Slope Failure Caused by 1894 Meiji Tokyo Earthquake in Hanno Town, Koma County, Saitama Prefecture

Investigations of disasters caused by past earthquakes are useful when taking measures against earthquake disasters that may occur in the near future. In western Saitama Prefecture, there have been few reports so far on damage caused by earthquakes occurring beneath the Tokyo metropolitan area; however, a remarkable description was found in the annual report of the Central Meteorological Observatory of Japan. According to the report, a slope in Hanno town failed over a width extending 640-660 m caused by the 1894 Meiji Tokyo earthquake. The author investigated the location of the failed slope and details of damage. A family in Kusumi, Hanno city (Hanno town at that time), suffered from a landslide caused by a past earthquake which is considered to be the 1894 Meiji Tokyo earthquake. The slope beside their residence extends for about 700 m to the east along the Hirayama ridge, and descends steeply toward the Iruma River. Many scars from small landslides are left on the entire surface of the slope. These topographical features suggest that several landslides occurred on this slope following the 1894 Meiji Tokyo earthquake. As a result, the author has come to the conclusion that the failed slope reported by the Central Meteorological Observatory of Japan was located along the Hirayama ridge, and several landslides occurred on this slope. It is possible to recognize that a strong quake shook Hanno town, which is located far from the epicenter.