Tsunami magnitudes in Taiwan, the Philippines and Indonesia |
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| Authors: | Tokutaro Hatori |
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| Institution: | (1) Suehiro 2-3-13, Kawaguchi, 332 Saitama, Japan |
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| Abstract: | The regional characteristics of tsunami magnitudes in the SE Asia region are discussed in relation to earthquake magnitudes during the period from 1960 to 1994. Tsunami magnitudes on the Imamura-Iida scale are investigated by the author's method (Hatori 1979, 1986) using the data of inundation heights near the source area and tide-gauge records observed in Japan. The magnitude values of the Taiwan tsunamis showed relatively to be small. On the contrary, the magnitudes of tsunamis in the vicinities of the Philippines and Indonesia exceed more than 1–2 grade (tsunami heights: 2–5 times) compared to earthquakes with similar size on the circum-Pacific zone. The relation between tsunami magnitude, m, and earthquake magnitude, M
s, is expressed as m = 2.66 M
s– 17.5 for these regions. For example, the magnitudes for the 1976 Mindanao tsunami (M
s= 7.8, 3702 deaths) and the 1992 Flores tsunami (M
s= 7.5, 1713 deaths) were determined to be m = 3 and m = 2.5, respectively. The focal depth of tsunamigenic earthquakes is shallower thand< 36 km, and the detectively of tsunamis is small for deep earthquakes being d > 40 km. For future tsunamis, it is indispensable to take precautions against shallow earthquakes having the magnitudes M
s> 6.5. |
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