Roger Bilham, of the University of Colorado in Boulder, and Rebecca Bendick, of the University of Montana in Missoula, presented their findings, published earlier this year, at the annual meeting of the Geological Society of America in October.
In a new study, researchers looked at every natural disaster since 1900 that registered a magnitude of 7 or larger and saw an uptick in the number of big quakes about every 32 years. They noticed that while most years, there were only around fifteen major earthquakes, there had also been five-year periods where the number of earthquakes had dramatically risen, which always occurred following a drop in the rotational speed of the planet.
More big earthquakes in 2018 as Earth slows slightly, theory suggests.
Such motion deep inside the Earth slightly changes the planet's rate of spin, adding to or subtracting from the 24-hour day by about a millisecond - a change that is regularly recorded by atomic clocks.
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. "In these periods there were between 25 to 30 intense earthquakes a year". All it takes is a little nudge to upset the world's balance, and 2018 looks set to be a very unbalanced year indeed.
"The rest of the time the average figure was around 15 major earthquakes a year".
But, according to the Guardian, the researchers "found that most of the intense earthquakes that responded to changes in day length seemed to occur near the equator".
Predicting where earthquakes will occur isn't something we can do now.
And in 2018, the Earth's rotation speed is set to slow down leading to a jump on the six magnitude seven or higher quakes we have had this year.
"We have had it easy this year". The last slowdown began four years ago. The U.S. Space Agency NASA has showed that seasonal patterns such as El Niño have the capacity to change the Earth's rotation, while huge quakes can shift the planet's axial tilt.
Tropical countries would be at risk under this assumption, which has divided geologists and common people alike due to what it entails.
The exact relationship between Earth rotation (a slight decrease in the duration of the day) and earthquakes worldwide is unclear.
"Its (the Earth's) waistline gets smaller, but its clothes, the tectonic plates on Earth, remain the same size, which means they get rumpled up".