Because the crust is lighter than the underlying mantle, gravity signals reveal variations in the thickness of the crust that were caused by tidal heating. (sciencedaily.com)
The method involves gravity signals which occur earlier than seismic waves. (techtimes.com)
When the Gravity Recovery and Climate Experiment (GRACE) satellites began measuring gravity signals around the world in 2002, scientists knew they would have to separate mass flow beneath the earth's crust from changes in the mass of the overlying ice sheet. (sciencedaily.com)