Many cities in Iran are constantly at risk of destructive earthquakes due to their location within seismically active zones. In these cities, outdated infrastructure, non-resistant buildings, and inefficient road networks amplify the potential for damage, casualties, and disruptions in post-earthquake rescue operations. To mitigate these risks, it is crucial to evaluate the factors contributing to urban vulnerability, which will help in developing effective mitigation and response strategies. This research assesses both the physical and social vulnerability of urban infrastructure in District 4 of Qom County, a densely populated and strategically important region in central Iran. The study’s findings are intended to guide future planning efforts aimed at reducing earthquake risk and enhancing urban resilience. Urban vulnerability is a multifaceted concept that encompasses a variety of physical and social components. In this study, key physical elements such as buildings, critical infrastructure, and road networks were evaluated. This evaluation also included specific components like bridges, road pavement, tunnels, and water and sewage pipelines. The vulnerability of these elements was analyzed under an earthquake scenario with a 475-year return period, a standard for seismic risk assessment.
Additionally, social vulnerability factors such as the anticipated percentage of casualties and injuries, along with population density, were incorporated into the analysis. The evaluation of building vulnerability indicates that several zones within District 4 are particularly susceptible to significant structural damage. Zones 3, 2, 9, 6, 7, 8, 16 and 17, along with parts of Zones 4 and 1, are expected to experience the most substantial destruction. This heightened risk is attributed to the high concentration of low- and medium-quality masonry buildings, many of which are older and lack proper seismic resistance. In contrast, the southern areas of District 4, including Zones 15, 14, 10, 12 and 13, feature newer construction with lower population densities. Buildings in these zones are generally of higher quality, which reduces the likelihood of severe damage or collapse during a seismic event. Zones with a higher concentration of vulnerable buildings also tend to have denser populations, leading to an increased risk of casualties and injuries. In northern District 4, where structural damage is expected to be more severe, the potential for human loss is correspondingly higher. In addition to buildings, the study also assessed the vulnerability of critical road network components, including bridges, tunnels, and road pavement. The findings suggest that one bridge in Zone 8 is at a high risk of experiencing severe damage. However, tunnels in the district are less vulnerable to collapse. The road pavement in Zones 15, 12, 10 and 14 is particularly prone to damage due to landslide risks and surface faulting, especially in Zones 10 and 12. Such vulnerabilities could lead to major disruptions in transportation, further complicating post-earthquake recovery efforts. The assessment of road blockages caused by debris from collapsed buildings revealed that the northern areas of District 4 would experience the most severe blockages, particularly in Zones 3, 16, 8, 1, 6 and 17.
This is primarily due to the high rate of structural collapse and the prevalence of narrow streets in these zones. By contrast, Zone 18, which mainly consists of low-rise industrial buildings, is expected to experience minimal road blockages. Lastly, the study examined the vulnerability of water and sewage pipelines in District 4. It was found that Zones 3 and 12 are at higher risk of pipeline ruptures due to the widespread use of long concrete pipes in these areas.
These materials are more susceptible to damage under seismic stress, making these zones particularly vulnerable to disruptions in water and sewage services during an earthquake.