The earthquake affected the Peruvian regions of Ancash and La Libertad. The epicenter of the earthquake was located 30 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 8 on the Mercalli scale.
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 wide and one mile (1.6 km) long. It advanced about to the village of Yungay at an average speed of more than 100 miles per hour. 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 (61,000,000 m³) of water, mud, and rocks.
The earthquake affected an area of about 83,000 km², an area larger than Belgium and the Netherlands combined, in the north central coast and the Sierra (highlands) of the Ancash Region and southern La Libertad Region.
It was a system-wide disaster, impacting such a widespread area that the regional infrastructure of communications, commerce, and transportation was destroyed. Economic losses surpassed half a billion dollars U.S.D.. Cities, towns, peasant villages as well as the homes, industries, public buildings, schools, electrical, water, sanitary, and communications facilities on them were seriously damaged or destroyed.
Areas hard hit were the coastal towns and cities of Chimbote (the largest city in Ancash), Casma, Supe, and Huarmey; but the Andean valley known as the Callejón de Huaylas suffered the most intense and sweeping damage, with the regional capital, Huaraz, as well as Caraz and Aija being partially destroyed. Trujillo, the nation's third largest city, and Huarmey suffered minor damages.
The Pan-American highway was also damaged, which made the arrival of humanitarian aid difficult. The Cañón del Pato hydroelectricity generator was damaged by the Santa River and the railway connecting Chimbote with the Santa Valley was left unusable on 60% of its route.
The Peruvian government has forbidden excavation in the area where the town of Yungay is buried, declaring it a national cemetery. The chidren who survived in the oca stadium were resettled around the world. In 2000, the tragedy inspired the government to declare May 31 as Natural Disaster Education and Reflection Day, in memory of the deadliest seismic disaster in the history of Latin America.
Every May 31, many schools of Peru practice an Earthquake drill in order to commemorate this disaster.