We could see twice as many big earthquakes this year, scientists warn — because the equator has shrunk

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• Geologists predict the Earth could see about twice as many earthquakes this year.
• That's because the world is turning a little slower than usual, prompting the equator to shrink slightly.
• A "skinny" equator makes the edges of tectonic plates squeeze together, so earthquakes happen faster.

You probably didn't notice, but the Earth is taking things a little slow right now.

Since 2011, our planet has been rotating at a pace a few thousandths of a second slower than usual.

Our planetary spin cycle changes constantly — ocean currents and atmospheric changes have an impact, as do the mantle and molten core under them. But the current pattern has a team of geologists worried about earthquakes.

Professors Roger Bilham and Rebecca Bendick warn that the Earth's slowing could lead to more than twice as many 7-plus-magnitude quakes in 2018.

Bilham, who studies earthquakes at the University of Colorado, told Business Insider that when the Earth’s pace lags for years at a time, its middle contracts. That shrinks the equator, but it’s hard for the tectonic plates that form Earth's outer shell to adjust accordingly.

Instead of falling in line with the slimmer waistline, the edges of those plates get squeezed together.

This all takes time for us to feel on the ground. But after five years without many high-intensity quakes, we're approaching the moment when the effects of this squeeze could be felt around the globe, Bilham said. He estimates the planet could see, on average, 20 high-magnitude earthquakes for each of the next four years. (By comparison, just seven earthquakes registered above a 7.0 in 2017.)Ako Rasheed - Reuters

This lagging-Earth phenomenon isn't prompting any quakes that weren't already in motion. Instead, Bilham said the slower spin adds more stress and pressure to some of the earthquakes that were already in the pipeline. That pushes the disasters to happen more quickly, especially in earthquake-prone zones around the globe. The effect may be felt the most in the tropics, near the equator.

Bendick, who studies geologic hazards at the University of Montana, co-authored a report with Bilham hinting at this phenomenon in 2017, though their latest findings are still under review.

She said it's important to remember that the Earth’s rotation changes all the time, for all kinds of reasons — large storms, winter snow buildup, and ocean patterns can all have an influence. But Bendick pointed out that the last 117 years of earthquake records suggest quakes are especially sensitive to a special kind of ten-year rotational slowdown like the one we seem to be experiencing now. 

This is likely due to “interactions of the lithosphere, mantle, and core,” Bendick told Business Insider in an email. 

The researchers hope that city planners and politicians in earthquake-prone zones will heed their latest warning and work quickly to retrofit buildings or update emergency plans. They also advise people to talk to loved ones about what their plan would be if a disaster strikes.

"There is no good reason for people not to take simple steps to be better prepared," Bendick said.

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