On the Deep-focus Earthquake of Feb. 20th, 1931 occurred in the Northern Part of the Japan Sea

A supplementary report to Mr. Isikawa's investigation

Abstract

This earthquake was precisely investigated by Mr. Isikawa in the last year. (this journal Vol. 10, No.4.) This report is a supplementary one to it, especially on the point of the focal depth and reflected waves, taking advantage of the travel time table calculated by the author and others.