Document Type : Article extracted From phd dissertation
Authors
1
Department of Urban Planning, Mara.C., Islamic Azad University, Marand, Iran
2
Department of Art and Architecture, Shab.C., Islamic Azad University, Shabestar, Iran
3
Department of Geography and Rural Planning, Faculty of Planning and Environmental Scienses, University of Tabriz, Tabriz, Iran
Abstract
A B S T R A C T
The city of Zanjan, due to its location within an active tectonic zone and its proximity to the Soltaniyeh and North Zanjan faults, together with the accelerated pace of urban development in recent decades, is exposed to a high level of seismic risk. The present study was conducted with the aim of seismic hazard zonation in Zanjan, with emphasis on urban development components and assessment of the degree of physical and spatial vulnerability. In terms of purpose, this research is applied, and in terms of nature, it is descriptive-analytical. To assess vulnerability, 5 main criteria and 21 sub-criteria were identified based on the theoretical foundations and the opinions of 20 experts. The weighting of the criteria was carried out using the Analytic Network Process (ANP), and the limit supermatrix was extracted. Spatial layers were standardized in the ArcGIS environment using fuzzy membership functions and were integrated through the Raster Calculator tool. The ANP results showed that the physical-structural criterion, with a weight of 41.839%, and the natural criterion, with a weight of 22.150%, had the greatest influence on the seismic vulnerability of Zanjan. The areal assessment of the overall hazard zonation indicated that 18.4% of the city’s area lies within the very high-risk zone, 32.1% within the high-risk zone, 28.5% within the moderate-risk zone, and 21.0% within the low to very low-risk zones. The southern and western areas of the city, as well as the northeastern areas, are the most unsafe parts of the city. Continuous spatial analysis shows that Zanjan’s vulnerability follows a patchy and heterogeneous pattern. In order to enhance urban resilience, it is essential to formulate strict construction regulations for new developments in the northeast and to undertake physical regeneration of the deteriorated central and southern urban fabrics.
Extended Abstract
Introduction
Earthquake is one of the most significant and destructive natural hazards, inflicting extensive damage annually on human societies, urban infrastructure, and national economies. Unlike many natural hazards, earthquakes often occur without prior warning and can, within a short period, cause widespread building destruction, disruption of critical network functions, reduction in urban service delivery capacity, and trigger socio-economic crises. Although preventing earthquake occurrence is impossible, the experience of various countries has demonstrated that the magnitude of human and material losses depends more on the physical and social vulnerability of cities, the quality of spatial planning, the manner of activity distribution, and the level of preparedness of the urban management system, rather than solely on earthquake magnitude. Consequently, over the past two decades, the disaster management approach has shifted from reactive crisis management toward preventive risk management, enhancement of urban resilience, and hazard-based planning—an approach that emphasizes the identification of high-risk zones, vulnerability reduction, and the guidance of urban development toward safe areas (UNDRR, 2022; Shafapour Tehrany et al., 2023).
Although earthquake hazard is inherently natural in nature, the extent of its damages is largely influenced by the physical and functional characteristics of cities. Factors such as distance from active faults, geological and geotechnical conditions, slope and topography, alongside indicators including building quality and age, construction materials, population density, building density, land use patterns, accessibility to road networks, distribution of emergency centers, and quality of urban infrastructure, play a decisive role in increasing or decreasing urban vulnerability. From this perspective, an earthquake is not merely a geological phenomenon but rather the consequence of a complex interaction between natural processes and urban development patterns. Therefore, risk reduction necessitates the adoption of an integrated approach that simultaneously addresses natural, physical, social, and managerial dimensions.
In such circumstances, seismic hazard zoning, as one of the most critical spatial planning tools, enables the identification of areas with relative risk, determination of intervention priorities, guidance of urban development, appropriate location of sensitive land uses, formulation of construction regulations, and optimal management of urban investments. Numerous studies have demonstrated that the use of Geographic Information Systems (GIS), Multi-Criteria Decision-Making (MCDM) methods, fuzzy logic, and network models significantly enhances the accuracy of hazard assessment and decision-making capability for urban managers, as these methods are capable of simultaneously considering multiple criteria and their complex interrelationships within the analysis process.
In this context, Zanjan City, as the political, administrative, and economic center of Zanjan Province, has experienced an increasing trend of physical development, expansion of urban settlements, and intensification of economic activities over the past three decades. The horizontal expansion of the city, development of new towns, increased building density, and concentration of critical infrastructure have rendered the importance of planning based on natural hazard assessment more evident than ever before. On the other hand, the city's location within a zone influenced by the active fault systems of northwestern Iran has meant that the probability of destructive earthquakes has consistently been regarded as one of the most significant threats to Zanjan's urban development. Geological studies indicate that the Mahneshan, Soltanieh, Sohrein, and Abbar faults constitute the most important active structures in the region, which have played a fundamental role in the tectonic evolution of the Zanjan Plain.
Accordingly, the primary objective of the present study is to conduct seismic hazard zoning in Zanjan City with an emphasis on urban development components and to provide an analytical framework to support spatial decision-making. In pursuit of this objective, the present study seeks to answer two fundamental questions: First, what are the most important criteria and sub-criteria affecting seismic hazard zoning in Zanjan City with an emphasis on urban development, and what is the relative contribution of each to the formation of the spatial vulnerability pattern? Second, what picture of the spatial distribution of seismic hazard zones in Zanjan City does the integration of the Analytic Network Process (ANP) model, fuzzy logic, and Geographic Information Systems (GIS) present, and what implications do the results hold for urban development policy and planning?
