GIS evaluation of the vulnerability of urban housing against earthquakes using AHP (a case study of worn-out fabric of Minab city)

Dissertation for Master's Degree in the field of

Remote Sensing and Geographical Information System

Abstract

Large and active faults located in the east of Minab city are considered to be one of the most important tectonic factors in the region, which have caused numerous and severe earthquakes in the past years, and their activity may cause heavy damages in the future. Therefore, the city of Minab and especially its worn-out fabric has a high risk tolerance against earthquakes. In this research, by combining GIS and AHP and introducing vulnerability indicators, the current state of the worn-out fabric of Minab city was examined in terms of the degree of vulnerability to earthquakes, and the vulnerable areas were identified. The required data, including urban road network, uses, population density, structural characteristics, etc. were collected and prepared to create a database. Then, according to the large amount of spatial indicators, in order to obtain information for decision-making, the data was processed using GIS and AHP method, and the final map of the vulnerability of worn tissue was produced and the areas with different degrees of damage were identified. Based on this map, Sheikh Abad, Shahid Abbaspur, Pakuh, Bagh Malik, Joy Bariko and Jangjango Baft Farsodeh neighborhoods (old neighborhoods) have been identified as highly vulnerable areas. This is despite the fact that the neighborhoods of Pakuh and Bagh Malek are among the high population densities in the worn-out Baft area. The results of this research show that most of the damages caused by the earthquake are due to the worn-out and low resistance of the buildings, the smallness of the buildings and narrow passages, which indicates the need to take special decisions in order to reduce the damage and manage the crisis. In the discussion of earthquake and city, the GIS system with the ability to collect spatial and descriptive data, store, change and transform, analyze, model and display spatial information along with non-spatial information can be used as optimal science and technology in order to organize and analyze information comprehensively and quickly and to help make quick and at the same time correct decisions in crisis management.

Key words: earthquake, vulnerability, geographic information system, hierarchical analysis, worn-out fabric of Minab city.

1st chapter

Research overview

1-1. Introduction

During the 20th century, more than 1,100 destructive earthquakes occurred in different parts of the world, as a result of which more than 1,500,000 people lost their lives, 90% of which were mainly caused by the collapse of buildings that did not have sufficient engineering and safety principles (Lantada [1], 2008). As an earthquake-prone country, Iran has suffered a lot of social and economic damage from numerous earthquakes in the past decades. This is due to the fact that the cities of our country are seriously vulnerable to earthquakes of five and a half and six magnitudes (Akashe, 1378). The most important thing is to save human lives against this natural event. Urban growth creates many facilities, but at the same time, crisis-causing factors increase and environmental facilities become a loss (Nakabayashi [2], 1994). The need to reduce the social (number of casualties and injured), economic (reconstruction costs, city economy failure) and physical (destruction of buildings) damage caused by an earthquake is not hidden from anyone. In addition to the destruction of the fabric, the delay in the evacuation of the resident population, the blocking of communication networks, the increase in damages, and the burial of thousands of people alive will be other issues. Many people who are left under the rubble, if there is no way to reach them and help them, they will also lose their lives. Reducing the vulnerability of urban communities against earthquakes will happen when safety in the face of earthquakes is considered at all levels of planning, which among all the levels of the intermediate level of physical planning, i.e. urban planning, is one of the most efficient levels of planning to reduce vulnerability against earthquakes (Habibi et al., 2017). 

1-2. Statement of the problem

Earthquake is a natural phenomenon that neglecting it will result in irreparable damages. The occurrence of severe earthquakes has prompted mankind to think of developing an infrastructure plan to reduce the risks and damages caused by it.Earthquake features of the country have made earthquake as one of the most destructive factors in the destruction of human life. Historical studies show that large areas of our country have suffered human and financial losses due to this natural disaster. According to the United Nations report, in 2003, Iran ranked first among countries in the world in the number of earthquakes with an intensity of more than five and a half Richter and one of the highest ranks in terms of vulnerability to earthquakes and the number of people killed as a result of this accident. According to the same report, in Iran, earthquakes have the dominant aspect among natural disasters (United Nations Natural Disaster Reduction Organization[3], 2004). It can be said that what causes an increase in casualties in an earthquake is not an earthquake, but non-resistant or low-resistance buildings, which due to negligence, ignorance, lack of sense of responsibility in the performance of duties by construction workers, including legislators, compilers of earthquake codes and urban and urban development regulations, designers and owners, which cause such disasters in proportion to their participation in unprincipled construction (Mahdian, 1381). Iran is facing the 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 with poor materials and design in the 1960s to 1980s. 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. Earthquake features of the country have raised earthquake as one of the most destructive and threatening factors of destruction of human life. Historical research shows that large parts or areas of our country have suffered life and financial damage due to this natural accident. The city is not only a collection of buildings, but human, social, cultural, economic and physical phenomena. In this way, the city is defined as a collection of elements in order to arrive at suitable methods for evaluating the city body and determining the physical indicators of vulnerability and also providing solutions to reduce vulnerability. Quantitatively modeled the different areas of Minab city's worn-out fabric with the help of GIS?

What is the most important effective criterion in the vulnerability of Minab's worn-out fabric during an earthquake?

1-3. The importance and necessity of research

Earthquake as a natural phenomenon is a dangerous and crisis-creating time when the society exposed to the earthquake is vulnerable to it. Earthquake is one of the natural hazards that there is always the possibility of this natural event occurring, especially when the conditions for its occurrence, including the presence of many faults, are present. Determining physical characteristics, building type, physical composition of parts and roads, types of uses, population density, suitable building type, low building density, using roads as escape and shelter spaces, etc., are among the methods of reducing vulnerability (Asgari, 2018). One of the most important activities in order to reduce the risks caused by earthquakes and increase public safety is seismic zoning studies of urban areas and determining the degree of vulnerability of various buildings in the city, which should be carried out on an appropriate and optimal scale (Consulting Engineers for Texture and Architecture Designers, 2018). Due to the Minab fault, this city is important in terms of seismicity and seismological issues, and the Minab area is where Zagros Tama and Makran begin, and the amount of seismic activity is high, for this reason, a seismic network was launched in Minab. This necessity is seriously felt that by creating a suitable model and using various types of spatial and non-spatial data and performing relevant analyzes in geographic information systems and multi-criteria decision-making systems, it is possible to help evaluate and analyze the vulnerability of the city of Minab against earthquakes and, in addition to obtaining the necessary preparations against this natural hazard, manage crises caused by natural disasters in a systematic process.

1-4. Research hypotheses

GIS-based location models have the ability to model the vulnerability of the worn-out tissue area of ??Minab city.

The building age criterion is the most important factor in the vulnerability of the worn-out tissue of Minab during an earthquake.

1-5.