain, can affect the results of different calculations in this regard.

In this research, in order to investigate the factors affecting this displacement, three time intervals were used to evaluate the vertical displacement of the area. The results indicate that the range of studies ranged from +107 to -40 mm. Given that the amount of positive displacement (uplift) was higher than the negative displacement (subsidence) and also the tectonic factors, the main cause of the displacement can be attributed to the tectonic factors, however, other factors such as groundwater depletion can affect the rate of subsidence in the northwest and southeast of Kermanshah urban area. Evaluation results in the second time period indicate that the study area had a vertical displacement of between +22 to -46 mm during the 12 day period before and after the earthquake, which could be attributed to the short-term period. Directly attributed to the earthquake of the Ezgele. The third study period also had a range of displacements of +102 to +33 mm, but the important and significant point in this period was the impact of the earthquake of the herd on the extent and trend of displacement in the study area. In fact, the results show that in the first period, the northwest and southeast areas of Kermanshah metropolitan area have subsided and the northeast and southwest areas have risen, while the northeast Kermanshah highlands have subsided. The first time has been uplift, during this period has been associated with subsidence due to the Kermanshah Ezgele earthquake. Also, the south-eastern areas of Kermanshah metropolitan area which had subsided in the first period, due to the direct impact of the earthquake from the Ezgele, in the third period has been rising. Therefore, it can be said that the earthquake in Kermanshah plain, while changing the vertical displacement process, can affect the results of different calculations in this regard.