Urban Morphology and Seismic Resilience: A Comparative Assessment of Organic and Grid-Based Urban Fabrics through Case Studies from Iran and Selected Global Cities

Urban morphology significantly influences the seismic resilience of cities through street networks, block patterns, and overall city form. This paper presents a comparative assessment of two major urban fabric typologies: organic (circular/rounded) layouts, typical of historic Iranian and ancient cities, and grid-based (rectangular) patterns, common in modern planned urban developments. The study investigates how these morphologies affect seismic risk mitigation by evaluating key parameters, including street connectivity, block size, open-space distribution, evacuation efficiency, and emergency-response accessibility. Employing a descriptive-analytical approach, the research examines major earthquake case studies, with particular focus on the Y.Bam earthquake in Iran, alongside selected international cases from Japan, Turkey, and Chile. The findings reveal that neither morphology is inherently superior. Organic fabrics often exhibit better adaptation to local topography but suffer from narrow and irregular streets that impede post-disaster rescue operations. Conversely, grid-based layouts generally offer superior connectivity and emergency access, although they may experience more uniform vibration patterns and concentrated damage under certain seismic conditions. Evidence consistently shows that building construction quality, population density, and soil characteristics remain the primary determinants of casualty rates, while urban fabric serves as a critical secondary factor. The study concludes that hybrid urban morphologies - integrating the redundancy of grid systems with the flexibility and open spaces of organic patterns provide the most effective strategy for enhancing seismic resilience in earthquake-prone regions. Practical recommendations are offered for Iranian cities, emphasizing the redevelopment of historic urban cores and the planning of new districts in accordance with national seismic codes.

کلیدواژه ها:

Urban Morphology ، Seismic Resilience ، City Fabric ، Organic Urban Layout ، Grid Pattern ، Earthquake Risk Mitigation ، Bam Earthquake ، Sustainable Urban Planning