What is the proper response to a tsunani?

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Ed Ruiz

Tsunamis are surviveable.

As pointed out by others, if you know what to do (or are very lucky) you can survive a tsunami. Usually, there are advance warnings that one is coming. (In this case, there were no tide gauges, but good communications between countries could have averted much loss of life.) With the exception of Indonesia, all the other places were hit by the tsunami multiple hours after the earthquake occured. That would be enough to warn people to evacuate the shores. In any case, if near the shore - get to higher ground quickly. If at sea - get to deep water quickly. ~ Happy sails to you ~ _/) ~
 
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Ed Ruiz

Tsunamis are surviveable.

As pointed out by others, if you know what to do (or are very lucky) you can survive a tsunami. Usually, there are advance warnings that one is coming. (In this case, there were no tide gauges, but good communications between countries could have averted much loss of life.) With the exception of Indonesia, all the other places were hit by the tsunami multiple hours after the earthquake occured. That would be enough to warn people to evacuate the shores. In any case, if near the shore - get to higher ground quickly. If at sea - get to deep water quickly. ~ Happy sails to you ~ _/) ~
 
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Bob

Pacific Basin Ring of Fire

The Pacific rim or known amongst geologists and seismologists as the ring of fire is well known for its plate techtonics and subsequent tsunami's (Japanese for Wave-Harbor). We are always reminded of the Poseidon Adventure movie where a monstrous wave washes over the stately oceanliner and turns it turtle. Can this happen in the open deep sea? No incident was ever recorded. Those pressure waves may not even be felt in the open ocean despite their speed. As the pressure wave gets closer to shallows the energy build up mounds the water to great heights while its velocity decreases. The brakes come on hard, but the outcome is no less terrifying. Regards Bob CAT 30
 
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Bob

Pacific Basin Ring of Fire

The Pacific rim or known amongst geologists and seismologists as the ring of fire is well known for its plate techtonics and subsequent tsunami's (Japanese for Wave-Harbor). We are always reminded of the Poseidon Adventure movie where a monstrous wave washes over the stately oceanliner and turns it turtle. Can this happen in the open deep sea? No incident was ever recorded. Those pressure waves may not even be felt in the open ocean despite their speed. As the pressure wave gets closer to shallows the energy build up mounds the water to great heights while its velocity decreases. The brakes come on hard, but the outcome is no less terrifying. Regards Bob CAT 30
 
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eds928gt

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Jun 7, 2004
91
Hunter 34 Selby Bay
Monster sea waves

are possible, but are usually the result of extreme weather phenomena. I guess a ship could be hit by a large wave created by a landslide, but the ship would have to be in the wrong place at the wrong time. Cruise ships to Alaska glaciers keep well outside the calving zone, where ice breaks off the glacier to form icebergs. If a cruise ship got too close it could be broached by a displacement wave. Otherwise, tsunamis in the open ocean pose no threat to vessels - at all. It's when they are in the harbor (shallow water) that the wave's height becomes significant. ~ Happy sails to you ~ _/) ~
 
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eds928gt

.
Jun 7, 2004
91
Hunter 34 Selby Bay
Monster sea waves

are possible, but are usually the result of extreme weather phenomena. I guess a ship could be hit by a large wave created by a landslide, but the ship would have to be in the wrong place at the wrong time. Cruise ships to Alaska glaciers keep well outside the calving zone, where ice breaks off the glacier to form icebergs. If a cruise ship got too close it could be broached by a displacement wave. Otherwise, tsunamis in the open ocean pose no threat to vessels - at all. It's when they are in the harbor (shallow water) that the wave's height becomes significant. ~ Happy sails to you ~ _/) ~
 
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Chris Swan

Tsunami Tactics

Tsunamis travel very fast, but away from shallow waters...less than 100 feet or so...they are imperceptible as they pass by. So, if you can manuever to deeper waters, away from shore, that is the best tactic. Alternatively, to go well up a river, far from the shoreline, would also work, or to be behind a long, and relatively wide, barrier island, to then dissipate or absorb the wave action.
 
