The March 5, 1987, Ecuador Earthquakes Mass Wasting and Socioeconomic Effects (1991) / Chapter Skim
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1 Introduction
1 Introduction
Pages 11-22
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From page 11... ...
, where two brick churches were severely damaged; several other brick buildings in Ibarra had to be reinforced subsequent to the quakes because of structural damage. In addition, considerable damage occurred to reinforced concrete buildings and foundations of wooden buildings in the village of Baeza (60 km SSW of the epicenters)
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From page 12... ...
Nearly all of the estimated 1,000 deaths from the earthquakes were a consequence of mass wasting and flooding. Because the mass wasting and flooding produced a high percentage of the economic and human losses resulting from these earthquakes, this report deals primarily with these processes, their socioeconomic effects, and the resulting social
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From page 13... ...
13 o~J~ ''. ~ , Reventador/~\ /1/ ~ Volcano ~~ ; Damaged Section of Pipeline W~oG~ /73< alado Pumping \ ~ Station ~°.5~O< - 'no _ ~ /Lumbaqui // ~ _ ~ - I rans-ecuacorlan /J ~ Pipeline Ceil Coca River ~ i/ \Destroyed Section of Pipeline 0 5 10km f it/ N FIGURE 1.2 Area of study of mass wasting and flooding caused by Me 1987 earthquakes, showing sections of damage to the Trans-Ecuadorian pipeline.
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From page 14... ...
The area of eastern Ecuador hardest hit by mass wasting due to the March 5, 1987, earthquakes was S of the epicentral area in the vicinity of Reventador Volcano (Figure 1.2~. Most casualties from the earthquakes occurred in this region (Figure 1.4~; the greatest damage to the Trans-Ecuadorian oil pipeline and highway occurred along the Coca River immediately SE of Reventador Volcano, upstream from beautiful San Rafael Falls (Figure 1.5~.
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From page 15... ...
employees who drowned in the Rio Coca near the mouth of the Rio Malo while trying to escape the flood caused by the March 5, 1987, earthquakes.
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The lip of the falls is formed by erosionresistant lava flows. This falls is the approximate downstream limit of serious landslide/flood damage along the Coca River.
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From page 17... ...
Widespread stripping of saturated surficial materials and jungle cover from steep slopes by earthquake shaking similar to that which occurred in the Reventador area in 1987 has been noted in other humid tropical areas in a few similar catastrophes in this century. In September 1935, two shallow earthquakes (M=7.9 and M=7.0)
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From page 18... ...
valley wall of the Malo River, showing extreme denudation of slopes due to slips/avalanches/flows caused by the March 5, 1987, earthquakes.
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From page 19... ...
Although the M=9.2 earthquake that struck southern Chile in May 1960 occurred in an area of temperate forest rather than in tropical jungle, it caused slope failures in the Valdivian Andes similar to those in Papua New Guinea and Panama Veblen and Ashton (1978) estimated that more than 250 km2 of forest slopes were denuded by mass wasting in the 1960 event.
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From page 20... ...
In summary, interrelated multiple hazards produced the catastrophic events of March 5, 1987, in the Reventador area. The tragic occurrence of two large earthquakes within 3 hr in an area of heavy antecedent rainfall, and steep slopes covered by unstable volcanic and residual soils with high water contents, resulted in massive slope failures of high fluidity.
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From page 21... ...
Note trimline in jungle cover along lower valley wall upstream of the river constriction. This trimline indicates position of the shoreline that was formed by damming of the river to a level 10-15 m above current river level.
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From page 22... ...
Proceedings of the Japan-China Symposium on Landslides and Debris Flows. Niigata, October 3, Tokyo, October 5, The Japan Landslide Society and The Japan Society of Erosion Control Engineering:273-278.
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