Then I take it we put this very limited data plus alot of assumptions through a finite element analysis (which would probably take a decent chunk of time even on a supercomputer, assuming you could free one up on a moment’s notice) repeat quite a few times for different assumptions due to our lack of data, and end up with something useful in the <2 hours before the tsunami hits? Unlikely.

It’s a pitiful exhibition of scientific incompetence IMHO. If the Government is too clueless to do it, tender it out to private enterprise and let them handle it properly.

As to your criticism that the CD prediction was wrong, one cannot guess the size of the wave coming in a particular direction soley from the magnitude of the earthquake. Ultimately you have to wait until you have measurements from bouys or shore observations in several directions before you can reliably predict where it is going with what strength. So either you advocate a lot more bouys being set up, or the CD have to play it safe and consider the worst case scenario till enough data is recieved to fit a model with. What’s the cost to install and maintain that many bouys in the ocean vs disrupting a some of the populus for a few hours once every one or more years? Cost/benefit ratio is probably not that good.

As far as I can say, what few predictions civil defence had were actually quite wrong.

http://nctr.pmel.noaa.gov/Jpg/kuril06-dart.jpg

The point I am making is that it doesn’t seem to me that our civil defence systems are making sufficient use of known science and are thereby causing a lot of people to run around like headless chooks instead of doing useful things.

Also, why was Raoul Island data suffering a two hour delay yesterday? It has recovered now, but surely as an early warning system it is useless if not current.

Mark Sainsbury’s best effort to date on Close-up:

“But you are alive Tony?”

When doing a live telephone interview with Tony.

Cutting edge stuff that.

That spokesman was Colin Feslier, who used to work for DIA before this debacle.

Poor Colin.

I am a born and bred Wellingtonian, even in the Hutt Valley (a place I always tried to spend as little time as possible in) you are not more than a couple of miles from a bloody big hill.

I would have thought that a tidal wave plan for Wellingtonians would be one of the cheapest and easiest to organise, look for the nearest hill and get to the top of it.

malcolm, it doesn’t matter how efficiently they travel – so long as they are being extended around a larger circular perimeter their energy is being directly attenuated by the increasing length of that perimeter. There will be further losses due to energy absorption en route due to various causes that may be variable but these losses will be on top of the direct attenuation by distance.

Yes, the height onshore will be affected by the local topography but the wave height at the worst affected close coastlines is surely a worst-case estimate to use as a rule-of-thumb for predicting via attenuation what would happen here.

Yes it may well be that the worst-affected close shore is the worst case, but not necessarily. Also true about the energy decreasing in proportion to the distance travelled (= proportional to wave front length), but there are many other factors in play. Just one example, reflected waves adding together or cancelling each other out. The 2004 tsunami was a good example. Much more devastating in Sri Lanka yet far less so in places closer to the epicentre. This was also a function of the orientation of the plate shift etc.

I’d rather we have over-reaction on behalf of Civil Defence but would be interested to know if they had a very clear tsunami plan or if anyone has done studies into likely effects of a tsunami on NZ.

Yes, the height onshore will be affected by the local topography but the wave height at the worst affected close coastlines is surely a worst-case estimate to use as a rule-of-thumb for predicting via attenuation what would happen here.

True, but it’s more complicated than that.

It certainly is. Waves that are channeled up a waterway or follow a deep ocean rift can go a lot further without loss of power. They reflect off land masses.

Alan Wilkinson wrote:

The energy of the wave must be dissipated as it radiates at least in proportion to its circular length = 2 x Pi x r.

Given that NZ is a factor of 10 further away from the epicentre than Samoa where it was apparently about 3 metres high why on earth is anyone surprised it is no more than 300 mm high when it reaches NZ?

True, but it’s more complicated than that. The waves travel more efficiently in deeper water and the impact when it hits land would be dependent on the profile of the seabed, harbour shape. Not to mention the shape, orientation etc of the earthquake (e.g if the plates shifted vertically). The 2004 tsunami went right across the Indian Ocean and did plenty of damage in Sri Lanka, but much less damage in places closer to the epicentre.