Head for Deep Water ?

[Jim Cate]

Originally Posted by cal40john

Did you or anyone you know leave harbor and head for deep water before the tsunami on the U.S. west coast or Hawaii?

John

G'Day John,

Being here on the SE coast of Oz there was no predicted hazard from this dreadful event, and we remained at anchor in Broken Bay.

But within the past two years we have indeed left an anchorage upon hearing a tsunami warning, once in New Caledonia (Baie de Orphelinat) and once here in Broken Bay. In both cases there was no significant surge, and we had "wasted our time". We were astonished in both cases that we were nearly alone in our efforts. In both cases the warnings were well implemented in good time, there were hundreds of boats in the affected areas, dozens of which were occupied, and only one other boat in each case took the trouble to protect themselves.

Perhaps because we had many friends whose boats were damaged or sunk in the Boxing Day tsunami we are more keenly aware of the destructive power of these things, but it was still a shock to see the lack of self-protective instincts on the part of other sailors.

As unpleasant as the events in Santa Cruz were, they pale into insignificance when compared to the seas of destruction we've been shown in Japan... those poor buggers.

Cheers,

Jim and Ann s/v Insatiable II lying Morning Cove, NSW, Oz

[psneeld]

Originally Posted by Jim Cate

G'Day John,

Being here on the SE coast of Oz there was no predicted hazard from this dreadful event, and we remained at anchor in Broken Bay.

But within the past two years we have indeed left an anchorage upon hearing a tsunami warning, once in New Caledonia (Baie de Orphelinat) and once here in Broken Bay. In both cases there was no significant surge, and we had "wasted our time". We were astonished in both cases that we were nearly alone in our efforts. In both cases the warnings were well implemented in good time, there were hundreds of boats in the affected areas, dozens of which were occupied, and only one other boat in each case took the trouble to protect themselves.

Perhaps because we had many friends whose boats were damaged or sunk in the Boxing Day tsunami we are more keenly aware of the destructive power of these things, but it was still a shock to see the lack of self-protective instincts on the part of other sailors.

As unpleasant as the events in Santa Cruz were, they pale into insignificance when compared to the seas of destruction we've been shown in Japan... those poor buggers.

Cheers,

Jim and Ann s/v Insatiable II lying Morning Cove, NSW, Oz

You could say the same...insurance companies sure have...of the folks who do little in the face on hurricanes every summer/fall in the SE United States.

[delmarrey]

Originally Posted by Pelagic

What I do need to understand better is why some areas on the US West Coast had such massive surges and others not?

What were the conditions necessary to make it an event?

Is the main thrust from a tsunami more directional than omni directional?

If you look at the contour along the Northern Cal & Oregon coast, you can see a beach like shelf that would allow for the building of the waves. Wall Map of Pacific Ocean Floor by National Geographic from Maps.com -- World's Largest Map Store.

I'm surprised Vancouver Island didn't get nailed.

[AK_sailor]

Originally Posted by Pelagic

What I do need to understand better is why some areas on the US West Coast had such massive surges and others not?

What were the conditions necessary to make it an event?

Is the main thrust from a tsunami more directional than omni directional?

It all depends on the local configuration of the shore and bottom. Similarly to what one sees with tides. In many repects a tsunami is just like a tide, only it changes much faster. Just like some areas can have a wicked tide current, others nearby may not. Or some areas may be bad in a flood tide, not so bad on ebb. Tsunamis are similar. Infinate variations on local conditions, therefore infinate variations in reponse. If you have sufficient warning, getting to open sea and deep water is probably nearly always the best choice.

[AK_sailor]

Originally Posted by Jim Cate

....We were astonished in both cases that we were nearly alone in our efforts. In both cases the warnings were well implemented in good time, there were hundreds of boats in the affected areas, dozens of which were occupied, and only one other boat in each case took the trouble to protect themselves.

......it was still a shock to see the lack of self-protective instincts on the part of other sailors.

Yes the all too common lack of self preservation instinct is amazing. My brother lives near the N. Oregon coast. He emailed that many, many people headed to the beach to watch for the tsunami. Note that in his area there are plenty of high headlands where one could watch in relative safety, but these idiots went down onto the beach! Fortunately, the tsunami was more or less an non event in his area. Further south at Newport, he said a guy actually went out onto the jetty to watch, and was nearly washed away. In N California, a photogapher was washed out to sea and not found. Idiots!

[Pelagic]

Originally Posted by GordMay

From the area where the tsunami originates, (omnidirectional) waves travel outward in all directions. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger than the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.

Life of a Tsunami ➥ Tsunamis and Earthquakes -Basics - USGS WCMG

More Tsunami Links ➥ Tsunamis and Earthquakes Links - USGS PCMSC

Thanks Gord and all for trying to answer my questions.

I understand the mechanics of ground effect and topography when it comes to an area being more vulnerable to a Tsunami event.

