The 1979 Tumaco earthquake occurred at on 12 December with a

moment magnitude The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pape ...

of 8.2 and a maximum

Mercalli intensity The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

of IX (''Violent''). The

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

was just offshore from the border between Ecuador and Colombia, near the port city of

Tumaco Tumaco is a port city and municipality in the Nariño Department, Colombia, by the Pacific Ocean. It is located on the southwestern corner of Colombia, near the border with Ecuador, and experiences a hot tropical climate. Tumaco is inhabited mai ...

. It triggered a major

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

, which was responsible for most of the estimated 300–600 deaths. The hardest hit area was Colombia's Nariño Department.

Tectonic setting

Coastal parts of Ecuador and southern Colombia lie above the

convergent boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more Plate tectonics, lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can ...

where the

Malpelo Plate The Malpelo Plate is a small tectonic plate (microplate) located off the coasts west of Ecuador and Colombia. It is the 57th plate to be identified. It is named after Malpelo Island, the only emerged part of the plate. It is bounded on the west ...

subducts beneath the South American Plate along the Colombia–Ecuador Trench. At this location the Malpelo Plate, the microplate northeast of 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 Carnegie Ridge is an aseismic ridge on the Nazca Plate that is being subducted beneath the South American Plate. The ridge is thought to be a result of the passage of the Nazca Plate over the Galapagos hotspot. It is named for the research ...

, 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.

Earthquake

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 , motto = Por Guayaquil Independiente en, For Independent Guayaquil , image_map = , map_caption = , pushpin_map = Ecuador#South America , pushpin_re ...

, Esmeraldas and

Quito Quito (; qu, Kitu), formally San Francisco de Quito, is the capital and largest city of Ecuador, with an estimated population of 2.8 million in its urban area. It is also the capital of the province of Pichincha. Quito is located in a valley o ...

) and Colombia (including

Bogotá Bogotá (, also , , ), officially Bogotá, Distrito Capital, abbreviated Bogotá, D.C., and formerly known as Santa Fe de Bogotá (; ) during the Spanish period and between 1991 and 2000, is the capital city of Colombia, and one of the larges ...

Cali Santiago de Cali (), or Cali, is the capital of the Valle del Cauca department, and the most populous city in southwest Colombia, with 2,227,642 residents according to the 2018 census. The city spans with of urban area, making Cali the second ...

Popayán Popayán () is the capital of the Colombian department of Cauca. It is located in southwestern Colombia between the Western Mountain Range and Central Mountain Range. It has a population of 318,059 people, an area of 483 km2, is locate ...

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.

Tsunami

The coast nearest the epicenter was hit by the first wave of the tsunami about three minutes after the earthquake. Three to four waves were observed, with the third being the highest. The third wave coincided with low tide, greatly reducing the extent of the inundation and the likely death toll. The maximum observed water height was 6.0 m at San Juan de la Costa, northeast of Tumaco. The tsunami was observed on the east coast of Japan, in Hawaii, Tahiti and Mexico.

Damage

The earthquake caused widespread damage, particularly in Tumaco, where about a tenth of all buildings were destroyed, including 1,280 houses, and 25 people were reported either dead or missing. The fishing village of Charco was almost completely destroyed by the tsunami, the waves washing the houses inland into a nearby lake. 93 of the original population of 4,000 were reported either dead or missing. The tsunami also destroyed all the houses in San Juan de la Costa, with 199 reported either dead or missing. The total death toll was estimated to be 500–600 with another 4,000 injured.

Aftermath

The damage caused by this earthquake and the 1983 Popayán earthquake, near central Colombia, led to the development of a national building code for

earthquake-resistant structures Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely immune to damage from earthquakes, the goal of earthquake-resistant construction is to ...

for Colombia, which came into law in 1984.

References

External links

* {{Portal bar, Ecuador, Colombia, Earth sciences 1979 earthquakes 1979 in Colombia 1979 in Ecuador 1979 tsunamis December 1979 events in South America Megathrust earthquakes in Colombia Megathrust earthquakes in Ecuador Tsunamis in Colombia Tsunamis in Ecuador