The other day the head of USAID remarked that the Tsunami waves came ashore at 500 miles per hour. Then the fellow who narrates for Nova, I think his name is Will ???, claimed that the tsunami waves in the Indian Ocean. were "unlike" other waves. This last was a program on the Discovery channel. At least that program admitted that there was some disagreement about the issue of "Mega Tsunami" which might be caused by the Island in the Atlantic, La Palma. This nonsense about the waves coming ashore at 500 miles an hour is pure rubbish and represents the heights to which hysteria can reach. Go take a look at the footage of waves coming ashore in Thailand. The wave strike at the wall on the beach is on the order of 50 knots or so. Tsunami waves behave in ways that can be described by general wave mechanics. Even in 12000 feet of water a wave with a length of 100 miles, traveling at 500 miles an hour is in technical terms a shallow water wave. The Abyssal ocean plain is generally about 12000 feet deep. The continental shelf generally is considered to be about 600 feet deep. If Tsunami waves did not behave as the rules of general wave mechanics describe then they would not be subject to refraction. Refraction is the byproduct of waves being slowed by bottom friction. If you take a close look at the simulations shown on TV you will notice that the model animations demonstrate refraction; as the waves are moving out in a circular pattern from the epicenter of the quake. In other words, 100 mile length waves are influenced by bottom topography even more than ordinary storm waves; in much deeper water. As bottom depth shallows out, incoming waves are slowed, this process happens until eventually the wave peters out, sometimes ashore. This slowing process results in refraction which generally causes waves to come ashore parallel to that shore. Tsunami waves are like all other waves, except for the tremendous length, in the open ocean. When they come ashore, the height increases and the wave length shortens and a byproduct is that the wave slows down. You can see the same process occurring on any normal beach. A wave comes in and rolls up the beach. If it does not complete flowing back into the surf line, then water will still be standing on the beach when the next wave sweeps in. The next wave RIDES on the base of water lying underneath it. This next wave is called a wave of translation and it's forward speed is directly related to the depth of the water underlying it. You have seen this process many times on any ordinary beach. If the water level is deep enough the incoming wave the speed of the following wave will be a vertical wall or "bore" and may come very fast, or very slow; almost at a standstill. There can be several layers of these "waves of translation". The ones higher up will be traveling faster than the ones underneath and eventually they will tumble over the face of the bore down below and then they too will slow down. All of these mechanics and many others are at work in ordinary waves as well as tsunami's. There is a lot to learn about waves. Don't assume that the what you see on TV is well founded. Especially if it involves Tsunamis and if it comes from some none wave-astute observer. Mike Capt. Mike Maurice Tualatin(Portland), Oregon

At 08:07 PM 1/11/05 -0800, you wrote: >Then the fellow who narrates for Nova, I think his name is Will ???, >claimed that the tsunami waves in the Indian Ocean. were The fellow is Will Lyman, he narrates for Frontline. The real issue is, who writes this stuff? After all, he just reads the script. > Capt. Mike Maurice Tualatin(Portland), Oregon