Posted on 12/30/2004 7:06:00 AM PST by dead
This is the point where it becomes truly deadly for those too close to escape.
Ah, nevermind...you all are right....
check this link there they are...
http://theory.stanford.edu/~iliano/pictures/2003/thailand/08-15-krabi/
I like tidal wave better than tsunami. While technically not correct, it's very descriptive. Tsumani just means harbor wave anyway.
No, a tsunami is not just a rapid rise in water. The first wave in the series comes in seemingly as a sudden flowing river, a super tide. But this 'tide' does have great forward velocity as it rushes forward along dry ground, as we have seen in many videos now. Then, after the first wave recedes, there is a "super trough" which sucks the ocean back very far. The next waves which come up after the suck back, over dry seafloor, come as raging walls of water, super waves, which come and come for many minutes as all the water in that miles-long ocean wave pile up and continue forward over the land.
Depending on the offshore islands etc, the waves may refract, double, quadruple etc. That is, in the pictures above we see that the waves are not miles apart. I suspect that in this unique case, the beach is receiving both direct waves and "reflected" waves, coming in more quickly together than if the beach only took the direct waves alone. (See my reply above about the crazy waves hitting the back side of Sri Lanka.)
Each open ocean tsunami wave has a height from trough to crest of a few meters at most, and a period of a mile or more, traveling at 500-600 mph. When reaching shallow water, the front of this wave interacts with the bottom and slows and piles up, going vertical. But the rest of that mile long wave keeps coming and coming, for many minutes, pushing the front of the wave far inland, even in some cases hundreds of feet up hillsides.
The wall of water was described as 30 feet tall. That's water in the background
From what I understand it wasn't the force of the water that did damage, it was simply a rise in the water level of about 15 feet which very quickly flooded the area and carried things with it. If you had on a life jacket you would likely have survived the tsunami if you didn't get caught under something.
The waves radiate outward in all directions from the disturbance and can propagate across entire ocean basins. For example, in 1960 an earthquake in Chile caused a tsunami that swept across the Pacific to Japan.
Tsunami waves are distinguished from ordinary ocean waves by their great length between peaks, often exceeding 100 miles in the deep ocean, and by the long amount of time between these peaks, ranging from five minutes to an hour.
The speed at which tsunamis travel depends on the ocean depth. A tsunami can exceed 500 mph in the deep ocean but slows to 20 or 30 mph in the shallow water near land. In less than 24 hours, a tsunami can cross the entire Pacific Ocean.
In the deep ocean, a tsunami is barely noticeable and will only cause a small and slow rising and falling of the sea surface as it passes. Only as it approaches land does a tsunami become a hazard.
As the tsunami approaches land and shallow water, the waves slow down and become compressed, causing them to grow in height. In the best of cases, the tsunami comes onshore like a quickly rising tide and causes a gentle flooding of low-lying coastal areas.
In the worst of cases, a bore will form. A bore is a wall of turbulent water that can be several meters high and can rush onshore with great destructive power.
Behind the bore is a deep and fast-moving flood that can pick up and sweep away almost anything in its path, such as what happened in Papua New Guinea in 1998 when more than 2,000 people were killed and villages destroyed.
Minutes later, the water will drain away as the trough of the tsunami wave arrives, sometimes exposing great patches of the sea floor. But then the water will rush in again as before, causing additional damage.
This destructive cycle may repeat many times before the hazard finally passes. Persons caught in the path of a tsunami have little chance to survive. They can be easily crushed by debris or they may simply drown. Children and the elderly are particularly at risk, as they have less mobility, strength and endurance.
Tsunamis typically cause the most severe damage and casualties very near their source. There the waves are highest because they have not yet lost much energy to friction or spreading.
In addition, the nearby coastal population, often disoriented from the violent earthquake shaking, has little time to react before the tsunami arrives.
The largest tsunamis, however, can cause destruction and casualties over a wide area, sometimes as wide as the entire Pacific Basin. These types of Pacific-wide tsunamis may happen only a few times each century.
Tsunamis are not usually very high, but the swell can be as far as a mile deep. A half mile of water 10 feet high traveling at a couple hundred miles an hour equals extreme force and a lot of water flooding in.
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WHen we had a tsunami warning in San Diego in 1986 afer an earthquake in Hawaii, everybody went TO the beach to watch. Thankfully, or unfortunately for the gene pool, the warning was a false one.
Yeah, I had the same experience, but remember that in each case, the photographer survived. What about those who did not?
Add...the link in #103 shows those hills...same outline.
That reminds me, when I was swimming in the Sea of Japan. The waves had one large and powerful break onto the beach. While heading to shore, my dad who was swimming with me, swam ashore first. I watched a wave carry him that threw him hard against the rocky beach. As the wave receded I saw him lying on the rocks feeling a little hurt, but OK - suffered a few bruises.
I was smarter. I observed the timing of the surf and swam between the waves. :)
No. In most cases a lifejacket would not help. The vast majority of victims did not have time to drown. They died of trauma injuries, from being swept at high velocity through buildings, rocks, poles, trees, cars etc. They were crushed, impaled, cut in bits, massively lacerated. Very few died 'peacefully' drowning. They were swept into sharp unyielding objects at high speed and killed. People on site say the victims look like they died in motor vehicle crashes.
Sure, a lifejacket might have helpes a small % of cases. But not many.
The shock wave at sea, which does not displace water, moves at 500mph. Water starts moving when the shock wave can no longer start transmitting energy due to the sea bottom shallowing and sloping up gradually. The waves then move at speeds from 20-60mph.
108: Great post. Thanks.
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