Earthquake Risk Assessment for Tehran, Iran

Abstract

<jats:p>The megacity of Tehran, the capital of Iran, is subjected to a high earthquake risk. Located at the central part of the Alpine–Himalayan seismic belt, Tehran is surrounded by several active faults that show some M7+ historical earthquake records. The high seismic hazard in combination with a dense population distribution and several vulnerability factors mean Tehran is one of the top 20 worldwide megacities at a high earthquake risk. This article aims to prepare an assessment of the present-day earthquake risk in Tehran. First, the earthquake risk components including hazard, exposure, and vulnerability are evaluated based on some accessible GIS-based datasets (e.g., seismicity, geology, active faults, population distribution, land use, urban fabric, buildings’ height and occupancy, structure types, and ages, as well as the vicinity to some critical infrastructures). Then, earthquake hazard maps in terms of PGA are prepared using a probabilistic approach as well as a surface rupture width map. Exposure and vulnerability maps are also provided deterministically in terms of population density and hybrid physical vulnerability, respectively. Finally, all these components are combined in a spatial framework and an earthquake risk map is provided for Tehran.</jats:p>

Evaluation of Seismic Vulnerability of Hospitals in the Tehran Metropolitan Area

“…According to the results, the disaster management plans of Tehran should be proactively reinforcing the critical structures such as health care clinics and hospitals before any major earthquakes occur in the city. The high seismic vulnerability of southern Tehran was also analyzed by Kamranzad et al In their study, they calculated earthquake risk assessment for Tehran considering site specifications and population density [7], for which the buildings need to be fortified effectively [43]. Similar studies suggest that the same district in southern Tehran has high vulnerability of building loss and physical damages [44][45][46].…”

“…The site response is gathered from the earthquake hazard map of Tehran with a return period of 475 years (Figure 3), which is integrated from seismogenic sources, including faults and geological features, and seismicity of the area, including the historical and instrumental seismic catalog of Tehran. The final PGA shown on the map is computed by a probabilistic model considering site-to-source distance, local soil properties, and fault mechanism [7,12]. The taxonomy of structures includes its age, height, and type.…”

“…Therefore, the results of this study are influenced by site parameters, such as site-to-source distances and site conditions, but not as direct inputs. Kamranzad et al considered surface rupture width and length, and near field effects such as cracks to account for seismic risk analysis of buildings in Tehran [7]; similarly, as future work, rupture zones can be considered in estimating vulnerability of healthcare centers. Moreover, the certainty of estimation can potentially increase using local fragility curves with real data, including data from earthquakes in Iran [15].…”

“…Generally, 8% of the most destructive earthquakes occurred in this country [5]. Tehran, the political and economic capital city of Iran, is globally one of the most populated cities with a high seismic risk [6,7]. The seismic catalog of Tehran shows that the return period of severe earthquakes in the urban areas is about 150 years, and the last relatively high magnitude (M > 7) earthquake occurred in 1830 [8].…”

“…This necessitates new efficient methods of structural seismic retrofitting with construction [9][10][11]. High urban population and building density, in addition to the concentration of resources in Tehran, increase the complexity of the crisis management plans in the case of earthquakes; therefore, a detailed evaluation of vulnerabilities and corresponding mitigation plans are required [7].…”