US scientists predict more big earthquakes in 2018
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 recently, argued that there is a clear correlation between the speed of earth's rotation and global earthquake activity, Xinhua news agency reported.
"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," the duo said in a research abstract.
"The correlation ... can be shown to precede seismicity by 5-6 years, permitting societies at risk from earthquakes an unexpected glimpse of future seismic hazard."
Fluctuations in 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.
They could not explain exactly what happened but they suspected that slight changes in the behaviour of earth's core may be responsible for this effect.
They also said the observed relationship is unable to indicate precisely when and where these future earthquakes will occur, but most of the additional strong earthquakes have historically occurred near the equator in the West and East Indies.
"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," they wrote.
"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."