Document Type : Original Article
1. Introduction
Earthquakes represent one of the most devastating natural hazards, posing serious risks to urban communities. Iran’s geotectonic positioning within a major seismic belt renders the country particularly vulnerable to frequent and high-magnitude seismic events. The metropolis of Shiraz, surrounded by active fault lines such as Zarghan and Qalat, faces considerable seismic exposure. Among its administrative districts, District 4 is especially susceptible due to specific physical, social, and infrastructural characteristics. This study aims to evaluate the housing vulnerability of this district using multi-criteria analysis and spatial modeling within a GIS framework. The ultimate goal is to support crisis management planning and offer targeted strategies to mitigate risk in this densely populated urban sector.
2. Materials and Methods
The research is an applied research study utilizing a descriptive–analytical methodology. Data collection encompassed field surveys, urban maps, demographic statistics, and literature reviews. Spatial analysis was conducted using the Analytical Hierarchy Process (AHP) in combination with GIS tools. Key indicators included plot enclosure ratio, number of building stories, structural density, construction quality, material type, parcel dimensions, land-use adjacency, and access network configuration. Each criterion was standardized, weighted, and incorporated into an Index Overlay model to generate a seismic vulnerability map. The final output categorized the residential blocks into five classes: very low, low, moderate, high, and very high vulnerability.
3. Results and Discussion
Findings reveal that over 57% of building plots in District 4 fall within the "high" and "very high" vulnerability categories. Northeastern and western sub-zones, especially the Keshan neighborhood, exhibit elevated risk due to narrow street widths, non-engineered materials, irregular parcel layouts, and aged urban texture. Conversely, planned developments such as Valfajr Town, Kouy-e Farhangian, and other large-scale residential complexes benefit from durable construction, standardized networks, and organized layouts, placing them in lower-risk zones. Age analysis showed that 18% of buildings are older than 22 years, many constructed with low-durability or traditional materials (e.g., adobe and timber). These structures present heightened collapse risk. Social indicators such as household density (1.19 households per unit) and room occupancy rate (1.23 persons per room) further compound evacuation and emergency response challenges during an earthquake.
The district's access network is largely fragmented, with narrow, dead-end streets and corridors less than 6 meters wide. These access constraints magnify the difficulty of post-disaster rescue operations. The enclosure ratio, defined by the height of building facades relative to street width, is also notably high in older areas, reducing visibility and obstructing relief logistics. Land-use adjacency analysis revealed that residential blocks are in close proximity to hazard-prone zones such as industrial facilities, fuel stations, and critical infrastructure. This spatial incompatibility increases the likelihood of secondary disasters (e.g., fire, gas leakage). Moreover, the district displays an overall spatial heterogeneity in its urban morphology, where organic, fragmented, and large-scale patterns co-exist without a unified planning framework, a condition referred to in urban planning terminology as spatial discontinuity or uneven spatial distribution. Such inconsistencies elevate systemic risks and undermine urban resilience.
4. Conclusions
District 4 of Shiraz presents a high level of seismic vulnerability, particularly in older residential sectors characterized by irregular form, dense population, and inadequate access infrastructure. To reduce potential damages from future earthquakes, the following strategic interventions are recommended:
This research underscores the utility of multi-criteria spatial modeling in GIS environments as a robust decision-support tool for urban crisis management and resilient planning.