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Greatest Earthquake: 1960, Chile, South America

Photo of subsidence
Flooding of village streets was due to subsidence of coastal land after the quake.

The Greatest Earthquake Ever Recorded

The honor of greatest earthquake of all time goes to the 1960 Chile earthquake because scientists were able to 'catch this one on tape'. In other words, there have been a lot of really big earthquakes throughout human history (and even greater ones before we came on the scene), but this one they were able to measure, record and verify its ground motion strength. The instruments that seismologists use to measure earthquake magnitudes are designed to detect the amount of energy released by the movement of the ground during a quake. In the case of the Chile earthquake, the amount of energy released during the quake, not the number of human deaths and damage to structures, earned it the title of greatest. This earthquake was the largest ever instrumentally recorded. It measured a 9.5 on the Moment Magnitude (Mw) scale, but registered only an 8.5 on the Ms scale.

The epicenter of the earthquake (the point on the earth's surface directly above the focus of an earthquake) was 60 meters down below the ocean floor about 100 miles off the coast of Chile out in the Pacific. The nearby towns of Valdivia and Puerto Montt suffered devastating damage because of their closeness to the center of such a massive quake. The loss of human life was not as bad as it could have been because there were large foreshocks that sent people into the streets talking.

About 30 minutes after the foreshocks, when the main jolt came, many people were still outside calming their jitters from the first shock. The buildings and homes that fell had pretty much vacated. However, damage cost estimates were over a half billion dollars.

Not only was there damage to man-made structures during the quake, but the earth itself was forever changed by the enormous amount of energy released from below. Huge landslides, massive flows of earthen debris and rock, were sent tumbling down mountain slopes. Some landslides were so enormous they changed the course of major rivers or dammed them up creating new lakes. The land along the coast of Chile, particularly in the Port city of Peurto Montt, subsided (sunk downward) as a result of the movement of the ground during the quake and the coastal city was flooded with ocean water.

The damage from the quake was not limited to the nearby shores of Chile. Enormous waves, or tsunamis (read about the world's biggest tsunami), traveled for thousands of miles across the vast expanse of the Pacific Ocean, reaching the shores of Hawaii, the Philippines, and even Japan devastating everything in their path. The tsunamis were created by the shifting of the sea floor that generated the huge temblor. It was as though someone had dropped a huge boulder in the ocean right over the epicenter of the quake, sending enormous ripples in every direction, traveling at speeds up to 200 miles per hour!

Tsunami damage from 1960 Chilean earthquake
This 1960 photo shows the tsunami damage to the Northern California coast at Crescent City, which is over 9,000 miles away from the epicenter of the Chilean earthquake.

Deep Rumblings

So what caused the earthquake? Whenever an earthquake of any size happens anywhere in the world the same basic thing happens; the ground along either side of a fault (a fracture or crack in the ground) moves.

Faults are cracks in the earth caused by buckling and stress from the movement of the tectonic plates. Movement along faultlines tends to happen along plate boundaries (where the edges of the tectonic plates meet). In the case of this enormous earthquake, the subduction (downward movement) of the Nazca plate under the the South American continent is what caused the major quake back in 1960. In fact, the Nazca plate continues to dive down below the continent and it's this constant slow movement (with some occasional rapid shifts leading to big jolts) that creates earthquakes throughout that region.

Chile has seen many earthquakes both before the 1960 record-setting temblor and after. Two very large contenders have happened on March 3, 1985, and another on July 30, 1995. These earthquakes both had a magnitude of about 8. Chilean earthquakes are not rare, nor are they small. Large earthquakes in Chile seem, through history, to occur about every 25 to 100 years. They'll continue as long as the Pacific plate continues subducting.


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