A JPL scientist says we ended up losing 1.26 millionth of a second of a day, and that the magnitude 8.8 quake also shifted the axis around which the Earth rotates.
When a magnitude 8.8 earthquake struck South America last weekend, the ground rumbled in Chile, the sea rose in the Pacific, and a day on Earth got shorter. Not by much. Earthlings ended up losing 1.26 millionth of a second of a day. You can’t sense it. Nor is your dog aware of it.
But while other experts charted the shift of tectonic plates and the swell of ocean waters wrought by the quake, geophysicist Richard Gross mathematically calculated the temblor’s disruption of the length of the day. The thrust-fault quake — in which plates under the Earth’s surface moved vertically — caused mass to be redistributed, said Gross, who works at the Jet Propulsion Laboratory in La Cañada Flintridge. "On average, the mass of the Earth got a bit closer to the rotation axis," he said. As a result, Gross said, the planet rotates faster — "just like a spinning skater brings her arms in closer to her body to rotate faster." When the planet rotates faster, the day shortens, he said. Gross studies the Earth’s rotation and how it is affected by cataclysmic forces of nature. "Anything that moves mass around on the Earth I take a look at," he said. And it takes a mega-earthquake to attract Gross’ attention.
