Yes, amplitude increases as water depth deceases and you are right bays can contribute to that. I suspect some of problem with these shores is the corresponding land is near sea level so it does not take a huge wave to translate into reaching a long way in shore. This was the case in Thailand. Atolls I suspect are small enough that they have little effect, not big enough land mass to concentrate the energy. There are many things contributing to height, exposure is one, it seemed Hawaii gave a small profile to this one, perhaps if it hit Hawaii broadside the damage and surge would have been greater.
There is energy loss from friction as the sea depth decreases, the case I refer to is a wave approaching a large land mass. If there is steep run up little of the waves energy would be released until it meets land causing the waves to break closer to shore, so more energy is released at the shore. I believe this is only the case from earthquakes IE the event happens on the sea floor. The sea depth decrease when approaching all land masses, with steeper approach the energy gets concentrated closer to shore. A tsunami caused by a meteor impact would be different. I remember reading that meteor impacts have created waves that have washed over much of N America, it would make no difference what your coastlines topography is. A dangerous undersea topography for a tsunami is a seafloor that becomes
shallower and shallower, as it allows the waves to build up dramatically -- see the illustration here: http://www.pmel.noaa.gov/pubs/outstand/gonz2088/images/image4.jpg . With an island atop a steep abutment, as with some Pacific atolls, the wave can just pass through, causing no harm. If that weren't the case I would have died in 1964. And the same island, Kwajalein, got through the recent tsunami without damage. Recently I heard that tsunami comes from the word for "harbor wave," because harbors are likely to have shallowing bottoms and a bowl-like structure that funnel the power of the tsunami in. But I have suspect that when one hits a really wide shore it causes damage regardless of the ocean bottom. Thanks, Joe
--- On Fri, 3/18/11, erikhansen@thebluezone.net <erikhansen@thebluezone.net> wrote:
From: erikhansen@thebluezone.net <erikhansen@thebluezone.net> Subject: Re: [Utah-astronomy] Japan Earthquake Discussion To: "Utah Astronomy" <utah-astronomy@mailman.xmission.com> Date: Friday, March 18, 2011, 3:38 PM
Anyone remember the Missouri earthquake? It was an area no one believed was at risk.
Salt Lake is full of houses that are poor in an earthquake, a 9th mag earthquake would ruin Salt Lake City.
BTW, did a little digging about tsunamis, seems the worse scenario is a steep shore line. This concentrates the kinetic energy on the shoreline. The initial event determines the energy contained in the waves.
Incidentally, I am currently working on a rehabilitation, including a
seismic upgrade, on a stone and adobe house in Ephraim. The Japan quake has me thinking more about these issues even more than usual. If you live in an unreinforced masonry home, make sure your will is in order.
Kim
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Rodger C. Fry Sent: Friday, March 18, 2011 2:01 PM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Japan Earthquake Discussion
This is mildly off topic but does talk about crustal tides and earthquake predictions.
I don't know much about this guy but what he is saying may provide for an interesting discussion.
Time will Tell.
Follow this link:
http://www.youtube.com/watch?v=xQXDt4VdS0E
Rodger Fry
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