You had me and then you lost me. An expanding wave on a surface must necessarily diminish in linear intensity as 1/d, since the wave has a certain amount of energy which is distributed over a perimeter of length 2pi d.
I saw a show some time ago depicting this type of wave, but confined to a channel, somewhere in Alaska. Of course, the narrative did not point this out explicitly, but it was quite clear that this was the case. They were just angling for hype. I took due notice!
It could have been hype, I don’t know. Just because a thing is on Nat Geo does not mean a thing is true.
However, tsunamis created by ocean floor displacement also travel huge distances without losing any significant energy.
They don’t even stop once they have hit land.
The program I saw, which I have looked for on youtube for any highlights but could not find, discussed high speed land slides, which was cliff face breaking off straight down into water, and they also discussed long run out landslides hitting water, where a large mass of land travels downhill and then into water, also displacing a large amount of water greater than the amount of land actually hitting it because of air pulled in behind it.
They gave the impression that whatever land event may have caused Hawaiian fossils to appear on Australian mountains would have been pretty epic, and I think, though I may be mistaken, that they associated it with volcanic activity and island creation.
EQ’s have only been shown to show maximum waves of about 30 meters iirc - due to the “limited” amount of uplift in any one event (on the order of tens of meters). Whereas a landslide can fall from hundreds of meters. Of course the landslide is a pinpoint as you say, and a fault can run for miles.
The following paper gives a rebuttal against the huge landslide tsunami. The probability is that a landslide would occur over a period of time, rather than one huge single block of rock.
http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/
I have read of the Alaskan wave - a man and his son rode it out in a boat. Got swept over a peninsula that was hundred+ feet tall iirc!! Quite the ride. And yes - it was a fairly tight fjiord. I think they also said the natives had stories of this happening in this fjiord - and so their camps were around a bend near the ocean.
I find it hard to believe that these huge boulders were tossed 800 feet up by a tsunami. Volcanic activity they say - I wonder if they are huge pyroclastic “bombs”? Although I would think there would be additional evidence for that.
You lost me on the math! But one thing - the tsunami (either due to submarine EQ or landslide) doesn’t show much if anything on the water surface mid-ocean. But it is the shallowing of the water at the shelf that concentrates the energy. Is your math more for waves at the surface?
EQ’s have only been shown to show maximum waves of about 30 meters iirc - due to the “limited” amount of uplift in any one event (on the order of tens of meters). Whereas a landslide can fall from hundreds of meters. Of course the landslide is a pinpoint as you say, and a fault can run for miles.
The following paper gives a rebutal against the huge landslide tsunami. The probablity is that a landslide would occur over a period of time, rather than one huge single block of rock.
http://blogs.agu.org/landslideblog/2013/12/13/canary-islands-tsunami/
I have read of the Alaskan wave - a man and his son rode it out in a boat. Got swept over a pennisula that was hundred+ feet tall iirc!! Quite the ride. And yes - it was a fairly tight fjiord. I think they also said the natives had stories of this happening in this fjiord - and so their camps were around a bend near the ocean.