Photographs of Japan earthquake and tsunami from out of space
This NASA photograph shows flooding from Tsunami near Sendai, Japan.NASA’s Terra satellite's first view of northeastern Japan in the wake of a devastating earthquake and tsunami reveal extensive flooding along the coast. The Moderate Resolution Imaging Spectroradiometer (MODIS) acquired the right image of the Sendai region on March 12, 2011, at 10:30 a.m.The left image, taken by Terra MODIS on February 26, 2011, is provided as a point of reference.Water is black or dark blue in these images. It is difficult to see the coastline in the March 12 image, but a thin green line outlines the shore. This green line is higher-elevation land that is above water, presumably preventing the flood of water from returning to the sea. The flood indicator on the left image illustrates how far inland the flood extends.

The devastating earthquake that struck Japan earlier this year may have rattled the highest layer of the atmosphere before it shook the Earth, a discovery which could be used to provide warning for big earthquakes.

The magnitude 9.0 earthquake struck the coast of Tohuku in March and ushered in what might be the world's first complex "megadisaster", as the quake triggered off a tsunami and a series of small quakes and tremors around the globe.

Scientists recently found that the surface motions and tsunamis the earthquake triggered also generated waves in the sky that reached all the way to the ionosphere, one of the highest layers of the Earth's atmosphere.

Now geodesist and geophysicist Kosuke Heki at Hokkaido University in Japan has reported that these ripples in the ionosphere could have in fact occurred before the quake struck.

Heki gathered data from thousands of GPS receivers - which communicate with satellites using signals than are easily disrupted by a slight surge in electrons.

He discovered a rise of around 8 per cent in the total electron content in the ionosphere about the area hit by the quake around 40 minutes before the temblor. The increase was at its highest around the epicentre and diminished further away.

"Before finding this phenomenon, I did not think earthquakes could be predicted at all," said Heki.

"Now I think large earthquakes are predictable."

After analysing date from other huge earthquakes, including the Sumatra magnitude 9.2 earthquake in 2004 and the 8.8 Chile earthquake in 2010, Heki found that a similar pattern occurred.

Right now the anomaly is only seen with earthquakes with a magnitude of 8.5 or higher. Heki also warned that solar storms can trigger changes in electron content, so before researchers can develop an early-warning system for earthquakes based on ionospheric anomalies, they would have to rule out non-earthquake causes.