Coming soon: Canterbury's 475th serious quake

WILL HARVIE
Last updated 13:24 15/06/2012

Al cartoonSometime in coming months, Canterbury will pass an important milestone that readers and policymakers outside the province should note.

Canterbury will soon experience its 475th significant earthquake since September 4, 2010.

Ha, you read stories recently that Canterbury had been shaken 10,000 times and we're fast closing in on 11,000.

As far as it goes, Friday's total of 10,958 (about noon) was precisely correct. But it doesn't mean anybody in Christchurch has experienced anything like that number of shakes.

That's because a huge majority (7386) measured magnitude 2.9 and less. Magnitude 3.0 is about the lowest level at which humans can detect earth movement.

So the foundation number of shakes is 3518, not almost 11,000. Even then, nobody has felt all 3518.

Being generous, let's say an average resident has felt half, or 1759. Even then, a 3.3 shake out towards Darfield is often no more frightening or disruptive to, say, eastern Christchurch residents than flatulence. And vice versa.

If we want figures on quakes that are disruptive and frightening, then we should select only those quakes magnitude 4.0 and greater. That number is 472.

By any measure, that's a remarkably high number and something to brag about  to the rest of New Zealand and the world.

I'm not intending to diminish anyone's experiences of bad quakes that measure less than 4.0 (I've been scared, too), but I am arguing  in a less-is-more way - that 475 packs more punch than 11,000.

Of course, Canterbury buildings are affected by quakes starting at about magnitude 3.0. This unusual wear and tear will be addressed by repairs. And  I'm happy for scientists to continue recording every last shake, because they need the data for research purposes.

The main point is that 11,000 hyperbole isn't helpful to the Canterbury cause.

- The Press

46 comments
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Ian   #1   01:38 pm Jun 15 2012

One of the worst we felt was right under our house and that was just 3.3 mag. We raced down the hall and dived on the kids beds. Even small quakes can fell bad.

Sonia   #2   01:40 pm Jun 15 2012

The quakes measuring under 4 may be considered "light", but if you are on or near the epicentre, they may shake just as much as a 5.9 registering somewhere else. Location, location, location...

Andy Male   #3   01:41 pm Jun 15 2012

No!! and niether is this story helpful....

Nothing like a good news story to cheer up a wet friday lunchtime read....

how about how many days we have had no earthqukes!!??

Lee   #4   02:21 pm Jun 15 2012

What a pointless story...

karen   #5   02:25 pm Jun 15 2012

"a 3.3 shake out towards Darfield is often no more frightening or disruptive to, say, eastern Christchurch residents than flatulence" lol well said!

2.5   #6   02:36 pm Jun 15 2012

2.5 and they closed Auckland Airport!!!

Dave From CHCH   #7   02:39 pm Jun 15 2012

Not sure whether its the land moving that causes the shaking or the combined moaning of all the Canterbury whingers complaining about how the Government, council, insurance companies etc aren't doing enough to help them. In my experience 99% of Cantabrians are happy with whats going on. If you were stupid enough not not have insurance or dumb enough to want to live in the red zone then by my guest just shut up about it "you're boring me"

Sarah   #8   02:41 pm Jun 15 2012

I have fully felt 2 quakes that was only a 2.8 so to say that you can't feel earth movement under a 3 is wrong...I've felt them in Christchurch and in the Bay of Plenty area. And they should base it on anything above a 3 then because sometimes 3's feel huge and the 4's don't feel that bad...its all depending on where its centered and where you are at the time.

Jeff   #9   02:51 pm Jun 15 2012

Ah well, when Fracking comes to Canterbury region and they lubricate some deep faults out west with their brew, we could end up with the Alpine fault rupturing due to cascade failures. Can then expect to add another 11,000+ to the running total. Perhaps we can set a world record? Will EQC pay out for artificially induced earthquakes?

bob   #10   03:06 pm Jun 15 2012

jeff #9 - why would fracking come to Canterbury?


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