What is a Tsunami

Japanese description meaning Harbour Wave (Soo-Nah-Mee) Tsu means harbour and Nami means waves.

Why is a Japanese term used? The definition was accepted Internationally in 1963 by the scientific community because the word Tsunami covers all forms of Oceanic Waves generated by destructive forces of nature. Tidal Waves are influenced by the Moon and other waves are wind blown. Tsunamis are unlike Tidal Waves and caused by the forces of gravity.

A Tsunami is a series of long wavelength waves that are generated from Marine Earthquakes,Volcanic eruptions and Undersea slides. Tsunamis generated by earthquakes are the result of causing an upward or downward(vertical) movement of the seafloor and a sudden displacement of water. Tsunami(Soo-Nah-Mee)is a Japanese word meaning "Harbour Wave" and also known by Oceanologists and Seismologists as Seismic Sea Waves. A series of Tsunami Waves could be anywhere from 500km( 300-600miles)to 1000km in length with open ocean speeds up to 800 km/per hour ( 500mph). In deep ocean a series of Tsunami Waves because of its long length LOSES VERY LITTLE ENERGY and can cross the Pacific in a day and speed is determined by depth of the ocean.

In deep ocean a Tsunami is hardly noticeable and just a mere ripple of shallow waves passing under ships and flying overhead are not noticeable because of thier long length and distance apart from crest to crest. The crest distance can be more than 150km(100miles)and the waves just 1metre (3feet) and often 30cm(1feet) in height. A Tsunami is like an undersea MONSTER sneaking under all eyes and can change
directions depending on the shape of the sea bottom like ridges and coral reefs. Following the 1964 Alaskan Prince William Quake 9.2 magnitude the West Coast/Alaska Tsunami Warning Centre was established in Palmer, Alaska in 1967 passing information to British Columbia,Washington,Oregon and California. The information enables these regions to prepare for the arrivals of Tsunamis in the Pacific Ring of Fire Zone. The Pacific Tsunami Warning Centre is based in Honolulu, Hawaii. The Pacific Ocean area with a number of deep trenches, undersea Mountain Chains,Island arcs and subduction zones are the recipe for long distance Tsunamis from Alaska, Kuril Islands(Russia) and South America.

The first sign of an incoming Tsunami occurs during the approach of the Leading Wave(Trough) which DRAWS the ocean back leaving fish stranded or a slight rise in water level when receding. However for those who are unaware of this sign the wave following the Trough will be larger waves coming in 5-10-30 minutes later. When the ocean RECEDES (1 kilometre - 500 feet) its time to EVACUATE and QUICKLY to a long distance in low lying areas or high ground 30 metres(100 feet)and more. The incoming waves vary in height like the Chilean Tsunami that hit Hilo Hawaii from the 1960 Chilean Quake. The series of waves came in just past 12 midnight 12.45am and 1.04am and the 3rd wave was 6.3 metres (21 feet) and took 61 lives and injured more than 280 seriously and a series of waves can continue for HOURS. The 3rd wave came surging in with a thunderous and water deafening sound. Those who did not heed the warnings or
came back to lower ground thinking the Tsunami was over following the second wave were the victims of the Tsunami from the 3rd wave.

Tsunami Waves can reach the height of 15 metres(50feet) and higher and to heights of 30metres(100feet). A series of waves from thier deep ocean speed of 500km/per hour to 800km(300-500mph) will slow down when approaching the coast area 17metres(60feet) deep at around 50-70km/per hour(30mph) and depends on the geography of the shoreline area. The height of the waves are the result following the 1st wave(crest) reaching the shallow shore which has slowed down to 60km/per hour and the following waves travelling at 700km and no longer spaced apart by thier 180km(100 mile)distance and deep ocean movement and being compacted in distance and pushing the following waves against each other. When approaching the shore a Tsunami resembles an ADVANCING TIDE without a WAVE feature pushing forward. Even for small fishing boats 20 miles offshore in deep water would not even notice a passing Tsunami and difficult
to even radio a shore warning.

When near a beach or shoreline area and one feels a quake lasting from 15-20 seconds is an indication that a Tsunami could be generated and approaching and the closer one is to an epicentre means an approaching Tsunami is coming in a matter of minutes. In July 1993 off of Hokkaido in Sea of Japan by Okushiri Island a quake generated Tsunami hit this region and following the shock, the waves came in less than 5 minutes and reaching runup of 10-20 metres (Example of how fast the waves came). The Hokkaido Tsunami was responsible for 120 deaths.

Before Dec. 26. Tsunami became a new word for many people worldwide and many did not know what a Tsunami was. Tsunamis are not only regional but also Transoceanic and spreads in many directions reaching the shores of many countries with different languages and dialects to contend with. Oceanographers, Geologists and Seismologists often use the term Seismic Sea Wave and accepted terminology and it would be easier for most regardless of what language and dialect they speak to understand the word Sea Wave. Sea Wave is self explained as a Wave and most people in any language can
say Sea Wave but difficulty in pronouncing Tsunami.

