چکیده:
هدف اصلی پژوهش حاضر ارائه یک روش شناسی برای ارزیابی سریع آسیب پذیری فضاهای شهری نسبت به زلزله می باشد. بسیاری از متغیرهای موثر بر آسیب پذیری لرزه ای شهرها از ماهیت مکانی برخوردارند و از اینرو استفاده از سیستم اطلاعات جغرافیایی در ترکیب و یکپارچه نمودن این متغیرها می تواند به نتایج مطلوبی منجر شود. با این حال، یکی از مهم ترین مسائل روی هم گذاری لایه ها در سیستم اطلاعات جغرافیایی مربوط به عدم قطعیت های وزن دهی و تصمیم گیری می باشد. در تحقیق حاضر سعی شد که با استفاده از توابع تئوری کاتاستروف اینگونه عدم قطعیت ها تا حد زیادی تعدیل شوند. در تئوری کاتاستروف، اهمیت هر یک از متغیرها از طریق مکانیسم درونی سیستم محاسبه می شود. در واقع، استفاده از رویکرد مذکور باعث تکرارپذیری نتایج مدل می گردد که مزیتی قابل توجه به شمار می رود. ارزیابی آسیب پذیری لرزه ای شهر ورزقان با استفاده از توابع تئوری کاتاستروف نشان می دهد که بالغ بر 9 درصد از محدوده قانونی شهر در کلاس آسیب پذیری بسیار زیاد و 12 درصد آن در کلاس آسیب پذیری زیاد واقع شده است. در این رابطه، بخش عمده ای از مرکز شهر ورزقان در برابر زلزله از آسیب پذیری بالایی برخوردار است. تراکم بالای مسکونی و ساختمانی، کیفیت پایین ساختمان ها، قدمت بالا و مصالح نامطلوب بناها، محصورشدگی و کمبود فضاهای باز شهری، لیتولوژی و زیربنای سست، عدم دسترسی مطلوب به خدمات بیمارستانی و آتشنشانی و غیره منجر به افزایش آسیب پذیری این بخش از شهر شده است
Introduction Earthquake is one of the most destructive natural hazards in the world that causes severe physical, social, and economic damages. The location of major cities in hazard prone regions, urbanization and population growth, and rising wealth measures are the main reasons for high vulnerability of urban spaces to earthquakes. The prediction of exact location, time, duration and intensity of earthquakes is not possible. However, probable damages can be estimated. Vulnerability maps of cities can help efficient post disaster response to be planned. Most of the variables affecting seismic vulnerability in cities are spatial in nature, so using a geographic information system for integration of these variables can lead to desirable results. However, one of the most important subjects in overlaying of layers in a geographic information system is the uncertainty in weighting and decision making. In the present study, attempts were made to modify such uncertainties to a large extent by using the functions of catastrophe theory. In fact, using mentioned approach makes the results of the model repeatable, which is a considerable advantage. Regarding the catastrophe theory, an attempt was made to present the basic equations of this model in a concise and simple way. Varzeqan city was selected to evaluate the seismic vulnerability based on the catastrophe theory. Methods and Material In the present study, the functions of catastrophe theory have been used to address some of the issues and uncertainties associated with the overlaying of thematic layers in the framework of a geographical information system. In the catastrophe theory, function variables of the system are divided into dependent state and control variables. Dependent state variables are internal variables of the system and control variables are external effective factors while system is running. For example in the current study, seismic vulnerability is state or response variable and landuse, slope, lithology, etc. are control variables. Catastrophe theory is the study of potential function V(xica), in which xi is the state variable and ca is the control variable. Rather than weights assigned by the users, catastrophic fuzzy membership functions determine the dependency of state variables on control variables. Different control variables have different effects on the state variable. First, this assessment was classified into several sub-systems with different indicators according to internal mechanism of the system. The initial data is normalized using catastrophe theory and fuzzy mathematics to give optimal or cleanest data. The multidimensional catastrophe fuzzy membership functions assign values ranging from 0 to 1 to resolve incompatibility of various initial data. There are seven catastrophe models namely, fold catastrophe, cusp catastrophe, dovetail catastrophe, butterfly catastrophe, swallowtail catastrophe, hyperbolic umbilical catastrophe and parabola umbilical catastrophe. As different control variables have different effects on the state variable, the seismic vulnerability was classified into several sub-systems. Each sub system includes some factor or indicator related to seismic vulnerability. In the case of Varzeqan, these sub systems can be divided into three general groups: natural, structural and planning indicators. As the range and unit of main data is different, it is not possible to use those units for data analysis, so normalization of data is necessary. Normalization