Combining tsunami hazard and vulnerability on the assessment of tsunami inundation probability in Taiwan

As earthquake and tsunami are closely related, the probability of tsunami hazard had been done by extending the approach used in earthquakes. However, the hazard of tsunami depends also on the vulnerability of neighboring structures and hence its hazard and vulnerability should not be assessed separately. The distribution of tsunami height varies so significantly that the traditional definition parallel to that in seismic risk should be modified. Besides, previous studies on the probability of tsunami focused on the occurrence possibility of tsunami hazard in a fixed period of time, but this information is not applicable for a specific tsunami incidence. For the above-mentioned problems, a new algorithm that comprises two components is proposed in the present study. The first component, the Probabilistic Forecast of Tsunami Inundation (PFTI), is the conditional inundation probability once a tsunami of a specific height occurs, or an earthquake is detected at some specific location with a specific magnitude. PFTI comprises the assessments of both tsunami hazard and vulnerability, and can be directly applied to a specific tsunami incidence. The second component treats the Tsunamigenic Earthquake Number (TEN) modified from previous studies on tsunami hazard. These two components are combined to give the inundation possibility in a fixed period of time dubbed Earthquake-induced Tsunami Inundation Probability (ETIP) and the result can be used in urban planning or disaster mitigation guidelines. Application of this methodology to the coast of Taiwan is also discussed.