After an earthquake, there is an instantaneous gravitational disturbance that could be recorded before the seismic waves that seismologists can detect. In a study published in Science on December 1, 2017, a team comprising researchers from CNRS, IPGP, the Université Paris Diderot and Caltech has managed to observe these weak signals related to gravity and to understand where they come from. Because they are sensitive to the magnitude of earthquakes, these signals may play an important role in the early identification of the occurrence of a major earthquake.