Numerical modeling of the 1995 Chilean tsunami. Impact on French Polynesia

On the 30th July 1995, an earthquake with magnitude of 8.1 occurred off the coast of Chile. The associated tsunami propagated across the Pacific ocean and reached French Polynesia 10 hours after the seismic event with maximum runup heights of about 2.5 meters. The most affected islands in French Polynesia were the Marquesas Islands that present few outer reefs, more gradual bottom slopes and large bays. The tsunami propagation has been modeled from Chile to Polynesian Islands, solving the shallow water equations. The water surface initialisation has been computed from Okada's formulas, using seismic parameters of Ruegg (1996). The tsunami propagation is simulated by a finite-difference numerical model using a system of multiple grids with different grid sizes. The computed waves are in fair agreement with the recorded waves along the Chilean coasts, in Tahiti and in Nuku Hiva. The numerical results obtained in the Marquesas Islands confirm the observations of numerous eyewitnesses.