Sunday, 28 February 2010

Tsunami and me

I woke this morning to a phone call warning me to turn on the radio because of the tsunami alert affecting the entire pacific - but no details. Since I live right on the coast, this was of no small concern.

Images of death and destruction echoing through my head from past tsunami disasters' news footage, I scrabbled for internet - my old water-wave physics skittering across my brain.

The thing about a tsunami warning, the important thing, is the height of the wave. While anyplace close to Chile are basically soggy toast, the wave prompting the warning was predicted between one and two meters high over here. As it washed down the coast, it was only going to get smaller. I went back to bed and resolutely slept through it.

It is better to be safe than sorry when it comes to mass alerts like this, so nobody did anything wrong with the alert. I know some families close by hurriedly went to higher ground and I hate to think what the motorway was like.

While a 1m swell at sea can get quite high as it comes ashore, I felt that the 10-20m cliffs between me and the sea would prove adequate. Hawaii can get 7m(!) breakers from normal sea swells because of offshore reefs - but there has never been anything remotely like that here. Besides, it is unlikely that the figure is for 1m at sea! Since even big tsunamis are seldom more that anyway. More likely the figure is trying to take shoaling near the Chathams into account. Harbours are more strongly affected - thus, Wellington's evacuation alert.

This i not to say that wee waves are not dangerous - you can still get pulled about or washed off something and people die from normal waves all the time.

Curiously, while reporting Civil Defense telling people to stay away from the coast and out of the water, TV News services are soliciting for video foothage of the waves as they come in. Guys: do you want to get people with cameras close to danger?

I really feel for our pacific island brothers and sisters, some of whom have already had bad luck with nature recently. To get hit twice...

Then there is Chile. A magnitude 8.8 are fairly uncommon (about 1 per year in range 8-9) and very devastating when they happen near a city. Nuclear comparisons are tempting but misleading: the nagasaki a-bomb shook to a mere 5.0 - this one was more than 1000 times bigger. But, nuclear devastation does not come from the ground shaking - an earthquake has the most gentle part of a wmd blast ony; no flash-burn, no blast, no radiation, no fallout. Releif efforts can start right away. Quite an improvement in fact.

Not that this is any consolation when you are in one!

I see releif teams are on the ground now. Recent events have sort of spelled out the importance of not hampering this process. Hopefully they will be better organized than at other times.

In this sort of thing we are reminded that the Earth is much bigger than us and anything we can do, She can do better.

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