Natural Hazards: Causes and Effects - Disaster Management Center ...

a deteriorating deficit situation that showed no signs of improving. The country’s balance of
payments also registered an unprecedented deficit that continued to grow.
The dramatic increase in economic growth rates during the period is somewhat deceiving. This
was due in large part to dynamism in construction, but this was construction to replace and
rebuild. 2
Chimbote, Peru, May 31, 1970
On May 31, 1970, about 25 kilometers (16 miles) west of the coast city of Chimbote, Peru,
occurred an earthquake with a magnitude of 7.75. In an area of 75,000 square kilometers
(about 30,000 square miles) in west-central Peru there were more than 50,000 deaths, and
50,000 injuries. Roughly 200,000 homes and buildings were destroyed and 800,000 people
were left homeless. Within the region affected by the earthquake, roughly 100,000 square
kilometers (40,000 square miles), numerous villages were almost totally demolished.
A large proportion of the people were killed in a secondary effect of the earthquake. At least
18,000 people were buried beneath the great rock avalanche from Mt. Huascaran that covered
the towns of Ranrahirca and most of Yungay.
The avalanche amounted to 50,000,000 or more cubic meters of rock and snow, ice and soil,
traveling 15 kilometers (9 miles) from the mountain to the town of Yungay with an estimated
speed of 320 kilometers per hour (200 miles per hour). Ridges as high a 140 meters (460 feet)
were overridden and boulders weighing several tons were projected 1,000 meters (3,300 feet)
beyond the avalanche margins.
A most graphic eyewitness account of the Huascaran avalanche was later given by Senor
Mateo Casaverde, a Peruvian geophysicist.
“As we drove past the cemetery in Yungay the car began to shake. It was not until I had
stopped the car that I realized that we were experiencing an earthquake. We immediately
got out of the car and observed the effects of the earthquake around us. I saw several
homes as well as a small bridge crossing a creek near Cemetery Hill collapse. After about
one-half minute the earthquake shaking began to subside. At that time I heard a great roar
coming from Huascaran. Looking up, I saw what appeared to be a cloud of dust and it
looked as though a large mass of rock and ice was breaking loose from the north peak. My
immediate reaction was to run for the high ground of Cemetery Hill 200 meters (700 feet)
away. I began running and noticed that there were many others in Yungay who were also
running toward Cemetery Hill.
“The crest of the wave had a curl, like a huge breaker coming in from the ocean. I estimated
the wave to be at least 80 meters (260 feet) high. I reached the upper level of the cemetery
just as the debris flow struck the base of the hill and I was probably only 10 seconds ahead
of it.” 3
Geographical Distribution
Fig. 2.1 shows that the majority of earthquakes occur in the seismically active Pacific basin
forming a belt around the region, along the Sundra arc, and as a diffuse band through the
mountain ranges of Asia and Europe also referred to as the Mediterranean and Trans-