New Zealand's quake-battered second city of Christchurch was shaken by a 5-magnitude tremor Friday as scientists were telling a special hearing that earthquakes and aftershocks could continue for decades, Xinhua reported.
The quake struck at 2:20 p.m. and was centered 5 kilometers below ground and 10 km northeast of Christchurch, according to the government-run GNS Science GeoNet monitoring service.
It came just one minute after a 3.5-magnitude tremor, at a depth of 10 km, centered 20 km east of the city, according to the GeoNet.
The quakes occurred the day GNS scientists were briefing Christchurch city councilors and Members of Parliament on the possibility of more strong aftershocks after those that struck on Dec. 23.
Kelvin Berryman, of GNS Science, told the hearing that the sequence of quakes in Christchurch and the surrounding Canterbury region would diminish over decades rather than years, Fairfax NZ News reported.
"Christchurch city has had a lot of quake activity. A lot of the stress must have been released in the city area, but around Canterbury there may well be an ongoing sequence over a period of a few decades," Berryman was quoted as saying.
He stressed the sequence would gradually become imperceptible.
"It is not a one to five-year period, it is a period of many decades," he reportedly said.
Christchurch Mayor Bob Parker told the briefing earlier that a tsunami warning system was likely to be in place in Christchurch by the end of June.
However, the probability of a 7-magnitude quake triggering a tsunami was "very low" and quakes of a 6-magnitude did not produce tsunamis of any significance, said Berryman.
"There is almost certainly still a 5.0 out there and we would guess quite a few 4s and 3s on a daily basis," said Berryman.
More than 9,500 tremors had hit Canterbury since the 7.1- magnitude quake on Sept. 4, 2010.
In February last year, a 6.3-magnitude quake killed at least 181 people in Christchurch.