[Coral-List] response to tsunami at Kwajalein

[Bill Allison]

Atolls in Maldives were affected by the Boxing Day 2004 tsunami, some
substantially. Apparently the effects were a function of features that
obstructed the tsunami and generated solitons, such as atoll size and
location, the depth and number of channels, and related to the last, the
length of reefs and islands, + idiosyncratic features (e.g., atoll open on
side of impact and largely closed on the other side, man-made channels where
solitons reinforced produced bores that ran up the channels etc).

On Fri, Mar 18, 2011 at 8:37 PM, Don Baker <reefpeace at yahoo.com> wrote:

> Hi Carly,
>
> Atolls have never (to my recollection) been affected by tsunami waves..but
> only storm generated waves from Typhoons. Why?  Well.....the tsunami is
> really a shock wave and rather deeply focused from its source event.  To try
> to note a case in point to demonstrate here was a tsunami that hit the
> Federated States of Micronesia island of Kosrae one evening near sunset.
> This event happened maybe in the 1980s. (can someone assist in a date here
> from the FSM?).   My good friend, Roger Emerson was sitting on his back door
> step when he saw a wave about 2 feet high quickly run across the shallow
> reef flat and smack into the road causeway.  Being only about 2 feet
> high...no one really thought it was anything to be concerned about.  The
> next day, spearfisher men came back into towen and reported what they saw on
> the outer reef front.  The coral was totally ripped apart, huge porites
> colonies rolled over and the large acropora plate corals knocked about.
>
> So what happened?   The depth issue is the key.  Atolls will get hit by the
> tsunami for sure but the wave may only be a foot or less high as it comes
> across the reef...and may never come across if its low tide. The small wave
> is the tsunami's top portion that skimmed off while the main shock wave hit
> the atoll's deep reef front wall. Tsunami waves are, again, deep shock
> waves.  The shock wave is most dangerous when the coastal region affected
> has relatively shallow off shore water. This allows the wave to build up and
> reach hts of 30 + feet.  Hawaii is typical as well as the coasts of Japan..
> Guam is not like Hawaii and tsunami waves may hit but be very small as the
> water gets quite deep off shore in less then a mile.  The biggest waves I
> saw on Guam was during Typhoon Pamela down at the Uof Guam Marine
> Lab.....they were about 25 + feet high as they slammed the reef margin and
> then the tops racing across the shallows and slam into the jungle.
>
> R/Don
>
>
> --- On Fri, 3/18/11, Carly Kenkel <carly.kenkel at gmail.com> wrote:
>
> From: Carly Kenkel <carly.kenkel at gmail.com>
> Subject: [Coral-List] response to tsunami at Kwajalein
> To: coral-list at coral.aoml.noaa.gov
> Date: Friday, March 18, 2011, 3:25 AM
>
> Hi All -
>
> In case anyone is interested - I've done some work on Kwaj and know one of
> the principal dive instructors there.  I emailed him this past weekend and
> he says Kwaj is fine.  He's always told me that Kwaj has never been
> affected
> by major waves...out of curiosity, does anyone know why this might be the
> case?
>
> And thanks Dean for all your efforts in monitoring reefs in the RMI!!!
>
> Best,
>
> Carly Kenkel
> Graduate Student
> Dept. of Integrative Biology
> The University of Texas at Austin
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>
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