2019 Volume 2019 Issue 50 Pages 45-64
In the 1920’s and 1930’s, three moderate to large inland earthquakes occurred in Honshu Island, Japan, namely the 1925 Kita-Tajima earthquake (M6.8), the 1927 Kita-Tango earthquake (M7.3), and the 1930 Kita-Izu earthquake (M7.3). Imperial Geological Survey of Japan (GSJ) sent geologists to these earthquake disaster areas soon after the earthquakes to investigate the geological effects including surface faulting, landslides, and their relation to damage. Their findings at the dawn of active fault research in Japan have made a great contribution to the subsequent earthquake and active fault studies. Curious to say, the geologists who were dispatched to the investigation are different every earthquake (Tsutomu Ogura for the 1925 Kita-Tajima earthquake; Kyukichi Watanabe and Hokoto Sato for the 1927 Kita-Tango earthquake; Keinosuke Ihara and Kiyohiko Ishii for the 1930 Kita-Izu earthquake). What are the reasons why those five geologists were sent to the investigations and why the geologists who engaged in the field investigation were different even though each of earthquakes occurred in a quite short period? In order to unravel these questions, the author has collected and investigated the materials that document the detail of annual activity of the geologists, their personal history, and the state of work at GSJ. According to the materials, they all experienced the disaster investigation of the 1923 Great Kanto earthquake and survived from massive dismissal by administrative reorganization due to the recovery of the earthquake in 1923 and 1924. Among them, the geologists who did not have engaged in an ordinary geological work such as Geological Sheet Map 1:75,000 by chance at the time of the earthquakes seem to have been dispatched to the earthquake disaster investigation. Furthermore, they were all not only the excellent and hardworking geologists but also the men who have manliness and were well-liked by their subordinates.
