Urban Area Earthquake Risk Assessment and Comparative Analysis of Weighting Methods Including Water Quality Risk of Water Supply Systems

Damage to water distribution networks during earthquakes disrupts both the supply and quality of water by increasing water age. However, existing seismic risk assessments have primarily focused on physical damage, with limited research addressing water quality safety or comparative analyses of weighting methodologies. Therefore, this study developed a comprehensive seismic risk assessment methodology by incorporating a water-age-based measure of water quality risk and comparing the entropy weighting method with an equal-weighting approach across 45 legal districts in the city of Gyeongju. An integrated assessment framework comprising five indicators was established by adding water quality risk to the existing four indicators. Water quality safety was evaluated using EPANET software, employing a 48-hour water age criterion. The analysis showed that water quality risk accounted for substantial weights in the entropy weighting method (M = 5.0: 38.3%, M = 7.0: 28.9%), and that a balanced risk assessment was achieved in 86.7% of areas, compared to the existing four-factor system. The findings provide scientific evidence for developing magnitude-specific disaster prevention strategies.