sourmìlk wrote:Can one estimate how tall the tsunami would be at a given distance from its origin? I would imagine that by the time it hit South America it would be significantly smaller than a normal wave.
The wave won't attenuate very quickly as it's a very low frequency with a long wave-length - hence why the Indonesian tsunami was still tossing boats up onto the shore in Kenya.
You can predict the wave functions - wavelength/frequency/amplitude as it spreads out, but height on shore depends on a whole raft of local conditions.
Waves break when they reach shallow water ("shallow" being a relative term and a function of the wave's amplitude - i.e. it's depth). If you live inland from the Barrier Reef in Australia for example, a tsunami would actually break over the reef and you would get a surge onshore, but the wave would have actually broken offshore and probably burned out a lot of it's energy before it made landfall.
On the other hand, if the shore isn't far from the continental shelf, and the water from the shoreline gets very deep very quickly, the wave actually won't start to break until it's practically on the beach. In mountainous areas like some of the South American sea board, it would break into bays, and the wave height would forced down narrow valleys, increasing in height if the valleys narrowed, or decreasing if the valleys became wider (allowing thew water to spread out).
If we take San Fransisco
as an example, the wave would become relatively shallow. As soon as it goes under Hway 101 it'll split 3 ways - North into San pablo Bay, South into San Fransisco Bay and North into Belvedere.
As it goes north, it's shallow as it spreads out into the relatively wide Bay area, but then anything going through corckett will rise again because the water is being forced into a narrow opening.
As it goes South it will initially fall in height as it spreads out into SFB, and what's left will rise in height as the Bay narrows to a point down by Santa Clara (although obviously not as high as the original wave).
This is assuming the Hway 101 gap is the only area forded and other areas aren't breached. Not too sure about the topography.