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.