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Yesterday’s earthquake has increased the likelihood Christchurch will be hit by another strong aftershock in the next 12 months.

New modelling completed by GNS Science after yesterday’s 5.7 magnitude earthquake shows there is a 63 per cent chance of another 5 to 5.9 magnitude earthquake hitting Christchurch within the next 12 months. That figure was 49 per cent before yesterday.

GNS Science duty seismologist Anna Kaiser said that percentage would drop quickly if there were no big quakes in the next week or so.

The chance of a 5 to 5.9 magnitude quake in the next week was 19 per cent and the likelihood of a 6 to 6.9 magnitude quake in the same time period was 2 per cent, she said.

The earthquake, in Pegasus Bay off New Brighton, was part of the 2010/2011 earthquake sequence and occurred in a similar location to the December 23, 2011, 5.9 magnitude quake.

However, Kaiser said it was not known if it was a rupture of that fault. It could have been an unknown fault line, she said.

The quake lasted for about 30 seconds, but most people probably only felt 10 seconds of shaking, depending on their location and what type of building they were in, Kaiser said.

Christchurch residents were expected to feel aftershocks for days and in the five hours after the quakes more than 30 aftershocks were felt, including a magnitude 4.3 quake at 6.27pm.

The last time Christchurch experienced a quake this large was nearly 4 years ago, on May 25, 2012 when a 5.2 magnitude quake hit 20 kilometres east of Christchurch.

The intensity of the shaking of Sunday’s event, recorded by peak ground acceleration (PGA), was at its highest in New Brighton at 0.4g. During the February earthquake the PGA was 2.2g and the September 4, 2010 quake it was 1.25g.

In Christchurch a PGA of 0.1g was needed to create liquefaction.