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Chris Swan

Tsunami Tactics

Tsunamis travel very fast, but away from shallow waters...less than 100 feet or so...they are imperceptible as they pass by. So, if you can manuever to deeper waters, away from shore, that is the best tactic. Alternatively, to go well up a river, far from the shoreline, would also work, or to be behind a long, and relatively wide, barrier island, to then dissipate or absorb the wave action.
 
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Peter

I survived one

Well, sort of! About 10 years ago we were off the NorCal coast, rounding the Farallon Islands in my Catalina 27, and returning to Half Moon Bay (about 25 miles from the Farallones). While sailing along, we heard on the VHF in the morning a warning about a tsunami from an earthquake that had occurred in Japan (as I recall). The forecast for the tsunami arrval at the Cal coast was about 1600 that afternoon. And we're scheduled to arrive at Half Moon Bay about 1600! We debated what to do. 1/2 the crew said stay out in the deep water, and rely on the "speedbump" effect of a tsunami in deep water. the other 1/2 said we should continue on, that it likely wouldn't happen, and by the time we could be sure it wouldn't happen, we'd be arriving in HMB after dark, in fog and rain, with large (albeit normal) seas. (It was blowing about 30 knots at the time.) They also said, if the tsunami did occur, what difference did it make, as we'd have no home to go home to, anyway! I'd always wanted to learn to surf, but doing it in my 27 on the back of a tsunami wasn't exactly what I had in mind! As it was, we continued on, and the tsunami never came ashore. Somewhere I've got a picture of one of the crew on my boat reading the next morning's paper, with the headline story of the predicted tsunami that didn't happen!
 
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Peter

I survived one

Well, sort of! About 10 years ago we were off the NorCal coast, rounding the Farallon Islands in my Catalina 27, and returning to Half Moon Bay (about 25 miles from the Farallones). While sailing along, we heard on the VHF in the morning a warning about a tsunami from an earthquake that had occurred in Japan (as I recall). The forecast for the tsunami arrval at the Cal coast was about 1600 that afternoon. And we're scheduled to arrive at Half Moon Bay about 1600! We debated what to do. 1/2 the crew said stay out in the deep water, and rely on the "speedbump" effect of a tsunami in deep water. the other 1/2 said we should continue on, that it likely wouldn't happen, and by the time we could be sure it wouldn't happen, we'd be arriving in HMB after dark, in fog and rain, with large (albeit normal) seas. (It was blowing about 30 knots at the time.) They also said, if the tsunami did occur, what difference did it make, as we'd have no home to go home to, anyway! I'd always wanted to learn to surf, but doing it in my 27 on the back of a tsunami wasn't exactly what I had in mind! As it was, we continued on, and the tsunami never came ashore. Somewhere I've got a picture of one of the crew on my boat reading the next morning's paper, with the headline story of the predicted tsunami that didn't happen!
 
