A Territorial-Configurational Index to evaluate seismic spatial vulnerability in urban-regional settings: Integrating network configuration and redundancy to risk

Natural disasters, such as earthquakes, landslides and floods, continue to pose significant threats to the urban society, resulting in human casualties, structural damage and economic losses. The impact of these extreme events is exacerbated by urbanization, infrastructural development and populational growth, emphasizing the demands for effective risk management strategies, above all during early emergency response stages. Existing approaches often focus mostly on structural aspects regarding risk, neglecting critical factors associated to road-circulation networks like first-responder accessibility, evacuation routes, road-system stability and citizen preparedness. These limitations may lead to an understatement of the real risk, reducing the effectiveness of disaster response plans and risk mitigation strategies. To address these issues, this approach develops a novel risk-index that integrates seismic hazards, built structures, and demographics data related to exposure to risks, and the configurational properties of the network, providing a territorial vulnerability layer for a comprehensive risk assessment. The configurational approach considers how the relative accessibility (Integration), the preferential routes (Choice), and the network redundancy (Kemeny-Based Centrality) contribute towards vulnerability, derived from seismic acceleration and resident population. The index is calculated for all residential structures within Tuscany, Italy. This multi-domain approach to risk has the objective to enhance accuracy in territorial vulnerability assessments at urban-regional scales, informing more effective disaster-risk preparedness and mitigation strategies, and emphasizing the importance of a multidisciplinary and integrated approach in risk assessment and emergency planning