عنوان مقاله [English]
Earthquake is one of the most natural hazards for cities, being dangerous, destructive, and unpredictable. According to Iranian Crisis Management Organization, seventy eight percent of the country's surface is in high seismic risk area, with 10% of human-caused mortality related to earthquakes. Golestan Province, the second-ranked province in this regard, always faces earthquake hazard, located in the first high-risk areas. In general, four main theories are related to cities’ vulnerability: first, the human ecology theory that has emphasized the unbreakable bonding of biophysical processes and social processes; second, the theory of political economy, which has integrated macro and micro perspectives, providing a better analytical framework for complexity and dependence comprehensive understanding of vulnerability-causing factors; third, the theory of community-oriented compatibility, which is based on identification, assistance, and implementation of community-based activities strengthening the capacity of local people to adapt to life in a risky and unpredictable situation; and fourth, resilience which is the capacity or ability of the community to predict, prepare, and respond quickly against the effects and consequences of disaster. According to the country's Crisis Management Organization, 78% of the country lie in high-risk seismic areas with 10% of human losses coming from earthquake-related disasters. Golestan Province belongs to second-ranked provinces facing earthquakes in Iran, being first in terms of the high risk from such disasters. Results from several surveys show that 840 earthquakes have been registered in Golestanwith many regions of the province susceptible to landslides. Seismic zoning maps has shown that Golestan Province has four zones, regardless of the effect of alluvial deposits. They include areas with very high, high, medium, and low seismic hazard. Gorgan, the capital city of this province is located in very very high and high areas. Accordingly, this research tries to measure and make a spatial analysis of vulnerability clusters in physical textures of Gorgan in critical conditions in order to determine immediate intervention. However, seismic zoning maps for seismic rock placement, based on the background of accelerated shifts of earth's powerful movement for the return period of 475 and 2475 years show that regardless of the effect of alluvial deposits Golestan Province has four zones, areas with high, high, medium and the city of Gorgan is low in many areas.
The current research was an applied one, its method being descriptive-analytical. It investigated the determinant criterion of physical texture vulnerabilitydegree in Gorgan in terms of five criteria, namely number of floors, fineness, buildings’ age, and therir materials. Once this criterion got evaluating and converted to comparable and standard scales, it was used from Analytic Network Analysis (ANP) to determine relative weight of each criterion. Indicator prioritization was done according to expert opinions and indicators’ evaluation. Finally, the blocks were classifiedwith VIKOR Model in terms of their vulnerability, resulting in the physical vulnerability map of building units at the urban blockslevel of Gorgan city. Then, vulnerable spatial clusters analysis of Gorgan city was carried out via the Getis-Ord model.
Results and Discussion
Results from the study show that the highest and lowest effective factors for vulnerability assessment of the Gorgan city blocks were related to the index of building materials with a weight of 0.425, and the index of pettiness with a weight of 0.126, respectively. Based on VIKOR Model results, the highest degree of physical vulnerability could be seen in the central and somewhat southern parts of Gorgan. Also, the eastern and western regions and somewhat north of the city fared better with regard to this index. The Hotspot analysis clearly showed the gap between the center, the south, and the margins of the eastern and western regions with other parts of Gorgan. As a result, the central and southern regions as well as the margins of the eastern and western regions of Gorgan were in an inappropriate situation in terms of vulnerability during the earthquake. At the same time, the northern, western, and eastern parts of the city suffered less damage during the earthquake, thanks to their buildings’ physical characteristics.
Researches like Ródenas et al. (2018), Rusydi et al. (2017), Ianoș et al. (2017), Kushe et al. (2017), Mehraban Motlagh and Motamedi (2018), and Paivastehgar et al. (2017) have emphasized zoning of vulnerable sites in cities such as Palu, Bucharest, Karonga, Shiraz, and Imamzadeh Hasan, Tehran. However, the present study focused on spatial analysis of the vulnerable zones of Gorgan, simultaneously determining their clusters. At the same time, this research did not overlook focusing on vulnerability zoning as well. The comparative analysis of vulnerability in Gorgan indicated that the central region had less residential units than the peripheral region of Gorgan. Buildings in the central part were more ancient. The periphery buildings had higher elevation than the center. Also, peripheral buildings were better in terms of access to passages, being wider than the central parts of the city. In general, the buildings in the peripheral parts proved to be less vulnerable than the central ones. In this regard, it is suggested to 1) establish crisis management centers and emergency services in the west and east of the city, 2) prevent congestion especially in hazardous areas, 3) open roads, and 4) give incentives to worn-out buildings regeneration by both the government and the municipality.
Through comparative analysis of vulnerability in Gorgan, it can be concluded that the central area has less residential units than the periphery of the city. Older buildings are more in the central part, while those in the periphery have higher elevation. Also, peripheral buildings are better off in terms of access to passages.
10. Armas, I.; Toma-Danila, D.; Ionescu, R. and Gavris, A., 2017, Vulnerability to Earthquake Hazard: Bucharest Case Study, Romania. Int J Disaster Risk Sci, No. 8, PP. 182-195.
11. Berquist, M.; Daniere, A. and Drummond, L., 2014, Planning for global environmental change in Bangkok's informal settlements. Journal of environmental planning and management, Vol. 58, No. 10, PP. 1711-1730.
12. Ghadiri, M., 2015, Socio- economic Factors in Residential Vulnerability to Earthquake in Tehran City, Journal of Geographic Space, Volume 15, Issue 51, pp. 241-262.
