TSUNAMIS ALONG WEST COAST OF LUZON, PHILIPPINES

Abstract

A detailed engineering study was made by Ebasco Services, Inc., (1977), for a proposed nuclear power plant in the Napot Point region of Bataan, between the entrance to Manila Bay and Subic Bay, Republic of the Philippines (about 14°- 37-12'N, 120°- 18-3/4'E), Figure 1. As a part of the oceanographic portion of this work, a study was made by the writer of the characteristics of tsunamis that had occurred in the region, and the statistics of occurrence (Wiegel, 1976). The study of tsunamis has been updated to the present time (May, 1980). The location of the site is such that the large tsunamis generated in some areas of the Pacific Ocean (such as off the coasts of Chile, Alaska, Japan and Kamchatka) are not likely to reach Napot Point with any appreciable amplitude (see, for example, Wiegel, 1976). There is good evidence that this is the case. Owing to the relative stability from the standpoint of earthquakes (aseismic) of Borneo, the Malaya Peninsula, most of Indochina and the intervening China Sea (Gutenberg and Richter, 1949, pp. 82 and 93), there is probably little, if any, chance of tsunamis being generated in this region; this appears to be a fact (Berninghausen, 1969). The great eruption of Krakatoa and the tsunami generated by it was not noticed on tide gages at either Singapore or Hong Kong, so that it would be reasonable that it would not have been detected at Manila (Wharton, 1888). Also, the large tsunamis that have been generated in the Sulu Sea and the Celebes Sea do not seem to reach the site with any appreciable amplitude. Thus, the tsunamis of importance to the site are those which will be generated in the local seas off the west coast of Luzon. In order to establish this fact, information is presented on a number of tsunamis generated in other regions, especially those generated in the seas off the west coast of the Philippine Islands.