Fault

In the history of the study of faults, Robert Mallet, an Irish engineer, was the first to believe that simple mechanics of the earth's crust cause earthquakes. Until 1859, when he proposed his theory, earthquakes were believed to be caused by huge explosions deep within the earth, and the origin of these explosions was never questioned. Mallet knew that iron, which appears indestructible, ruptures under extreme stress, and Mallet theorized that earthquakes are caused "either by the sudden flexure and constraint of the elastic materials forming a portion of the earth's crust, or by their giving way and become fractured." Mallet was not supported, primarily because he was not a scholar and lived in Ireland where earthquakes seldom occur. In 1891, however, Professor Bunjiro Koto, a Japanese specialist in seismology, or the study of earthquakes, endorsed Mallet's theory. After the Mino-Iwari earthquake, which occurred along a remarkably clear fault line crossing the island of Honshu, he said the shaking earth caused quakes and not the other way around. Harry Fielding Reid, an American scientist, was the first to relate the stresses along faults to tectonic plate boundaries after the 1906 Great San Francisco Earthquake.