image source: NASA

Last Saturday’s deadly earthquake in Chile may have slightly shortened the day and affected the position of the Earth’s axis, according to NASA scientists.

The quake measured 8.8. on the Richter scale and is estimated to have shifted the Earth’s axis by 2.7 milliarcseconds (8 cm or 3 in) and shortened the length of the day by 1.26 microseconds (millionths of a second) according to an article from Bloomberg. So much land was moved during the earthquake that it may have significantly changed the Earth’s distribution of mass enough to affect such changes.

Previous earthquakes have had a similar effect, according to Richard Gross, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, California:

The magnitude 9.1 Sumatran in 2004 that generated an Indian Ocean tsunami shortened the day by 6.8 microseconds and shifted the axis by about 2.3 milliarcseconds, Gross said.


The length of the day shortens due to something called the ‘Ice Skater Effect’, in which balance influences speed of rotation, like when in ice skater pulls her arms in to speed up during a spin.

From a similar CNN report:

On the other hand, the length of a day also can increase. For example, if the Three Gorges reservoir in China were filled, it would hold 10 trillion gallons (40 cubic kilometers) of water. The shift of mass would lengthen days by 0.06 microsecond, scientists said.

Such consequences of the quake vis-à-vis the Earth’s axis are interesting, but insignificant in terms of what we experience and of course do not detract from the human cost of the disaster.