MaximusFebruary 7, 2013
The Boy Who Cried Wolf
It seems like I heard this a long time ago, but I’m sure you all have too. A boy cries out “Wolf” as a joke, and everyone runs for cover. He does this again, a few too many times, and the townspeople get weary of his false alarms. When the wolf really does come, and the boy shouts once more, the people just assume he is joking once again, and he gets eaten by the wolf. Something like that – you can tell I have no knack for children’s tales. They didn’t all live happily ever after.
But the Civil Defence organisation in New Zealand is just like this boy crying wolf. Yesterday, as you no doubt know, there was a massive earthquake in Santa Cruze, which has flattened villages and killed some people. The quake was hardly felt in Honiara, the capital of the Solomon Islands, which is the nearest landmass. Undoubtedly, attention should be paid to such events, and I would have thought that the first priority would be to offer assistance, if needed, to the islanders involved.
But Civil Defence chose instead to scare people in New Zealand into thinking that they might be the ones in danger. A tsunami warning was issued for NZ, from North Cape right down to Nelson, with waves forecast to hit the north at 6.00pm and hit Wellington at 7.30ish. Police were apparently spotted on beaches as far south as Nelson, telling people to get out of the water and evacuate the area, in the middle of the afternoon. Completely stupid response.
Civil Defence leader John Hamilton was on the 10.30 news tonight, looking hot and flustered, trying to justify his pointless over-reaction and saying that there could still be surges in the harbors, up to 48 hours later. No John, that really won’t happen. You need a basic lesson in Physics. Primer One physics, probably. We’ve all seen the real tsunami footage, the terrible, AWEsome footage of heart-breaking devastation in Japan, where the massive undersea quake immediately off the coast, sent waves straight onto the shoreline of Japan. Waves, several metres high, thick, black, fast, inexorable, a huge earth-tilted mass of water from that quake caused massive damage in Japan on their nearby coast, surges in Harbour levels elsewhere in Japan and even some storm-like surges over in California and down in Peru, but in NZ we had a barely perceptible 10cm “surge” which no-one saw.
A wave was reported today from the quake at 90cm high near the epicenter, which shouldn’t be underestimated, but is barely bigger than a hobbit in a fat suit. Here we are, several thousand kilometers away, and we get spun a line about how we might be in danger? No, I don’t think so. Waves in a straight line, in a box with rigid sides, yes, they can travel long distances without losing much amplitude – but as we all can remember from basic physics, waves in a pond from a ripple spread out and out, losing effect as they go. And the Pacific ain’t nothing if it ain’t a big pond.
Wikipedia notes: A point source is vibrating at a single frequency f with phase = 0 at t = 0 with a peak-to-peak magnitude of 2a. A spherical wave is propagated from the point. The phase of the propagated wave changes as kr where r is the distance travelled from the source. The magnitude falls off as 1/r since the energy falls off as r−2. There are all sorts of wicked formulas I could quote, but that last bit is the essential point – in a wave propagating out in a spherical pattern, the energy falls off and the magnitude of the wave dies down. The effect by the time it gets to New Zealand is pitifully small.
There was never any real danger to New Zealand from a tsunami, not today, but I don’t begrudge them the warning. The “advisory” was cancelled at 9.00 last night, 2-3 hours after the possible effect had passed, and no wave action was noticed. It could have been, and perhaps should have been, just a warning early on, and cancelled by about 4pm, when they knew that nothing had happened at points closer to the epicenter. But instead people were panicking, ordering people out of the water, imploring sinners to repent and find Jesus, and generally thinking selfishly of themselves instead of the people needing help in the Solomons. We need to get our priorities right.
Me? I went swimming. The sky was blue, the sun was hot. The water was beautiful, dead calm, barely a ripple.