日本海中部地震津波の波源における水位変動
―波源の海面変動体積と地震モーメントの関係―
1984 年 37 巻 1 号 p. 23-29
詳細
1984 年 37 巻 1 号 p. 23-29
By applying the Greens's law, the sea-level disturbance at the source area of the Nihonkai-Chubu tsunami (May 26, 1983) is calculated from the coastal inundation heights. By means of the same method, the volumes of the displaced water at the source area, V0, for 18 tsunamis are calculated, where the tsunami source area and the shoaling and refraction factors of the coastal heights are analyzed on the inverse and refraction diagrams, respectively. It is found that V0 is closely related to seismic moment, M0.
1) For the 1983 Nihonkai-Chubu tsunami, the height of the sea-level disturbance averaged over the tsunami source area is estimated to be 123cm, and the peak of 202cm seems to have disturbed in the southern part of the source area. The volume of the displaced water V0 is 12.3×1015cm3.
2) The relation between V0 and tsunami magnitude (Imamura-Iida scale, m) is expressed as
logV0=0.6m+14.7,
where the unit of V0 is ×1015cm3. Combining V0 and the seismic moment M0 (dyne-cm), which is empirically expressed as
logV0=0.78logM0-6.23.
However, the V0 values for the 1896 Sanriku and 1946 Aleutian tsunamis such as “tsunami earthquake” and the Japan Sea tsunamis (the 1940 Shakotan, 1964 Niigata and the present tsunamis) generated by the high angle fault are three times larger then those of the obtained from the above equation.
