The geographical location of Iran has placed many of its cities at risk from earthquakes. Lorestan, located in the western Zagros of Iran, is among the regions with high seismic risk. Positioned on the seismically active Alpine–Himalayan belt and at the collision zone between the Arabian and Iranian plates, the area experiences frequent and significant earthquakes. The central and western parts of the province are closely linked to the active Zagros faults, facing a high likelihood of seismic events. Beyond tectonic conditions, construction practices in Lorestan also contribute to increased vulnerability. Despite awareness of Lorestan’s seismicity and its history of severe earthquakes, evidence indicates that preventive measures and urban planning aligned with the existing risks have not been adequately implemented. Non-engineered buildings, substandard materials, high building density in deteriorated urban areas, and the absence of early warning systems are among the main weaknesses in reducing vulnerability.
In this study, the main data sources included 1:100,000 geological maps of the area, layers of earthquake epicenters occurring in the region between 1907 and 2023, Landsat 8 and Sentinel-1 satellite imagery, the 30-meter SRTM digital elevation model, and statistical information on the population and percentage of deteriorated urban fabric in the studied cities. The primary tools used were ArcGIS (for preparing the required maps), Google Earth Engine (for mapping urban land use and determining the percentage of open spaces), SuperDecisions (for weighting parameters using the Analytic Network Process model), and SPSS (for statistical data analysis). Based on the subject and objectives, the research was conducted in several stages. In the first stage, data layers related to the selected parameters were prepared, and after producing the layers for each parameter, the status of 11 cities in Lorestan Province (county centers) was evaluated according to each parameter. In the second and third stages, the information layers were normalized and weighted, respectively.
The analysis of earthquake epicenters show that the cities of Poldokhtar, Chaghabel, and Khorramabad have the highest concentration of earthquake epicenters and, therefore, the greatest potential vulnerability in this regard. In terms of distance from major faults, the cities of Aleshtar and Dorud, due to their proximity to main fault lines, have the highest vulnerability potential. Regarding slope, the cities of Nourabad and Dorud, with an average slope of 7 percent, have the highest mean slope percentage and thus the highest vulnerability potential for this parameter. In terms of population and population density, Khorramabad, Borujerd, and Dorud, with populations of 373,416, 264,947, and 112,638 respectively, have the highest population and consequently the highest potential vulnerability. In terms of population density, Nourabad, Aligodarz, and Borujerd, with densities of 10,254, 9,174, and 9,168 people per square kilometer respectively, show the greatest vulnerability. Regarding the percentage of deteriorated urban fabric, Borujerd (15%) and Aligodarz and Cheghabel (14% each) rank highest in vulnerability. For open space percentage, Aligodarz (13%), Dorud (14%), and Khorramabad (15%) have the lowest open space ratios and thus greater vulnerability. Additionally, in terms of compactness ratio, Borujerd, Aligodarz, and Aleshtar, with ratios of 1.24, 1.37, and 1.46 respectively, have the lowest ratios, indicating the highest compactness and greater vulnerability for this parameter.
A comprehensive assessment of seismicity parameters, distance from faults, slope percentage, population and population density, deteriorated urban fabric, open space percentage, and compactness ratio in the cities of Lorestan Province revealed significant differences in their vulnerability to earthquakes. The findings indicate that Lorestan, due to its location in the Zagros belt and proximity to active faults—particularly in cities such as Khorramabad, Dorud, and Borujerd—has a high seismic hazard potential. Khorramabad, with the highest vulnerability score (75.1), ranks first because of its high population density, closeness to major fault lines, and concentration of earthquake epicenters. Following it, Dorud (74.1) and Borujerd (72.1) show high vulnerability, resulting from a combination of natural and human factors such as high average slope, population density, and compact urban fabric. In contrast, Cheghabel (score 40) and the cities of Sarabdoreh (47) and Azna (52) exhibit lower vulnerability due to smaller populations, greater distances from main faults, and fewer earthquake epicenters. This analysis highlights that, in addition to geomorphological and seismic factors, urban physical and demographic characteristics play a decisive role in vulnerability levels. It also shows that deteriorated urban fabrics, a shortage of open spaces, and high population density significantly increase risk.