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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Oral Presentation 1782
Probabilistic tsunami hazard analysis - results for the Pacific and Indian
Oceans
Dr. Hong Kie Thio
Jascha Polet, Paul Somerville
We have developed a series of probabilistic tsunami hazard maps for the coasts of western North
America Australia and along the Indian Ocean based on fault source characterizations of the circum-
Pacific subduction zones as well as local offshore faults. The maps show the probabilistic offshore
exceedance waveheights at 72, 475, 975 and 2475 year return periods, which are the return periods
typically used in Probabilistic Seismic Hazard Analysis (PSHA). Our method follows along similar lines as
(PSHA) which has become a standard practice in the evaluation and mitigation of seismic hazard in
particular with respect to structures, infrastructure and lifelines. Its ability to condense complexities,
variability and uncertainties of seismic activity into a manageable set of ground motion parameters
greatly facilitates the planning and design of effective seismic resistant buildings and infrastructure.
Because of the strong dependence of tsunami wave heights on bathymetry, we use a full waveform
tsunami waveform computation in lieu of attenuation relations that are common in PSHA. By precomputing
and storing the tsunami waveforms at points along the coast generated for sets of subfaults
that comprise larger earthquake faults, we can rapidly synthesize tsunami waveforms for any slip
distribution on those faults by summing the individual weighted subfault tsunami waveforms. This
Green's function summation provides accurate estimates of tsunami height for probabilistic calculations,
where one typically integrates over thousands of earthquake scenarios. We have carried out tsunami
hazard calculations for western North America and Hawaii, and based on a comprehensive source model
around the Pacific and Indian Oceans. We will present the tsunami hazard maps and discuss how these
results are used for probabilistic inundation mapping, including a follow-up inundation study of the San
Francisco Bay area that is based on disaggregation results of the probabilistic analysis. We will also
show that even for tsunami sources with large uncertainties (e.g. submarine landslides) a probabilistic
framework can yield meaningful and consistent results.
Keywords: tsunami, earthquakes, hazard