World's fifth strongest earthquake in a century

The world's fifth strongest quake in a century hit southern Asia yesterday, triggering a speeding tsunami that crashed into Sri Lanka and India and swamped tourist islands in Thailand and the Maldives.

Here is a factbox showing the five strongest earthquakes in the last century by magnitude.

May 22, 1960 - Chile - An earthquake measuring 9.5 on the Richter scale struck Santiago and Concepcion, triggering tidal waves and volcanic eruptions. Some 5,000 people were killed and two million made homeless.

March 28, 1964 - Alaska - An earthquake and ensuing tsunami claimed 125 lives and caused about $311 million in property loss. The quake, measuring 9.2, was felt over a large area of Alaska and in parts of western Yukon Territory and British Columbia, Canada.

March 9, 1957 - Alaska - An earthquake measuring 9.1 hit the Andreanof Islands. On Umnak Island, Mount Vsevidof erupted after being dormant for 200 years, generating a 15-metre high tsunami that continued to Hawaii.

November 4, 1952 - Russia - An earthquake with a magnitude of 9.0 generated a tsunami which struck the Hawaiian islands. No lives were lost.

December 26, 2004 - Indonesia - A quake measuring 8.9 struck the coast of Aceh province on the northern Indonesian island of Sumatra and triggered a tsunami that killed thousands in Sri Lanka, Thailand, Indonesia and India.

Source Reuters/US Geological Survey Earthquake Web site - http://earthquake.usgs.gov/

Tsunamis

¤ Tsunami is a Japanese word that translates as "harbour wave". Often a tsunami is incorrectly referred to as a tidal wave, which, strictly speaking, describes the periodic movement of water associated with the rise and fall of the tides.

¤ Oceanographers call tsunamis seismic seawaves because they are usually caused by a sudden rise or fall of part of the earth's crust under or near the ocean. Less powerful tsunami waves can also be triggered by volcanic activity. They are most common in the Pacific Ocean.

¤ A tsunami is not a single wave, but a series of waves that can travel across the ocean at speeds of more than 800 kilometres an hour. In the deep ocean, hundreds of kilometres can separate wave crests; many people have lost their lives during tsunamis after returning home thinking the waves had stopped.

¤ As the tsunami enters the shallows of coastlines in its path, its velocity slows but its height increases. A tsunami that is just a few centimetres or metres high from trough to crest can rear up to heights of 30 to 50 metres as it hits the shore, striking with devastating force.

For those on shore there is little warning of a tsunami's approach. The first indication is often a sharp swell, not unlike an ordinary storm swell.

¤ In 1883, a tsunami following the eruption of Krakatoa volcano between the Indonesian islands of Java and Sumatra killed 36,000. The tsunami's passage was traced as far away as Panama.

¤ In July 1998, two undersea quakes measuring 7.0 created three tsunamis that killed at least 2,100 near the town of Aitape on the north coast of Papua New Guinea.

Villagers said the massive walls of water, which washed two kilometres (1.2 miles) inland, sounded like a jet fighter landing.
source: http://www.tsunami.org/faq.htm