Optimization of municipal bridge retrofitting based on nationwide spatial clustering integrating seismic risk and fiscal capacity in Japan

This article presents a nationwide framework for prioritizing seismic retrofitting of municipally managed bridges in Japan by combining bridge-level seismic risk, municipal fiscal capacity, spatial clustering of recovery capacity, and budget-constrained optimization. Its goal is to help identify which municipalities and which bridges should be prioritized to strengthen post-earthquake resilience under limited public budgets. 

The findings reveal that municipal recovery capacity varies significantly across Japan and that clusters of municipalities with low recovery capacity are concentrated in several regions, making them especially vulnerable to delayed post-earthquake recovery. It also shows that municipalities with similar recovery capacity can still obtain very different economic benefits from bridge retrofitting, depending on factors such as bridge vulnerability, spatial distribution, and seismic hazard, meaning retrofit investments can be made more effective through targeted optimization.