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Japan earthquake shifted Earth's gravitational field, satellites' orbit

GRACE gravitational satellites change courses, suggesting Japan's massive earthquake even larger than we thought

by Mariella Moon | Last updated 8:35PM EST on December 7, 2011

Filed under: News | Computers

The earthquake that hit Japan this March was apparently so powerful that it changed Earth's gravitational field, enough to knock a couple of satellites off their orbits. Called the Gravity Recovery and Climate Experiment (GRACE) satellites, these identical unmanned vehicles map our planet's gravity field and monitor its changes and variations.

The GRACE satellites reflect significant changes in the Earth's gravitational field by altering their courses and the 220 kilometer distance between the two of them. Gravity field changes are usually detected after severe floods, snowfall, melting of ice caps, and earthquakes. Up until now, the only events that have affected the satellites' orbits since their launch in 2002 were the earthquakes in Sumatra and Chile in 2004 and 2010, respectively.

In the future, the GRACE satellites could be used to make more accurate measurements of ground tremors. Using the data gathered from their recent changes, researchers determined that the 2011 earthquake in Japan was actually 9.1 in magnitude, which is higher than the 9.0 magnitude that was recorded.

NASA and German space agency DLR are currently planning to tweak the satellites so they can detect weaker earthquakes with magnitudes as low as 7.5 that occur almost every month across the globe. When that happens, the GRACE satellites could work well in conjunction with possible early earthquake detectors like toads and ionosphere disturbances in our quest to understand natural disasters better so that we can be more prepared for their arrival.

[Image credit: Wikimedia]

(Source)