Canterbury was struck by a magnitude 4 earthquake on Sunday night, which has raised anxieties about whether more could follow.
"That's always the big question. We cannot always predict it," GeoNet seismology and strong motion specialist Dr Muriel Naguit told Newshub.
The quake hit 10 kilometres east of Christchurch at a depth of 12 kilometres. The epicentre was approximately 5 kilometres offshore. In just 15 minutes, more than 7600 people reported feeling it.
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The region hasn't had an earthquake of this magnitude in six months, so it may have come as a shock to some people. It has raised the question: should Canterbury worry about more aftershocks to come?
GeoNet says there is a 45 percent chance of aftershocks of magnitude 5 to 5.9 happening in Canterbury, but it's "extremely unlikely" there will be an aftershock of magnitude 7 or more.
According to GeoNet, the probability of an aftershock happening decreases as magnitude increases, and a magnitude increase of one means a probability decrease of roughly 10 times.
This means that a magnitude 7.9 aftershock is roughly 100 times less likely than a magnitude 6.0 aftershock. As each month passes without a major aftershock, probabilities will continue falling.
However, GeoNet experts warn that if another large aftershock happens it can "re-energise the system" and "spark a resurgence of earthquake activity" for a month or so, as was seen with both the February and June 2011 magnitude 6.3 earthquakes.
The maximum magnitude of an earthquake is also limited by what scientists know about the size of faults in the region. Scientists aren't aware of any faults in Canterbury that are long enough to be able to produce a magnitude 7.9 earthquake. However, they cannot rule out this out with 100 percent certainty.
"At present there is no scientific way to accurately and reliably predict when and where a big earthquake is going to happen," the organisation says.
Newshub.
