A quantitative methodology for analysing physical damage and recovery dynamics from concurrent and consecutive hazards: forensic insights from Puerto Rico

Space and time play a crucial role in multi-hazard impact assessment. When two or more natural hazards oc- cur simultaneously or in sequence at the same location, the physical integrity of assets and infrastructures can be com- promised, and the resulting damage can be greater than that generated by individual hazards occurring in isolation. De- spite widespread conceptual recognition of these interac- tions, the literature lacks quantitative, standardised meth- ods for the systematic analysis of multi-hazard impacts. This study presents a quantitative methodology for evaluat- ing multi-hazard physical damage to the built environment, translating qualitative impact dynamics into a transparent and reproducible analytical framework, implemented as modular Python code. The approach covers both concurrent and con- secutive hazards by modelling: (i) the increased damage re- sulting from the combined impact of two or more concurrent hazards that overlap in space and time, and (ii) the effects of cumulative damage on asset vulnerability and the recovery dynamics in the case of consecutive hazards that overlap in space. Using the Python implementation, a model behaviour analysis is conducted to systematically explore how variations in inter-event time intervals, vulnerability interactions, and recovery trajectories affect cumulative physical damage. The methodology is applied to a real multi-hazard sequence in Puerto Rico, including the concurrent wind and flood im- pacts of Hurricane Maria and the consecutive seismic im- pacts of the 2019–2020 earthquake sequence. The recon- struction of past damage dynamics highlights that ignoring residual hurricane damage would significantly underestimate the subsequent earthquake losses, and that damage accumu- lation is path-dependent, strongly influenced by event timing and recovery processes. By providing a generalised, transpar- ent, and reproducible quantitative structure, this study offers a tool for forensic analysis of past multi-hazard events, sys- tematic exploration of damage drivers, and scenario-based assessment of alternative hazard and recovery conditions, supporting both post-disaster learning and planning-oriented applications.