If it happens, it happens

GNS Science seismologists are reported to be predicting another decent 'quake in the centre of the country; Stuff reports:

Another large shake on both sides of Cook Strait is highly likely over the next week, experts say.
The chance of a jolt of magnitude 5 or more in the next seven days is 90 per cent, according to GNS Science seismologists, and the likelihood of a magnitude 6 or more quake is about 21 per cent.
Seismologist Caroline Holden warned people to be vigilant and expect another large shake. Since Friday afternoon's 6.6 tremor, there had been another 59 aftershocks reaching magnitude 4 or more, by 4pm yesterday.
Dr Holden's colleague Martin Reyners said the area near Seddon where the earthquakes were recurring was known as an active one. There was a magnitude 6 quake there in 1966, and another in 1977.
The level of horizontal acceleration, which is the amount of movement people feel from a quake, was similar to that felt during the Christchurch earthquakes, but not as significant.
"It's a different experience for everyone, depending on what soil your house is built on. At its worst acceleration, there were reports of people not being able to stay standing upright," he said.
The sequence of quakes was slowly tracking southwest, away from Wellington, but on to land in Marlborough.
"Friday's quake was situated so that the people of Seddon were sitting pretty much on top of it, which explains the damage. Each quake changes the stresses in the fault. In areas where the stress has gone up, near a fault, it can trigger another event."
In the case of the recent quakes, there had been some triggering as the stresses shifted south. This would mean the effects would be felt less in Wellington, but more in Seddon. 

Predicting earthquakes is a terribly inexact science. After the July 6.5 magnitude quake near Seddon, GNS was reported as saying that there was a one-in-three chance of another six-plus earthquake. On Friday of course, there was another significant earthquake.

Back in July, GNS seismologist Martin Reyners said this:

Because of the changing stress levels in the region's faults, Dr Reyner says it's impossible to predict whether there will be another quake to match Sunday's.

"What this 6.5 will have done… will have changed the stress regime around it, and some faults will be moved away from failure – so less likely to fail – and some might have been nudged a bit towards failure. But we don't know how close to failure all these faults are, and that's one of the very difficult questions that seismologists need to answer."

Now we're not having a go at the seismologists here; they are doing the best job that they can in an ever-changing situation on one of earth's more difficult landscapes. But the media seems to be determined to "inform" us. And today's headline on Stuff borders on scaremongering.

There will always be earthquakes in New Zealand, and there's precious little that we can do about it. If another significant aftershock happens this week, it happens. But treating the probablility like TAB odds is an exercise in futility.