MATHEMATICAL SIMULATION OF TSUNAMI EXCITATION BY DISLOCATIONS OF OCEAN BOTTOM

A simplified model of acoustic tsunami precursor is developed in order to have a more reasonable physical understanding of an audible boom on the coast heard just after the occurrence of a big earthquake and just before the first tsunami arrival. Such acoustic precursors have been found in the historical descriptions on the coast of the northwestern Pacific. A quite similar remark was found also in a recent report of the 1977 Sumbawa tsunami prepared and issued by the Indonesian Governmental Publication Office. The model introduced in this work deals with the problem of an acoustic ray generated by a sound source associated to an undersea earthquake and subsequently refracted across the air–sea interface. A theoretical estimate of the audible boom is studied to give a possible case of an audible tsunami precursor. This model is yet hypothetical, though it is clear that the past hazardous tsunamis in the northwestern Pacific accompanied the large undersea earthquakes with audible offshore or atmospheric booms that were real tsunami precursors. So that, the boom can be exploited for a short–range prediction if this model is appropriately improved. * A part of this work was presented at Society held in Bologna in March 1988. the general assembly of the European Geophysical