ارزیابی میزان آسیبپذیری بافت‌های شهری در برابر زلزله مطالعه موردی شهر کرمانشاه
محورهای موضوعی : شهرسازی اسلامی
ایرج تیموری
1
*
,
هادی حکیمی
2
,
رحیم حیدری چیانه
3
,
آرام حمیدی
4
1 - دانشیار جغرافیای برنامه‌ریزی شهری دانشگاه تبریز، ایران
2 - دانشیار جغرافیای برنامه‌ریزی شهری دانشگاه تبریز، ایران
3 - دانشیار جغرافیای برنامه‌ریزی شهری دانشگاه تبریز، ایران
4 - دانشجوی دکترای جغرافیای برنامه‌ریزی شهری دانشگاه تبریز، ایران
کلید واژه: آسیبپذیری, زلزله, کرمانشاه, تحلیل سلسله مراتبی, GIS,
چکیده مقاله :
زمین‌لرزه ویرانگر‌ترین و مرگبار‌ترین رخداد طبیعی است که کشور ایران نیز با عنایت به وضعیت ویژه تکتونیکی در بیشتر نواحی خود با آن مواجه است. در میان مناطق زلزله‌خیز ایران، منطقه چین، گسل زاگرس که کلانشهر کرمانشاه نیز در آن واقع شده به‌عنوان بخشی از کمربند کوه‌زایی آلپ، هیمالیا از نواحی فعال و با احتمال وقوع زلزله با شدت بالا است. شهر کرمانشاه به‌عنوان بزرگ‌ترین کلانشهر در مرکزیت غرب کشور به لحاظ سیاسی، اجتماعی، اقتصادی و جمعیتی دارای تأثیر منطقه‌ای بسیار است، این کلانشهر به سبب وضعیت نامناسب کالبد شهری، در صورت رخداد زمین‌لرزه به‌شدت آسیب‌پذیر گردیده و احتمال بروز مشکلات و وضعیت بحرانی در آن بسیار خواهد بود. لذا ارائه روش‌هایی نظام‌مند و کارآمد جهت استفاده در مدیریت بحران به‌منظور کاهش میزان آسیبپذیری در آن ضرورت دارد. هدف این مقاله شناسایی عوامل مؤثر در آسیبپذیری کالبدی شهر و ارائه روش و مدلی به‌منظور ارزیابی میزان آسیبپذیری مناطق شهر جهت کمک به مدیریت شهری در راستای کاهش تلفات و خسارات ناشی از زلزله در مراحل قبل، حین و پس از بحران است. نوع پژوهش کاربردی و روش آن توصیفی، تحلیلی است. در این مقاله با استفاده از مدل تحلیل سلسله‌مراتبی در محیط نرم‌افزار ARC GIS میزان آسیبپذیری مناطق شهر کرمانشاه سنجش و اولویت‌بندی شده است. نتایج مبین آن است که به‌لحاظ معیار پایداری فیزیکی ۳۱/۶۹ درصد از ساختمان‌های شهر در ناحیة آسیبپذیری خیلی زیاد و زیاد هستند و در این معیار منطقه 3 آسیبپذیرترین منطقه شهر است. همچنین از نظر معیار کارایی امدادرسانی به هنگام بحران ۱۳/۶۵ درصد از بنا‌های شهر در ناحیه آسیبپذیری خیلی زیاد و زیاد هستند که با توجه به این معیار، منطقه پنج آسیبپذیرترین منطقه شهر است. به لحاظ آسیبپذیری کالبدی هم ۷۸/۲۳درصد از ابنیه شهر در ناحیه‌ی آسیبپذیری خیلی زیاد و ۰۹۷/۳۴ درصد در پهنه آسیبپذیری زیاد واقع شده‌اند. مناطق ۳، ۷، ۴ و ۲ به ترتیب آسیبپذیرترین مناطق شهر کرمانشاه در صورت وقوع زلزله هستند.
