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Megaquake felt in space

AFP-JIJI

A European Space Agency satellite circling the Earth was able to detect the massive 2011 quake that ravaged Japan, resulting in the loss of some 19,000 lives and causing massive destruction, a new study said Sunday.

“The atmospheric infrasounds following the great Tohoku earthquake . . . induced variations of air density and vertical acceleration of the GOCE platform,” said a report published in the journal Geophysical Research Letters.

The Gravity Ocean Circulation Explorer is the European Space Agency super-sensitive satellite that acts like an orbital seismologist.

Scientists argue that earthquakes not only create seismic waves that travel through Earth’s interior, but large tremors also cause the surface of the planet to vibrate like a drum. This produces sound waves that travel upward through the atmosphere.

GOCE is designed to capture and register these signals.

According to the report, the magnitude 9 temblor on March 11, 2011, sent shock waves through the atmosphere that were picked up by the satellite.

“These signals were detected at two positions along the GOCE orbit corresponding to a crossing and a doubling of the infrasonic wavefront created by seismic surface waves,” the study said.

It noted that perturbations up to 11 percent of air density and a vertical acceleration of air waves were observed following the quake. “These perturbations were due to acoustic waves creating vertical velocities up to 130 meters per second,” the report said.

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.

“Seismologists are particularly excited by this discovery because they were virtually the only Earth scientists without a space-based instrument directly comparable to those deployed on the ground,” said Raphael Garcia from the Research Institute in Astrophysics and Planetology in France. “With this new tool, they can start to look up into space to understand what is going on under their feet.”