I’m always wary of earthquake “predictions” for obvious reasons. I’ve heard enough of them that never came to anything more than panickmongering, but still, I berated a number of luminaries for announcing the 2010 NZ Greendale quake to be a “once in 16000 year event” when another earthquake could occur at any moment. Lulling everyone into a false sense of security. In fact 2011 tuned out to be a big year for seismic activity right around the Ring Of Fire (except, as usual, the West Coast USA). So It might pay to take heed of this article:
Scientists have warned there could be a big increase in numbers of devastating earthquakes around the world next year. They believe variations in the speed of Earth’s rotation could trigger intense seismic activity, particularly in heavily populated tropical regions.
Although such fluctuations in rotation are small – changing the length of the day by a millisecond – they could still be implicated in the release of vast amounts of underground energy, it is argued.
The link between Earth’s rotation and seismic activity was highlighted last month in a paper by Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula presented at the annual meeting of the Geological Society of America.
“The correlation between Earth’s rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes next year,” Bilham told the Observer last week.
In their study, Bilham and Bendick looked at earthquakes of magnitude 7 and greater that had occurred since 1900. “Major earthquakes have been well recorded for more than a century and that gives us a good record to study,” said Bilham.
They found five periods when there had been significantly higher numbers of large earthquakes compared with other times. “In these periods, there were between 25 to 30 intense earthquakes a year,” said Bilham. “The rest of the time the average figure was around 15 major earthquakes a year.”
The researchers searched to find correlations between these periods of intense seismic activity and other factors and discovered that when Earth’s rotation decreased slightly it was followed by periods of increased numbers of intense earthquakes. “The rotation of the Earth does change slightly – by a millisecond a day sometimes – and that can be measured very accurately by atomic clocks,” said Bilham.
“It is straightforward. The Earth is offering us a five-year heads-up on future earthquakes”
Roger Bilham of the University of Colorado in Boulder
Bilham and Bendick found that there had been periods of around five years when Earth’s rotation slowed by such an amount several times over the past century and a half. Crucially, these periods were followed by periods when the numbers of intense earthquakes increased.
“It is straightforward,” said Bilham. “The Earth is offering us a five-year heads-up on future earthquakes.”
This link is particularly important because Earth’s rotation began one of its periodic slowdowns more than four years ago. “The inference is clear,” said Bilham. “Next year we should see a significant increase in numbers of severe earthquakes. We have had it easy this year. So far we have only had about six severe earthquakes. We could easily have 20 a year starting in 2018.”
Exactly why decreases in day length should be linked to earthquakes is unclear although scientists suspect that slight changes in the behaviour of Earth’s core could be causing both effects.
In addition, it is difficult to predict where these extra earthquakes will occur – although Bilham said they found that most of the intense earthquakes that responded to changes in day length seemed to occur near the equator. About one billion people live in the Earth’s tropical regions.
Here’s an outstanding visualisation of 2011:
Update: NZ Scientists “critical”:
“New Zealand earthquake scientists have been critical of a theory from two American scientists that the frequency of earthquakes is linked to a slowing in Earth’s rotation, one saying “I tend to think of them in the context of [Moon Man] Ken Ring”.
Last month, Roger Bilham, from the University of Colorado at Boulder, and Rebecca Bendick, from the University of Montana, presented a paper at a conference that posited that a year with a high number of earthquakes around the world coincided with a slowing in the rotation of the Earth.
“A striking example is that since 1900 more than 80 per cent of all earthquakes on the eastern Caribbean plate boundary have occurred five years following a maximum deceleration (including the 2010 Haiti earthquake).”
The paper concludes that 2017 marks six years since deceleration began in 2011, “suggesting that the world has now entered a period of enhanced global seismic productivity with a duration of at least five years”.
GNS Science have commented that the paper has not been peer-reviewed and has no detail to examine, while Dr Virginia Toy from the Department of Geology at the University of Otago says correlations are often made between natural events and other phenomena.
“Some of these yield statistically defendable correlations; others don’t,” she said.
“I tend to think of them in the context of Ken Ring… the man who writes about apparent statistical correlations between the phase of the moon and the weather.
“[The Americans’ paper] sounds like we will get a jump from six to 20 large earthquakes per year. I don’t think this is likely.”
Dr Tim Stahl, a lecturer in tectonic geology from the University of Canterbury, says it is difficult to judge the scientific merit of the claims being made until additional testing is carried out by other research groups.”