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.