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Old 15-11-2012, 03:22   #61
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Re: Tsunami- Head Out To Sea?

I know little of the science regarding tsunamis, but it seems to me that depth has less to do with building the height of the wave, than would the gradient of the sea floor off the coast.

Splash in a half filled bath tub and see the difference between the ripple height at the plug end, and the ripple height and fetch at the shallow end. Then try the same exercise in a large paint roller tray. It seems a wave could more effectively dissipate it's power if the gradient was gradual rather than sudden.

If this is the case, and I reiterate my tsunamic ignorance, one would need to know the submarine topography of the ocean floor close to the coast, rather than just a specific depth of water, above which one could assume a degree of safety.

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Old 15-11-2012, 16:02   #62
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Re: Tsunami- Head Out To Sea?

Yes, i would to save my boat if boat was high priority, period, did this years ago during hurricane and it resulted in victory, However i strongly recommend dropping andéor disconnecting all sails and storing them below decks. The wavwves will |clear| your decks of dingys, fuel cans, and anything else not stored beneath. enough said, cheers

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Old 15-11-2012, 16:56   #63
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Re: Tsunami- Head Out To Sea?

Auzzee, you are on to something however your models are of the wrong scale. That is, the amount of water is much more immense to the paint tray. Likely is the paint tray would be completely submerged and would do little to "dissipate" the energy. Yes, eventually water will return to it's own level but that is more a function of time than it is loss of energy from sea floor topography.

Remember, the wave length of tsunamis is measured in miles. Go watch some You Tube videos showing the spilling waves at places like Teahupoo or Shipwrecks. Compare that to a spilling wave at places like east coast of Florida. In the former, it seems the entire ocean is coming down into the trough, in the latter it is relatively benign as the top of one wave spills sloth-like.

Quite literally a tsunami is the ocean pouring into the trough. But that the wave length is so enormous it is outside our comprehension of what a breaking wave should look like.
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Old 15-11-2012, 18:13   #64
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Re: Tsunami- Head Out To Sea?

Just watch the uTube videos of the Japanese tsunami. No breaking waves, just a wall of water destroying almost everything in its path.
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Old 24-02-2013, 20:15   #65
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Re: Tsunami- Head Out To Sea?

Here in Crescent City the wise mariners all take their boats to sea when there is a serious threat.

The last boat out in the last Tsunami went across the bar as the wave was coming across the bar too. They had a rough ride, but nothing they couldn't handle.

The boats offshore only went far enough to get some elbow room, certainly not past the 30 fathom mark, and rode it out without knowing when the waves passed them.

In the inner basin the less intelligent mariners went through hell, and even the few boats saved are still badly damaged. It is a miracle that the handful of men on their boats survived.

Not every boat will have someone near enough to take her to sea, and not every boat with an owner close enough to take her to sea will be taken to sea, but every boat taken to sea reduces the risk of damage to that it faces on every voyage.

To leave your boat at the dock in the face of a timely Tsunami warning is lubberly.
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Old 01-05-2013, 23:26   #66
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Re: Tsunami- Head Out To Sea?

My boat is on a mooring within a couple hundred feet of Dexterbase's in Monterey. The reason there was so much damage in Santa Cruz and none in Monterey is that Santa Cruz harbor is long and narrow and Monterey is much more open. The tsunami surges sloshed in and out of Santa Cruz, but in Monterey the effect was like a somewhat exaggerated version of the winter storm surge that we get with swells generated by storm winds hundreds of miles away. The Boatworks people I talked to who were watching said there was just a series of gentle slow surges, rising and falling maybe a couple of feet. A few boats went out and milled around on the bay when the tsunami was scheduled to arrive. The 1964 Alaska earthquake caused a surge in Monterey of less than two feet, that caused a 30-foot sailboat anchored off the beach to break free and drift gently to the beach, where the keel worked itself into the sand. Salvage was attempted by bulldozer, breaking the keel off. A friend of mine bought the boat from the insuror and made a new 3,000 pound keel from bullets from Fort Ord pistol ranges.

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