Document Type : Research Article
Authors
1
Yazd University, Yazd, Iran
2
Yazd University
3
Isfahan University of Technology
Abstract
One of the most significant impacts of earthquakes is ground displacement, which plays a major role in causing both human and financial losses. Dehloran, located in the southern part of Ilam Province, is a region that is frequently affected by both small and large earthquakes. In this study, 10 Sentinel-1A radar images, both before and after earthquakes, were used to analyze the subsidence and uplift in cities, dams, and surrounding areas. To validate the results of ground displacement, pixel coherence evaluation was conducted, which indicated high accuracy in interferometric measurements. The results showed that the northern regions of Dehloran experienced subsidence, while the southern areas experienced uplift. Displacements from earthquakes with magnitudes above 4 on the Richter scale in the region were recorded as centimeter-scale displacements. This study shows that even small earthquakes can cause significant damage in this area. The findings of this research can be useful for identifying high-risk and low-risk areas to reduce damages in urban development, dam construction, and oil and gas projects.
Extended Abstract
Introduction
Ground displacement caused by natural factors such as earthquakes and anthropogenic factors like subsidence can lead to significant changes in the landscape and the occurrence of natural disasters. Dehloran, due to its oil resources and improper construction practices, is one of the most vulnerable regions to earthquakes. With the advancement of remote sensing technologies, methods like Synthetic Aperture Radar Interferometry (InSAR) have become precise tools for monitoring such changes and evaluating the extent of ground displacement. Compared to traditional methods like geodetic surveys, these technologies are faster, more cost-effective, and more accurate, allowing for large-scale monitoring of natural hazards.
Study Area
Dehloran County, located in Ilam Province in southwest Iran, is a seismic region rich in oil and gas reserves. It is the second most populous county in Ilam Province and lies 130 km from the provincial capital. Dehloran spans from 46.31°E to 48.2°E longitude and from 32.3°N to 33.19°N latitude. It is bordered by Abdanan County to the north, Iraq to the south, Khuzestan Province to the east, and Mehran County to the west. The region is also intersected by active faults, including the Mountain Front Fault, which is the primary seismic source in the area.
Results and Discussion
In this study, to estimate ground displacement in Dehloran County, 10 Sentinel-1A images were analyzed using SNAP and ArcGIS software in combination with radar interferometry (InSAR) techniques. The results of data processing showed that the northern parts of Dehloran County experienced the most significant subsidence, while the plains and southern areas showed signs of uplift.
Displacement maps from 2015, 2019, and 2020 revealed notable land surface elevation changes. In 2015, the most significant subsidence was observed in the northern parts of the county, likely caused by fault activity and seismic events. In 2019 and 2020, displacement levels initially decreased; however, in 2020, a sharp increase in displacement was recorded, again likely due to new earthquakes and reactivation of faults.
An analysis of soil types overlaid on displacement maps revealed that clay and limestone soils exhibited displacements ranging from +7 to -3 cm, while badlands showed displacements between +3 and +2 cm. These findings indicate serious implications for infrastructure and water resources, particularly in urban and rural areas located near active faults.
Conclusion
This research demonstrates that radar interferometry (InSAR) is an effective and reliable tool for estimating ground displacement caused by low-magnitude earthquakes in Dehloran County. This study is the first to investigate displacements resulting from earthquakes below magnitude 5 on the Richter scale in the region. The findings indicate that small earthquakes, despite their low magnitude, can have cumulative and significant impacts on urban infrastructure, oil and gas fields, and rural communities.
Displacements in areas such as Pahleh City and around active faults between 2015 and 2020 ranged from +7 cm to -10 cm, highlighting the vulnerability of the region’s infrastructure to seismic activity. Furthermore, the repeated occurrence of small earthquakes in various locations suggests a potential for larger seismic events and ongoing ground deformation in the future.
These displacements, particularly in sensitive zones such as oil and gas fields, carry serious risks. Therefore, continuous monitoring and reinforcement of infrastructure are essential to mitigate potential damage, especially given the ongoing threats from subsidence and active ground deformation.
Keywords
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