The detection of gravity signals created by earthquakes could potentially improve early warning times a study in Nature Communications reports this week. These findings could herald new developments in early warning systems for earthquake hazards, such as tsunamis. However, new instruments need to be developed and tested before such a system could be implemented.

Earthquake early warning systems are reliant on the detection of seismic waves, but these can only be detected after the rupture has occurred. We also know that earthquakes generate changes in the Earth’s gravitational field, but thus far only static changes in the gravitational field have been detected after rupture. Theoretical studies have predicted that a transient gravity change created during rupture could be detected globally (as a prompt gravity signal) before the arrival of seismic waves. By examining data from the 2011 Tohoku-Oki earthquake, Jean-Paul Montagner and colleagues, for the first time, have detected a prompt gravity signal that can be observed before the arrival of the seismic waves. The discovery of the prompt gravity signal could thus provide earlier earthquake warnings for earthquakes such as the 2011 Tohoku-Oki earthquake, which generated devastating tsunamis leading to the Fukushima Nuclear Power Plant disaster. The authors caution that although this method has great potential, networks of gravity gradiometers (instruments for detecting gravity waves) will be required to be developed alongside the traditional seismometers.