Theories and applications of earthquake-induced gravity variation: Advances and perspectives

Earthquake-induced gravity variation refers to changes in the earth’s gravity field associated with seismic activities. In recent years, development in the theories has greatly promoted seismic deformation research, laying a solid theoretical foundation for the interpretation and application of seismological gravity monitoring. Traditional terrestrial gravity measurements continue to play a significant role in studies of interseismic, co-seismic, and post-seismic gravity field variations. For instance, superconducting gravimeter networks can detect co-seismic gravity change at the sub-micro Gal level. At the same time, the successful launch of satellite gravity missions (e.g., the Gravity Recovery and Climate Experiment or GRACE) has also facilitated applied studies of the gravity variation associated with large earthquakes, and several remarkable breakthroughs have been achieved. The progress in gravity observation technologies (e.g., GRACE and superconducting gravimetry) and advances in the theories have jointly promoted seismic deformation studies and raised many new research topics. For example, superconducting gravimetry has played an important role in analyses of episodic tremor, slow-slip events, and interseismic strain patterns; the monitoring of transient gravity signals and related theories have provided a new perspective on earthquake early warning systems; the mass transport detected by the GRACE satellites several months before an earthquake has brought new insights into earthquake prediction methods; the use of artificial intelligence to automatically identify tiny gravity change signals is a new approach to accurate and rapid determination of earthquake magnitude and location. Overall, many significant breakthroughs have been made in recent years, in terms of the theory, application, and observation measures. This article summarizes the progress, with the aim of providing a reference for seismologists and geodetic researchers studying the phenomenon of gravity variation, advances in related theories and applications, and future research directions in this discipline.