Kamchatka 2025 Earthquake fault dislocation from GRACE-FO and sensitivity with future gravity mission MAGIC/NGGM

Slow fault dislocation and viscoelastic deformation are detected by geodetic observations of earthquakes, but are processes that are largely absent from seismological records because they do not generate seismic waves detectable by conventional seismic networks. Detecting the aseismic component of fault slip is therefore essential for characterizing the complete rupture process and the associated stress drop.
In this study, we invert satellite-observed gravity-field variations to estimate fault dislocation on a fault plane defined by seismological observations. Earthquake-related gravity changes reflect the coseismic dislocation responsible for seismic wave generation, combined with contributions from possible slow fault deformation. Consequently, dislocation values inferred from gravity data in excess of those derived from seismology provide information on aseismic slip.

The 2025 Kamchatka earthquake (moment magnitude M_w=8.8), which occurred on 29 July 2025 in the southern Kamchatka Peninsula at the subduction interface between the Pacific and Okhotsk plates, produced a detectable gravity signal. GRACE-FO observations at monthly resolution show a peak-to-peak amplitude of nearly 20 µGal at the mission’s spatial resolution. Detecting such coseismic signals in GRACE-FO data is challenging due to the relatively high noise level. We show that earthquakes of comparable magnitude observed by future satellite gravity missions, such as the inclined-pair NGGM (Next Generation Gravity Mission) constellation and the MAGIC double-pair configuration (NGGM combined with the GRACE-C follower of GRACE-FO), would be detected with substantially reduced noise and significantly improved inverted dislocation. Moreover smaller sized tectonic events will be observable.