Assessing vulnerability caused by earthquakes using RADIUS model, multi-criteria decision making systems and GIS (case study of Yazd city)

Introdution
The occurrence of severe earthquakes has prompted mankind to think of developing an infrastructure program to reduce the risks and damages caused by it. The purpose of this research is to investigate the damages caused by the earthquake in Yazd using the RADIUS model and the hierarchical analysis process in the GIS environment in the proposed scenarios.
According to the United Nations report, in 2003, Iran ranked first among countries in the world in the number of earthquakes with an intensity greater than 5.5 on the Richter scale and one of the highest ranks in terms of vulnerability to earthquakes and the number of people killed. As a result of this phenomenon, [4].
The country of Iran with seismic vulnerability of certain groups of constructions such as: public buildings with non-reinforced construction materials, old densely populated buildings in urban centers, dilapidated structures, residential houses and concrete structures that were built in the 1960s. Until 1980, they faced poor design and materials [1]. Cities are places of population gathering and increasing environmental and economic loads, the existence of this important issue raises the need to reduce vulnerability to earthquakes.
According to the earthquake risk zoning map of Iran, the city of Yazd is located in a zone with a relatively low risk, however, due to the existence of earthquake faults in the province that can affect this area and the city of Yazd. Assessing its vulnerability using effective and appropriate models is one of the essentials of urban crisis management. It should be stated that the research that has been done in relation to earthquake and its risk assessment has mostly examined the earthquake in the city with spatial data and based on multi-criteria decision-making models and about buildings, but in this research, the combination of RADIUS and AHP models. Used. So far, many analyzes and evaluations have been carried out in connection with damage estimation and earthquake vulnerability assessment, each of which has used multiple models and methods according to goals and assumptions.
Materials and methods
The type of research in this study is applied and the research method is qualitative-analytical. The data collection for this research is mainly based on field observations, including the collection of the desired features about the city's structural and physical features, and in the form of a library, including the use of 1:2000 city maps and satellite images to update the maps and also use From the available statistics and information related to the subject of research, it has been done.The data used in this research includes population density, road network, number of floors, slope, position relative to the fault, type of structure and age of the building, ArcGIS and RADIUS software were used.
Discussion and results
The results of damage estimation due to earthquake in Yazd city
To estimate the damage caused by the earthquake in Yazd city using AHP and TOPSIS models, initially RADIUS model was used to design the earthquake scenario and calculate the intensity of the earthquake in different parts of the region, to calculate the intensity of the earthquake in different parts of the region, Yazd city to The equal network, 2000 meters by 2000 meters, the division and the information required by the program, separately for each network, entered the software.
Estimating the vulnerability of buildings and their distribution in the region based on the scenario of the Anar  fault.
The results indicate that 21% of cities will suffer heavy damage, 31% will suffer significant damage, 33% will suffer moderate damage, and 27% will suffer low damage. The most damage is related to area two and part of area one. Another problem of these types of tissues is their inappropriate and limited access, which makes it difficult to provide relief. The least amount of damage is related to the third area.
Estimation of the vulnerability of buildings and their distribution in the region based on the Mehriz Taft fault scenario
The amount of damage in this scenario is higher than the previous scenario. The results indicate that 38% of the city will suffer heavy damage, 32% will suffer significant damage, 20% of the city will suffer moderate damage, and 11% of the city will suffer low damage. Most of the damage is related to area two and a part of area one.
Conclusion
One of the most important concerns of city officials is reducing the effects of earthquakes among city residents and urban environments, both before and after its occurrence. In this regard, it is essential to identify urban areas vulnerable to earthquakes.
 Examining the results of the earthquake damage estimation in the study area based on the two developed scenarios, indicates that the most damage to the area will be caused by the Mehriz-Teft fault in the area. According to the indicators and models used during the earthquake, the most vulnerable area will be the two-city area of ​​Yazd.
 Due to the fact that the city of Yazd has the possibility of facing an earthquake due to its geographical location and existing faults, and in the meantime due to the existence of many faults near and inside the city, the vulnerability of this city to the risk of earthquake increases. Another case is the presence of old and automobile structures in the two cities of Yazd, which have little stability against earthquakes, and another problem is their inadequate and limited access, which makes it difficult to provide relief to their residents after an earthquake and can become critical. The situation provoked a human disaster.