NEW YORK, Nov.21 (Xinhua) -- The number of devastating earthquakes might increase sharply in 2018 due to the periodic slowdown of the Earth's rotation, a new study has revealed.

The change in the speed of the Earth's rotation is likely to trigger intense seismic activities next year, particularly in the heavily populated tropical regions, according to the study, published recently in the U.S. academic journal Geophysical Research Letters.

The Earth experiences periodic slowing in the speed of its rotation, which could change the length of the day by a millisecond, and such periods often last about five years.

Analyzing the Earth's seismic record over the last 100 years, researchers from the Universities of Colorado and Montana found that the periods when the Earth's rotation slowed down were often followed by periods with a significantly increased number of major earthquakes.

"In these periods, there were between 25 to 30 intense earthquakes a year. The rest of the time the average figure was around 15 major earthquakes a year," said Roger Bilham, one of the study's lead authors.

This year marks the end of the latest five-year slowdown in the Earth's rotation, thus pointing to an upcoming increase in magnitude 7 or greater earthquakes.

"The Earth is offering us a five-year heads-up on future earthquakes, which is remarkable," said Bilham.