1989 年 42 巻 2 号 p. 183-188
Based on tide-gauge records, the characteristics of tsunami associated with aftershock and swarm near Japan during 1896 to 1983 are investigated, comparing with tsunami of the main shock. The obtained results are as follows:
1) The main shocks having magnitude more than M 6.8 have been accompanied with the second tsunami. Seventy percent of the main shocks with M7.8 to 8.1 have the maximum aftershocks accompanied with tsunamis. These tsunami magnitudes on the Imamura-Iida scale, m, are 1 to 2 smaller than those of the main shock.
2) Tsunami source of the aftershock is situated near the edge of long axis or neighborhood of the main shock area. The area of the tsunami source is 1/5-1/10 of that of the main tsunami source.
3) Most of the tsunami magnitudes for the swarms are in the range of m -1-0. A part of the source area overlaps each other.
Tsunamis which generated by the aftershock of large earthquake hit locally. As we need tsunami warning for the main shock, so we need precaution against tsunamis associate with aftershocks.