Three earthquakes in a row in 'reinvigoration' of Canterbury aftershock activity

The Valentines Day earthquake caused a "reinvigoration of aftershock activity" in Canterbury.

Three earthquakes have rocked Christchurch in the last 12 hours, something seismologists say is nothing out of the ordinary.

The first earthquake, which was downgraded from magnitude 3.9 to 3.4, struck 10 kilometres east of Amberley at 12.23am on Saturday.

That was followed by magnitude 3.5 and 3.4 earthquakes at 6.51am and 7.09am. Both were centred 10km west of Christchurch.

GeoNet classified each earthquake as "moderate".

GNS seismologist Anna Kaiser said the three earthquakes were typical of an aftershock city.

"We've had a reinvigoration of aftershock activity following the [magnitude] 5.7. We are still in the Canterbury earthquake sequence," Kaiser said.

There have been hundreds of earthquakes in the Canterbury region since a magnitude 5.7 quake struck Christchurch on Valentine's Day. 

GeoNet's long-term forecasts, issued on March 24 for the coming year, give probabilities of further earthquakes in the entire Canterbury region aftershock zone.

According to the forecasts, there is a 57 per cent probability of one or more earthquakes of magnitude 5 to 5.9 occurring in the region."It is expected that there will be between zero and three events of this magnitude during the coming year."

There was just a seven per cent chance of a magnitude 6 to 6.9 earthquake, and less than a one per cent chance there will be an earthquake registering magnitude seven or greater.

http://www.stuff.co.nz/the-press/news/78735167/three-earthquakes-in-a-row-in-reinvigoration-of-canterbury-aftershock-activity