New mission concepts, such as the Mass change And Geosciences International Constellation (MAGIC), and advancements in instrumentation, such as quantum gradiometry, are expected to enhance the spatial and temporal resolution of gravity field observations. Simulations of these new constellations of instruments describe radical improvements in the error budget with respect to the signals arising from geophysical phenomena, including earthquakes. We assess the impact of these improvements in terms of earthquake detectability. In order to do so, we model an ensemble of synthetic earthquake gravity signals, using QSSPSTATIC [1], in terms of the spherical harmonics (SH) coefficients of the geopotential change due to an earthquake, as co-seismic signal of a dislocation and its variation in time due to viscoelastic relaxation. We test detectability with SH-domain SNR between the earthquake signal and the gravity model errors. The SH coefficients of both quantities undergo a spatio-spectral localization procedure [2] and are compared in terms of their localized degree variances.We perform a parametric study of the effect on detectability of moment magnitude and source parameters. Magnitude is a first-order predictor of detectability, while the effect of the other parameters is generally one order of magnitude smaller. We also assess the omission due to the point-source approximation, which we compare to finite fault solutions of real events. The results show that at the involved spatial scales and magnitudes, the point source approximation does not influence detectability significantly. [1] Wang et al., 2017 DOI:10.1093/gji/ggx259 [2] Wieczorek and Simons, 2005 DOI:10.1111/j.1365-246X.2005.02687.x
Modelling the co- and post-seismic gravity signal and assessing its detectability with Next Generation Gravity Missions
Alberto Pastorutti
;Carla Braitenberg
2023-01-01
Abstract
New mission concepts, such as the Mass change And Geosciences International Constellation (MAGIC), and advancements in instrumentation, such as quantum gradiometry, are expected to enhance the spatial and temporal resolution of gravity field observations. Simulations of these new constellations of instruments describe radical improvements in the error budget with respect to the signals arising from geophysical phenomena, including earthquakes. We assess the impact of these improvements in terms of earthquake detectability. In order to do so, we model an ensemble of synthetic earthquake gravity signals, using QSSPSTATIC [1], in terms of the spherical harmonics (SH) coefficients of the geopotential change due to an earthquake, as co-seismic signal of a dislocation and its variation in time due to viscoelastic relaxation. We test detectability with SH-domain SNR between the earthquake signal and the gravity model errors. The SH coefficients of both quantities undergo a spatio-spectral localization procedure [2] and are compared in terms of their localized degree variances.We perform a parametric study of the effect on detectability of moment magnitude and source parameters. Magnitude is a first-order predictor of detectability, while the effect of the other parameters is generally one order of magnitude smaller. We also assess the omission due to the point-source approximation, which we compare to finite fault solutions of real events. The results show that at the involved spatial scales and magnitudes, the point source approximation does not influence detectability significantly. [1] Wang et al., 2017 DOI:10.1093/gji/ggx259 [2] Wieczorek and Simons, 2005 DOI:10.1111/j.1365-246X.2005.02687.xPubblicazioni consigliate
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