process makes the data dimensionless, thus remove inappropriateness of indicators. In the present study, complementary principle was used in order to calculate the catastrophe progression of each control variable. After weighting each indicator, related layers were combined using geographic information system. Result and discussion The final result of the combination of thematic layers by using catastrophe theory is shown in Fig. 1. This figure indicates spatial vulnerability of Varzeqan to earthquake. In a comparative manner, the map zones the city in terms of vulnerability, considering twelve selected variables. So, it can help identify critical places of the city to earthquake. Generally, the legal area of Varzeqan in terms of vulnerability to earthquake was classified into five classes. In fact, considerable part of the main core of the city lies in high and very high vulnerability classes. The other parts have moderate vulnerability. Approximately 21 percent of the total area of Varzeqan lies in the high and very high vulnerability classes. Given that the area of the city's built-up lands is about 32 percent, considerable percentage of these lands in the city is in high and very high vulnerability classes. Distribution of these zones is impressive, especially in the center of the city. In fact, these zones can be considered the most critical regions of Varzeqan. Unstable geological formations, high residential and population density, fine grained building, low quality buildings and lack of urban open spaces have caused that this region to have severe vulnerability to earthquake. Fig. 1 Spatial vulnerability zonation of Varzeqan to earthquake using catastrophe theory Conclusion The main purpose of the current study is to provide a methodological framework for quick and efficient assessment of the vulnerability of urban spaces to earthquake. Almost, all of the multivariate decision making models are based on subjective weighting and influenced by decision makers' judgment. In the present study in order to decrease subjectivism, the functions of catastrophe theory was used for determining weights of different variables. In this method, the importance of each criterion to the other is calculated through its internal mechanism, therefore the disadvantage of subjectivism decreases greatly. Mathematical foundation, reduction in decision making uncertainty during weighting process and to some extent in classification uncertainty, consideration of spatial differentiation of variables, the ability to repeat the results by different researchers, high flexibility in the number of variables ,and usage in all geographic conditions (physical and human) are the most important advantages of this model. Therefore, it overcomes disadvantages of subjectivity and uncertainty. In order to evaluate the efficiency of this model in the vulnerability assessment of urban spaces to earthquake, Varzeqan was selected as the case study. For the seismic microzonatio of the city using the catastrophe functions, twelve important natural, structural and planning variables effecting the vulnerability were used. The results indicate the high efficiency of this model and the high vulnerability of the most parts of the city to earthquake.
خلاصه ماشینی:
ارزیابی آسیب پذیری لرزه ای فضاهای شهری با کاربست تئوری کاتاستروف (مورد: شهر ورزقان ) پریچهر مصری علمداری ١- استادیار اقلیم شناسی، دانشکده علوم اجتماعی، دانشگاه پیام نور، تهران ، ایران منصور خیریزاده آروق - دانش آموخته دکتری ژئومورفولوژی، دانشگاه تبریز، تبریز، ایران تاریخ دریافت : ١٣٩٩/٥/١٣ تاریخ بازنگری : ١٣٩٩/٩/٣٠ تاریخ تصویب : ١٣٩٩/١٠/٦ چکیده هدف اصلی پژوهش حاضر ارائه یک چارچوب روش شناسی برای ارزیابی سریع و کارآمد آسـیب پـذیری فضاهای شهری نسبت به زلزله است .
در این زمینه میتوان به قنبری و همکاران (١٣٩٢)، نیری و همکاران (١٣٩٥)، رمضانی کیاسج محله و همکاران (١٣٩٥)، فلاحی و اسدی (١٣٩٥)، فاضل و همکاران (١٣٩٦)، نوروزی طیولا و بینایی (١٣٩٧)، طبیبیـان و 6 مظفری (١٣٩٧)، کرمی و امیریان (١٣٩٧)، جعفرنیا و همکـاران (١٣٩٨)، خـدادادی و همکـاران (١٣٩٩)، ارمـاس 1 Sanders and Clark 2 Alcántara-Ayala and Goudie 3 Duzgan 4 Moradi 5 Multiple Criteria Decision Making 6 Armas (٢٠١٢)، راشد و ویک ١ (٢٠١٢)، مرادی و همکـاران (٢٠١٤)، سـین ها٢ و همکـاران (٢٠١٤)، ارمـاس و همکـاران (٢٠١٧) و ژنگ ٣ و همکاران (٢٠٢٠) اشاره نمود.
در این پژوهش ، شاخص های مورد استفاده به منظور ارزیابی آسیب پذیری لرزه ای شهر ورزقان را میتوان از سه جنبه مورد توجه قرار داد: الف ) شاخص های سازه ای که شامل کیفیت بنا، عمر بنا، نوع مصـالح بنـا و تعـداد طبقات میباشند؛ ب ) شاخص های برنامه ریزی که در بستر موضوعاتی مانند توزیع فضایی ایستگاه های آتش نشـانی، بیمارستان ها، دسترسی به فضاهای باز، تراکم مسکونی و فاصله از تأسیسات خطرزا مورد توجـه قـرار گرفتنـد؛ ج ) شاخص های طبیعی که در این رابطه از دو متغیر شیب و لیتولوژی استفاده به عمل آمد.