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Japan quake tremors felt in space

Mar 14 (): The effects of the massive  Tohoku earthquake of magnitude-9 that hit Japan two years ago on March 11, 2011 were also felt in space by ESA’s hyper-sensitive GOCE satellite.

Scientists say the great earthquake sent a ripple of sound, called infrasound – upwards through the atmosphere that was picked up by the GOCE satellite.

Large earthquakes create seismic waves that travel through the interior of the Earth, as well as cause the surface of the planet to vibrate like a drum. The sound waves produced from the quake travel upwards through the atmosphere, with sizes that start at centimetres at the surface of the Earth, to kilometres in the thin atmosphere at high altitudes.

The GOCE satellite is orbiting at a distance of less than 270 km above the Earth. Its super-sensitive instrumentation was able to detect the disturbance caused by the earthquake.

The accelerometers of GOCE are about a hundred times more sensitive than any other previous instrumentation and the scientists detected the acoustic wave not once, but twice – passing through it over the Pacific and over Europe, said the mission manager.

These perturbations caused due to the acoustic waves created vertical velocities up to 130 metres per second. The satellite first recorded the signal as it passed over the Pacific Ocean about 30 minutes after the quake and then again 25 minutes later as it moved across Europe.

Raphael Garcia from France’s Research Institute in Astrophysics and Planetology said earthquakes are generally monitored using land-based seismographs. Satellites are not used to observe or monitor earthquakes when they strike.

Japan Meteorological Agency uses some 250 seismographs on land in addition to about three dozen underground units and about 10 seismographs placed on the bottom of the Pacific waters off Japan. But the agency would welcome it if the satellite provided a technical breakthrough to advance the study of earthquakes.

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