Study of vertical displacement caused by 2019 Turkmanchay earthquake based on InSAR method

Large earthquakes are one of the most devastating natural disasters, often resulting in extensive casualties and high mortality, which are considered to be the most significant effects of earthquakes. But earthquakes, in addition to their tangible effects, also have intangible effects that may have long-term effects. In fact, high-power earthquakes cause vertical displacement of the earth by subsidence and uplift, which can adversely affect the residential areas and facilities as well as geomorphological landforms. One of the most recent earthquakes in Iran was the 5.9 earthquake on 2019/11/07 in the Turkmanchay, which caused considerable damage to the settlements in the region and was accompanied by significant vertical displacement. Vertical displacement of the area, in addition to its effects on habitat areas, has a significant impact on groundwater fluctuation, causing problems in groundwater calculations and slope ruptures. For this reason, calculating the vertical displacement rate can be very important. Different methods are used to evaluate the vertical displacement of each area that the radar interferometry is among the best methods. Therefore, the purpose of this study is to evaluate the vertical displacement caused by the Turkmanchay earthquake on surrounding cities using the radar interferometry method.
This research is based on analytical-descriptive and software methods. Research data include Sentinel-1 radar images, DEM 30m, and statistical information related to the Turkmanchay earthquake. The software used in the research also includes SNAP (pre-processing and mapping displacement rates), Snaphu (Phase Unwrapping), and ArcGIS (preparing output maps). In this research, the radar interferometry method is used to assess the displacement rate of the study area. Radar interferometry is one of the most powerful tools for monitoring the subsidence phenomenon. This method, by comparing the phases of two radar images of the region taken at two different times, can determine the changes in the surface of the earth at that time interval. The phase taken from a feature on the Earth's surface is proportional to its distance to the radar sensor. Therefore, the change in this distance affects the measured phase. In this research, Sentinel-1 images are used for radar interferometry.
The Turkmanchay earthquake occurred on 2019/11/07 near the city of Turkmanchay in Azerbaijan province. The magnitude of the earthquake was reported by various authorities from 5.8 to 6 and its depths up to 10 km. The earthquake also had 610 aftershocks, with the largest one being 4.8, and the closest cities to its hypocenter are Turkmanchay, Mianeh, Turk, Sarab, and Hashtrud. The Turkmanchay earthquake has had many tangible and intangible effects. Due to its magnitude, the earthquake has caused a lot of damage to residential areas including rural areas. One of the tangible effects of the Turkmanchay earthquake was the destruction of residential areas and facilities. The earthquake also caused considerable vertical displacement in the region, given the final map, with a range of 13 to 96 mm. Evaluation of the displacement map of the region indicates that most displacements occurred at the margin of the earthquake hypocenter and, in a general trend, the western areas of the area have experienced subsidence, with a decreasing trend toward the eastern regions and some areas were experiencing uplift.
The Turkmanchay earthquake has left many tangible and intangible effects. Among the tangible effects were the destruction of residential areas, with approximately 370 home experienced destruction of between 5 and 100 percent. Also, according to the statistics, 5 people were killed and more than 300 were injured. Among its intangible effects has been the vertical displacement of the area. The results of the evaluation of vertical displacement in urban areas indicate that the city of Sarab with a 41 mm subsidence has the highest vertical displacement. The cities of Turkmanchay, Mianeh, Hashtrud, Turk, Aghkand, and Nair experienced subsidence rates of 30, 3, 28, 18, 14 and 32 mm respectively. In addition to residential areas, geomorphological units have also witnessed a displacement, which can be very important. One of the units where the vertical displacement is very important is the lowland area where the final map shows that the Turkmanchay, Sarab, Hashtrud and Nair plains have been subsided and the Mianeh plain has been uplifted. The vertical displacement in the plains of the area can be effective in fluctuating groundwater and making it difficult to calculate various parameters including the groundwater level drop. Another effect of vertical displacement is the impact on slopes. Given that much of the area is covered by the mountain unit, this displacement can  intensify slope movements in the coming years.