1970 Ancash earthquake
The Ancash earthquake of 1970, known locally as the terremoto del 70, was an earthquake that occurred on Sunday, May 31, 1970, at 3:23 p.m., local time. It had a magnitude of 7.9 on the moment magnitude scale and an intensity of degree IX (violent) on the Mercalli scale. It was felt throughout the coast and mountains of the department of Áncash and the bordering regions in the south and north. The earthquake produced the detachment of an ice cap and rocks from the snowy Huascarán, which caused a flood that buried the city of Santo Domingo de Yungay and its twenty thousand inhabitants.
It was the most destructive earthquake in the history of Peru, not because of the magnitude, but because of the number of human losses. It affected the Ancash region and several provinces in the departments of Huánuco, Lima and La Libertad, and damaged an extensive area of approximately 450 km in length and 200 km in width of the Peruvian coast and highlands.
Due to this catastrophe, in 1972, the Government of Peru founded the National Civil Defense Institute (Indeci), which, in addition to preparing the population to act during an earthquake, commemorates May 31 with a simulation of nationwide earthquake.
Features
The earthquake began on May 31, 1970, at 15:23:32. Its epicenter was located 20 km west-southwest of the city of Chimbote, in the Pacific Ocean, at a depth of 1 km. Its magnitude was 7.9 on the seismological scale of moment magnitude, according to the IGP and USGS, and it reached a maximum intensity of grade IX on the Mercalli scale modified in Casma. It also produced a violent avalanche in the cities of Yungay and Ranrahirca. The intensities evaluated in several cities were:
| Place | Intensity in Mercalli (MM) |
|---|---|
| Casma, Chimbote | IX (Violent) |
| Huallanca, Aija, Caraz, Carhuaz, Yungay, Huaraz | VIII (Severe) |
| Chacas, San Luis, Huari, Pomabamba, Piscobamba, Llamallín, Trujillo, Santiago de Chuco, Huarmey | VII (Very strong) |
| Huacho, Lima and Callao, Cerro de Pasco, Chavín | VI (Fort) |
| Cajamarca, Chiclayo, Huánuco, Tingo María | V (Moderate) |
| Ica, Chincha Alta, Juanjuí, Huancayo, Tarapoto, Yurimaguas | IV (Ligero) |
| Iquitos, Tumbes, Guayaquil | III (Dable) |
Effects on Ancasino territory and Peru
The Andean zone of Áncash and the picturesque area of Callejón de Huaylas, were the area hardest hit by the earthquake. The city of Huaraz was 97% destroyed and lost more than 10,000 inhabitants (50% of the population). After the quake, the area was obscured by a black blanket of dust that remained for days. The rest of the cities and towns of the Callejón de Huaylas were also almost completely destroyed, from Recuay in the south to Huallanca in the north. The second most important city, Yungay, ended up buried next to Ranrahirca by an avalanche, with twenty-five thousand inhabitants disappearing. Avalanches and landslides blocked roads and highways and dammed parts of the Santa River. The railway that linked Chimbote with Huallanca disappeared.
The Andean zone following the Callejón de Huaylas, known as Conchucos, was left with moderate damage due to the large amount of seismic energy absorbed by the Cordillera Blanca massif, a natural barrier that divides the Callejón de Huaylas from the eastern Sierra de Ancash, even so, many of the buildings were left uninhabitable, and dozens of people died while they were working in agricultural areas due to landslides in the adjoining hills. The area was isolated for several months from the rest of the country.
In the coastal area, the effects of the earthquake destroyed large sections of the Pan-American highway between Huarmey and Trujillo (La Libertad department). Both the city and the port of Chimbote were left with unquantifiable damage, in the areas of San Pedro and Lacramarca all the buildings collapsed, as well as the fishing industries, and similar damage to the metallurgical, in some areas the ground cracked until expelling jets of water up to a meter high, the city lost more than 2,800 inhabitants.
In Casma, an old adobe city, eight hundred people died, and further south, in Huarmey, one hundred. The Province of Bolognesi, with 1,800 victims, reported large landslides that cut off entire towns, where there are reports that some people buried their relatives without notifying them.
In total, deaths were estimated at eighty thousand and there were approximately twenty thousand missing. The hospitalized wounded were counted at 143,331, although in places like Recuay, Aija, Casma, Huarmey, Carhuaz and Chimbote the destruction of buildings ranged between 80% and 90%. The Pan-American highway suffered severe cracks between Trujillo and Huarmey, making the delivery of aid even more difficult. The Cañón del Pato hydroelectric plant was also affected by the onslaught of the Santa River and the railway line that connected Chimbote with the Santa Valley, and was left unusable for 60% of its route.
With this catastrophe, the Peruvian Government created by decree law the Peruvian Civil Defense Brigade, later the Indeci, in order to prevent and prepare the population for similar events.
The flood in Yungay
The strong and prolonged 45-second earthquake caused the detachment of the northern peak of Nevado Huascarán, producing an avalanche estimated at 40 million cubic meters of ice, mud and rocks that measured 1.5 km wide and that advanced the 13 km, at an average speed of 200 to 500 km/h. The avalanche took only three minutes to reach the city. The Yungaín population was disoriented due to the echo produced by the alluvium in the hills of the Cordillera Blanca. When the alluvium hit the wall of the Ranrahirca river ravine, it formed a reservoir and violently diverted its course about thirty degrees in a southerly direction.
...I watched a giant wave of light grey mud on the high part of Yungay, very similar to a wave of sea breaking in a crest, had an approximate height of twenty-five or thirty meters...About a survivor in 2012.
A third of the mass jumped the ravine (which had already saved Yungay from an alluvium in 1962) completely burying the second most important city of the Callejón de Huaylas, while the largest current swept away the town of Ranrahirca, killing in total more than twenty thousand people.
...We felt a tremendous noise that came from both sides... the noise resembled that of many planes... we didn't know where it came from or what happened, at that time we didn't remember Huascaran... Finally, we saw the alluvium of completely black mud with more than forty meters of height that progressed throwing sparks of different colors...About a survivor in 1970.
In Yungay only approximately three hundred people were saved, separated into three groups: ninety-two people who ran towards the city cemetery (an old pre-Inca fortress raised), twenty-five people on a hill next to the city and a large group of children who attended a flea circus called Verolina and which was located in the stadium seven hundred meters from the main square.
The rescue and evacuation work launched by the central government only proceeded by air two days after the tragedy due to the dense cloud of dust that rose 2,700 meters above the level of the area of the tragedy, this cloud remained for a week causing the ice blocks to thaw two weeks due to the low incidence of the sun. The mass of mud took a month to dry out and caused several people to become trapped when they tried to cross it.
So the province of Yungay reached the highest figures in terms of mortality: twenty-five thousand people. The international contribution was of great importance at the time of the emergency, various world organizations offered their support. The magnitude of their cooperation was not only at the time of the emergency but also in the rehabilitation of the affected area and in the future development of the region. However, the destruction of communication routes in the area and the lack of planning gave it a share of inefficiency. For this reason, the Indeci was created on March 28, 1972 to be in charge of coordinating prevention and aid in the event of subsequent disasters.
Following the 1970 earthquake that devastated several cities of the Callejón de Huaylas and which motivated the solidarity of various countries, Yungay received the name Capital of International Solidarity.
Deaths
- Huaraz and surrounding area: 25 000.
- Yungay, Ranrahírca, Mancos and surrounding area: 11,000.
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