عنوان مقاله [English]
Earthquake Risk and Assessment on the Texture of Informal Settlements in Tabriz Using ELECTRE FUZZY Method and Geographic Information System (GIS)
According to the latest UN report, the global population in 2018 was 6.6 billion and the urban population 4.2 billion. By 2050, the global population will reach 7.9 billion and 68 percent of the population will live in urban areas (2020, Liquan et al). The rapid increase in urbanization is leading to the growth of informal settlements in high-risk areas such as landslides, increasing the risk among low-income populations. Although technical and social methods of earthquake risk management are known, in underdeveloped countries these measures are often difficult for complex social, economic, political, and institutional reasons (Smith et al. 2020). The growing trend of urbanization in underdeveloped countries and the housing crisis causes an increase in Halabiabad and the construction of housing without the necessary urban development standards (Valizadeh Kamran et al., 2013). Since informal settlement arises from a context larger than its location and also affects a larger environment, the solution to this problem requires policy and action not only at the small level, but also at the large level (Hakimi and Et al., 1397). Because informal settlements are of relatively poor quality and do not use earthquake-resistant designs, they are expected to be highly vulnerable to earthquakes. In addition, these settlements often occupy areas with a high seismic risk, which may cause landslides and fluids. Hence, hazard and vulnerability pose a significant seismic hazard (2008, et al Castillo).
This study is descriptive-analytical in terms of method and its purpose is applied. To collect data in this study, written documents, statistical data, visual documents and field studies have been used. Also, topographic maps were 1.25000, geological maps were 1.100000, urban maps were 1.000, digital elevation model (DEM) ten meters, main and secondary fault maps and land use maps were used in the research. In the present study, in order to explain the vulnerability situation caused by earthquake risk in informal settlements of Tabriz, a list of criteria was extracted based on the research background and according to the available data, 13 criteria were selected. In order to weight the indicators, the fuzzy model has been used and to rank the indicators and variables, the ELECTRE FUZZY model has been used. Finally, weighted parameters were put into a function to determine the vulnerability of informal settlements in Tabriz using GIS software. • Introduction of variables and indicators.In this study, in order to investigate the risk and risk of earthquake on the context of informal settlements in Tabriz, thirteen indicators have been used, which shows the flowchart Figure 2 of the indicators and research stages.
• Data fuzzy
Fuzzyization is done directly or using algorithms and logical expressions. In the present study, two methods, direct calculation and expert calculation, have been used to fuzzy numbers. In expert calculation, first the range of changes of each parameter is determined, then, according to previous researches, and finally, they are weighted manually, based on reality and according to experts. In order to create fuzzy sets, mathematical functions such as sigmoidal linear threshold, S-shaped, hyperolithic, etc. can be used. • ELECTRE FUZZY method.
• ELECTRE FUZZY method
The ELECTRE method is one of the most widely used decision-making methods. The ELECTRE FUZZY method is used to consider its uncertainty and to complete the decision performance array. ELECTRE technique means the method of cleaning and selection in accordance with reality. One of the most important compensatory techniques, based on the concept of non-ranking, the answer of this method is based on a set of rankings. This method does not lead to non-ranking relationships, ie it does not necessarily lead to the classification of options but may eliminate options. In this model, all options are evaluated by non-rank comparisons and pairwise comparisons are based on the degree of agreement of the weights and the degree of difference of the weighted values.
The calculation steps of the mentioned method are as follows:
Formation of fuzzy decision matrix- Normalization of the decision matrix- Formation of a normal weighted matrix- Calculate the distance between both options- Build an agreement set and create an agreement matrix- Formation of Boolean matrix agrees- Build the opposite set and create the opposite matrix- Formation of opposite boolean matrix- Formation of the final matrix- Final ranking of options.
Investigating the situation of informal settlements in Tabriz in relation to the occurrence of a possible crisis will play a vital role in efficient management in the event of a crisis. Due to the large fault zone in the city of Tabriz, the informal settlements of this city are often at risk of earthquakes. In the study area, due to high population density, the use of low quality buildings, small parts, etc. during an earthquake, the effects of the disaster will be irreparable. Therefore, determining the vulnerability of informal settlements in Tabriz to earthquakes is of great importance. Which will play a vital role both in planning for resilience and in managing crisis and emergency housing. According to the findings of the present study, the fuzzy electrode method and its integration with GIS has the ability to integrate information with different structures. Therefore, in the present study, data analysis was performed using fuzzy electr model and GIS. The results of the fuzzy electrode method calculations indicate that the informal settlements located in region 3 will experience the lowest vulnerability with a rank of 1, while the informal settlements located in regions 1 and 10 with a rank of 5 will have the highest vulnerability. They will experience vulnerability to earthquake risk. Also, more than 34% of the area of informal settlements in Tabriz is exposed to very high vulnerability and more than 27% are exposed to high vulnerability and more than 25% are exposed to moderate vulnerability and only 12.69% of the texture of settlements Unofficially, the city of Tabriz is exposed to low vulnerability to earthquake risk. In terms of vulnerability spectrum, informal settlements in zones 1 and 10 are in the very high range, informal settlements in zones 7 in the wide range, settlements in zones 4 and 5 in the high to medium range, and informal settlements. Located in Zone 3, they are in the medium to low vulnerability range. Informal settlements located in areas 10 and 1, which are in a very high range of vulnerabilities, include neighborhoods (Yousefabad, Silab, Mola Zeinal, small spring, large spring, Loti Ibrahim, Ahmadabad, Beheshti, 40 meters, Ismail Baqal, Ghorbani, Idelu, Khalilabad). These neighborhoods have the highest population density and fine-grained texture, most of them do not have strong buildings and are built without proper planning, and in terms of the passage parameter, they have narrow and narrow passages. And have mostly spread in the area of North Tabriz fault. Therefore, increasing the values of parameters such as population density, building quality, distance from the fault, building density, etc. have caused informal settlements located in these neighborhoods to be in a very high range of vulnerabilities. In general, it can be concluded that if the construction is properly managed and the rules of 2800 earthquake regulations are strictly observed in the informal settlements of Tabriz, we will see a decrease in earthquake hazards.
Informal settlement; Earthquake; Risk; Baft; Tabriz