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Dennis Thomas

Lots of good ideas in each reply

First, a few definitions: wavelength is the distance between wave crests (or troughs), frequency is the time between wave crests, wave height or amplitude is the distance between the top of the crest and the bottom of the trough. Wave depth is the point where water is no longer disturbed by the passing wave. Wave depth is always equal to one half wave length, always. Wave height is inversely proportional to the wavelength for a given amount of energy in the wave. Frequency is also an indication of the energy in the wave as this is a function of the speed along with the wavelength. As Dave of Mystic wrote, the motion of a given bit of water in a wave is circular and it ends up back where it started. The energy travels, not the water. The size of the circle decreases downward until there is no motion below the wave depth. An ordinary wind wave on the ocean has a wavelength of a few meters, say 20 for example. Its wave depth would then be 10 meters. When it reaches a water depth of 9 meters the wavelength is forced to shorten to 18 meters and this causes a proportional increase in the wave height. The frequency of the wave doesn’t change but the wavelength has shortened. That means the speed has been reduced. The energy that was in the greater speed is used to raise the wave height. As the water shoals, the wave length continues to shorten and the wave height to increase till the wave is no longer stable and it breaks as surf. A Tsunami is produced when there is a major disturbance of the seafloor. As stated by Ed Ruiz, this could be an underwater landslide but is most often associated with earthquakes. Of course underwater landslides are themselves often associated with earthquakes. During the earthquake a large piece of the seafloor is displaced a few inches or in the case of the recent Indonesian temblor, about 30 meters! In this instance most of the movement was horizontal but some was vertical. I don’t know weather it was mostly up or down but it doesn’t really matter. What counts is that a big hunk of ocean was suddenly several inches maybe feet higher or lower. As Dan of Bull Shoals described it this dome (or basin) covers many square miles and this oscillation is the source of the wave. The width of the area uplifted or dropped determines the original wavelength of the Tsunami and the vertical displacement about equals the height. As the wavelength cannot be more than twice the wave depth the wave is immediately modified by the depth of the water at the epicenter. In this case, the wavelength was probably over 8 miles as it occurred in the Java trench which is almost 5 miles deep at its deepest point. The average depth of the Indian Ocean between Java and Sri Lanka is 3 miles which would result in a wavelength of 1.5 miles. If the wave passed under your boat even at 500 miles per hour it would take 11 seconds. Depending on sea conditions at the time you could easily miss that extra motion. If it were dead calm you still would only describe it (as eds92Sgt did) as an ocean swell. Japanese fishermen didn’t experience the wave at sea but found their village destroyed in the harbor, thus the name Tsunami which is translated as harbor wave (thanks Bob of Atlanta). Because the wavelength is so great compared to a wind wave they don’t act quite the same as they come ashore. The height of a wind wave is much greater compared to its length. The base of the wave hits bottom late, the height builds up fast and it tumbles forward. For the Tsunami the base of the wave hits bottom miles off shore. The height builds but over a much broader area. It almost never “breaks” as surf. Instead it comes in almost like the storm surge of a Hurricane but much faster and without the hours of warning weather. It’s as if the ocean is being sloshed out of its basin. In videos you do see some crashing surf because the ocean still has ordinary waves riding on top of this flood. Dan of Bull Shoals is right on his other point. The shape of the shoreline can focus or disperse the force of the wave. s/v Anodyne Catalina 36
 
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Dennis Thomas

Lots of good ideas in each reply

First, a few definitions: wavelength is the distance between wave crests (or troughs), frequency is the time between wave crests, wave height or amplitude is the distance between the top of the crest and the bottom of the trough. Wave depth is the point where water is no longer disturbed by the passing wave. Wave depth is always equal to one half wave length, always. Wave height is inversely proportional to the wavelength for a given amount of energy in the wave. Frequency is also an indication of the energy in the wave as this is a function of the speed along with the wavelength. As Dave of Mystic wrote, the motion of a given bit of water in a wave is circular and it ends up back where it started. The energy travels, not the water. The size of the circle decreases downward until there is no motion below the wave depth. An ordinary wind wave on the ocean has a wavelength of a few meters, say 20 for example. Its wave depth would then be 10 meters. When it reaches a water depth of 9 meters the wavelength is forced to shorten to 18 meters and this causes a proportional increase in the wave height. The frequency of the wave doesn’t change but the wavelength has shortened. That means the speed has been reduced. The energy that was in the greater speed is used to raise the wave height. As the water shoals, the wave length continues to shorten and the wave height to increase till the wave is no longer stable and it breaks as surf. A Tsunami is produced when there is a major disturbance of the seafloor. As stated by Ed Ruiz, this could be an underwater landslide but is most often associated with earthquakes. Of course underwater landslides are themselves often associated with earthquakes. During the earthquake a large piece of the seafloor is displaced a few inches or in the case of the recent Indonesian temblor, about 30 meters! In this instance most of the movement was horizontal but some was vertical. I don’t know weather it was mostly up or down but it doesn’t really matter. What counts is that a big hunk of ocean was suddenly several inches maybe feet higher or lower. As Dan of Bull Shoals described it this dome (or basin) covers many square miles and this oscillation is the source of the wave. The width of the area uplifted or dropped determines the original wavelength of the Tsunami and the vertical displacement about equals the height. As the wavelength cannot be more than twice the wave depth the wave is immediately modified by the depth of the water at the epicenter. In this case, the wavelength was probably over 8 miles as it occurred in the Java trench which is almost 5 miles deep at its deepest point. The average depth of the Indian Ocean between Java and Sri Lanka is 3 miles which would result in a wavelength of 1.5 miles. If the wave passed under your boat even at 500 miles per hour it would take 11 seconds. Depending on sea conditions at the time you could easily miss that extra motion. If it were dead calm you still would only describe it (as eds92Sgt did) as an ocean swell. Japanese fishermen didn’t experience the wave at sea but found their village destroyed in the harbor, thus the name Tsunami which is translated as harbor wave (thanks Bob of Atlanta). Because the wavelength is so great compared to a wind wave they don’t act quite the same as they come ashore. The height of a wind wave is much greater compared to its length. The base of the wave hits bottom late, the height builds up fast and it tumbles forward. For the Tsunami the base of the wave hits bottom miles off shore. The height builds but over a much broader area. It almost never “breaks” as surf. Instead it comes in almost like the storm surge of a Hurricane but much faster and without the hours of warning weather. It’s as if the ocean is being sloshed out of its basin. In videos you do see some crashing surf because the ocean still has ordinary waves riding on top of this flood. Dan of Bull Shoals is right on his other point. The shape of the shoreline can focus or disperse the force of the wave. s/v Anodyne Catalina 36
 
