An internally consistent framework for calculating cascading probabilistic earthquake risk and its application to a case study in New Zealand

Abstract. Quantifying the combined effects of earthquakes and their cascading hazards is essential for realistic risk assessment, yet such approaches remain limited in practice. Dynamic frameworks that explicitly correlate hazard intensities and their uncertainties across cascading perils provide more consistent and physically plausible impact estimates, offering greater value for resilience planning and risk management.

This study introduces a probabilistic risk assessment framework that integrates ground shaking, tsunami inundation, liquefaction, landslides, and their combined impacts into a unified modelling approach. The framework employs a fully correlated Monte Carlo–based hazard and damage model, ensuring that secondary perils and their effects on assets are conditionally linked to the triggering ground motions. This dynamic correlation maximises the representation of realistic damage scenarios.

The framework was tested in Napier, a city of 65,000 inhabitants situated directly above the Hikurangi Subduction Zone (HSZ), New Zealand’s largest earthquake source with an estimated maximum credible magnitude of about Mw9.1. A 100,000-year stochastic catalogue of ruptures was generated and applied to ~30,000 residential buildings, with ground shaking, tsunami inundation, liquefaction severity, and landslide runouts explicitly modelled.

Results include damage state and damage ratio metrics for individual and combined perils. Earthquake shaking and liquefaction emerge as the dominant drivers of risk, followed by tsunami, lateral spreading, and landslides. These findings demonstrate the importance of capturing interdependent hazards in earthquake risk analysis. The framework provides decision makers, urban planners, and the (re)insurance sector with actionable metrics to guide resilience investments, refine underwriting, and minimise losses from cascading hazard events.