1979 Tumaco earthquake
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| Date | December 12, 1979 |
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| Origin time | 02:59 local time |
| Magnitude | 8.2 Mw |
| Depth | 33 km (21 mi) |
| Epicenter | 1°35′53″N 79°21′29″W / 1.598°N 79.358°WCoordinates: 1°35′53″N 79°21′29″W / 1.598°N 79.358°W |
| Areas affected | Colombia, Ecuador |
| Total damage | $8 million |
| Max. intensity | IX (Violent) |
| Tsunami | 6 m (20 ft) |
| Casualties | 300–600 |
The 1979 Tumaco earthquake occurred at 02:59 local time on 12 December with a moment magnitude of 8.2 and a maximum Mercalli intensity of IX (Violent). The epicenter was just offshore from the border between Ecuador and Colombia, near the port city of Tumaco. It triggered a major tsunami, which was responsible for most of the estimated 300–600 deaths. The hardest hit area was Colombia's Nariño Department.
Coastal parts of Ecuador and southern Colombia lie above the convergent boundary where the Nazca Plate subducts beneath the South American Plate along the Colombia–Ecuador Trench. At his location the Nazca Plate is moving to the east relative to South America at a rate of 58 mm per year. North of the Carnegie Ridge, the subduction interface has four recognisable segments, from south to north, the Esmeraldas, Manglares, Tumaco and Patia segments. This plate boundary has been the location of several great historical earthquakes, most associated with damaging tsunamis. In 1906 a 5–600 km long segment of the plate interface ruptured, causing a M 8.8 earthquake (rupturing all four segments) and a trans-Pacific tsunami.
This event was the last of three earthquakes that ruptured adjacent parts of the plate interface, forming a northeastward migrating sequence. The 1942 earthquake ruptured the Esmeraldas segment, the 1958 earthquake ruptured the Manglares segment and the 1979 event ruptured the Tumaco and Patia segments. Together they ruptured the same part of the megathrust as the 1906 earthquake. The rupture area of the 1979 earthquake measured 280 km long by 130 km wide.
The earthquake was widely felt in both Ecuador (including Guayaquil, Esmeraldas and Quito) and Colombia (including Bogotá, Cali, Popayán and Buenaventura). The coast in the epicentral region subsided by up to 1.6 m during the earthquake and the land movement locally disrupted river drainage.
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