Science of Tsunami Hazards (Jan 2012)
THE SAMOA TSUNAMI OF 29 SEPTEMBER 2009 Early Warning and Inundation Assessment
Abstract
On 29 September 2009 at 17:48:11 UTC, a large earthquake of magnitude 8 struck off-shore of the Samoa Islands and generated a large tsunami that destroyed several villages and caused more than 160 fatalities. This report first presents the characteristics of the earthquake and discusses the best estimations for the fault parameters, which are the necessary input data for the hydrodynamic tsunami calculations. Then, the assessment of the near-real time systems invoked by the Global Disasters Alert and Coordination System (GDACS)1 and the post-event calculations are performed, making comparisons with the observed tidal measurements and post-event survey. It was found that the most severely damaged locations are the Southern section of the Western Samoa Islands, Tutuila Isl in American Samoa and Niuatoputapu Isle in Tonga. This is in agreement with the locations indicated by the Red Cross as the most affected and with the results of the post-tsunami surveys. Furthermore, an attempt was made to map the inundation events using more detailed digital elevation models (DEM) and hydrodynamic modelling with good results. The flooded areas for which we had satellite images and post-tsunami surveys confirm the inundated areas identified correctly by the hydrodynamic model. Indications are given on the DEM grid size needed for the different simulations.
