Earth's gravitational field changed after the earthquake
The GOCE research satellite, launched by the ESA, has been investigating the Earth’s gravitational field for 4 years, compiling its maps, but at first no one assumed that the GOCE data would show any changes in the gravitational field over time. Nevertheless, a thorough analysis revealed the trail left by the 2011 earthquake on gravity maps. Large earthquakes are accompanied not only by deformations of the earth's crust, but also by local changes in the gravitational field.
The force of gravity is not the same in different parts of the earth. These differences are due to several reasons, one of which is the heterogeneity of the material of which our planet consists. Earthquakes that move rocks in the surface layer tens of kilometers thick and change the depth of the ocean can make their own adjustments to the distribution of gravity.
GOCE was faced with the task of accurately measuring the parameters of the Earth's gravitational field and plotting them on a map. The satellite lasted about 2 times longer than planned, but in November 2013, it consumed all the xenon used as a working fluid and burned out in the Earth’s atmosphere. Nevertheless, the work of scientists is just beginning: they have to analyze the data collected by the satellite over the years in orbit. This information touches on various aspects of the existence of our planet, from heat flows in the ocean and winds in the atmosphere to geodynamic processes in the earth's crust and mantle.
Scientists who analyzed the distribution of vertical gravity gradients over Japanese territory and the water area found that the earthquake made noticeable changes to its picture. The ESA press release also noted that the magnitude of these gradients is different from the values predicted by existing models. A joint study of GOCE and GRACE data (a satellite originally designed to detect changes in the gravitational field over time) will clarify these models and better understand the nature of earthquakes.
According to ESA