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A map of epicenters.

An earthquake is the result of a sudden release of energy in the Earth's top 700 km that creates seismic waves. These waves are detected with seismometers and amplified electronically so they can be displayed as a function of time by a seismograph as a seismogram. The size of an earthquake is given by its open ended logarithmic scale of magnitude, often referred to as the Richter scale. Shocks smaller than magnitude 2.5 are usually not felt and those with magnitude 7 cause serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale, ranging from 1 far from the epicenter to a maximum near it, which can reach 12 in the strongest earthquakes..

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed sometimes is uplifted enough to cause a tsunami. The shaking in earthquakes can also trigger landslides and occasionally volcanic activity. (read more...)

A propagation of seismic waves.

Seismology (from the Greek seismos(σεισμός) = earthquake and λόγος,logos = knowledge ) is the scientific study of earthquakes and the propagation of elastic waves through the Earth. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, and artificial processes (explosions). A related field that uses geology to infer information regarding past earthquakes is paleoseismology.

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Tsunami strikes, Ao Nang, Thailand.
The 2004 Indian Ocean earthquake was an undersea (subduction) earthquake that occurred at 00:58:53 UTC on December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The earthquake triggered a series of devastating tsunamis along the coasts of most landmasses bordering the Indian Ocean, killing more than 225,000 people in eleven countries, and inundating coastal communities with waves up to 30 meters (100 ft) high. It was one of the deadliest natural disasters in history. Indonesia, Sri Lanka, India, and Thailand were hardest hit.

With a magnitude of between 9.1 and 9.3, it is the second largest earthquake ever recorded on a seismograph. This earthquake had the longest duration of faulting ever observed, between 8.3 and 10 minutes. It caused the entire planet to vibrate as much as 1 cm (0.5 inches)[1] and triggered other earthquakes as far away as Alaska.[2] The disaster is known by the scientific community as the Great Sumatra-Andaman earthquake,[3] and is also known as the Asian Tsunami and the Boxing Day Tsunami.

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  • 7/14 - Three earthquakes have occurred since last Monday that are over magnitude 6.1 on the Moment magnitude scale.

Did you know...

  • ...that the 1946 Nankaido earthquake caused a 5-6 meter (16-20 feet) tsunami that took out another 2,100 homes after the initial destruction of the earthquake?
  • ...that the 2003 Hokkaido earthquake was not given a cost in US dollars because it occurred offshore and did not cause as much damage as it would have on the mainland of Japan?


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WikiProject Earthquakes is the central point of coordination for Wikipedia's coverage of earthquakes, seismology, tsunamis, and related subjects. Please feel free to join and help!

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  1. ^ Walton, Marsha. "Scientists: Sumatra quake longest ever recorded." CNN. May 20, 2005
  2. ^ West, Michael; Sanches, John J.; McNutt, Stephen R. "Periodically Triggered Seismicity at Mount Wrangell, Alaska, After the Sumatra Earthquake." Science. Vol. 308, No. 5725, 1144–1146. May 20, 2005.
  3. ^ Lay, T., Kanamori, H., Ammon, C., Nettles, M., Ward, S., Aster, R., Beck, S., Bilek, S., Brudzinski, M., Butler, R., DeShon, H., Ekström, G., Satake, K., Sipkin, S., The Great Sumatra-Andaman Earthquake of December 26, 2004, Science, 308, 1127–1133, doi:10.1126/science.1112250, 2005