In the Indian language the word is PRALAY, means disaster due to floods. In Vietnamese the term used would be SONG THAN meaning Titan Wave and people in these areas could only perhaps identify an incoming dangerous wave name in thier own language with any degree of comfort. Perhaps the best compromise is the official accepted term and Seismic Sea Wave an accepted oceanography term is to have warnings and education material with the official name Tsunami in BOLD LETTERING along with
name Seismic Sea Wave and the name from a country like India adding in PRALAY and the information down in English and Indian language as an example along with images to show what a Tsunami is with graphic information so all eyes and ages can understand visually. Many languages do not even have a description to describe the workings of a Tsunami and mainly descriptions of large waves. In Chinese the term Hoi Sui would be used.

The South Asian Tsunami reaching the shores of East Africa hitting Somalia, Kenya and Tanzania resulting in over 200 deaths and thousands homeless and Africa with a combination of African languages and East
Indian population in Tanzania how should warnings be given where the name Tsunami is a strange word. In the main Tsunami areas in the Pacific where education and information is more available along with warnings these areas would be Tsunami educated and updated information during a Tsunami Raid. However this would not be the case in underdeveloped countries were confusion means the loss of hundreds and perhaps thousands of lives. Only the EDUCATED OR WELL OFF would have access to info
while MOST WOULD NOT. Would not is another major problem.

The Hawaiian Pacific Tsunami Museum is located in Hilo at 130 Kamehameha Ave. Hilo, Hawaii 96720 fax 808-935-0842 or for other information THE INTERNATIONAL TSUNAMI INFORMATION CENTRE 737 BISHOP ST. STE 2200, HONOLULU, HAWAII 96813 e-mail itic...@noaa.gov. Should anyone able to visit Hilo, Hawaii(Big Island) visiting the Pacific Tsunami Museum will give a clear understanding on what a Tsunami is and how Hawaii has been affected by the many Tsunamis local and Trans Pacific. The Museum Bookstore has a number of excellent books available for sale on Tsunamis written with the Hawaiian experience and the surviviors tales. The e-mail address sal...@tsunami.org is the stores e-mail. The website for the Museum is http://www.tsunami.org and check out the Bookstore for thier fine books for sale and other parts of the website for excellent Tsunami information. Perhaps some of the geography teachers should consider getting books and info on Tsunamis for teaching and the information may save lives from the education and material from these books.

The South Asian Quake off of Banda Aceh at 9.0 and following the British Navy findings with thier multi-beam sonar indicated that the collision of the India Tetonic Plate pushed under the Burma Plate crumpled the Burma Plate like a folding carpet 10 kilometres wide and ridges up to 1,500 metres pushing the water upward. When a Tsunami is generated from a quake the waves will travel in BOTH directions towards land and out to sea and most deaths are due to drowning from the flooding. No one can outrun a Tsunami Wave. A number of quake generated Tsunamis have hit Indonesia as well including Flores Island and Java and in July 1998 a Tsunami hit Papua, New Guinea taking more than 2,000 lives with wave heights reaching 15 metres.

Puerto Rico with a history of past quakes and Tsunamis and some of the Volcanic Islands in the Lesser Antillees in the Caribbean are possible Tsunami targets in the future. Nicaragua, Peru and Mexico on the Pacific side have also been hit in recent and one must not be in fear of Beachside resorts but more educated as to the dangers.

How far can a Transoceanic Tsunami travel? In the 1960 Chilean Quake 9.5 the Tsunami generated reached past Hawaii to Japan and taking more than 120 lives in Japan and reaching Philipines and New Zealand as well. The Chilean Tsunami took more than 2,000 lives in Chile and the toll would have been higher if not for the smarts of many residents who noticed the receding ocean. The SE Asian Tsunami is considered Transoceanic in force and distance having been stopped by Africa in its tracks. In recent weeks during 2005, Japan has been rocked twice by Quakes(land) and Indonesia got hit by another major ocean quake, but no Tsunami was generated and often nature has a habit of baffling oceanographers and the quake was sufficient to generate a Tsunami and underocean quakes over 8.0 normally do.

Closer to home, one must not forget that Alaska and Chile are in regions prone to the transmission of Ocean going Tsunamis should a major quake occur and has the potential to hit all shores along North America, Hawaii and the whole of the Pacific region in Asia. For those visiting a trip to the Pacific Tsunami Museum in Hilo, Hawaii(Big Island) will open up ones eyes on Tsunami education and thier books are
worth the price of just the education alone.

Tsunamis can also flow upriver or split when hitting a series of Islands and geography of the area hit is the final outcome of how much damage a Tsunami can cause.

The writer Len Chan has seen the aftermath in Hawaii(1960) Alaskan Tsunami that hit Vancouver Island in 1964 and witnessed a regional Tsunami in Japan. This writeup is just to give readers a glimpse of what a Tsunami is since so many have not heard of a Tsunami in non Tsunami areas and inland from the Pacific Region.

Source: National Oceanic and Atmospheric Administration(National Weather Service)
Written By: Len Chan