EDUCATE

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Tsunamis

Tsunamis are ocean waves produced by earthquakes or underwater landslides.

The word is Japanese and means 'harbor wave,' because of the devastating effects these waves have had on low-lying Japanese coastal communities. Tsunamis are often incorrectly referred to as tidal waves, but a tsunami is actually a series of waves that can travel at speeds averaging 450 (and up to 600) miles per hour in the open ocean. In the open ocean, tsunamis would not be felt by ships because the wavelength would be hundreds of miles long, with an amplitude of only a few feet. This would also make them unnoticeable from the air. As the waves approach the coast, their speed decreases and their amplitude increases. Unusual wave heights have been known to be over 100 feet high. However, waves that are 10 to 20 feet high can be very destructive and cause many deaths or injuries.

Tsunamis are most often generated by earthquake-induced movement of the ocean floor. Landslides, volcanic eruptions, and even meteorites can also generate a tsunami. If a major earthquake is felt, a tsunami could reach the beach in a few minutes, even before a warning is issued. Areas at greatest risk are less than 25 feet above sea level and within one mile of the shoreline. Most deaths caused by a tsunami are because of drowning. Associated risks include flooding, contamination of drinking water, fires from ruptured tanks or gas lines, and the loss of vital community infrastructure (police, fire, and medical facilities).
From an initial tsunami generating source area, waves travel outward in all directions much like the ripples caused by throwing a rock into a pond. As these waves approach coastal areas, the time between successive wave crests varies from 5 to 90 minutes. The first wave is usually not the largest in the series of waves, nor is it the most significant. Furthermore, one coastal community may experience no damaging waves while another, not that far away, may experience destructive deadly waves. Depending on a number of factors, some low-lying areas could experience severe inland inundation of water and debris of more than 1,000 feet.

Tsunami Watch - An alert issued to areas outside the warned area. The area included in the watch is based on the magnitude of the earthquake. For earthquakes over magnitude 7.0, the watch area is 1 hour tsunami travel time outside the warning zone. For all earthquakes over magnitude 7.5, the watch area is 3 hours tsunami travel time outside the warning zone. The watch will either be upgraded to a warning in subsequent bulletins or will be cancelled depending on the severity of the tsunami.

Tsunami Warning - Indicates that a tsunami is imminent and that coastal locations in the warned area should prepare for flooding. The initial warning is typically based on seismic information alone. Earthquakes over magnitude 7.0 trigger a warning covering the coastal regions within 2 hours tsunami travel time from the epicenter. When the magnitude is over 7.5, the warned area is increased to 3 hours tsunami travel time. As water level data showing the tsunami is recorded, the warning will either be cancelled, restricted, expanded incrementally, or expanded in the event of a major tsunami.

DART (Deep-ocean Assessment and Reporting of Tsunami stations)

 NOAA INCREASES TSUNAMI WARNING CAPABILITY FOR THE MOST THREATENED PARTS OF THE UNITED STATES

Dec. 22, 2006 — NOAA announced today the deployment of six new Deep-ocean Assessment and Reporting of Tsunami, or DART, stations in the southwest Pacific. The new stations provide increased lead time for tsunami detection to the U.S. coastal areas at most risk of tsunamis traveling long distances, including the coastlines of Hawaii, Alaska, Washington, Oregon and California.

“We have drastically improved our tsunami detection and warning capability since the Indian Ocean tsunami two years ago,” said retired Navy Vice Adm. Conrad C. Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator. “These buoys are the latest achievement in an ongoing effort to increase the tsunami program at home and abroad.”
Over the last two years, NOAA expanded the U.S. warning system to include the Atlantic coast, Gulf of Mexico, Puerto Rico and the U.S. Virgin Islands. The agency has deployed a total of 25 DART tsunameter stations in U.S. waters; installed 15 new and upgraded 33 existing tide stations; completed inundation models for 17 communities; and recognized 26 new TsunamiReady communities. NOAA also hired new employees to fully staff its two tsunami warning centers in Honolulu, Hawaii, and Palmer, Alaska, around the clock.
“We have reached our initial operating capability for the Untied States, which is to say we have met our goals of aggressively expanding every facet of the tsunami program,” added Lautenbacher. “Additionally, we have strengthened the Indian Ocean tsunami warning system program.”

NOAA partnered with the government of Thailand to launch the first DART station in the Indian Ocean earlier this month. The DART system is a U.S. contribution that provides real-time tsunami detection as waves travel across open waters. It is the first of 22 tsunameters envisioned for an Indian Ocean regional tsunami warning system through the UNESCO Intergovernmental Ocean Commission. The tsunameters also are part of a larger end-to-end warning system that includes tide gauges, communications upgrades, inundation modeling and dissemination systems.

In 2007 NOAA, an agency of the U.S. Commerce Department, celebrates 200 years of science and service to the nation. Starting with the establishment of the U.S. Coast and Geodetic Survey in 1807 by Thomas Jefferson much of America's scientific heritage is rooted in NOAA. The agency is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of the nation's coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, more than 60 countries and the European Commission to develop a global monitoring network that is as integrated as the planet it observes, predicts and protects.

FAQs about Tsumani’s can be found at: http://ioc3.unesco.org/itic/files.php?action=viewfile&fid=415&fcat_id=137