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Although the Christchurch earthquakes seem to be going on forever, they are likely to reduce in size and frequency over the next two years, University of Otago seismologist Dr Andrew Gorman says.
The first in a series of big quakes in the area yesterday afternoon occurred at 1.58pm and was rated at magnitude 5.8.
It was centred just off the coast of New Brighton.
Dr Gorman said that in March he had spent a week aboard the Niwa research vessel Kaharoa as part of a scientific expedition which undertook acoustic testing of the seafloor geology off the New Brighton coast.
This was after a 6.3 magnitude earthquake in the city on February 22 which killed more than 180 people.
The aim of the expedition was to undertake acoustic mapping and to check for past or recent earthquakes in the shallow sediments off the Christchurch coast.
Little activity had been detected and yesterday's first big afternoon quake was centred at a much lower level, about 10km down.
Dr Gorman was mindful that many Christchurch people were facing continuing disruption as a result of the latest pre-Christmas quakes, and because of earlier quake-related damage.
"You can't really get on with your life if you have damage to your house or your business," he said.
The latest quakes were all linked to the first of the recent big Canterbury quakes, a 7.1 magnitude event which had occurred west of Christchurch on September 4 last year.
Nevertheless, the Canterbury quake activity was likely to reduce over the next couple of years, and Wellington actually faced a larger long-term earthquake risk, he said.