A new earthquake on Monday is indeed ‘shocking’ to the psyche – including kids…
Children are amongst those most affected by Christchurch’s aftershocks. Police escort children from a preschool after a building collapsed on the corner of Worcester and Stanmore.
GNS Science seismologists said the newly confirmed fault had already generated a number of quakes since the deadly February 22 event.
Dr Bill Fry said the dominant energy in Monday’s magnitude 5.7 and 6.3 aftershocks had been horizontal compared with vertical in February’s 6.3 quake.
This meant they were felt differently.
Unfortunately for Cantabrians, rather than reduce the statistical probability of another big quake, yesterday’s violent shakes will, for a time, increase the risk of another large aftershock of similar magnitude.
However, GNS Science hazard modeller Dr Matt Gerstenberger said that elevated level of risk would not last long.
It was also important to realise the risk estimates, and any other aftershock forecasts, were only computer models based on average quake sequences and not derived from any physical evidence, he said.
The calculations from GNS Science warned of a 23 per cent probability of a quake of magnitude 6.0 to 6.9 hitting the Canterbury aftershock zone within the next 12 months.
GNS Science said the risk of an aftershock of that size occurring under or close to Christchurch was much lower – around 6 per cent.
Yesterday’s largest earthquakes were located close to the coast and slightly south of the eastern tip of the Port Hills fault, which generated the magnitude-6.3 quake on February 22.
Given their similar positions, scientists say the 1pm earthquake is believed to be a foreshock of the second quake.
GNS Science seismologist Dr John Ristau said it would take time for more precise locations and magnitudes to be assigned to yesterday’s quakes.
Ristau said after the Queen’s Birthday Monday 5.5-magnitude aftershock the trend had been for the large aftershocks to get larger – up from magnitudes 5.0 to 5.1 to 5.3 to 5.5 in recent months. However, there was no evidence that trend would continue.
“Every aftershock sequence is different,” he said yesterday.
The quakes would probably kick off a more active spell of aftershocks.
“We can probably expect to get some [magnitude] fours for the next few days, [and] we may have another magnitude 5.0,” he said.
Ground on either side of the fault that caused the two aftershocks had slipped sideways to the right and land on the southern side of it had lifted up against the northern side.
Natural Hazards Platform manager Dr Kelvin Berryman , of GNS Science, said the strongly felt shakes were “within the range of forecasted aftershocks as modelled by scientists”.
“These aftershocks were within the existing Canterbury aftershock zone and were within probabilities.
“This size of events is likely to produce its own aftershock sequence, therefore rejuvenating aftershock activity at least in the short term. We would expect a number of aftershocks in the magnitude 4.0 to 5.0 range in the coming days and weeks.”
Asked if it was the “big” quake forecast as a one-in-four chance in the next year, Berryman said “possibly”.
“Whether it is the one or not, this in itself kicks the probabilities again, so we have to go back and recalculate.”
- The Press
@ John Baker #10 There’s no volcano building under Christchurch. A magma chamber would have show up like dog’s balls on the recent mag and seismic surveys. Despite your interpretation the pattern of faulting is actually fairly normal given the nature of the tectonics of the region
It was a full moon again folks. Of course GNS won’t predict quakes..too much prestige tied up in their degrees, peer pressure and unwillingness to take a punt. All they can do is keep the score and make backwards looking discoveries..oh look. a new fault..wow..time to deliver another paper at some sunny location overseas… GNS do a wonderful job tracking the quakes..no argument..but getting them to predict one? Maybe they should go outside and see if it’s a full moon. Yup. Tie down the TV again.
Ken Ring said that activity would die down after April, he was clearly wrong again
Trevor #1, Crane #2, and Nancy #3: Scientists don’t get paid for predicting these things, they get paid to find out about them. They are studying what is happening now in order to get a better idea of what might happen in the future. If scientists already knew all there was to know, we wouldn’t need them any more – we could just look things up in books. They would undoubtedly rather be in their labs doing the work they love to do, rather than being asked questions by journalists only to have scorn thrown on their answers by ignorant members of the public.
Nancy – scientists can’t say for sure because there is no rule book for earthquakes,including those affecting Christchurch. What scientists can do is observe phenomena,collate evidence,propose explanations based on their observations then test those theories in the real world. It’s called science, and along with much else it led to the computer you composed your “opinion” on and the means for you to share it with the world. If you would rather have mumbo jumbo I suggest Ken Ring. Me,- I’ll keep listening to the scentists.
Perhaps volcano i building up under Christchurch. This is not normal set of quakes.
#1 and #3 — What you fail to recognize is that most complicated things (such as earthquakes) involve both uncertainty and an element of probability. Scientists can work to reduce uncertainty, but fundamental randomness can only be quantified. So, I can say with perfect certainty that a coin flip has a 50% chance of being a head…. but no level of science can predict whether it will be or not. The fact that we can’t predict events perfectly does not make it less important to understand the probabilities involved.
YEAP … that’s it guys, lets all start fighting amongst ourselves, that will DEFINITELY solve the problem. Who cares about the whos, what, whys and maybes, we are all living with the reality of today. So lets remember that unity that we have felt over the last few months, and hold it close to ourselves again.
I find it amazing how we have lost sight of the fact that this is a daily occurance around the world for people. We write about it as if we are the only ones to ever have been placed in this situation. The ground will settle down eventually. We all know it’s an inaccurate science and need to just get over it. I live in Rangiora and my house foundations broke up on Sept. 4th. My place of work was destroyed in the Feb. 22nd one. Lets just all try and chill out a bit.
- Aftershocks Fray Nerves in Christchurch (online.wsj.com)
- Aftershocks Fray Nerves in Christchurch – Wall Street Journal (news.google.com)
- Video: New Zealand Quake Shook Ground Like Jelly (livescience.com)
- Aftershocks Hit Christchurch (online.wsj.com)
- Strong earthquakes rock shaken New Zealand city – again (csmonitor.com)
- Christchurch New Zealand hit hard again (echlinm.wordpress.com)
- Christchurch earthquake: buildings destroyed by strong aftershocks (telegraph.co.uk)
- One person killed after Christchurch aftershock (independent.co.uk)
- Months after devastating earthquake, New Zealand hit again by aftershocks (thestar.com)
- Big aftershocks rock damaged New Zealand city (abclocal.go.com)