Analysis of the Vulnerability of Urban Decayed Textures of Kashan City against Earthquake

Due to the increasing occurrence of natural disasters in recent years around the world, especially earthquakes, and consequently the increase in losses and damages caused by earthquake in human societies, especially cities, the reduction of vulnerability against these events have particular importance. The old urban textures in developing countries, for various reasons, are at more risk of earthquake. Therefore, the understanding of earthquake crisis management principles in urban areas may be a first step in the crisis management and one of the most basic guidelines for the implementation of earthquake crisis management. Due to having numerous faults, seismicity background, and lots of old textures, Kashan is at relative risk of moderate seismicity. This necessitates taking measures in earthquake disaster management in Kashan.

This was a descriptive - analytic study in terms of methodology. Given the nature of data, this was a non-experimental research. In the first step, the data were collected studying the library various texts and documents texts on earthquake and its damage in urban areas, particularly old textures. In the next step, the data were collected by field study and using local information and statistics and information of consulting engineers and related organizations. Finally, the data were transformed to maps. In the analysis, first all the data and values of parameters were extracted. Based on Analytical Hierarchy Process (AHP) and Expert choice, the relevant indices were weighted. Using GIS software, the zoning map of district vulnerability was provided with FUZZY logic. Finally, conclusions and recommendations were provided with respect to all discussed information.

The indicators such as the type of material, age of buildings, floors of the building, access to roads, and etc. are important in assessing the vulnerability of cities to earthquake. The synthesis using GIS and multi-criteria assessment AHP methods had an effective role in vulnerability assessment. Also, it made possible the comparing of various indicators and final vulnerability with regard to different indices. The techniques used in this study can be generalized to other cities in Iran. After reviewing the different perspectives and approaches in the field of crisis management and cities earthquake vulnerability, the systematic approach was selected as the theoretical framework of research. This approach is actually originating from crisis management perspective. According to the study purpose which is reduction of vulnerability and earthquake damages, the risk reduction which is mainly related to pre-crisis was selected as policy of this study. According to studies which were conducted on desired area, it was concluded that Mohtasham, Kashan district, with its numerous fault, was among Iran’s high-risk areas. The binary comparison of indicators suggested that given its importance against earthquake, the building materials had the highest score. The experience of recent earthquakes has shown that the type of building materials used to construct is one of the important factors affecting vulnerability caused by the earthquake. In total, nine indices were used to assess vulnerability. The level of damage to buildings in this urban district was divided into five groups including very low, low, medium, high, and complete vulnerable zones.

The results showed that 10% of area had very low vulnerability, 19% had low vulnerability, 15% had medium vulnerability, 47% had high vulnerability, and 9 percent had very high vulnerability. The spatial distribution of vulnerability in area was associated with lack of using resistant materials, poor quality, and old buildings. The lowest vulnerability was in major part of texture, especially in the southeastern part of area. The crisis management includes 8 principles. Finally, the results showed that the use of crisis management principles, access to open space, and the use of forward-looking crisis management principles may greatly reduce vulnerability against earthquake risk in Mohtasham area.