عنوان مقاله [English]
Earthquake risk analysis on the context of informal settlements in Tabriz using WASPAS model and geographic information system (GIS)
Today global population growth has led to the rapid development of urbanization and the growth of informal settlements. These settlements are often developed in areas that are exposed to hazards such as earthquakes. Although technical models of earthquake management have been identified, but in third world countries due to social, economic and ... complexity, these measures are often associated with many problems (Smith et al. 2020: 67). Addressing vulnerability in informal settlements where severe natural disasters pose multiple risks to millions of people is critical. Understanding the effects of adjustment and adaptation strategies in the housing sector helps decision makers to choose options that improve the quality of life and reduce development and equality gaps in cities. Adaptation measures such as hazard mapping, development of early warning systems (EWS), preparedness plans and preventive risk strategies, especially in informal settlements, can support decision makers and stakeholders in reducing exposure and vulnerability to potential earthquakes. Kend (2018, Emma Purio et al) Catastrophic natural hazards, such as earthquakes, are serious threats to human life in informal settlements. Therefore, assessing the degree of probability and vulnerability in disaster management is necessary in order to manage the city and help decision makers to recognize the impact of various factors and understand the deficiencies in each area, appropriate guides are necessary. The critical condition of buildings and their zoning in terms of vulnerability should be included in government observations and risk reduction programs should be improved. The lack of distribution of suitable space inside the city and improper planning of urban development can be dangerous factors in the future (2020, Ratiranjan et al).
Methodology: The method of this research is descriptive-analytical and its purpose is applied. The data used in the research are: statistical block, geological map, topographic map of 1.25000, digital elevation points of ten meters, fault map of the area, land use map of the studied area and field studies. Also with the aim of determining the vulnerability of informal settlements in Tabriz due to earthquake risk indicators (width of passage, quality of buildings, material, number of floors, distance from public open space, distance from urban facilities, distance from medical centers Population density, building density, distance from the fault, geological type, plot area, land use) were selected as the final criteria according to the possibility of data access. Also, in order to analyze the data, GIS ARC software and WASPAS model, which is one of the newest and most efficient ranking methods, have been used.
WASPAS technique: The Vaspas technique was announced by Zavadskas in 2012 (Zavadskas, 2012). This method is one of the relatively new methods of multi-criteria decision making with very high accuracy, which is actually derived from two models (total weight model) and (weight multiplication model) (Zavadskas, 2012).
The calculation steps of the mentioned method are as follows:
Forming a decision array according to the current situation.
Calibrate and deregulate the decision array.
Calculate the weight of each criterion using one of the weighting methods such as Shannon entropy, AHP or ANP
Estimation of veriəns values of standardized criteria.
Calculate the relative veriəns of the samples and determine the values of the eigenvectors.Perform the final ranking.
Results and discussion:In order to form a matrix (options and criteria) in the WASPAS technique, the options must be specified. Therefore, the areas where the informal settlements of Tabriz are located were considered as WASPAS model options. (Option 1 includes informal settlements in Zone 1, option 2 includes informal settlements in Zone 3, option 3 includes informal settlements in Zone 4, option 4 includes informal settlements in Zone 5, option 5 includes informal settlements Located in Area 7, Option 6 includes informal settlements located in Area 10). In the next step, the values of each criterion for each option were determined. Finally, based on the mentioned relations for WASPAS technique, calculations were performed in MATLAB software environment, the results of the mentioned model are presented in Table 2.
The weights assigned to each of the criteria are normalized and are presented in Table 2. According to the table above, informal settlements in District 10 are ranked first in terms of vulnerability, and settlements in District 5 are ranked 6th. Therefore, according to the results of the table above, the most vulnerable informal settlements belong to District 10. In the next step, the changes in the weights measured according to the research technique were analyzed on each of the research indicators. Therefore, all research indicators were extracted in terms of vulnerability and maps related to each of the parameters were produced (Figure 2).
Analyzing the situation of informal settlements in Tabriz in the face of a possible crisis will play an important role in proper management during a crisis. Due to the fact that there is a large fault area in the city of Tabriz. Therefore, its informal settlements are always at risk of earthquakes. substandard materials, etc. in the event of an earthquake, the effects of the disaster will be irreparable. As a result, determining the vulnerability of informal settlements in Tabriz to earthquakes is of great importance. Which will play a very important role both in terms of planning for resilience and in terms of crisis management and providing emergency accommodation. The findings of the present study indicate that the WASPAS model and its integration with GIS can integrate layers with different structures. Accordingly, in this study, data analysis was performed using WASPAS and GIS techniques. The results of the WASPAS technique indicate that informal settlements in District 5 will have the lowest vulnerability in the event of an earthquake with a rank of 1, but informal settlements in District 10 with a rank of 6 will have the highest vulnerability. Also, more than 57% of the area of informal settlements in Tabriz is exposed to very high vulnerability and 11.05% is exposed to high vulnerability and 03.27% is exposed to moderate vulnerability and only 4.01% of the informal settlements in Tabriz They are at low vulnerability. Also in terms of vulnerability spectrum of informal settlements located in zones 10 and 1 in the very high range, informal settlements located in zone 7 in the high to medium range, then informal settlements located in zone 3 in the medium range And informal settlements in zone 4 are in the medium to low range and informal settlements in zone 5 are in the low to medium range of vulnerabilities. Due to the location of the study area in the zone with high earthquake risk, to deal with any hazards caused by these hazards, construction must be done in accordance with the 2800 earthquake regulations. Also, the use of durable materials such as steel frame or reinforced concrete will reduce the risks of earthquakes.
Informal settlement؛ earthquake؛ risk؛ texture؛ Tabriz