A probabilistic tsunami hazard assessment (PTHA) in the ports of Hong Kong (China) and Kao Hsiung (Taiwan) will be presented in this seminar, with consideration of tsunamis generated by earthquakes in the Manila subduction zone. We propose a new PTHA methodology which consistently takes into account the aleatory uncertainty of the earthquake slip distribution and location. The generation of slip samples employs a Karhunen-Loève expansion and a translation model to account for any desired marginal distribution. The uncertainty propagation, on the other hand, adopts a stochastic reduced order model which is more accurate than classic Monte Carlo simulations. As an extension of this project, we also assess the impact of some sources of epistemic uncertainty in the PTHA. They are the probability properties of the uncertain slip distribution and location, the average earthquake recurrences and the tsunami propagation model, which are assessed by adopting sensitivity analyses.
According to our assessment, small tsunami hazards are estimated in Kao Hsiung and Hong Kong. In Kao Hsiung port, maximum tsunami amplitudes do not exceed 0.4 meters for return periods of 100 years. In Hong Kong, on the other hand, the maximum tsunami amplitude is smaller than 0.2 meters for return periods of 100 years. According to our epistemic uncertainty assessment, we also conclude that the earthquake recurrence model is a dominant source of uncertainty in the PTHA. Estimations of the maximum tsunami amplitude may differ in more than 100% when different earthquake recurrence models are adopted in the Manila subduction zone.