Earthquakes are the most destructive and deadly natural disasters. Kermanshah, as the largest metropolitan city in the central-western part of the country, has significant regional influence politically, socially, economically, and demographically. Due to the city's poor urban structure, Kermanshah is highly vulnerable to earthquakes, and the probability of emerging problems and critical situations is very high in the event of an earthquake. Therefore, it is necessary to provide systematic and efficient methods for crisis management to reduce the level of vulnerability. This study aims to identify the factors affecting physical vulnerability and provide a method and model to assess the vulnerability of urban areas to help urban management reduce casualties and damages caused by earthquakes before, during, and after the crisis. The research is applied, and the method used is descriptive and analytical. The study uses the Analytic Hierarchy Process (AHP) model in the ARC GIS software environment to measure and prioritize the vulnerability of different regions of Kermanshah city. The results indicate that 31.69% of the city's buildings are located in very high and high vulnerability zones regarding physical sustainability, with Region 3 being the most vulnerable area. In terms of crisis relief efficiency, 13.65% of the city's buildings are in very high and high vulnerability zones, with Region 5 being the most vulnerable area. Regarding physical vulnerability, 23.78% of the buildings are in very high vulnerability zones, and 34.97% are in high vulnerability zones. Regions 3, 7, 4, and 2 are the most vulnerable areas in Kermanshah in the event of an earthquake.
Keywords: Vulnerability, Earthquake, Kermanshah, Analytical Hierarchy Process, GIS
Introduction
The variety and frequency of natural disasters worldwide emphasize the need for effective management in urban planning to enhance resilience against the shocks of natural or human-made disasters. Iran, due to its geographical location and position on the Alpine-Himalayan seismic belt, is constantly exposed to high-magnitude earthquakes. Kermanshah Province, located near the main Zagros fault and secondary faults such as Nahavand, Qarun, Sahneh, and Morvarid, is highly susceptible to earthquakes, with events exceeding magnitudes of 6 and 7 in 1957 and 2017 serving as evidence of this vulnerability. Therefore, it is essential to provide systematic and efficient methods based on urban planning principles to manage crises and reduce Kermanshah city's vulnerability to earthquakes.This study examines the theoretical foundations and concepts related to earthquakes, urban planning, and city resilience. It evaluates the physical vulnerability of Kermanshah city in the event of an earthquake and identifies the factors, criteria, and variables affecting this vulnerability. Ultimately, 11 sub-criteria and two main criteria are identified as effective factors contributing to the city's vulnerability. After analyzing and processing the data, vulnerability maps were created for all sub-criteria, and it was found that the highest vulnerability is related to the sub-criterion of open spaces, followed by the proximity to fire stations. The highest vulnerability in the main criteria is related to the efficiency of the urban fabric during a crisis. According to the results, more than half of the buildings in the city are located in very high and high vulnerability zones in the event of an earthquake. The main objective of this research is to identify, analyze, categorize, and determine the impact of each factor affecting the physical vulnerability of the city to earthquakes. The research aims to use scientific methods and models to assess, measure, determine, and prioritize the vulnerability of urban areas in Kermanshah to potential earthquakes.
Research Methodology
The required data were collected through library and documentary methods, using available information from the GIS unit of Kermanshah Municipality, satellite images (LANDSAT), and fieldwork. The aim of this study is to evaluate Kermanshah city's vulnerability based on the city's physical criteria. To determine the factors and variables affecting vulnerability, the study considers the current conditions of the city, as well as relevant previous research. The two main criteria of physical sustainability of the urban fabric and the efficiency of the fabric during a crisis, along with 11 sub-criteria (variables) such as land area, building coverage ratio, population density, number of floors, street width, building age, construction type and materials, access to open urban spaces, access to emergency centers, distance from hazard zones, and urban fabric type, were identified as key factors affecting the physical vulnerability of Kermanshah to earthquakes. After entering the spatial and descriptive data for each sub-criterion into GIS software, the data were stored, processed, and analyzed. Vulnerability maps for each sub-criterion were created, and in order to combine the layers (variables) and generate an overall vulnerability map, the importance and priority of each sub-criterion were determined. For this purpose, expert opinions were collected using questionnaires, and the Analytic Hierarchy Process (AHP) was applied using Expert Choice software to calculate the final weights of the criteria and sub-criteria and ensure the consistency of judgments. The vulnerability of each sub-criterion was categorized into four zones: very high, high, medium, and low, based on the impact of each indicator.
