100 aftershocks and counting in Canterbury
The rate of aftershocks following Saturday's magnitude 7.1 earthquake appears to be lower than usual for a quake of that size, but people around damaged buildings in Canterbury should still be taking extreme care, says an expert.
The aftershocks could be big - within one order of magnitude of the original quake - so there is still the chance of a magnitude 6 shake hitting the un-reinforced masonry around Christchurch and in surrounding towns of mid-Canterbury.
Nearly 100 aftershocks have hit so far, the biggest of them rating at magnitude 5.5, and some have come from different directions from the original shake.
"It is still possible that we'll have a magnitude 6 in the next week, and people ought to be aware of that, particularly if they are around structures which are already damaged," said the manager of the geohazards monitoring section which runs the GeoNet at GNS Science, Ken Gledhill.
"For a shallow earthquake like this, they will go on for weeks," Dr Gledhill told NZPA.
"And if a building is badly damaged, it won't take much shaking to push it over."
But it was no more possible to predict the timing or size of an aftershock than it was possible to do that for the original quake.
There was unlikely to be a problem with the most common aftershocks, which were "small and jolty" but where ground-shaking continued for a long time, there was risk of more damage.
"Make sure you move to somewhere secure if you feel that shaking start", he said.
A severely damaged building today collapsed in the Christchurch suburb of St Albans, and people in the building, on the corner of Cranford and Westminster streets, had a narrow escape.
A sharp 4.5 magnitude aftershock about 12.35pm caused part of a damaged block of shops to collapse further, and the owners of vintage store La Boutique, mother and son Rose and Myles Lennon, made a run for it when the shaking began. They escaped unharmed.
Christchurch police Inspector John Price said safety was paramount and he warned of a "small number of people interfering with taped-off areas and removing safety cones.
"Removal prevents the protection and safety of everyone."
Buildings might be placed off limits partly because of weather conditions and aftershocks.
Despite the aftershocks, contractors have begun tearing down dangerous buildings half destroyed in Saturday's quake, including a two-storey food market opposite Knox Church on Victoria and Bealey Street.
- NZPA
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