(3)The Geiyo Earthquake (June 2, 1905, M 7 1/4)
The source region of The Geiyo Earthquake is estimated to have been near the Akinada Sea in the western part of the Seto Inland Sea. This event is thought to have occurred in a somewhat deep location related to the subduction of the Philippine Sea Plate because of no tsunami accompanied, although the focal depth is not clear. The earthquake caused strong ground motion on the coasts of Hiroshima and Ehime Prefectures. It was particularly strong in Hiroshima City, Kure City, Edajima Town, Ujina (in Hiroshima City), Matsuyama City, Mitsuhama (in Matsuyama City), and Iyo City, where seismic intensity 5 to 6 in JMA scale was observed (Fig.8-15). There were 11 fatalities, and 56 completely collapsed houses in Hiroshima Prefecture. Eight houses were completely collapsed in addition to other damage sustained in Ehime Prefecture (Fig.8-16). There was marked damage at Hiroshima Prison in Hiroshima Prefecture. This stood on reclaimed land, and Plant No.14 collapsed, killing 2 and injuring 22. In Ehime Prefecture, some houses were completely collapsed at Mitsuhama, and damage also occurred in Iyo. There was slight damage to houses and other structures in Yamaguchi Prefecture. The greatest damage caused by this earthquake is thought to have occurred in Kure. There were military facilities in Kure at that time, so detailed information on the extent of damage is not available. About 5 hours after the earthquake, a large aftershock (M 6.0) occurred to the south, causing some damage. The largest aftershocks occurred at 0:08 p.m. (M 6.1) and 1:25 p.m. (M 6.2) on December 8. Of these, the latter was the largest.
Many earthquakes occurred near the source region of the Geiyo Earthquake over the period between 1903 and the occurrence of the Geiyo Earthquake. There were nine in 1903, three in 1904, and three before June 2, 1905. The earthquake on March 21, 1903 was measured at M 6.2.