09:30 〜 09:45
[SGD02-03] Detectability of earthquake-induced signals in future gravity mission observations
キーワード：測地学、重力、地震、衛星重力計測、地震後重力変化
Mass transport on the Earth’s surface, driven by atmospheric, oceanic, glacial, hydrological, and solid Earth deformation processes, contributes to variations in the time-variable gravity field. This study focuses on co- and post-seismic deformations caused by large earthquakes. To date, only events with a magnitude of approximately 8.0 or greater have been detectable by the GRACE (Gravity Recovery and Climate Experiment) and GRACE-FO (Follow-On) missions (Han et al., 2014; Chao et al., 2019; Chen et al., 2022). However, with the advent of the future double-pair constellation MAGIC (Mass-Change and Geosciences International Constellation), which features significantly enhanced measurement sensitivity, this detection threshold is expected to decrease to magnitude 7.4 (Daras et al., 2024). This advancement will allow for the detection of a substantially larger number of seismic events. Furthermore, cumulative gravity changes caused by a regional seismic activity may also be detectable via satellite gravimetry. Therefore, this study aims to investigate the gravity change behaviors associated with both individual and cumulative seismic events with magnitude greater than 7.0.
To discuss the detectability by the future satellite gravity mission, anticipated co- and long-term post-seismic signals are simulated for different focal mechanism, magnitude and geographical locations with varying earth structures. Our modelling is based on the spectral-finite element code VEGA, which assumes Burgers rheology with 3D viscosity distributions in a self-gravitating sphere. From a global earthquake catalogue, we will discuss how the derived signals affect the gravity field variations detectable from space. A preliminary simulation using the ISC-GEM catalogue shows that the amplitude of the coseismic gravity change due to the December 21, 2010 M7.4 event in Japan increases from 0.02 microGal to 0.25 microGal as the cut-off spherical harmonic degree increases from 40 to 100, where a Gaussian filter with radius of 500 km and 200 km is applied in the former and the latter, respectively. We will identify key parameters—including viscosity, source depth, magnitude, focal mechanism, and cut-off spherical harmonic degree—which influence the spatiotemporal patterns of individual and cumulative post-seismic deformation time series.
To discuss the detectability by the future satellite gravity mission, anticipated co- and long-term post-seismic signals are simulated for different focal mechanism, magnitude and geographical locations with varying earth structures. Our modelling is based on the spectral-finite element code VEGA, which assumes Burgers rheology with 3D viscosity distributions in a self-gravitating sphere. From a global earthquake catalogue, we will discuss how the derived signals affect the gravity field variations detectable from space. A preliminary simulation using the ISC-GEM catalogue shows that the amplitude of the coseismic gravity change due to the December 21, 2010 M7.4 event in Japan increases from 0.02 microGal to 0.25 microGal as the cut-off spherical harmonic degree increases from 40 to 100, where a Gaussian filter with radius of 500 km and 200 km is applied in the former and the latter, respectively. We will identify key parameters—including viscosity, source depth, magnitude, focal mechanism, and cut-off spherical harmonic degree—which influence the spatiotemporal patterns of individual and cumulative post-seismic deformation time series.