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.
Research from Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula looked at earthquakes with a magnitude higher than seven since 1900. They also uncovered that the Earth's rotation, which follows a cyclical pattern of slowing and then speeding back up, slowed for a five-year period before each uptick in quakes.
The correlation between Earth's angular deceleration and global seismic productivity is far more vivid increasing the seismicity by 5-6 years, exposing people to higher and unexpected earthquakes, they wrote.
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. If the two geophysicists' research is correct, 2018 should bring a significant increase in the number of major earthquakes. The Earth is offering us a five-year heads-up on future earthquakes'. "We could easily have 20 a year starting in 2018", Bilham said.
So what is it about the Earth's rotation speed that could be bringing on an increase in major earthquakes?
It is hard 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. The variations in the speed of Earth's rotation could possibly trigger intense seismic activity, mainly in the tropical areas, as per the scientists.
The last slowdown in seismic activity began four years ago, after Haiti and Japan were devastated by massive earthquakes that killed over 118,000 people in 2010 and 2011.
While Nace says this is still speculation and correlation, being able to sense when earthquakes will be a greater threat will help helpful, as earthquakes are one of the least predictable natural disasters.
The planet's rotation is slowing down because of tidal forces between Earth and the moon.
Though Bilham and Bendick don't know for sure, they believe that every so often the Earth's mantle might stick a little more to the crust. Often times, geologists are limited to historical trends in data to predict the likelihood an quake will occur.