But that was not my question.

What I am trying to understand is one of the graphics I saw showed more focused points of stronger waves in general rather than total blanket risk from radiated waves.

There was one showing red (high danger) to large region areas while adjacent areas to the sides showed lesser danger. It was too general to be topography driven

For this tsunami, any area on an ESE heading from the epicenter seemed to be high risk.

Was that because of reflected energy coming off of the Japanese coast?

On the first thread this graphic showed it a bit, but I saw another graphic much more developed that illustrated what I am curious about.

Would love to understand their modeling theory better.

http://www.cruisersforum.com/forums/...3&d=1299844509

[mbianka]

IMO I think heading out into deep water might be the best option followed by a boat at anchor in an uncrowded location with a LOT of scope. I certainly would not feel comfortable to have my boat at a dock with an approaching tsunami as this video of what happened in Santa Cruz shows:
THE BIANKA LOG BLOG: TSUNAMI: SANTA CRUZ CALIFORNIA

[SkiprJohn]

Our club has a few boats that could not be hauled on trailers so we sent them to sea. The first waves hit the island about 0330 so these folks were out beyound the breakwall from about 0001 until the harbor opened between 1430 and 1600 on Friday. What a mess. The Coast Guard would not let folks reenter the Bay until the all clear was given by civil defense. People were dead tired, ran out of fuel, didn't have enough food and water aboard and one woman had to be towed by the CG back to port. They gave her a lot of fines because her battery died when she used it for navigational lights, she didn't hook up her VHF and didn't have any provisions aboard. She only had the problem because the CG would not let her back into port earlier.
Anyway, the best policy is to take your boat to sea if you can. That prevents you from crashing into another boat or other solid object or another from crashing into you when the big waves come. The duration of the waves are much longer than regular shoreline action which causes steady stress on your mooring lines until they give way. Keehi Lagoon on Oahu really was a mess.
We went to sea last year when the tsunami was headed our way in February too.
kind regards,

[Pelagic]

Mike, good to hear your friend in Okinawa felt nothing. That is what we need to understand better, is how that energy can somehow not affect an area so close, yet hit Santa Cruz?

[matauwhi]

G'day, mates. We had been anchored in 15 feet of water in a nice little bay down here in New Zealand. We set the alarm and headed out for deeper water and waited. Had the morning cuppa and brekkie and the first small surges came in. Reanchored in a slightly deeper bay. Still getting some same small surges as I write this. No regrets on hauling the anchor and heading out at "O'dark thirty".

A tip for those that live aboard. Here in the Bay of Islands, where we base out of most, we do not have a formal tsunami alert system. We are notified via the AM/FM radio or VHF 16. I have made arrangements with a mate back in the states to monitor the Pacific Tsunami warning system on the net and call us if an alert comes up while we are "off watch". We'll take all the "heads up" we can get. Cheers.

[mbianka]

Originally Posted by Pelagic

Mike, good to hear your friend in Okinawa felt nothing. That is what we need to understand better, is how that energy can somehow not affect an area so close, yet hit Santa Cruz?

Yes, I too was really surprised how little effect he felt despite being part of Japan. I guess he was lucky that Okinawa was south of "mainland" Japan and the Tsunami's force was primarily concentrated in an east and west direction. With the Japanese coast around the epicenter getting the brunt of it.

[speakeasy]

Originally Posted by Pelagic

Thanks Gord and all for trying to answer my questions.

I understand the mechanics of ground effect and topography when it comes to an area being more vulnerable to a Tsunami event.

But that was not my question.

What I am trying to understand is one of the graphics I saw showed more focused points of stronger waves in general rather than total blanket risk from radiated waves.

There was one showing red (high danger) to large region areas while adjacent areas to the sides showed lesser danger. It was too general to be topography driven

For this tsunami, any area on an ESE heading from the epicenter seemed to be high risk.

Was that because of reflected energy coming off of the Japanese coast?

On the first thread this graphic showed it a bit, but I saw another graphic much more developed that illustrated what I am curious about.

Would love to understand their modeling theory better.

http://www.cruisersforum.com/forums/...3&d=1299844509

Interesting question. We need a good wave theorist. This page has some amplification of your earlier graphic and some research links.

NOAA Center for Tsunami Research - Tsunami Event - March 11, 2011 Honshu

[speakeasy]

Originally Posted by mbianka

IMO I think heading out into deep water might be the best option followed by a boat at anchor in an uncrowded location with a LOT of scope. I certainly would not feel comfortable to have my boat at a dock with an approaching tsunami as this video of what happened in Santa Cruz shows:
THE BIANKA LOG BLOG: TSUNAMI: SANTA CRUZ CALIFORNIA

That amazing video, plus the footage out of Japan are quite sobering and instructive in their way. Looking at the Santa Cruz shots, I wonder if breakwaters, well positioned might mitigate that surge, using wave theory again.