Map of the Physical Vulnerability of Kermanshah City Due to Earthquake
Table of Physical Vulnerability of Kermanshah City Due to Earthquake
(Number of Buildings and Percentage)
|
Very High Vulnerability |
High Vulnerability |
Medium Vulnerability |
Low Vulnerability |
Very High Vulnerability |
High Vulnerability |
Medium Vulnerability |
Low Vulnerability |
|
|
Region One |
1957 |
4516 |
4721 |
2704 |
1.175 |
2.711 |
2.834 |
1.623 |
|
Region Two |
4529 |
6422 |
3986 |
3305 |
2.719 |
3.855 |
2.393 |
1.984 |
|
Region Three |
14977 |
10545 |
3653 |
4737 |
8.991 |
6.331 |
2.193 |
2.844 |
|
Region Four |
6724 |
3811 |
2748 |
1476 |
4.037 |
2.288 |
1.650 |
0.886 |
|
Region Five |
2271 |
14638 |
7896 |
5850 |
1.363 |
8.788 |
4.740 |
3.512 |
|
Region Six |
386 |
2205 |
6032 |
5313 |
0.232 |
1.324 |
3.621 |
3.190 |
|
Region Seven |
7839 |
10382 |
6315 |
620 |
4.706 |
6.233 |
3.791 |
0.372 |
|
Region Eigh |
935 |
4277 |
2950 |
7852 |
0.561 |
2.568 |
1.771 |
4.714 |
|
Sum |
39618 |
56796 |
38301 |
31857 |
23.784 |
34.097 |
22.994 |
19.125 |
|
MAX |
14977 |
14638 |
7896 |
7852 |
8.991 |
8.788 |
4.740 |
4.714 |
|
The most vulnerable area |
Three |
Five |
Five |
Eigh |
Three |
Five |
Five |
Eigh |
Conclusion
In the event of an earthquake in Kermanshah city, the sub-criteria of access to open spaces and distance from fire stations will have the worst conditions. Specifically, 71.53% of buildings (119,159 buildings) are in very high vulnerability zones regarding access to open spaces, and 65.76% (109,539 buildings) are in very high vulnerability zones regarding access to fire stations. In these two sub-criteria, the worst conditions are found in Regions 3, 5, and 7, respectively. The sub-criteria of urban fabric type, access to healthcare centers, and building coverage ratio fall into the very high vulnerability zone, each with frequencies ranging from 35% to 43%, ranking second. The most vulnerable areas in these sub-criteria are Regions 3, 7, and 2.In the physical sustainability criterion, 34.27% of the city's buildings are located in very high vulnerability zones, and 35.04% are in high vulnerability zones, which is a significant and concerning number. In this criterion, the most vulnerable regions are Regions 3, 4, and 2. In terms of the efficiency of the urban fabric during a crisis, 33.08% of the city's buildings are in very high vulnerability zones, and 31.93% are in high vulnerability zones. The worst conditions in this criterion are found in Regions 5, 7, and 3.Regarding the overall physical vulnerability of the city to potential earthquakes, 39,618 buildings are in the very high vulnerability zone, and 56,796 buildings are in the high vulnerability zone. This means that 96,414 out of 166,500 buildings in the city (57.81%) are located in very high and high vulnerability zones. The final results of this study reveal the harsh reality that, in the event of an earthquake, unfortunately, more than half of Kermanshah city will be in very high and high vulnerability zones. If proper planning, scientific policy-making, and timely implementation of operational programs are not carried out, the casualties and damage resulting from the earthquake will be catastrophic and irreparable.
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