Tsunami Information

A tsunami (pronounced su na mi - meaning harbour wave) is a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction when they crash ashore.

These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly it displaces the water above it and launches the rolling waves that will become a tsunami.

Most tsunamis, about 80 percent, happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.

Tsunamis may also be caused by underwater landslides or volcanic eruptions. They may even be launched, as they frequently were in Earth’s ancient past, by the impact of a large meteorite plunging into an ocean.

Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour, about as fast as a jet airplane. At that pace they can cross the entire expanse of the Pacific Ocean in less than a day. And their long wavelengths mean they lose very little energy along the way.

In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously.

A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami, because the wave’s crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives.

A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations.

Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.

The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Similar systems are proposed to protect coastal areas worldwide.

Natori Tsunami 11 March 2011 - Credit : AP Photo/Kyodo News
Worlds worst 40 Tsunami disasters by death toll
Year Day/Month Time Primary Magnitude Country Location Latitude longitude Max Water Height Deaths
2004 26 December 00:58:53 9.1 INDONESIA OFF W. COAST OF SUMATRA 3.316 95.854 50.9 227899
2011 11 March 05:46:24 9.0 JAPAN HONSHU ISLAND 38.297 142.372 38.9 18482
1976 16 August 16:11:07 8.0 PHILIPPINES MORO GULF 6.292 124.09 9 4376
1952 04 November 16:58:27 9.0 RUSSIA KAMCHATKA 52.755 160.057 18.4 4000
1960 22 may 19:11:17 9.5 CHILE SOUTHERN CHILE -38.143 -73.407 25 2223
1998 17 July 08:49:16 7.0 PAPUA NEW GUINEA PAPUA NEW GUINEA -2.943 142.582 15.03 2205
1963 09 October 21:39:00 ITALY VAJONT DAM, VAJONT RIVER 46.267 12.329 235 2000
1979 18 July INDONESIA LOMBLEN ISLAND [LEMBATA] -8.6 123.5 9 1239
1992 12 December 05:29:26 7.8 INDONESIA FLORES SEA -8.48 121.896 26.2 1169
1951 03 August 00:23:58 6.0 NICARAGUA COSIGUINA VOLCANO 13 -87.5 1000
2006 17 July 08:19:28 7.7 INDONESIA SOUTH OF JAVA -9.254 107.411 20.9 802
1979 12 December 07:59:03 7.7 COLOMBIA COLOMBIA OFF SHORE PACIFIC OCEAN 1.598 -79.358 6 600
1971 19 March PERU CHUNGAR -11.116 -76.5 30 600
1969 23 February 00:36:56 6.9 INDONESIA MAKASSAR STRAIT -3.1 118.9 4 600
2010 25 October 14:42:22 7.8 INDONESIA SUMATRA -3.487 100.082 16.9 431
1965 28 September PHILIPPINES TAAL, LUZON ISLAND 14.002 120.993 4.7 355
1994 02 June 18:17:34 7.8 INDONESIA SOUTH OF JAVA -10.477 112.835 13.9 238
1993 12 July 13:17:11 7.7 JAPAN SEA OF JAPAN 42.851 139.197 32 208
1968 14 August 22:14:19 7.8 INDONESIA BANDA SEA 0.2 119.8 10 200
2009 29 September 17:48:10 8.0 SAMOA SAMOA ISLANDS -15.489 -172.095 22.35 192
1977 19 August 06:08:55 8.0 INDONESIA SUNDA ISLANDS -11.085 118.464 15 189
1992 02 September 00:16:02 7.7 NICARAGUA NICARAGUA 11.727 -87.386 9.9 170
2010 27 February 06:34:11 8.8 CHILE CENTRAL CHILE -36.122 -72.898 29 156
1999 17 August 00:01:39 7.6 TURKEY KOCAELI, TURKEY 40.76 29.97 2.52 155
1964 28 March 03:36:14 9.2 USA PRINCE WILLIAM SOUND, AK 61.017 -147.648 67.1 124
1996 17 February 05:59:30 8.2 INDONESIA IRIAN JAYA -0.891 136.952 7.7 110
1983 26 May 02:59:59 7.8 JAPAN NOSHIRO, JAPAN 40.462 139.102 14.93 100
1979 12 September 05:17:51 7.9 INDONESIA IRIAN JAYA -1.679 136.04 2 100
1994 14 November 19:15:30 7.1 PHILIPPINES PHILIPPINE ISLANDS 13.525 121.067 7.3 81
1965 24 January 00:11:12 7.6 INDONESIA SANANA ISLAND -2.4 126.1 71
1960 20 November 22:01:56 6.8 PERU N. PERU -6.8 -80.7 9 66
2007 01 April 20:39:56 8.1 SOLOMON ISLANDS SOLOMON ISLANDS -8.46 157.044 12.1 52
1968 16 May 00:48:55 8.2 JAPAN OFF EAST COAST OF HONSHU ISLAND 40.8 143.2 6 52
1952 04 March 01:22:41 8.1 JAPAN SE. HOKKAIDO ISLAND 42.15 143.85 6.54 33
1965 19 February CHILE SOUTHERN CHILE -41.755 -72.396 60 27
2001 23 June 20:33:14 8.4 PERU S. PERU -16.265 -73.641 8.8 26
1964 16 June 04:01:44 7.5 JAPAN NW. HONSHU ISLAND 38.65 139.2 5.8 26
1967 11 April 05:09:12 5.5 INDONESIA MAKASSAR STRAIT -3.7 119.3 13
1996 21 February 12:51:01 7.5 PERU N. PERU -9.593 -79.587 5.1 12
                   
Data Courtest of NOAA - National Geophysical Data Center.

 

 

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