The Landslide, Steam Explosions, and Debris Avalanche Sequence of May 1997 at Sumikawa Spa, Akita Prefecture, Japan

概要

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Hydrothermal activity, a common phenomenon in volcanic regions, may cause a very special type of landslide. Such a complex landslide, about 6 million m^3 in volume, occurred at about 8 : 00 a.m. on 11 May 1997 at Sumikawa Spa, Akita Prefecture, northern Japan. The landslide's shear zone was approximately at the boundary between the underlying hydrothermally altered, impervious pyroclastic rocks and overlying pervious lava flows at depths of 60 to 70 meters. Many fumaroles were located near the toe of the landslide, and the landslide's foot closed their steam vents, resulting in later steam explosions. The steam explosions, in turn, converted the foot into a debris avalanche and debris flow. The landslide probably was triggered by groundwater recharged by snowmelt and heavy rain. Because of immediate evacuation there were no casualties, in spite of the large size and rapid movement of this landslide.
日本自然災害学会の論文