The Strategies for Vulnerability Mitigation of Residential Context against the Earthquake (A Case Study for 6th Region of Tehran City)

Introduction The hazards management is required in urban planning to reduce human death and casualties resulted from natural and human hazards. Urban vulnerability evaluation based on different dimensions of the factors is important ro determine hazard degree. It can reduce physical frame and socio-economic damage. The vulnerability analysis showed that there are different relations among social, biologic and physical processes which affect the society, namely population growth, urbanism, economic forces and environmental destruction. The research related to vulnerability has a vast range of different hazards in various scales. There are different categories pertaining to vulnerability which help to understand the various aspects of vulnerability. There are three aspects of vulnerability including bio-physical or confronting to hazards, social vulnerability (community and human oriented) and combined aspect. Disharmonic and irregular development in Tehran city together with its establishment in the vicinity of fault and unstable lands will cause enormous losses in the occurrence of a severe earthquake. As the region 6 of Tehran has a centrality in the city and presence of ministries, embassies, higher educational institutes, health centers and general hospitals, large economic companies makes it an important region in the country. In this study, the evaluation of earthquake vulnerability was conducted according to vulnerability of building, residential texture, habitation, physical frame and social and human dimensions. In this regard, the most important research questions are: How was the spatial distribution of vulnerability in physical frame in the region? What were the strategies for reduction of vulnerability of physical frame against the earthquake in the region? The purpose of this research is to introduce strategies for reduction of vulnerability of residential texture in region 6 of Tehran against the earthquake.   Methodology In order to find out the vulnerability reduction strategies, the method is conducted in two stages. In the first stage, the vulnerability of residential texture was investigated in different dimensions including building, habitation, physical frame, and social and human aspects. Statistical population was family heads of the region 6 which were 331 families according to the proportion of population of the region. The measurement was conducted by questionnaire and the validity was approved by experts. The validity of awareness, preparedness and reaction against the earthquake were 0.682 and 0.792. The ideas of the experts were used two times in this study. Firstly, we used the opinions of 9 academic people, 4 PhD students in geography and urban planning, 5 academic persons and 3 PhD students in municipality engineering and 3 academic people and 3 MSc students in disaster management. The opinions were used to calculate the weights for FUZZY AHP models. Secondly, the opinions of 6 academic people in geography, 3 academic people in municipality engineering, 5 people in disaster management and 8 people from municipality in different districts of the region 6 of Tehran city were also used to determine strategies for vulnerability reduction. FUZZY technique and Kriging interpolation method were used to evaluate vulnerability and spatial analysis, respectively. In addition, Fuzzy AHP was used to determine the importance of the factors employed and the total vulnerability in the region for five dimensions. Results and discussion The building, habitation, physical frame, social and human dimensions were analyzed to make a zonnation of vulnerability. The results showed that the vulnerability of the Amirabad, Nosrat, Ghezel Ghaleh, University of Tehran and Laleh Park districts were from 0.60 to 0.73 (48 percent out of 100) as the low vulnerability. The values for Shariati, Argentina- Saei, Behjatabad and Gandi districts were ranged from 0.4 to 0.60 (45 percent out of 100) as moderate vulnerability. In the second phase, to recognize vulnerability mitigation strategies, we declared strength, weakness, opportunity and threat using questionnaire for the 22 experts and academic people. Eventually, the strategies of vulnerability mitigation were recommended by SWOT model for the region. The results revealed that the final score was 2.57 for interior factors. Relative stability of building structures has a weight of 0.296, proper distance from the major ways has a weight of 0.284, regular texture and penetrable transit network and proper distance from tributary ways has also a weight of 0.264 as the most important strength points. In addition, the high density of population with a weight 0.112, oldness of buildings with a weight 0.065 and the high percentage of built relative to the surfaces were recognized as the most important weakness points. The final score in the matrix of exterior factors was 2.514. When the score was less than 2.50, it indicates the favorable conditions to reduce vulnerability of physical frame against earthquake. Moreover, the total scores of opportunities and threats were 1.866 and 0.628, respectively. The most important opportunities were high number of educational centers with a 0.156 score. The attitude of respondents to the role of collection and improvement regulation for reduction of earthquake hazard impacts is scored0.152. The tendency for participation in educational courses to prepare against earthquake and the evacuation of the region at night is also scored 0.148 by the respondents.   The most important threats were destruction of equipment house with a 0.068 weight, access to first aid box and fire extinguisher with a 0.066 weight, and the existence of installation networks in the region with a 0.064 weight.   Conclusion According to cross matrix elements of SWOT analysis, the aggressive type strategies can be selected for this study area. Accordingly, the most important strategies were as follow: 1. Extending the buffer zone for national and transnational buildings due to high density of population in the region for reduction of probability hazards, 2. Widening the passages according to buildings function and density, 3. Transferring vital centers to the places in the vicinity of crisis management center, and 4. Increasing the public awareness to understand damage for enhancing rescue actions.