Methodology
The present study is applied in terms of purpose and descriptive-analytical in nature, conducted through an exploratory sequential mixed method approach. In this research, the most important indicators affecting seismic vulnerability and urban development were first extracted through documentary studies, review of scientific literature, and examination of domestic and international research. Subsequently, the identified indicators were refined and finalized using expert opinion. In the qualitative phase, the primary role of the research was to identify and explain the criteria and sub-criteria affecting seismic hazard zoning, while in the quantitative phase, these indicators were converted into measurable variables, and weighting, standardization, and spatial analysis were performed. Thus, the point of integration between the qualitative and quantitative sections occurred at the stage of forming the decision-making model and spatial analysis, such that the output of the qualitative phase served as the basis for designing the quantitative model and producing the final zoning map. The statistical population of the specialized section of the research comprised experts in the fields of urban planning, urban development, crisis management, geology, civil engineering, and geographic information systems. Purposive sampling was employed, and 20 specialists with at least a Master's degree, relevant academic or executive experience, and sufficient familiarity with urban planning and natural hazard topics participated in the research. Pairwise comparison questionnaires were distributed to experts both in person and electronically. After collection, the reliability of the instrument was assessed using Cronbach's alpha coefficient, which yielded a value of 0.802, indicating acceptable reliability of the questionnaire.
Following indicator extraction, 21 sub-criteria were organized within five main criteria, including Natural Factors, Physical-Structural Factors, Accessibility, Socio-Economic Factors, and Urban Services. To determine the relative importance and interrelationships among these criteria, the Analytic Network Process (ANP) model was employed, as unlike the hierarchical AHP method, this model enables the analysis of dependence and feedback among criteria (Saaty, 2005). Pairwise comparison matrices were completed based on Saaty's 9-point scale, and after calculating the eigenvectors, the initial supermatrix, weighted supermatrix, and limit supermatrix were derived, and the final weights of the criteria were extracted. Furthermore, the inconsistency ratio of all matrices was less than 0.10, indicating satisfactory consistency of expert judgments. The weights obtained from the ANP model were assigned to the standardized layers, and all spatial data were integrated in the ArcGIS software environment using the Weighted Overlay method. The application of this method enabled the simultaneous combination of criterion weights with fuzzy membership degrees, and the final seismic hazard zoning map of Zanjan City was produced in five classes: very low, low, moderate, high, and very high. The final classification was performed using the Natural Breaks (Jenks) method to achieve maximum differentiation among different zones. Finally, the results of the zoning were compared with the physical characteristics of the city, building quality, building density, road network accessibility status, and spatial distribution of urban land uses to assess the degree of correspondence between the obtained spatial pattern and the actual conditions of the city.
Results and Discussion
The research findings demonstrated that the seismic risk pattern in Zanjan City does not follow a uniform distribution, and there exist considerable differences among various areas of the city in terms of vulnerability levels. Based on the weights derived from the ANP model, the Physical-Structural criterion exerted the greatest influence on the formation of the final risk pattern, indicating the decisive role of built environment quality, building characteristics, and the physical structure of the city in reducing or increasing earthquake-induced damages. Furthermore, it was determined that natural, service-related, and demographic factors, in interaction with one another, shape the final risk pattern, and none of these alone can explain the city's vulnerability status.
From an urban planning perspective, the research results indicate that earthquake risk reduction necessitates the adoption of an integrated approach in urban development management. Directing the city's future development toward suitable zones, enhancing construction quality, regenerating deteriorated urban fabrics, strengthening the road network, improving the distribution of healthcare and emergency centers, and preserving and developing urban open spaces represent the most critical measures that can enhance the city's resilience capacity against earthquakes. Therefore, the zoning map produced in this study can serve as a practical tool for prioritizing urban interventions, revising development plans, and formulating crisis management programs for use by urban managers and planners.
The primary innovation of this research lies in the simultaneous integration of the ANP model, fuzzy logic, and GIS for multi-criteria seismic risk assessment with an emphasis on urban development. This approach, in addition to determining the relative importance of criteria, enables the spatial analysis of complex interrelationships among them and presents a more comprehensive picture of the city's vulnerability status. Accordingly, the proposed framework of this research has the potential for application in other seismically active cities across the country.
Conclusion
Nevertheless, the research results are influenced by the quality and scale of input data. Limitations in accessing certain up-to-date geological data, precise information on building characteristics, and some spatial layers constitute constraints of this study and may affect the accuracy of the final assessment. Therefore, it is recommended that future research employ higher spatial resolution data, updated seismotectonic information, remote sensing imagery, machine learning models, and analysis of various earthquake occurrence scenarios to conduct a more comprehensive assessment of seismic risk and vulnerability in Zanjan City and other cities of the country. Furthermore, examining the institutional, economic, and social dimensions of urban resilience alongside physical assessments can contribute to the formulation of more effective policies for risk reduction and the achievement of sustainable urban development.
In sum, the research findings indicate that enhancing Zanjan City's safety against earthquakes is not achieved solely through building retrofitting; rather, it requires a comprehensive perspective on urban development in which physical quality, distribution of public services, road network accessibility, open spaces, demographic characteristics, and natural considerations are simultaneously incorporated into urban development and management policies. Such an approach, while reducing vulnerability, can provide the foundation for realizing sustainable urban development and enhancing the city's resilience against natural hazards.
Funding
There is no funding support.
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved the content of the manuscript and agreed on all aspects of the work declaration of competing interest none.
Conflict of Interest
Authors declared no conflict of interest.
Acknowledgments
We are grateful to all the scientific consultants of this paper
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