Washington, Nov 20 (IANS): The world could see an increase in the number of strong earthquakes in 2018 and the next few years due to periodic slowing of the Earth's rotation, scientists have warned.

There is a clear correlation between the speed of the earth's rotation and global earthquake activity, said Roger Bilham of the University of Colorado and Rebecca Bendick of the University of Montana, who presented their research at the annual conference of the Geological Society of America.

Fluctuations in the Earth's rotation are tiny, changing the length of the day by several milliseconds, but these minute changes could be enough to release vast amounts of underground energy, the two scientists said.

"On five occasions in the past century, a 25-30 per cent increase in annual numbers of (earthquakes of magnitude 7.0 or greater) has coincided with a slowing in the mean rotation velocity of the Earth, with a corresponding decrease at times when the length-of-day (LoD) is short," Xinhua news agency quoted the scientists duo as saying.

Slight changes in the behaviour of the Earth's core may be responsible for this effect, according to the scientists.

"Whatever the mechanism, the 5-6 year advanced warning of increased seismic hazards afforded by the first derivative of the LoD is fortuitous, and has utility in disaster planning," the scientists said.

In their study, the researchers looked at earthquakes of magnitude 7 and greater that had occurred since 1900, the Guardian reported.

"The year 2017 marks six years following a deceleration episode that commenced in 2011, suggesting that the world has now entered a period of enhanced global seismic productivity with a duration of at least five years," the researchers added.

While the research did not indicate precisely when and where these future earthquakes will occur, it showed that most of the intense earthquakes that responded to changes in day length seemed to occur near the equator.