13. Gharakhlou, M., 2009, Crisis risk in urban slum. CAG, ETAVA, PP. 25-31.
14. Ianoș, I.; Merciu, G.L.; Merciu, C. and Pomeroy, G., 2017, Mapping Accessibility in the Historic Urban Center of Bucharest for Earthquake Hazard Response. Natural Hazards Earth System Science, No. 13, PP. 1-24.
15. Imani, B.; Kanoni, R.; Biniaz, M. and Ali Mohammadi, A., 2016, Strategies to reduce the vulnerability of worn tissues to earthquakes (case study: Imamzadeh Hassan neighborhood of Tehran), Bagh-e Nazar Journal, Volume 13, Issue 39, pp. 67- 82.
16. Jain, G., 2015, The role of private sector for reducing disaster risk in large scale infrastructure and real estate development: Case of Delhi. Environment & Urbanization, Vol. 23, No. 2, PP. 238-255.
17. khodarahm, b.; Sadeghi, N.; Khajeh Shahkouei, A. and Rezaei, H., 1396, An Analysis of Vulnerability Indicators of Urban Settlements Against Earthquake (Case Study: Gorgan City), Geographical Planning of Space Quarterly Journal, Volume 7, Issue 25, pp. 73-88.
18. Kushe, J.; Manda, M.; Mdala, H. and Wanda, E., 2017, The earthquake/seismic risk, vulnerability and capacity profile for Karonga town. African Journal of Environmental Science and Technology, Vol. 11, No. 1, PP. 19-32.
19. Mahdavian, A., 2013, Seismic zonation of Golestan province. Journal of GeoScience, Vol. 23(89), pp. 165-174.
20. Mahdnezhad, H., 2015, Assessment and Spatial Analysis of Urban Poverty Areas (Case Study: Varamin), Thesis for PhD, Geography and Urban Planning, Faculty of Geography, University of Tehran, Tehran.
21. Malladi, V. P. T., 2012, Earthquake Building Vulnerability and Damage Assessment with Reference to Sikkim Earthquake 2011. Master of Science in Geo-information Science and Earth Observation, Faculty of Geo-information Science and Earth Observation, Twente: University of Twente.
22. Mayunga, J. S., 2008, Understanding and Applying the Concept of Community Disaster Resilience: A capital-based approach. Paper prepared for the summer academy for social vulnerability and resilience building, 22 -28 July 2007, Munich, Germany.
23. Mehraban Motlagh, H. and Motamedi, M., 1397, Analyzing the Level of Vulnerability of Bojnourd City’s Spatio-Physical Texture against the Natural Hazards (with special reference on earthquake), Quarterly Journal of North Khorasan Police Science, Volume 5, Issue 17, pp. 67-82.
24. Peyvastehgar, Y., Mohammadidoost, S.; Heydari, A. A. and Meshksar, P., 2017, Assessing the vulnerability of urban distressed areas of the metropolis Shiraz against earthquakes using Analytical Hierarchy Process (AHP), Quarterly of Geography (Regional Planning), Volume 8, Issue 1, pp. 33-56.
25. Pickett, S. T. A.; Burch, W. R.; Jr. Dalton, S. D. and Foresman, T. W., 1997, Integrated urban ecosystem research. Urban Ecosystems, No. 1, PP. 183-184.
26. Prüfung, T. D. M., 2014, Exploring Social Vulnerability to Natural Disasters in Urban Settlements- Perspectives Flooding in the Slums of Lagos. Lagos: Universität zu Köln.
27. Ródenas, J. L.; García-Ayllón, S. and Tomás, A., 2018, Estimation of the Buildings Seismic Vulnerability: A Methodological Proposal for Planning Ante-Earthquake Scenarios in Urban Areas. Applied Sciences, Vol. 1208, No. 8, PP. 2-17.
28. Ruiter, M. C.; Ward, P. J.; Daniell, J. E. and Aerts, J. C. J. H., 2017, A comparison of flood and earthquake vulnerability assessment indicators. Natural Hazards Earth System Science, No. 17, PP. 1231-1251.
29. Rusydi, H. and Rahmawati, R. E., 2017, Vulnerability zoning of earthquake disaster of Palu. International Journal of Science and Applied Science: Conference Series, Vol. 1, No. 2, PP. 137-143.
30. Siami, Gh.; Latifi, Gh.; Taghinezhad, K. and Zahedi Kalaki, E., 2013, Pathology of Defensive Urban Structure using Analytical Hierarchy Process AHP and GIS. Case Study: Gorgan, Geographical Planning of Space Quarterly Journal, Volume 3, Issue 10, pp. 21-42.
31. Schütte, S., 2004, Urban Vulnerability in Afghanistan: Case Studies from Three Cities. Kabul: Afghanistan Research and Evaluation Unit.
32. Thinda, T. K. A., 2009, Community-Based Hazard and Vulnerability Assessment: A case study in Lusaka Informal Settlement, City of Tshwane, Degree of Masters in Disaster Risk Management. University of the Free State, Faculty of Natural and Agricultural Science Centre for Disaster Risk Management Education and Training for Africa.
33. Tromeur, E.; Menard, R.l Bailly, J. B. and Soulie, C., 2012, Urban vulnerability and resilience within the context of climate change. Hazards Earth Syst, No. 12, PP. 1811-1821.
34. World Bank (WB)., 2010, Natural hazards, unnatural disasters: the economics of effective prevention. Washington: The International Bank for Reconstruction and Development.
35. Zangiabadi, A.; Ghaed Rahmati, S. and Soltani, L., 2012, Planning for Earthquake Crisis Management in Cities, Mashhad: Sharia Toos.