Abstract
In the present tsunami warning system, the predominance of the approaching tsunami is estimated, taking account of the earthquake magnitude and focal depth. However the predominance of tsunami also depends on other focal parameters, e.g. the rise time of the source time function, fault length etc. Accordingly it is quite natural that great tsunamis due to earthquakes with relatively small magnitudes have been sometimes observed. For the improvement of the tsunami warning system, it is necessary to develop the method to find the focal parameters before the tsunami wave arrivals and to make clear the dependence of the generation of tsunami on the above parameters. Effects of the focal parameters on the generation of tsunami and Rayleigh waves are investigated in a previous and in the present paper respectively. If the focal parameters are pre-estimated by the use of early arrival Rayleigh waves, the predominance of tsunami can be predicted. Although some of the focal parameters have fairly complex effects on both waves, it is shown that there is some possibility of the improvement of the present warning system by the use of tectonic features and body waves in addition to sub-oceanic Rayleigh wave observation.
