South Island earthquake: when can we expect the big quake?

Greta Simpson — Mon, 15 Oct 2007 22:21:59 +0000

The earth moved for South Islanders in the early hours of this morning.
An earthquake measuring 6.7 on the Richter scale shook Southland. While there were no reports of injury or damage, the quake was felt strongly across the South Island. GNS Science duty seismologist Mark Chadwick said the quake, which struck at 1.29am, was centred 60km from Milford Sound at a depth of 24km. A 4.6 magnitude aftershock followed at 2.50am and a second aftershock was felt at 6:34am. There was no risk of a tsunami, although further aftershocks are likely over the next couple of days.

As Carl’s earlier post mentioned, Geonet provides up-to-date information on New Zealand quakes – here they keep us clued up on the most recent earthquakes, including today’s shake-up and aftershocks. They operate a nationwide network of seismic stations that transmit their data to the GeoNet Data Management Centre (DMC) where it’s analysed by automated processes. The information is released to the public if the Duty Officer confirms that the earthquake is real and significant.

They’re clever with their seismic reporting after the event, but will they be able to predict a big quake?
As Wikipedia, the great equalizer, tells us: “the reliability and reproducibility of prediction techniques have not been established.” So it’s unlikely that we’ll be warned before a big one strikes, although seismologists can calculate the probability that a quake will occur in a particular location. And when the earth experiences a flurry of seismic activity, there’s no need to panic; a ‘swarm’ of earthquakes doesn’t necessarily indicate a high-magnitude quake is on the way. You may be comforted or frightened by this fact, but GeoNet records around 15,000 earthquakes in and around New Zealand each year, only 250 of which are big enough to be felt.

Read more about NZ earthquakes, but don’t get too shook up about it!

Where was that earthquake?

Carl Cerecke — Wed, 25 Jul 2007 22:19:07 +0000

There’s no escaping earthquakes in New Zealand. Even the Chatham Islands is susceptible to them. Small earthquakes happen every day in New Zealand, but most are not felt. Larger earthquakes (above about Magnitude 3.0) are recorded by GeoNet and usually make it onto their website within a few minutes, showing the time, location, depth and magnitude. This lets you know whether it was a small earthquake close by, or a whopper a long way away. You can even help them with their research by telling them if you felt it or not.

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South Island earthquake: when can we expect the big quake?

Where was that earthquake?