Earthquake in Chile Shortened Day, Shifted Axis, NASA Says

By Nathan Eddy  |  Posted 2010-03-04

The 8.8-magnitude earthquake that rocked Chile and sent a wave of tsunamis across the world may have been powerful enough to slightly tilt the Earth's axis and shorten the length of a day, according to NASA scientists. Geophysicist Richard Gross, who works for NASA's Jet Propulsion Laboratory (JPL), calculated the massive quake, the result of an oceanic tectonic plate sliding under a South American plate, shortened the earth's rotation by 1.26 microseconds-just more than one-millionth of a second.

While the Earth's rotation has been impacted by earthquakes before (ocean currents and wind can also have an effect) and the results are too infinitesimal to notice, Gross told The Wall Street Journal it is still important to understand how the rotation of the planet changes. "It helps us figure out where a spacecraft is and to navigate it for a precise pinpoint [extraterrestrial] landing," he said, noting JPL conducted a similar study following 2004's 9.1-magnitude earthquake in Indonesia. In an interview with the Los Angeles Times, Gross compared the Earth to a kind of elastic putty. "If you have a sudden shock to it, it will continue to deform later in response to that shock," he explained.

NASA also reported the agency's Aquarius instrument, and the Argentinian spacecraft that will carry it into space, the Satelite de Aplicaciones Cientificas (SAC-D), successfully rode out the earthquake with no problems. The instrument and spacecraft are at the satellite systems contractor's satellite integration facility in Bariloche, Argentina. The city of Bariloche, located approximately 365 miles from the epicenter of the quake, experienced light shaking, as indicated by the Modified Mercalli Intensity Scale, which evaluates the effects of earthquakes as experienced by people in the region. No damage was reported to the facility or spacecraft.

Aquarius/SAC-D is an international mission between NASA and Argentina's space agency, Comisi??n Nacional de Actividades Espaciales. The primary instrument on the mission, Aquarius is designed to provide monthly global maps of how salt concentration varies on the ocean surface -- a key indicator of ocean circulation and its role in climate change. Seven Argentine space agency-sponsored instruments will provide environmental data for a wide range of applications, including natural hazards, land processes, epidemiological studies and air quality issues.

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