ESA’s GOCE satellite revealed earlier this month that the great Japanese Earthquake from 2011 caused a tiny change in the local gravity. The satellite mapped Earth's gravity for four years and clearly shows a disturbance after 2011.
The strength of gravity is different on every point on the planet. It is GOCE’s task to map these differences. The value of gravity depends on the material and density of the rocks underneath the surface. Since earthquakes move those layers, they can also cause change in the local gravity. But the 2011 Earthquake was significant for one more reason – the epicenter was under the ocean, so the layers movement also caused a displacement of large water body, which also could have an effect on gravity.
The GOCE satellite accomplished its mission and is not in orbit any more. The information it gathered will be analyzed for years - concerning warm water movements in the oceans, atmospheric density and of course gravity. Surprisingly the satellite even caught sound waves from the earthquake.
The rupture in the gravity field was discovered by the German Geodetic Research Institute, GDFI and by Delft University of Technology in the Netherlands. The scientists are still working on a better picture of the actual rupture. They are combining the information from GOCE with every other information they have available in order to better understand the changes and their impact on the Earth.