On 06/03/2011 08:27, RussellMc wrote:
> Tsunami can be dealt with pretty much on an immediate coastal basis in
> most cases. MUCH more so than eg earthquake itself.
>
> Once you decide there is a prospect you can easily [tm] minimum quake
> to Tsunami arrival times and can have a moderately good idea of
> maximum wave amplitude and "reach".
>
> If probabilities were high enough you can easily put in monitoring for
> an actual wave and alarms. Once people are convinced this is serious
> they tend to cooperate reasonably well. Satellite and other aerial
> before and after photos of Bunda Aceh (which are available)(I have
> some somewhere) and photos of Samoa (many available) help convey
> conviction. The large majority in most possibly affected areas need
> only move very short distances taking only short times to be out of
> tsunami risk in most cases.
>
> Photos of Bunda Aceh give and extremely good idea of what is and isn't
> liable to provide protection and how far inland things can happen in
> certain locations.
>
>   A Tsunami is essentially a step change in incoming water velocity -
> NOT a normal wave. Once you see what they do and how they work you can
> have a fair idea what you need to do in a given case.
>
> Arrival time would need expert input. Open ocean velocities are v high
> (100-200 kph or even more) and amplitudes low, and speed drop and
> height rises as depth drops. There are std depth/height/speed formulae
> available. The Kaikoura trench is an anomaly. You have deep ocean
> depths in a slot with continental shelf either side. How that shapes
> and directs a wave and how fast/slow / high is utterly beyond me.
>
> 5 minutes warning should save most people affected.
> 2 minutes warning helps heaps if you are alert.
> In Samoa tens of seconds was enough for some.
>
>

That makes sense - I suppose a tsunami might be a little easier to deal=20
with than an earthquake, given (as you mention) you at least know=20
roughly where it's coming from (i.e from the sea) and how far inland it=20
may travel.
Would be interesting to know what the experts predict (or are even aware=20
of) for the Kaikoura trench scenario - probably a combination of smaller=20
scale models and computer simulations might help to give at least some=20
idea, though I'm sure there would be some serious work involved.




--=20
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