1970 Ancash earthquake

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Coordinates: 9°28′S 78°19′W / 9.47°S 78.31°W / -9.47; -78.31

1970 Peru earthquake
Peru zemlyatrus.jpg
1970 Ancash earthquake is located in Peru
1970 Ancash earthquake
Date May 31, 1970 (1970-05-31)
Magnitude 7.9 Mw,[1] 7.8 Richter scale
Depth 30 kilometres (18.6  mi)
Epicenter near Chimbote in Ancash Region
Areas affected Peru
Casualties 100,000 confirmed (75,000 dead and 25,000 missing) and 200,000 injured

The 1970 Ancash earthquake or Great Peruvian Earthquake was an undersea earthquake that occurred on May 31 of that year. Combined with a resultant landslide, it was the worst catastrophic natural disaster ever recorded in the history of Peru. Due to the large amounts of snow and ice included in the landslide and its estimated 100,000 fatalities (74,000 people dead and 25,600 missing)[2] it is also considered to be the world's deadliest avalanche.[3][4]

The earthquake affected the Peruvian regions of Ancash and La Libertad. The epicenter of the earthquake was located 35 km off the coast of Casma and Chimbote on the Pacific Ocean, where the Nazca Plate is being subducted by the South American Plate. It had a magnitude of 7.9 to 8.0 on the Richter scale and an intensity of up to VIII on the Mercalli scale. No significant tsunami was reported.[5]

The earthquake struck on a Sunday afternoon at 15:23:31 local time (20:23:31 UTC) and lasted 45 seconds. The quake destabilized the northern wall of Mount Huascarán, causing a rock, ice and snow avalanche and burying the towns of Yungay and Ranrahirca. The avalanche started as a sliding mass of glacial ice and rock about 3,000 feet (910 m) wide and one mile (1.6 km) long. It advanced about 11 miles (18 km) to the village of Yungay at an average speed of 280 to 335 km per hour.[5] The fast-moving mass picked up glacial deposits and by the time it reached Yungay, it is estimated to have consisted of about 80 million cubic meters (80,000,000 m³) of water, mud, and rocks.

Yungay Viejo (2500 m) as seen from the cemetery hill. The light shaded area shows the location of the landslide (ice, mud, debris avalanche) on 31.05.1970, caused by an earthquake, in which a part of the western flank of Huascaran Norte broke (6652 m). Yungay Nuevo is behind the shaded area in the center.


  1. ^ "IRIS SeismoArchive for 1970 Peru earthquake". Archived from the original on 2009-10-08. Retrieved 2009-10-05. 
  2. ^ Thériault, Annie (31 May 2009). "Yungay 1970-2009: remembering the tragedy of The Earthquake". Peruvian Times. Retrieved 17 February 2014. 
  3. ^ http://www.guideto.com/science-nature/earth-climate/snow-ice/the-worst-avalanches-in-history.html
  4. ^ Huascarán
  5. ^ a b Geological aspects of the May 31, 1970, Perú earthquake, by George Plafker, George E. Ericksen and Jaime Fernández Concha; Bulletin of the Seismological Society of America; June 1971; v. 61; no. 3; p. 543-578 (134MB PDF)

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