Probabilistic Earthquake-tsunami Hazard Assessment: The First Step Towards Resilient Coastal Communities

As more population migrates to coastal regions worldwide, earthquake-triggered tsunamis pose a greater threat than ever before. Stakeholders, decision makers, and emergency managers face an urgent need for operational decision-support tools that provide robust and accurate hazard assessments, when human lives and built environment are at risk. To meet this need, this study presents a new probabilistic procedure for estimating the likelihood that seismic intensity and tsunami inundation will exceed given respective hazard levels. The novelty of the procedure is that a common physical rupture process for shaking and tsunami is explicitly taken into account. The procedure consists of generating numerous stochastic slip distributions of earthquakes with different magnitudes using scaling relationships of source parameters for subduction zones and then using a stochastic synthesis method of earthquake slip distribution. Coupled estimation of earthquake and tsunami intensity parameters is carried out by evaluating spatially correlated strong motion intensity through the adoption of ground motion prediction equations and by solving nonlinear shallow water equations for tsunami wave propagation and inundation. The main output of the proposed procedure is the earthquake-tsunami hazard curves, representing the one-to-one mapping between mean annual rate of occurrence and seismic and inundation tsunami intensity measures. Results are particularly useful for coupled multi-hazard mapping purposes. The developed framework can be further extended to probabilistic seismic and tsunami risk assessment.