Water waves are only different at the very small scale, where surface tension dominates (capillary waves) there is no difference in the physics of straight 'gravity' waves. You can easily get tens of metres of height.īut, apart from the dimensions, the tsunami has to behave the same as small waves breaking on the shore. If the deep water height is 1m and the wavelength is 1km then it stands on its end when entering shallow water. It's down to the total volume of water displaced, I suppose. The water flows backwards in front of the crest and accounts for the draining of water away from the coast just ahead of the breaking tsunami wave.įWIW, the vertical displacement due to tsunamis traveling in the deep ocean is typically very small. the speed gets slower for shallow water and the peaks overtake the troughs to make a breaking wave. The peakiness of a wave is brought about for high amplitude and also when the water becomes shallow. If the water at depth is moving in a closed curve then there must be acceleration and that implies there must be varying force (therefore varying pressure) at depth. This hyper physics link gives a simple model of a continuous wave. The path of the water particles is the same for all deep water waves - vertical circles with a radius that decreases with depth and the shape of the path becomes flattened and the motion is mostly forward and backward rather than up and down. The height of a Tsunami wave as it travels over the deep ocean may be very great and the effect on a boat out at sea will be relatively mild at all as the acceleration is very low.
The effect that you get with ordinary waves, breaking on a gently sloping beach is the same. If you are using the term 'shallow', referring to the depth with respect to the wavelength and the amplitude then I agree. The wave pulses can be measured at any depth from sea floor to the surface as they pass by When a tsunami wave crosses the Pacific Ocean from say, Japan to Hawaii. One reason is because they are, in general, created at depth
#Ocean waves from above full#
The tsunami wave pulse(s) covers the full depth of the water that is in. Wind etc waves are created at the surface and don't penetrate to any great depth. You cannot compare tsunamis with surficial waves caused by winds etc as you have done, tech99, they are very different beasts You are agreeing with incorrect comments, tech99īoth these comments are incorrect as anorlunda pointed out with his comments It is rather like the situation when an airliner flies overhead - we are not all crushed by an increase in pressure. We only see seaweed waving in fairly shallow water. A wave is held up by the dynamics of movement, its inertia, and the pressure effect must die out when we get a few wavelengths below the surface. AFAIK, the frequency spectrum of sea waves is in the 0.1Hz - 1Hz band, so my filter could not be all that effective. I got a very precise pressure sensor, measured the sensor output frequency, calculated the apparent depth, did some low-pass filtering and presented the answer - they got a number and they were happy.īack to the original question - is the pressure at, say, 10 m below the surface, independent on the amplitude of the waves on the surface? I still do not know, but my low-pass filter was meant to minimize any such effect. To which I answered "below what?" This was in a rather large inlet, with waves seldom below half a meter. When I asked what precision they wanted on the depth, they more or less automatically answered "1 cm". The main function of my system was to show the depth of one of the flotation pods. I was asked to create a backup system (in the case that the expensive measurement system crashed). That reminds me - in the start of the 1980s my research company were hired to do the instrumentation of the collapsed oil platform "Alexander Kielland" before attempting to turn it right side up.
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