A concerning new report suggests that 2018 may be a very busy, and possibly devastating, year from earthquakes.
This could be a very bad year for earthquakes, according to a worrying new report, and it may all be due to something that happened four years ago. Specifically, the Earth’s rotation slowed slightly, and researchers from the University of Colorado predict this will mean more earthquakes in 2018.
The findings, presented in October at the annual meeting of the Geological Society of America, suggests a trend between slower Earth rotations and more earthquakes. They say that there has been a 25 to 30 percent increase in the number of significant earthquakes when the rotation of the Earth slows down, and that trend has held up for the past century.
Because the rotation of the Earth slowed down around five years ago, scientists think there could be two to five more magnitude 7 earthquakes than usual in 2018. However, there’s no indication on whether on the globe these earthquakes would be likely to strike.
The abstract from the presentation before GSA follows below.
On five occasions in the past century a 25-30% increase in annual numbers of Mw≥7 earthquakes 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 correlation between Earth’s angular deceleration (d[LoD]/dt) and global seismic productivity is yet more striking, and can be shown to precede seismicity by 5-6 years, permitting societies at risk from earthquakes an unexpected glimpse of future seismic hazard.
The cause of Earth’s variable rotation is the exchange of angular momentum between the solid and fluid Earth (atmospheres, oceans and outer core). Maximum LoD is preceded by an angular deceleration of the Earth by 6-8 years corresponding to a π/4 phase lag of the 24-33 year peak-to-peak period of multidecadal oscillations of Earth’s rotation. We show delayed global seismic productivity is most pronounced at equatorial latitudes 10°N-30°S. Two mechanisms may be responsible: (1) decreased oblateness (a reduction in J2) that attends a slowing of Earth’s rotation and (2) lithospheric overshoot, a process whereby the equatorial lithosphere sluggishly overrides the decelerating underlying mantle westward, much as a loose cannon slides upon the deck of a rolling ship.
The observed relationship is unable to indicate precisely when and where these future earthquakes will occur, although we note that most of the additional Mw>7 earthquakes have historically occurred near the equator in the West and East Indies. A striking example is that since 1900 more than 80% of all M≥7 earthquakes on the eastern Caribbean plate boundary have occurred 5 years following a maximum deceleration (including the 2010 Haiti earthquake).
Calculations show the asthenosphere to have an appropriate viscosity to account for the delay between deceleration and subduction zone seismicity, however, a geodetic test of the anticipated westward overshoot would be of utility. 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 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.
Wikipedia describes earthquakes on the Richter scale between 7.0-7.9 in the following way: “Causes damage to most buildings, some to partially or completely collapse or receive severe damage. Well-designed structures are likely to receive damage. Felt across great distances with major damage mostly limited to 250 km from epicenter”
For 8.0 to 8.9: “Major damage to buildings, structures likely to be destroyed. Will cause moderate to heavy damage to sturdy or earthquake-resistant buildings. Damaging in large areas. Felt in extremely large regions.”
For 9.0 or greater: “At or near total destruction – severe damage or collapse to all buildings. Heavy damage and shaking extends to distant locations. Permanent changes in ground topography.”