Recent landslides in western Hokkaido, Japan

Western Hokkaido, the northernmost island of Japan: is prone to landsliding due to geologic, geomorphologic and climatic change. From 1985 to 1997, ma ny rapid large-scale landslides occurred in western Hokkaido, several of wh ich are reviewed in this paper. The 1988 Kamaya Slide, the 1991 Tachimachi- misaki Slide (which was preceded by the 1985 Orito Slide), the 1993 Okushir i-Port Slide, and the 1994 Motochi Earthflow are described. Finally, two se a-cliff rockfalls are also described. The Okushiri-port Slide and the Toyohama Tunnel Rockfall claimed 29 and 20 lives, respectively. Except for the Okushiri-port Slide, which was induced by Hokkaido Nansei-oki Earthquake, most of the slides and rockfalls were pr obably related to geological structures, such as gentle-dipping strata inte rbedded with clayey tuffs and were triggered by long-duration and/or high p recipitation, causing increased groundwater levels and/or high water pressu res.