Why quakes weren't caused by seismic blasting or 'unzipping' faultline
Big earthquakes like the ones experienced this week can be unnerving and often lead to people searching for answers in unconventional places.
During the days since the earthquake, a handful of theories have emerged in an attempt to explain why the country shook early Monday morning.
We'd usually ignore these types of theories, but conspiracies and hoaxes as to the cause of the quakes are circulating on social media, so we think it's important to address the rumours.
Earlier this week there was a lot of talk about the moon causing the North Canterbury quakes. We will be looking at why the moon myth, along with talk of seismic blasting ships and an unzipping Alpine Fault aren't worth your worry.
UNZIPPING ALPINE FAULT
Most Kiwis are aware of the imminent danger posed by the Alpine Fault - when it ruptures, it's expected to be a big one.
However, an "unzipping" fault is not responsible for the latest spate of quakes - if the Alpine Fault had gone, we'd all know about it.
GeoNet seismologist Dr John Ristau says the term "unzipping" isn't one scientists use, but it refers to the fault rupturing.
"Eventually the Alpine Fault is going to have an earthquake on it. Maybe even the entire fault will break."
The fault, located beneath the South Island, is currently building pressure, Ristau says.
But it hasn't done anything since 1717.
Based on past patterns, the fault ruptures every 329 years, on average. We will be at 300 years next year. Though there is a margin of error of about 70 years either side.
The Alpine Fault marks the boundary between the Australian Plate to the west and the Pacific Plate to the east. Ultimately, the movement of these plates causes earthquakes in New Zealand but the Alpine Fault itself wasn't involved this time.
Ristau says it's natural for people to look to the Alpine Fault whenever there's an earthquake in New Zealand, especially in the South Island.
"There's a fairly high probability of having that earthquake," he says. But thankfully, that's not what happened this time.
SEISMIC BLASTING SHIP
Another theory doing the rounds on social media is one of a ship stationed off Wellington's coast being to blame.
What's being touted as the world's largest seismic blasting ship, the Amazon Warrior, was stationed off Rarangi in Cloudy Bay, in the Cook Strait, when the quake hit.
A raft of bloggers and social media users have since blamed the quakes on the ship's activities.
One of the Facebook posts linking te seismic blasting ships to the earthquakes. CREDIT: FACEBOOK
The ship was contracted by Statoil and Chevron to look for oil off Wellington's coast. And as part of their exploration, the ships send energy down into the earth through explosions or the use of an airgun.
Theorists say the Amazon Warrior was on top of a faultline and the blasts were enough to make the country shake.
But Ristau says the Warrior isn't to blame for Monday morning's quake.
Firstly, the quake originated about 100 kilometres south of where the ship was stationed.
There is also no way the blasts were deep enough - quakes originate well beneath the earth's surface.
And the energy from the explosions or airguns wouldn't have had the power to cause a shake, he says.
For context - South Island quarries constantly set off explosions bigger than those the ship would have used.
Seismologists have repeatedly stated there's no known link between the oil drilling practice of fracking and earthquakes.
Despite these reassurances from the country's leading earthquake researchers, Stuff has received comments and questions from readers about this supposed link since Monday's big shake.
In 2012, GNS Science released a study – commissioned by Taranaki Regional Council – in response to growing public and media scrutiny of fracking.
The report stated that there was no evidence that hydraulic fracturing activities have had any impact on natural earthquake activity, nor would it cause any future earthquakes.
However, opponents of the oil drilling practice were unmoved by the report.
While many are opposed to fracking and oil drilling for a variety of reasons, the science doesn't show any link between the activity and earthquakes.
We've touched on this one already this week, but let's revisit the moon.
More than a hundred years of scientific research into the relationship between the moon, tidal forces, and earthquakes has not produced any reliable evidence of a link between the moon's gravitational pull and quakes.
Tidal stresses and their effects on the earth are tiny, but measurable, although many scientists remain unconvinced by the theory of "tidally-triggered earthquakes".
University of Melbourne associate professor Mark Quigley and University of Melbourne applied geoscience lecturer Brendan Duffy addressed this very point in a recent post.
"Given the earthquake happened on the eve of a supermoon full moon, and the closest the Earth and moon will be since 1948, it wasn't long before some tried to make a connection," they write.
Basically, they say there's a small chance tides could have a small effect on the size of a rupture.
"But the specific time, magnitude and location of this or any other large earthquake has not been successfully predicted in the short-term using tidal stresses or any other possible precursory phenomenon.
"Deliberately vague predictions that provide no specific information about the precise location and magnitude of a future earthquake are not predictions at all. Rather, these are hedged bets that get media air time due to the romantic misinterpretation that they were valid predictions."
In a bizarre twist, a person took to social media on Thursday morning claiming to be a GeoNet employee.
The impersonator claimed seismologists are being muzzled by the government and that there is really a 70 per cent chance of the Alpine Fault rupturing due to the recent quakes.
Some people have used our brand & been impersonating us on social media, putting out incorrect info. Correct info at https://t.co/sYWRotJN1I— GeoNet (@geonet) November 16, 2016
GeoNet's Ristau says sometimes it takes a while for New Zealand's earthquake scientists to get information to the public because the data is very complex.
"But we're not trying to hide anything."
As soon as GeoNet has information, they did their best to get it out into the public arena.
His best advice to people worried about all the quake rumours circulating online is: get your information from the experts.
Visit verified social media accounts and websites of organisations like GeoNet, GNS Science and Victoria University.