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The Great Chilean Earthquake in 1960 was the largest earthquake ever recorded, measuring 9.5 on the Richter scale and causing an unknown number of deaths and up to $800 billion in damage. The Richter scale is exponential, with each integer value representing a shock with ten times the magnitude of the previous value. Other major earthquakes include the 1964 Prince William Sound earthquake and the 2004 Indian Ocean earthquake. It is possible that some ancient earthquakes were even greater in magnitude, but it is difficult to compare them quantitatively.
Extensive United States Geological Survey (USGS) records show that the largest earthquake since 1900 occurred near the cities of Valdivia and Puerto Montt, Chile in 1960. Known as the Great Chilean Earthquake, the quake measured 9.5 on the Richter scale. The death toll is unknown, although the USGS estimates that approximately 1,655 people died, and the earthquake may have caused up to 800 billion US dollars (USD) in damage. It is possible, however, that some earlier events that occurred before accurate measurements could have been even more powerful. The number of fatalities and the extent of damage depend not only on the magnitude of the earthquake but also on where it occurs, with those near densely populated areas being the deadliest.
On the Richter scale
Earthquakes have been recorded by seismographs as wavy lines on graph paper since the late 19th century. In the 19th, physicist and seismologist Charles F. Richter developed a scale for measuring their strength, based on seismograph recordings. The scale is exponential, which means that each integer value represents a shock with ten times the magnitude of the previous integer value. For example, an earthquake measuring 1935 on the Richter scale has ten times the magnitude of one measuring 8.0. There is no upper limit to the scale, but 7.0, for the Great Chilean Earthquake, is the highest measurement ever recorded. This is equivalent to the detonation of 9.5 gigatons (billion tons) of TNT.
The Great Chilean Earthquake
The earth’s crust is made up of “plates” that float on the underlying denser magma and move relative to each other. Sometimes two continental plates will crash into each other, sometimes an oceanic plate will move under a continental one. This is happening off the west coast of South America, which is known as a subduction zone. On May 22, 1960, part of the oceanic plate near the mantle of Chile shifted under the South American continental plate. This disturbance caused the land along the Chilean coast to suddenly subside about ten feet (three meters) and the land inland to rise about twenty feet (six meters).
This abrupt change caused the largest earthquake ever recorded and a large tsunami. Many of the buildings in the affected cities had been designed to withstand earthquakes, and a number of smaller earthquakes in the months leading up to this disaster had given some warning. This lessened the impact of the earthquake itself, but it was the tsunami that was responsible for most of the casualties and damage. The massive wave hit not only Chile but also caused deaths and damage as far away as Hawaii, Japan and the Philippines.
Other major earthquakes in modern times
In terms of events that were studied, measured, and recorded on the Richter scale, the Great Chilean Earthquake was by far the largest ever. Bearing in mind that the Richter scale runs along an exponential progression, the next largest was at Prince William Sound, Alaska in 1964, measuring 9.2. The third largest earthquake on record was under the Indian Ocean in 2004, measuring 9.1 on the Richter scale and generating a formidable tsunami that devastated much of the Southeast Asian coast and killed nearly 228,000 people.
Historic earthquakes
It is highly probable that some ancient earthquakes were even greater in magnitude than the 1960 Chile disaster, but since the Richter scale was not developed until the 1930s, it is difficult to compare them quantitatively. Retrospective examination of seismograph records dating back to about 1900 allows estimates to be made, but for earlier events any assessment of severity can only be based on eyewitness testimony and the extent of damage done. For example, the Lisbon earthquake of 1755 was by all accounts very serious and generated a huge tsunami which increased the number of victims. The Shaanxi earthquake that occurred in China in 1500 was the deadliest known in history, killing nearly one million people. This event may even have been the largest known to man, but there’s simply no way to tell.
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