Integrated Engineering–Economic Analysis for Multihazard Damage and Loss Assessment

Abstract

This paper presents a methodology to evaluate the direct and general equilibrium losses for a testbed community subjected to a megathrust earthquake and tsunami hazard originating in the Cascadia Subduction Zone. The testbed community studied consists of buildings for all residential and commercial sectors in the economy. A fragility analysis and functionality model are applied to estimate the direct damage and losses of these buildings at the parcel level. The process relies on Monte Carlo simulations (MCS) that propagate uncertainties from the hazards through to the damage and loss models. A computable general equilibrium (CGE) model is used to assess aggregated general equilibrium losses to the community. As an important mitigation strategy, seismic retrofit reduces the direct loss to building functionality and general equilibrium losses. Results show that the vulnerability of economic sectors depends on the hazard type, hazard intensity, economic zone, and building type, and the risks vary with the recurrence interval. The highest risks are associated with 500-year and 1,000-year mean recurrence intervals for joint seismic–tsunami hazards, respectively. Results from assessing different design alternatives show that whereas retrofitting all buildings to the highest code level considered results in the lowest losses, retrofitting only commercial buildings can be an efficient retrofit option for enhancing community resilience when controlling for costs. Last, a sensitivity analysis shows that losses and associated risks are sensitive to the definition of building functionality, which highlights the necessity for a common definition of building functionality when performing vulnerability analyses.