[Imalaycle]

March 11 TOKYO earthquake created largest disturbance ever seen in ionosphere



August 9, 2011

TOKYO – The giant 9.0 earthquake that struck Japan on March 11,
this year not only shook the Earth, but also rattled the highest layer of the atmosphere,
scientists find. This research could lead to a new type of early warning system for
devastating tsunamis and earthquakes. Past research revealed the surface motions
and tsunamis that earthquakes generate can also trigger waves in the atmosphere.
These waves can reach all the way to the ionosphere, one of the highest layers of
the atmosphere. Now scientists report the Tohoku quake generated the largest such
disturbances seen yet, creating ripples in electrically charged particles reaching
nearly 220 miles (350 kilometers) above the Earth. Investigators measured these
disruptions, called seismo-traveling ionospheric disturbances, using about 1,000
global positioning system (GPS) receivers in Japan and Taiwan. Disruptions of the
electrically charged particles in the ionosphere would lead to anomalies in radio signals
between the ground receivers and the GPS satellites, data that scientists can measure.
Scientists detected a disc-shaped rise in electron density in the ionosphere about
seven minutes after the earthquake. Concentric waves of fluctuating electron density
then flowed out in the ionosphere from this disk at speeds of about 450 to 500 mph
(720 to 800 kph). All in all, this disruption was about three times greater than the
next largest one ever seen, which came after the 2004 magnitude 9.3 Sumatra
earthquake. The ripples that flowed from the initial disc-shaped disturbance in the
ionosphere appear to be linked to the tsunami, a connection that has the potential
to save lives. “This signature in space that we can see with GPS could provide early
warning that a tsunami is coming,” researcher Jann-Yenq “Tiger” Liu, an atmospheric
scientist at Taiwan’s National Central University, told Our Amazing Planet.