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Thread: Tsunami Survival Strategies in PWS

  1. #1

    Default Tsunami Survival Strategies in PWS

    All the coverage on the 50th anniversary of the 64 quake has been interesting. The wave heights quoted in one of the ADN articles indicates that Passage Canal had a 104' wave, Blackstone hit 79', Valdez 30' and other places had waves from 4' (Juneau) to 220' (Shoup Bay). The link is here: http://www.adn.com/2014/03/24/339158...-tsunamis.html

    So, given the range of possibilities, what are the best strategies in the event of a tsunami warning?

    Getting to deep water, if possible, would seem best - but how deep does the water need to be and far from shore does one need to be for safety? Is Port Wells enough? It is hard to tell, but from the listings even some fairly open areas of water got hammered with big waves - Port Nellie Juan for instance.

    Common sense says that the amount of time you have, and the distance to deep, open, bodies of water, will be the important factors, but how deep an how open?

    This is an issue that crosses my mind every time I am out, particularly with the family.

    So, a fer instance: You and the family are dead asleep in Deep Water Cove, a warning comes over channel 16, you have a marginal amount of time to make it open water between Perry and Main Bay. How do you decide weather to scramble up the mountain and be stranded without your boat, or make a run for it?

    In doing the analysis, how do you figure out how deep "safe" water is and how far out into open water you need to be for safety?

    Any insights will be appreciated!!

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    Moderator Daveinthebush's Avatar
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    If you looking at a 30 foot wave traveling at 30-500mph, you might as well kiss your stern goodbye.

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    Just one more thing that can end 'you'. Just take the Alfred E. Newman approach and save the heartache.
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    Quote Originally Posted by Daveinthebush View Post
    If you looking at a 30 foot wave traveling at 30-500mph, you might as well kiss your stern goodbye.
    http://www.drgeorgepc.com/Tsunami1958LituyaB.html

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    Quote Originally Posted by Daveinthebush View Post
    If you looking at a 30 foot wave traveling at 30-500mph, you might as well kiss your stern goodbye.
    I don't buy it, Dave - at least not in all situations. Let's say the quake is centered somewhere that gives an hour or more warning of the impending wave (which is entirely possible). In that case, the question is totally valid.

    I don't think there's a perfect answer to your question, but if I'm on a boat, I'm heading to deep water. If I'm already on land, I'm climbing like a goat. That's just my initial reaction and is not based on data analysis, but either way I think you'd be good if you have adequate warning (~15+ minutes depending on the speed of your boat or the speed of your legs, depending on whether you were on land or sea)

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    Member jrogers's Avatar
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    I think I would go for deep and open water in most cases. As to the question about being anchored up for the evening and hearing a warning, how many of you leave your radios on all night? It would be nice to have it on, but in most places there is always some chatter where I end up turning it off.
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    Forum Admin Brian M's Avatar
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    Quote Originally Posted by jrogers View Post
    .... how many of you leave your radios on all night? It would be nice to have it on, but in most places there is always some chatter where I end up turning it off.
    Good point. I don't leave it on all night when out with my family. When out commercial fishing we'll leave it on for the early AM weather briefing, but that's it. I used to leave it on 16 all night, but I grew weary of the unnecessary wake-ups at 2:00...and 2:15...and 2:55...and so on.

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    Moderator Daveinthebush's Avatar
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    I never leave the radio on so hearing a message while I'm sleeping is not going to happen. I think the NOAH weather channel would issue the alert and not the Coast Guard so the possibility of hearing a message..... you would have to be on that channel. If the wave travels at 500 mph, I would think anywhere in PWS you are not going to have time to react. They say that if you can see it, it is too late. You would probably know that something was amiss even before NOAH knew if you were out there.

    I just would not worry about it.

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    Member Akheloce's Avatar
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    A tsunami only goes 500 mph in deep water, with a long frequency, and low amplitude. As I reaches shore, it slows down dramatically.

    A typical tsunami has a 3 minute drawback period followed by a 6 minute build to crest at shoreline.
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    I've always been interested in how folks rate risks. Plenty of folks have a fear of flying. In almost ever case the ride to the airport is much risker than the flight. The difference is the sense of control that folks have. I've had lots of folks come up to Alaska and taken them out on my boat and many of them ask me how risky it is to be out in PWS. My response is that the most risky thing we'll do on the enitre trip is the drive from Anchorage to the dock... Once we're on the water many of the risks have to do with who is at the helm and what decisions they make. On the road we're just praying that someone isn't drunk or tired or didn't properly hitch up thier trailer.
    At any rate, to get back to the question, given the number of folks who have been killed in tsunamis over the last hundred years and the number who have been killed by a drunk coming across into oncoming traffic, I'd say that paying attention to what other drivers are doing and being prepared to take defensive action is probably going to pay off the best. And yes sometimes even in that situation heading for deep water may be your best option.....
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  11. #11

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    Go deep, young man. Go deep.

    That's standard wisdom and it worked for the guys in 64. The rule is 100 fathoms.

    Radio's off? You're a statistic.

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    Member Alaskanmutt's Avatar
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    When I was in the Coast Guard we recommended you get into 600 feet or deeper if possible. Away from channels and any other feature that would channel water (like steep cliffs nearby)
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    So do you take it head on - on step at WOT?

    I am taking my stern and whoever else is with me to shore and climbing.

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    Member Alaskanmutt's Avatar
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    At 600 feet deep it would be like a foot tall on the surface is that. Unless you are in a narrow channel
    They don't rise until they reach shallow water which causes the incoming water to stack up behind the moving front as it slows down which pushes the water up.

    If you are ever in Seward during a good earthquake you will watch the Mustang run out of the harbor but slowdown and stop about a mile from the harbor.
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    Moderator Paul H's Avatar
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    The odds of another mega quake occurring in our lifetime is pretty slim, the Good Friday quake was a once in every 600-1000 year event. And I'm thankful every time we have a moderate quake as the faults are gradually relieving stress vs. building over time. The sound is an interesting area as most anchorages are near to deep water, but we also have a tremendous number of fjords that channel it. If I was on the water and knew a Tsunami was imminent I'd head for the deepest most open water. If on shore or near shore I'd head high as quickly as possible. The sitting duck scenario of being on anchor is the scariest, I'd likely cut the anchor line and head as far out at as high a speed as I could.

    That said, I'm much more concerned with a rogue wave in a storm or an uncharted rock.
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    Member Alaskanmutt's Avatar
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    Or shrimp pot thieves
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    Member Bullelkklr's Avatar
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    I would like to think that the coast guard would issue a warning with recommendations to vessels. I am going to ask the CGA tonight during class at the BSS training tonight and see what they say.

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    you have options so learn what they are for where you are. it is a long shot of ever happening compared to other things but there are somethings you can do in the event which can affect your well being.

    a drunk hitting you also is a long shot but you wear seat belts to improve your chances and have air bags.

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    Japanese boat in open water from the Tsunami in Japan. Not sure how deep the water was. Looks like a small boat would be fine.

    https://www.youtube.com/watch?featur...&v=OdhfV-8dbCE

  20. #20

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    Good info, and the 600 foot mark is a good reference point. Re risks, yes, the risks are statistically small, but if it happens that won't be much comfort. Like any outdoor activity, there are risks - avalanches, drowning, falling etc. etc.. But accepting risks is not the same as being uninformed about them and minimizing them where you can. It will be interesting to hear what the Coast Guard has to say on this subject. This discussion has been worthwhile, thanks all.

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