Document Type : Research Article
Authors
1
Yazd University, Yazd, Iran
2
Yazd University
3
Isfahan University of Technology
10.22067/geoeh.2025.85880.1443
Abstract
Title: Investigating the Ground Displacement Caused by Earthquakes Using Radar Interferometry: A Case Study of Ilam Province and the Mountain Front Fault
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.
Keywords: Dehloran, Radar, Earthquake, Displacement, Fault, Sentinel-1
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, is one of the vulnerable regions against earthquakes. With the advancement of remote sensing technologies, methods like Synthetic Aperture Radar Interferometry (InSAR) have become precise tools for monitoring these changes and evaluating the extent of ground displacement. Compared to traditional methods like geodetic surveys, these technologies are faster, cost-effective, and more accurate, allowing for wide-scale monitoring of natural disasters.
Study Area: Dehloran County, located in Ilam Province, southwest Iran, is one of the seismic regions with abundant oil and gas reserves. It is the second most populous county in Ilam Province and is situated 130 km from the provincial capital. Dehloran spans from 46.31°W 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 also hosts 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, SNAP and ArcGIS software, and radar interferometry (InSAR) were utilized. The results from data processing showed that the northern parts of Dehloran County had the most significant subsidence, while the plains and lower regions experienced uplift. In the years 2015, 2019, and 2020, displacement maps of the land surface elevations showed significant changes. In 2015, the most substantial subsidence was observed in the northern sections of the county, likely due to fault movements and seismic activity. In 2019 and 2020, displacement changes gradually decreased, but in 2020, a significant increase in displacement was observed, likely due to new earthquakes and active fault movements. Additionally, soil types were analyzed on the displacement maps, showing that clay and limestone soils experienced displacements ranging from +7 to -3 cm, while badlands experienced displacement between 3 and 2 cm. These results indicate significant impacts on the region's infrastructure and water resources, especially for urban and rural areas near faults.
Conclusion:This research shows that radar interferometry (InSAR) is an efficient tool for estimating ground displacement caused by small earthquakes in Dehloran County. This study is the first to investigate displacements caused by earthquakes with magnitudes less than 5 on the Richter scale in this region. The results indicated that small earthquakes, despite their low magnitude, can have significant cumulative effects on urban infrastructure, oil and gas fields, and rural areas. Displacements in areas such as Pahleh City and around faults between 2015 and 2020 ranged from +7 to -10 cm, highlighting the vulnerability of infrastructure to these displacements. Moreover, the impact of repeated earthquakes in various areas suggests the possibility of larger earthquakes and ongoing ground displacement in the future. These displacements, especially near faults and sensitive areas such as oil and gas fields, have serious implications. Therefore, continuous monitoring and strengthening of infrastructure in this region is critical to prevent potential damages, especially in the face of threats from subsidence and ongoing ground level changes.
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