Assessment of the impact of temporal and spatial factors on the emergency evacuation capacity of external spaces in high-density urban communities during earthquake disasters

The frequent occurrence of earthquakes, their high intensity, shallow focus and wide distribution pose severe challenges to urban safety and economic development. In high-density urban districts, the challenges of evacuation during earthquakes are further compounded by dynamic population distribution, traffic restrictions and limited emergency shelter space. This study develops an Agent-Based Model (ABM) to assess evacuation capacity under different scenarios, including baseline conditions, time-segmented evacuations, and earthquake-induced disruptions, using Nanjing's Gulou District as a case study. The simulation results reveal significant temporal and spatial variations in evacuation success rates. Areas with high population density and insufficient open space experience severe congestion and overloaded emergency shelters, especially in immediate evacuation scenarios. Road damage critically undermines evacuation success in directly affected zones, which emphasizes the need for a resilient road network. Moreover, weekday and weekend evacuations follow distinct patterns—office districts suffer from peak-time congestion, while commercial areas face evacuation delays during late-night hours. Vulnerable groups, including children and the elderly, face additional challenges due to mobility constraints and increased congestion in affected areas. By combining physical vulnerability (static) with time-varying population distribution (dynamic), it analyzes shifting evacuation demands. At the community scale, the research collected data on emergency spaces, evacuation routes, and population data for different time periods. This comprehensive analysis reveals the core dilemmas of the evacuation system and provides a basis for optimization strategies. The study underscores the need for better spatial planning and improved evacuation management to enhance disaster resilience in high-density urban districts. The findings provide valuable insights for urban planners and emergency response teams to optimize evacuation efficiency and minimize risks during earthquakes.