Probably, according to scientists, it has to do with slight changes in the behavior of the fluid and hot iron nucleus of our planet, which can release vast amounts of energy and have "side effects" in the upper layers, namely the mantle of the earth.
Further investigation into these periods of high seismic activity resulted in the identification of a few correlations. "In these periods, there were 25 to 30 intense earthquakes a year", he said.
In studying every natural disaster to shake the Earth with a magnitude of 7.0 or greater since 1900, Bendick and Bilham found there were five different periods where the Earth experienced a noticeably higher number of these large quakes.
American scientists say they have found a correlation between sporadic slowing of the Earth's rotation and an increase in the number of severe earthquakes - and a surge is due next year. All the major earthquakes that have happened over the last century have been well recorded, said Bilham. According to experts, the earth's rotation is slowing down, which will cause intense seismic activity, especially in tropical areas which are heavily populated.
Bilham and Bendick found that periods when the number of intense earthquakes had increased followed periods of about five years when the Earth's rotation slowed slightly.
"The rest of the time the average figure was around 15 major earthquakes a year".
Bilham and Bendick looked at earthquakes of magnitude 7 and greater since 1900, finding five periods when the number of big quakes increased significantly. "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. Crucially, these periods were followed by periods when the numbers of intense earthquakes increased.
This link is particularly important because Earth's rotation began one of its periodic slowdowns more than four years ago.
"Consequently", Bilham said, "we will see a significant increase in the numbers of major earthquakes over time".
"We have had it easy this year".
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. Until now, we only had six powerful earthquakes. This year we made it clean.
"The inference is clear".
For context, seasonal changes like El Niño have been shown to affect the Earth's rotation, while massive earthquakes can cause shifts in the planet's axial tilt, according to NASA.