著者

伯野 元彦 大草 垂康 道上 正規 Hakuno Motohiko Okusa Sigeyasu Michiue Masanori

出版者

新潟大学積雪地域災害研究センター

雑誌

新潟大学積雪地域災害研究センター研究年報 (ISSN:03877892)

巻号頁・発行日

vol.10, pp.35-50, 1988-12

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At 20:57 and 23:09 local time on the 5 March 1987 locally destructive earthquakes of Ms=6.1 and 6.9 shocked the northeastern part of Ecuador. The name Ecuador means the equator in Spanish, and Quito, the capital of this country, is located just 15 km south of the equator. Ecuador is approximately the same size as Japan except for the island of Hokkaido, and its population is approximately 9.4 million. Lt was primarily an agricultural nation until petroleum was discovered in the western Amazon area in 1972. Even with the substantial reduction in the price of petroleum in 1986, 45% of its total exports constituted petroleum. At present, exports other than petroleum consist of agricultural products such as bananas and coffee. Because of damage to its petroleum pipeline, (a major source of the nation's wealth) caused by the many landslides that took place after the 5 March 1987 earthquakes, Ecuador now has an international debt of 9 billion dollars that is a serious burden on its economy. Structural damage done by the earthquake ground motion was slight because the events took place in a mountainous area 80 km east of the comparatively dense populated central basin. The major damage was from landslides and flooding. Flooding occurred several hours after the earthquakes following the collapse of natural dams formed by sliding rocks and soil that barricaded rivers. The Nagano Prefecture-Seibu earthquake of 1984 in Japan had damage characteristics similar to those seen in Ecuador. The number of dead and missing people resulting from the Ecuadorean earthquakes is estimated as being several hundred to several thousand. The Japanese government dispatched a team of three experts (one each from the Ministry of Foreign Affairs, the National Land Agency, and the Japan International Cooperation Agency) to Ecuador to do earthquake reconnaissance. Our group was sent independently by the Ministry of Education. Culture and Science to survey the damage done by these earthquakes and was at the site from April 23 to May 7. The earthquakes occurred along the west foot of the volcano named Reventador, 80 km east of Quito. Damage caused by the earthquake can be roughly divided into three categories. The first was damage to the oil pipeline and to roads by massive slope slides that occurred over an area several kilometers square on the slopes of Mt. Reventador, rather, than by the shocks of the earthquakes themselves. The second was damage to bridges and the oil pipelines produced by river flooding because of the breaking of natural dams that had formed from the influx of slide material from the volcano's slope. The third was the collapse of houses caused by ground motion. We could not reach the area where most of the serious slope slides occurred using surface transportation because of the severe damage to roads and bridges. Therefore, we made our survey by helicopter The survey of damage to houses was made by truck because inhabited areas were not close to the area of severe slides and were accessible by truck.

著者

道上 正規 清水 正喜 矢島 啓 檜谷 治 白木 渡 宮本 邦明

出版者

鳥取大学

雑誌

基盤研究(B)

巻号頁・発行日

1998

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わが国では、現在では2000を越えるダムが存在しており、地盤条件あるいは降雨条件の厳しいわが国では、地震あるいは豪雨によって貯水池周辺で大きな崩壊が生じる確率は無視できず、崩壊土が貯水池に流入する可能性は低くない。多量の崩壊土が貯水池内に流入すると、イタリアのバイオントダムのように巨大な波が発生し、大災害を引き起こしかねない。このような災害は、大崩壊の発生確率とともに、貯水池数に依存しており、わが国でのその発生確率は年々高くなっていると考えられ、貯水池の流域管理が重要な課題である。そこで、本研究は、このような貯水池内での大崩壊にともなう段波形成について検討することを目的としたものであり、具体的には1)災害事例(特に眉山災害)に関する研究2)土砂崩壊の予測法に関する研究3)崩壊土砂の運動特性に関する数値解析的研究4)崩壊土塊の水域流入に伴う段波の形成と伝播遡上特性に関する数値解析的研究を実施するとともに、最終的に上記の研究を総合し、200年前島原で発生した眉山の大崩壊に伴う災害の数値シミュレーションを試み、大崩壊に伴う段波災害をある程度予測することが可能であることを実証した。