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One of most strong earthquake that struck the Napo mountainous Region, NE Ecuador, occurred the 5th March 1987 of Ms 6.9, nucleation depth about 3-12 Km and 22:10 local times; at the 19h54 an beforeshock of Ms 6.1 was also recorded in the epicentral area. The maximum epicentral intensity was of Io=IX (MM-1956 scale) (Egred, 1988); however, significant environment effects cannot be studied at detail for not having a tool that determine real epicentral damage.
During these two seismic events, extensive landslides were triggered over an area of ca. 33.000 km2, with a total volume from 75 million cubic-m to 110 million cubic-m (Nieto et al.,2000). Indeed, huge ground-mass landslides and vast floods were triggered from SW flank El Reventador Volcano, damming the main rivers and damaged important Ecuador's infrastructures. Along the Coca stream, the biggest damage was reported of ca. 12 km of trans-Ecuadorian pipeline (oil and gas propane); as well as 30 Km of the main highway that joins Quito (Ecuador's capital) with Lago Agrio (chief city in the Ecuadorian oil fields). Loos of bridges by debris flows were reported in the Salado and Aguarico streams, rising ca. 20m above the stream levels. Moreover, local debris avalanches reaching the flood plains of the Quijos stream. Along the Coca river in the sector of San Rafael's Cascade a temporary dams caused severe damages by flood at surrounding villages. Surface faulting and liquefaction were observed in the Cascabel sector. Small landslides were generated in slopes and stream banks. Ground cracks in the highways exceeding 1-m-wide. Subsidence phenomenon were also reported in the El Salado pumping station.
The application of the ESI 2007 Scale to the above listed geological effects has allowed re-construct an independent Macroseismic field. A maximum intensity of X ESI should be well assigned to the area SW El Reventador Volcano and an Intensity of IX ESI to the settings described in the Aguarico and Malo stream sectors.
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