Research insights and challenges in multi-hazard dynamic vulnerability assessment of physical infrastructure

To date, risk models and the literature on infrastructure vulnerability have focused on single hazards. Yet in practice, no natural hazard occurs in isolation. Within the context of one hazard event, the built environment may be subjected by a number of diverse actions. For example, fault movement in an earthquake and subsequent ground shaking may trigger soil liquefaction, landslides or even tsunami. Such hazard effects on infrastructure may occur at the same time as the triggering event, or some time afterwards, with each event potentially adding to the asset damage or functional downtime. Indeed, the time dimension is commonly neglected in risk modelling, with the treatment of hazard occurrence as a Poissonian process and the use of generic vulnerability functions based on broad asset classes, which assume as-built conditions for the assets at the time of the hazard events. Recent research has seen significant progress in the development of time-dependent hazard models. However, infrastructure asset vulnerability is still largely treated as stationary in time. The fact that the physical properties of assets can degrade over time and that assets may have been subjected to a number of hazard occurrences during their lifetime, is neglected. In this talk, I will reflect on the current state of art of multi-hazard vulnerability assessment of physical infrastructure, drawing from experience of generating fragility functions using expert elicitation, empirical and numerical methods. I will also discuss how neglecting the history of hazards that affect physical infrastructure during their lifetime may result in serious under-prediction of their vulnerability and hence unconservative risk estimates. Finally, I will highlight outstanding research needs, including considerations on gaps in existing taxonomies and exposure data.