Reexamination of Theoretical Methods Employed by the Physicist Hantaro Nagaoka for Earthquake Studies from the 1900s through the 1920s

Abstract

This paper aims to reexamine the theoretical methods employed by the physicist Hantaro Nagaoka (1865–1950) for earthquake studies from the 1900s through the 1920s by conducting an in-depth analysis of his academic papers. He used two theoretical methods for earthquake studies. One used the principle of elasticity studies against the background of the current that succeeded in France in the first half of the 19th century. The other defined potential functions and explained phenomena from continuous equations of the nature of waves against the background of new currents that emerged in Britain or Germany from the mid-19th century onwards. The differences between these methods were not related to his research subjects or the timing of his research activities. He tried to understand and explain local natural disaster phenomena such as earthquakes through both kinds of theoretical methods.