Geologists have warned that deadly earthquakes could become more frequent in the coming year and that they are likely to be caused by the slowing down of the Earth's rotation.

Scientists, who presented their research to the Geological Society of America recently, have found that variations in the speed of the Earth's rotation could set off intense seismic activity, particularly in the tropical-equatorial regions where over a billion people live.

The slowdown in Earth's rotation is small, measuring in milliseconds, reports the Guardian, but enough to release vast amounts of underground energy. The link between seismic activity and the planet's rotation was brought out in a paper by Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula.

"The correlation between the Earth's rotation and earthquake activity is strong and suggests there is going to be an increase in numbers of intense earthquakes next year," said Bilham.

It is unclear why decreases in the speed of the Earth's rotation should have this effect on the surface, but geological activity deep in the core could possibly be the cause of both slowing down as well as earthquakes. Most of the earthquakes are also likely to happen around the equatorial regions, said Bilham.

Bilham and Bendick, for their research, studied all the major earthquakes that registered a magnitude of 7 and above since 1900. All the major earthquakes that have happened over the last century have been well recorded, said Bilham. Using this data, they identified five periods that registered higher large earthquakes when compared with other periods. "In these periods, there were 25 to 30 intense earthquakes a year," he said. The other periods identified only averaged 15 quakes a year, he added.

Further investigation into these periods of high seismic activity resulted in the identification of a few correlations. They found that soon after periods when the Earth's rotation decreased in speed slightly, there were a large number 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," noted Bilham.

Bilham and Bendick also found that there were periods of five-year stretches when the Earth's rotation slowed down over the last century by a millisecond. These periods were followed by periods of massive earthquakes. "The Earth is offering us a five-year heads-up on future earthquakes," said Bilham.

One of the Earth's periodic slowdowns began four years ago and by 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."

This year has already seen a raft of earthquakes -- most notably the ones that killed hundreds in Greece, Turkey, Southwest China, Indonesia, Italy, Mexico, and most recently, Iran. The study indicates the situation about to get worse, with more loss in terms of life and property.

In 2017, so far, 84 earthquakes with a magnitude of between 6 and 6.9 have been recorded, five between 7 and 7.9 and one between 8 and 8.9.