Cities they have not been safe from damage to natural and man-made disasters throughout history. One of the issues that most people face, especially the human settlements in the world's major cities, is the issue of natural hazards. An earthquake generates many financial and financial losses everywhere in the world. Earthquake damage to life and property every year creates a lot in different parts of the world. Since Iran is considered as the world's most seismic region, the need to confront this phenomenon is strongly felt. One of the secondary effects of the earthquake is liquefaction. Liquefaction caused serious damage to many structures especially buildings and residential areas. In addition to the low quality of buildings, Tehran's location on important faults and the presence of earthquake-induced liquefaction phenomena due to high water levels in some parts of southern Tehran have increased the vulnerability of urban areas against earthquakes. Most of Tehran's soils are alluvial and sandy soils due to lack of sewage channels and rising water levels, especially in the southern part of the study area, forms a loose, sandy and saturated water layer due to the earthquake of this layer. The earthquake of this layer is dumped and tilted into a building that is not damaged even by the earthquake's horizontal force.
Yasuda and Hashimoto discussed the damage caused by liquefication in residential areas during the Great Japanese earthquake in 2011 and reviewed the pattern of land improvement in damaged areas and the effects of reducing groundwater levels in damaging residential properties. In this study, we have tried to consider, in addition to considering the parameters that affect vulnerability (ground and underground factors), The groundwater surface parameter and its effects on the liquefication and vulnerability of the buildings are examined. The main objective of this study is to prepare a map of seismic vulnerability of urban buildings in three areas of Tehran and to study the effect of groundwater level using two groups of physical parameters (with underground and without underground factors) and human parameters.
Methodology
The study area in this study is 11, 16 and 20 municipalities of Tehran. These areas have been selected since the height of water varies between the northern and southern regions. In order to prepare a seismic vulnerability map emphasizing the level of groundwater aquifers, at first, three different types of building vulnerability criteria were extracted using library and documentary studies and experts' opinions. Indicators were determined and collected, then data were prepared and a number of criteria were prepared based on the type of indicators (land, underground, human) 15 output map provided. Then to apply the mathematical model of the base set for each of the three sections, separate rules were written. In general, 25 laws have been extracted and the rules have been correctly segregated. After applying the rules and combining the data used in accordance with the correct rules extracted, 3 output maps were obtained. The compilation of these maps by Rough method provides a final map of the physical seismic vulnerability of three districts in Tehran. In this research, in order to investigate the uncertainty of the theory of rough collections (Rough Set Theory) in determining the seismic zoning of urban buildings in three areas of Tehran, taking into account human factors, ground and underground factors with emphasis on groundwater level and thus, the seismic vulnerability of urban buildings is modelling.
Results of its implementation and analysis
One of the goals of this research is to reduce uncertainty in parameters, which causes uncertainty in the issue of determining seismic vulnerability. The output of seismic vulnerability maps shows that although the vulnerability map is based on the Rey fault active scenario, However, considering the underground factors in estimating the vulnerability of the parts of the north and part of the southwest of the region are highly vulnerable. This is due to the geology and soil of the studied area, including old river alluvial and dense sand. Also, from the north to the south of the region, the depth of the groundwater level decreases, which makes it possible to transfer the vulnerability from north to south and to a large part of the center, south, and south-east of the study area by adding the groundwater depth parameter.
Conclusion
In this paper, considering the underground factors and the effect of the parameters of groundwater depth, along with other parameters of the vulnerability level in three areas of Tehran, was estimated. The results of Physical vulnerability without underground water indicate that 40% of buildings have a very low vulnerability, 26% of buildings have moderate vulnerability and only 10% of the buildings are a high vulnerability. In the event that results of the physical vulnerability to underground water show that only 2% of the buildings have a very low vulnerability, 15% of the moderate vulnerability and 60% of the buildings are a high vulnerability. By adding the parameter, the depth of the surface of groundwater vulnerability in the large part of the center and south of the study area has expanded and has increased significantly in all domains. After implementation of the Rough Model, 25 correct rules were extracted from the available information, and a seismic vulnerability map was developed in three areas of Tehran. The results of the region's final vulnerability indicate that 6 percent of urban buildings encounter very low vulnerability, with more metal skeletons, 20% of the buildings in the area are low vulnerability, moderate vulnerability group is 39% of the buildings, 19.9% of the buildings in the area are high vulnerability and 13.8% very high vulnerability.