Kamis, 07 April 2011

CHILE's 1960's EARTHQUAKE


Disaster Struck Valdivia Chile on May 22 1960
The Great Chilean Earthquake, the largest seismic event ever recorded, occurred off the south central coast of Chile and caused a devastating tsunami in the Pacific
On May 22, 1960, the earthquake that struck Valdivia Chile had a magnitude of 9.5 on the Richter scale. This is the strongest earthquake ever recorded by instruments in the world. On the previous day, an earthquake with a magnitude of 7.5 struck the city of Concepción which is north of Valdivia.
The second strongest earthquake in the world occurred on December 26 2004 and had a magnitude of 9.3. The epicenter was on the ocean floor near the west coast of Sumatra, Indonesia and caused a deadly tsunami in the Indian Ocean.
The third strongest earthquake occurred on Good Friday, March 27, 1964 in Alaska, an earthquake with a magnitude of 9.2 struck Prince William Sound and caused extensive damage in Anchorage.

Cause of the 1960 Great Chilean Earthquake

There is a subduction zone where the Chile Ridge oceanic plate is slipping under the South American plate. This was a thrust earthquake because the Chilean Ridge plate moved downward. The epicenter was on the floor of the Pacific Ocean, approximately 100 miles off the coast of Chile.

City and Towns Affected by the 1960 Chilean Earthquake

The coastal area of Chile was worst hit from the city of Concepcion spreading southward to Isla Chiloe.
Near the city of Valdivia, several landslides near Tralcan Mountain blocked the outflow of Riñihue Lake. In addition, 18 people were killed and homes were destroyed. The landslides created new challenges which caused immediate action to reinforce dams in the Seven Lakes chain. In the end, the courses of major rivers were changed forever and new lakes were created. At Valparaiso, many buildings collapsed. Extensive damage was done to the industrial city of Concepcion.
The coastal city of Peurto Montt sunk downward and causing the ocean water to rush in.

The Tsunami Caused by the 1960 Chilean Earthquake

The damage caused by the Tsunami far exceeded the destruction resulting from the earthquake itself. The wall of water spread across the Pacific reaching Hawaii, the Philippines, and even Japan.
Within 10 to 15 minutes after the earthquake, the tsunami waves struck the coast of Chile. Waves of approximately 25 meters high (1 meter = 3.28 feet) smashed the coastline and traveled inland for almost half a mile.
In particular, the south end of Isla Chiloe suffered the worst damage because it was closest to the epicenter. Approximately 200 people were killed in that area alone.
Approximately 15 hours later, the tsunami reached the Hawaiian Islands. There was not much damage to most areas except for the city of Hilo on the east side of the Big Island of Hawaii. Ten meter waves wiped out the waterfront and 61 people were killed.
Tsunami waves of similar size hit Japan were 138 people were killed and the Philippines where 32 deaths were reported.

Damage and Death Toll from the 1960 Chilean Earthquake and Tsunami

  • Approximately 130,000 homes and buildings were destroyed.
  • There were 2 million people displaced.
  • The death toll was estimated at 2,000 and 3,000 people injured. (Some sources say as high as 6,000 people killed)
  • Total loss and damage to property was approximately $500 million (1960 valuation)
Since 1960, there have been two earthquakes registering around 8 on the Richter scale. Chile will continue to experience earthquakes because of the subduction activity the South American Plate.

Sources:

  • U.S. Dept. of Commerce Environmental Science Service Administration
  • Extreme Science

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