Document Type : Research Paper
Assessment and classification of seismic zones of the city of Tabriz with Fuzzy logic in Combining AHP and TOPSIS environment ARCGIS
Possibilities of seismicity due to geological position, tectonic condition, numerous faults in cities accompany with human factors like urban population, increase of weak urban shelters, disproportionate urban planning to earthquake disaster, have increased the seismic vulnerability of cities, as far as %90 of cities of Iran have been fragile. According to researches of National Context Plan of Iran by department of housing and urban development, Iran has been divided to very high risk, fairly medium-risk, fairly low-risk and low-risk regions, and %50 of urban population of Iran live in fairly high and high and very high-risk regions. In other words, zoning map of relative earthquake risk in Iran indicate that the majority of urban areas are in fairly high-risk range and approximately all of the country are in upper-middle-risk range and only few area of country are in low-risk region. Among the various levels of physical planning, the most efficient level to reduce earthquake vulnerability of cities, urban planning is the intermediate level. Assessment of damages or injuries directly or indirectly y are related to the adverse situation, planning and urban design. Bad condition of the physical elements and improper usages of land, inefficient city networks, urban compact, high density, the establishment of infrastructure, shortage and poor distribution of urban open spaces And the like play a vital role in increasing the amount of earthquake damage to their cities. Therefore what makes the phenomenon of earthquake disaster in cities in many cases, urban status is inappropriate. According to importance of assessment of vulnerability of cities to earthquake in Geography and Urban Planning, in this research for developing estimation of vulnerability of cities to earthquake and determination effect of each criterion in vulnerability of cities, fuzzy logic method integrating with analytical hierarchy process were used in GIS by utilizing spatial and descriptive data of elements. Physical dimensions can be regarded as the most tangible and important role in urban planning and earthquake mitigation. Body shape and the city, which includes various elements of their organization through planning and urban design takes place. This section can be through physical divisions of the city and neighborhood classification system, the communication network and hierarchy of urban centers, filled and empty levels, sectors and localities, urban signs, the block segmentation and classification of different patterns of urban, urban open spaces, population and building densities, distribution and growth of the app and the direction the city is implemented.
This research is analytic- exploratory research and according to nature of data and lack of control of effective data this research is non-experimental. Method of collecting data at first stage is Library and documentation and studying various texts about earthquake and consequent damages. The region of this study is Tabriz. According to importance of assessment of vulnerability of cities to earthquake in Geography and Urban Planning, in this research for developing estimation of vulnerability of cities to earthquake and determination effect of each criterion in vulnerability of cities, fuzzy logic method integrating with analytical hierarchy process were used in GIS by utilizing spatial and descriptive data of elements. Needed criteria were chosen by using former studies and expertise comments. At next stage weight of criteria gained by analytical hierarchy process. After that the weight of criteria transmitted to fuzzy by triangular numbers. After that, negative and positive ideal obtained by using TOPSIS model. At the end, ultimate map were prepared in GIS.
There are two subject in assessment of hazard of disasters: the method of urban planning in relation with prevention of disasters which surrounds structure and context of city because this plan is capable to determine vulnerable areas, and the other one, estimating demand of countermeasures to damages resulted by earthquake which will assumed for next earthquake. Estimating of damage, develops preparation and countermeasure after earthquake. The first one is "assessment of vulnerability of region" and former is "estimation of damage". Assessment of vulnerability of region requires data of region in small scale (geographical data). New urban development plans, regulation of infrastructures, environmental improvement and other confronting plans to disasters, can be used in relation to this topic. Totally principles of urban planning are:
For disaster risk assessment, It is necessary to prepare hazard zonation maps and geographic data about the geology, land use, population, buildings, equipment and other urban areas, urban activities. This information is updated by the GIS and has been used.
The results show according to the criteria of selection, the northern city of Tabriz has the highest risk. These areas do not have well conditions in terms of physical conditions, economic, social and cultural. And the populations of these areas are informal settlements of the city of Tabriz. As a result, attention to these areas is necessary and must take priority enabling of the regions. Due to the earthquake is inevitable in Tabriz by reviewing the past years, Probability of an earthquake is possible at any time in Tabriz, the area is about 2 percent of the area includes the city of Tabriz, As a result of, easier to plan and manage this area. North and east of the city of Tabriz with high risk are the next priority. These areas are included as an area of approximately 9 percent of the city of Tabriz. Considering that a large part of the fabric of the old city of Tabriz is located in this area, planning for empowerment in this area should also be priorities. Central and southern areas of the city of Tabriz have less risk than other areas. In whole, the city of Tabriz, the risk is high. Should be more attention to all issues that will increase the safety against earthquakes, especially the rules of construction. Compliance with regulations in 2800 Ministry of Roads and Urbanization Will lead to sustainable buildings against earthquakes.