Evaluation of vulnerability of metropolitan gravity centers of Tabriz from the perspective of passive defense

The main objective of this research is to identify and provide a solution for the vulnerable infrastructure of Tabriz city from the perspective of passive defense. Therefore, this research is a type of applied-developmental study with a descriptive-analytical method. Data was collected using library sources and a supplementary questionnaire filled by 20 experts in the fields of architecture, urban planning and passive defense. The findings of the research indicate the desirable condition of passive defense safety considerations in providing suggestions. The research planning process is as follows: 1. The quantitative model for determining the levels of the centers of gravity of the Metropolis of Tabriz shows that, from the total 32 infrastructures, 17 infrastructures are classified as vital and critical infrastructures and 15 are classified as important and maintainable centers, representing the significant number of vital and critical centers. Creating a large number of vital and critical centers instead of a single critical center and increasing the distribution of important centers in the city to promote the security of the city against military attacks are regarded as key issues in the discussion of damages and threats in passive defense. 2. According to the quantitative threat model in Tabriz metropolitan area, the threat of missile and airborne strikes were selected as the base threat: 20 centers of gravity out of the total of 32 centers are at stake of this threat, indicating the predominance of this threat on the assets of the city. Therefore, missile and airborne strikes were considered as a major threat in the modeling, network analysis and layer standardization in the GIS environment. 3. The final map of the vulnerability of the metropolitan areas of Tabriz drawn using fuzzy overlapping functions in the ARC_GIS environment with 22 effective indexes in the form of five criteria (vital arteries, crisis management centers, military and police centers, urban facilities and support centers), the basic threat of airborne and missile attacks and coefficients of the criteria and indexes obtained from the Super Decision analysis software model show that the vulnerable zones of Tabriz are classified into five levels: The area with very low vulnerability is 13.7%, the low vulnerability area is 9.5%, average vulnerability area is 23.5%, high vulnerability area is 32.3%, and extreme vulnerability area is 21% of the total metropolitan area of Tabriz, which is in contradiction to the principles of passive defense and increases the spatial vulnerability of the city. It is therefore necessary to develop a strategy based on passive defense principles to reduce the vulnerability of the city. 4. According to the average model, the nearest neighbor, the average expected distance between infrastructures of Tabriz metropolitan area is 455 meters, but the average infrastructural gap is 264 meters. The ratio of the nearest neighbor is 58%, showing the cluster distribution of Tabriz city centers. This ratio is in contradiction to the principles of passive defense and exacerbates the spatial vulnerability of the city. It is thus necessary to apply the principle of dispersion of passive defense regarding centers of gravity in Tabriz. 5. According to the SWOT model, the results of evaluating the strengths and weaknesses of internal factors by studying and identifying critical centers in Tabriz metropolitan area indicate that the city’s weaknesses are more than its strengths. Therefore, drawing on the strengths, some strategies must be used to reduce vulnerabilities caused by the weaknesses and threats of the city.