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Figure 1: GRACE gravity and geoid variations of the Sumatra Dec. 2004 earthquake (Mw 9.1). Left: Co-seismic gravity variation (µGals), from Han et al. (2006). Right: post-seismic geoid change (mm) from April 2005 to September 2007 attributed to broadscale visco-elastic mantle relaxation, from Panet et al. (2010).
Understanding and modelling the deformation processes during the different phases of the seismic cycle is a key challenge of Earth’s sciences, and a major goal for the mitigation of seismic hazards. With a unique sensitivity to mass redistribution at all depths within the Earth, and a homogeneous spatial coverage of epicentral areas on land as well as undersea, GRACE satellite gravity has provided a new image of great earthquakes (Fig. 1), complementing seismic data and space-geodetic observations of ground displacements.
In the SING project, our objective is to assess the impact of the NGGM and the MAGIC missions in detecting and quantifying the co- and post-seismic gravity variations of earthquakes for a broader range of magnitudes (Mw 7.5 and above) than achievable from GRACE (Fig. 2). We then aim to design methodologies for integrating the NGGM and MAGIC-based information with surface displacement data and seismology-based rupture mechanisms, to improve co-seismic slip models. Finally, we will assess the ability of NGGM and MAGIC to characterize post-seismic deformation mechanisms, considering visco-elastic crust/mantle relaxation and aseismic afterslip. These results will enable improved estimates of stress redistribution after an event in the vicinity of the plate boundaries.
Figure 2: Detectability of Mw 8.2 earthquakes from a MAGIC-type constellation, as described by a comparison of localized spectra of signals and errors (Daras et al., 2024).
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