ارزیابی آسیب‌پذیری کالبدی شهر بجنورد در مقابل زلزله با رویکرد توسعه پایدار شهری

اثرات و آسیب‌پذیری ناشی از مخاطرات طبیعی در جهان در حال افزایش است و ابعاد این اثرات در زمینه های فیزیکی، توسعه اقتصادی اجتماعی، از دست دادن جان و مال، منابع و تخریب همه‌جانبه، شدید و گسترده است. تلاش برای کاهش آسیب‌پذیری نشان می دهد که باید راهبردی ارزشمند برای کاهش اثرات مخرب ناشی از بحران در دستور کار سیاست های اجتماعی روز قرار گیرد. با وقوع زلزله‌های مخرب در جامعه حوادثی ازاین‌دست اتفاق می‌افتد: فروریختن ساختمان‌ها، زخمی یا کشته شدن مردم، آسیب دیدن زیرساخت‌ها و متوقف شدن اقتصاد، بنابراین برنامه ریزی کاهش مخاطرات و بهسازی برای تاب‌آوری جوامع در مقابل مخاطرات بسیار ضروری است. ازاین‌رو این مقاله به بررسی کاهش آسیب‌پذیری و ساماندهی کالبدی – فضایی شهر بجنورد در مقابل زلزله از طریق برنامه‌ریزی کاربری زمین شهری با رویکرد توسعه پایدار شهری می‌پردازد. روس تحقیق در پژوهش حاضر توصیفی – تحلیلی بوده که در ابتدا با جمع‌آوری اطلاعات و داده‌های لازم اقدام به تشکیل بانک اطلاعاتی در محیط سیستم اطلاعات جغرافیایی گردید ، سپس با استخراج و ترکیب نقشه‌های جدید، تحلیل نهائی انجام‌شده است. برای مشخص کردن میزان آسیب‌پذیری شهر بجنورد، به شاخص مراکز خطرزا، دانه‌بندی قطعات، تراکم ساختمانی، تراکم جمعیتی، کیفیت ابنیه، دسترسی به مراکز امدادی و زمین و اراضی عمومی و باز  انتخاب‌شده و قطعه‌های ساختمانی آسیب‌پذیر در مقابل زلزله مشخص‌شده است. با توجه به نقشه آسیب‌پذیری شهر نتایج نشان می‌دهد  محدوده‌هایی که خیابان های آن عرض کافی داشته و ازنظر دسترسی به مراکز امدادی در وضعیت بهتری قرار داشته و تراکم جمعیتی و ساختمانی و .. در آن‌ها پایین است، ازنظر آسیب‌پذیری در وضعیت بهتری قرار دارند. به‌عبارت‌دیگر این محدوده‌ها با توجه به تقسیم‌بندی نقشه آسیب‌پذیری به 5 قسمت، آسیب پذیری نسبتاً پایین، پایین، متوسط، بالا و آسیب پذیری بسیار بالاگرفته‌اند.

Assessing the physical vulnerability of Bojnourd city against earthquakes with the approach of sustainable urban development

Extended AbstractIntroductionThe issue of urban safety against natural hazards is one of the main goals of urban planning and it is very important to raise awareness about the vulnerability of urban issues and to know their vulnerability to natural hazards. Paying attention to these risks and crises is an undeniable necessity of the crisis management system and structure. Natural hazards in many cases have devastating effects on human societies. The consequences of these phenomena are the occurrence of changes in environmental conditions, which in turn leads to the disruption of the normal life process of people and the occurrence of destructive effects on their habitats and imposes extensive economic and social damage on communities. Among natural disasters, earthquakes are more common. And in the absence of the power to prevent and prepare society, it turns into a human disaster that has direct, indirect and secondary destructive effects on both individuals and their habitat and society. Iran is one of the countries that are very vulnerable to natural disasters in terms of geographical and geological conditions. On the other hand, the city of Bojnourd due to its special geographical location and being located between the mountains of KoppehDagh and AlaDagh and the existence of canals and rivers in it on the one hand and being located on faults on the other hand has great vulnerability to It is a natural hazard. Another case that causes the vulnerability of the wornout structures of this city is the existence of spontaneous and old structures in the heart of this city, which are generally composed of onestory and twostory houses with low floor space which have been denselybuilt. These houses often do not have a technical standard and do not have the necessary resistance to natural hazards. Therefore, the general purpose of the present study is to determine the degree of physical vulnerability of Bojnourd city to earthquakes. According to the raised issues in the study area and also based on the importance and determined objectives, the question of this research is as follow: What is the situation of urban areas of Bojnourd in terms of earthquake vulnerability?Due to the problems that have occurred in recent years in the field of natural disasters, much attention has been paid to studies in this field. For example, evaluating the resilience of wornout textures against natural hazards in Semnan is the title of a study that Hassanzadeh Tavakoli et al. (2017), by using of the ANP model, have prioritized resilience criteria in this city. And they have come to the conclusion that the resilience of the wornout texture of Semnan city is not in a desirable condition. Assessing the structuralnatural resilience of urban landuse of region 4 of Tehran is the title of another study that has conducted by Jalalian in 2018 and by FANP method, it has been concluded that the average structuralnatural resilience of landuse of region 4 of Tehran was 0.86 and resilient. MethodologyThe present research is based on the purpose of the applied type which has been done through descriptiveanalytical method. The method of data collection is based on library studies and questionnaires. The statistical population of the present study is experts related to the fields of urban planning and crisis management and water resources of Bojnourd.In this regard, due to the specialization of the research topic, questionnaires were distributed and completed by 15 managers and senior experts of Bojnourd Municipality and specialists related to crisis management by purposeful sampling method. In order to measure the vulnerability of physical spaces in the city to earthquakes,12 indicators in two ranges of structuralphysical indicators including (building quality, building structures, hazardous centers, population density, building density, granulation, city road network, relief centers and open and public space and natural including (distance from fault lines, soil resistance and land slope) have been used. Results and discussionAfter confirming the indicators by comparing the mean of the index and the component, the effectiveness of the existence of vulnerability assessment indicators of Bojnourd was examined through fivepoint Likert scale. According to the results of the pairwise comparison matrix of physical indicators, it was found that among the physical factors, the quality of the building with a normalized score (0.223), building structure (0.220), location of hazardous centers (0.140), population density (0.112), building density (0.110), granulation (0.074), city road network (0.049), location of relief centers (0.046), and open space with a score (0.026) are more preferable, respectively. Accordingly, the most vulnerable neighborhoods are mostly in the suburbs of Bojnourd. Considering that the mentioned neighborhoods in the past decades have been villages around the city and generally have a rural function and their physical growth towards the city has been spontaneous and unplanned, which have caused these neighborhoods in terms of indicators such as quality, buildings, antiquities, building structures and distance from relief centers, etc. do not have suitable conditions. And for these reasons, they are less vulnerable than other parts of the city, especially the newly built areas of the city, which are built and developed according to the plan. ConclusionThe final obtained result from the study of the research criteria indicates that most of the suburbs are unsuitable. Therefore, prioritizing this area with the aim of earthquake resistance is of great necessity. Although the southern parts of Bojnourd city are less vulnerable than the east and north of the city, considering that in recent years the highest rate of development of Bojnourd city is towards the southern and western regions  and according to the earthquake risk zoning map, this part of urban development has reduced its distance from faults in the south of the city day by day and in an unplanned process is moving to highrisk areas, so that  it is necessary to control and pay attention to this part of the city.