Some Investigations of Shallow Earthquakes (I)

Abstract

The “pull-push” distribution of initial motion of P-wave no shallow earthquake were studied by Mrs. Kawasumi and Minakami, taking into account the effect of Moho_??_ovi_??_i_??_'s layer. But, on the other hand, Dr. Wadati, and others denied the existence of such a layer and in a depth corresponding to it, velocities of scismic waves become nearly constant.
The present author has calculated the distribution of the amplitudes of initial motion in the latter case with the following results:-
1. The distance corresponding to the radius of “Inflexion c'rcle” in the former case, can be com_??_etely explained by the latter and the shape of nodal line is slightly different from the former.
2. The calculated distribution of the amplitude of initial motion is in good agreement with the observed fact. We have calculated the vertical angle of nodal cone and the displacement near the epicenter in some shallow earthquakes.