Large quake probability continues to drop
The probability of a large aftershock somewhere in the central Canterbury earthquake zone continues to drop as a result of lower seismic activity in recent months.
In GNS Science's updated calculations released today, the probability of a magnitude 5.0 to 5.4 shake in the next 12 months is 69 per cent, compared with 82 per cent in January.
Over the same period there is a 29 per cent chance of a magnitude 5.5 to 5.9 quake in the aftershock zone, which runs from the foothills in the west to Pegasus Bay in the east and from Rangiora in the north to Tai Tapu in the south.
That has fallen from a 39 per cent probability in January.
The chance of a magnitude 6.0 to 6.4 aftershock is now 9 per cent, down from 13 per cent in January, while there is only a 2 per cent probability of a magnitude 6.5 to 6.9 event in the next year, down from 4 per cent at the start of the year.
GNS Science says the probability of a magnitude 7 or higher quake in the next year remains unchanged at 1 per cent.