A Probabilistic Framework for Coseismic Tsunami Design-PPT Presentation

PPT Presentation

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The presentation proposes a probabilistic framework for designing structures against earthquake ground shaking and coseismic tsunamis together. It extends probabilistic seismic hazard analysis by estimating the joint probability that an earthquake will produce both a specified ground-motion intensity and tsunami amplitude. The approach uses hazard curves and deaggregation to relate seismic and tsunami demands to earthquake magnitude, distance, and associated probabilities.<br /><br />The framework was applied to the Friday Harbor Ferry Terminal on San Juan Island, an important Washington State Ferries facility now being upgraded for seismic resilience. The analysis focused on spectral acceleration at a five-second period, selected because it is mainly influenced by Cascadia Subduction Zone earthquakes. The study used Cascadia earthquake-source and ground-motion models, while assuming that distant sources contribute little to the site’s ground-motion hazard and local sources contribute little to its tsunami hazard.<br /><br />Joint hazard estimates were developed across a range of correlations between seismic motion and tsunami amplitude. Results were presented for 1,033-year and 2,475-year return periods. The authors note that independently selected seismic and tsunami design events may correspond to different earthquakes; combining those independent extremes can therefore be conservative. Although structures must still withstand the separate seismic and tsunami design loads, demands from coupled seismic–tsunami loading may be substantially lower.<br /><br />Determining which joint-probability combinations, and how many of them, should be included in design remains an area for further research.

Keywords

probabilistic framework

earthquake ground shaking

coseismic tsunamis

joint hazard analysis

seismic hazard analysis

tsunami amplitude

hazard curves

deaggregation

Cascadia Subduction Zone

Friday Harbor Ferry Terminal