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Ed Ruiz

Peter, I'm glad you dodged a bullet, but...

Have you considered what might have occured if the tsunami did arrive? I don't think your decision to make port as scheduled was a very wise one. You were lucky, and I'm glad for that. The next time ??? :^( ~ Happy sails to you ~ _/) ~
 
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Ed Ruiz

Peter, I'm glad you dodged a bullet, but...

Have you considered what might have occured if the tsunami did arrive? I don't think your decision to make port as scheduled was a very wise one. You were lucky, and I'm glad for that. The next time ??? :^( ~ Happy sails to you ~ _/) ~
 
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Peter

Ed, you're right...

but we did have some more info. They had had tsunami warnings in Hawaii, about 3000 miles closer to the epicenter than we were. There were other areas around the Pacific that were under warning for times several hours before our warned time of the T. to hit California. We listened to the VHF and to commercial news radio all day, and they indicated that no T. ever arrived in Hawaii, or anywhere else, so we felt the likelihood has fairly remote of us being hit by anything problematical. I'm sure we wouldn't have gone in if there had been any reports of actual tsunamis hitting anywhere. But we certainly did sweat for awhile! Even in the cold temps, rain and 30K winds! Peter
 
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Peter

Ed, you're right...

but we did have some more info. They had had tsunami warnings in Hawaii, about 3000 miles closer to the epicenter than we were. There were other areas around the Pacific that were under warning for times several hours before our warned time of the T. to hit California. We listened to the VHF and to commercial news radio all day, and they indicated that no T. ever arrived in Hawaii, or anywhere else, so we felt the likelihood has fairly remote of us being hit by anything problematical. I'm sure we wouldn't have gone in if there had been any reports of actual tsunamis hitting anywhere. But we certainly did sweat for awhile! Even in the cold temps, rain and 30K winds! Peter
 
Alan

Alan

.
Jun 2, 2004
4,174
Hunter 35.5 LI, NY
What is the proper response to a tsunani?

Our Pacific earthquake and tsunami warning center in Hawaii knew about this event almost as soon as it happened and was aware of the impending wave with its associated danger. They did nothing. When asked, 'Why' the answer given was, 'it was not their responcablility to mointor anything other than the Pacific rim. From what I have been told there is an volcanic island in the central Atlantic that is in the process of spliting in half. When it finally breaks apart, the resulting tsunami will affect the entire Atlantic rim. The resulting wave has been predicted to be a 1/4 mile high and would give the NY area about 7 hours to evacuate. Every city on the east coast will be under water.
 
Alan

Alan

.
Jun 2, 2004
4,174
Hunter 35.5 LI, NY
What is the proper response to a tsunani?

Our Pacific earthquake and tsunami warning center in Hawaii knew about this event almost as soon as it happened and was aware of the impending wave with its associated danger. They did nothing. When asked, 'Why' the answer given was, 'it was not their responcablility to mointor anything other than the Pacific rim. From what I have been told there is an volcanic island in the central Atlantic that is in the process of spliting in half. When it finally breaks apart, the resulting tsunami will affect the entire Atlantic rim. The resulting wave has been predicted to be a 1/4 mile high and would give the NY area about 7 hours to evacuate. Every city on the east coast will be under water.
 
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