World’s Most Powerful Earthquakes 8.5 Magnitude and Stronger, From 1900 to 2011

Earthquakes are detected by seismographs – instruments that “record a zig-zag trace that shows the varying amplitude of ground oscillations beneath the instrument”. The force or magnitude of an earthquake is measured on the Richter scale, “developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes”.

Scientists use certain descriptors or adjectives to denote the severity of earthquakes. Per these descriptors, it is surprising just how frequently earthquakes take place every year. In fact, depending on the size, earthquakes strike every day. Here is the average frequency of earthquakes in order of how strong or powerful the quake is:

• Minor earthquake: magnitude 3.0 to 3.9; 49,000 minor earthquakes every year; over 134 minor earthquakes a day
• Light earthquake: magnitude 4.0 to 4.9; 6,200 light earthquakes every year; almost 17 light earthquakes a day
• Moderate earthquake: magnitude 5.0 to 5.9; 800 moderate earthquakes every year; more than 2 moderate earthquakes a day
• Strong earthquake: magnitude 6.0 to 6.9; 120 strong earthquakes every year
• Major earthquake: magnitude 7.0 to 7.9; 18 major earthquakes every year
• Great earthquake: magnitude 8 or higher on Richter scale; 1 great earthquake every year. The great 9.0 earthquake that struck Japan on March 11, 2011 should be the only earthquake of that magnitude this year if the law of averages holds true.

The United States Geological Society lists the world’s great earthquakes since 1900.

• 9.5 magnitude earthquake, Chile, May 22, 1960.
• 9.2 magnitude earthquake, Prince William Sound, Alaska, March 28, 1964
• 9.1 magnitude earthquake, off the coast of Northern Sumatra, December 26, 2004
• 9.0 magnitude earthquake, Kamchatka, November 4, 1952
• 9.0 magnitude earthquake, Japan, March 11, 2011
• 8.8 magnitude earthquake, off the cost of Equador, January 31, 1906
• 8.8 magnitude earthquake, offshore Maule, Chile, February 27, 2010
• 8.7 magnitude earthquake, Rat Islands, Alaska, February 4, 1965
• 8.6 magnitude earthquake, Assam, Tibet, August 15, 1950
• 8.6 magnitude earthquake, Andreanof Islands, Alaska, March 9, 1957
• 8.6 magnitude earthquake, Northern Sumatra, Indonesia, March 28, 2005
• 8.5 magnitude earthquake, border between Chile and Argentina, November 11, 1922
• 8.5 magnitude earthquake, Kamchatka, February 3, 1923
• 8.5 magnitude earthquake, Banda Sea, Indonesia, February 1, 1938
• 8.5 magnitude earthquake, Kuril Islands, October 13, 1963
• 8.5 magnitude earthquake, Southern Sumatra, Indonesia, September 12, 2007

Source:

• http://earthquake.usgs.gov/learn/topics/richter.php
• http://earthquake.usgs.gov/earthquakes/world/10_largest_world.php
• http://www.vency.com/Earthquakes.html