5:15 PM - 6:45 PM
[SGD01-P07] Discussion on the time constants of post-seismic gravity changes and scaling
Keywords:Post-seismic gravity changes, viscoelastic relaxation
Post-seismic crustal deformation and post-seismic gravity changes are mainly considered to be caused by afterslip and viscoelastic relaxation. Some reports suggest that the viscoelastic relaxation can be separated into short- and long-term components.
Co- and post-seismic gravity changes are easily seen, for example, in the GRACE Plotter ( https://thegraceplotter.com/ ). Those caused by three M9-class earthquakes after the launch of the GRACE satellite, the 2004 Sumatra earthquake (Mw 9.2), the 2010 Maule earthquake (Mw 8.8), and the 2011 Tohoku earthquake (Mw 9.0), appeared clearly. However, no detailed investigations of the time constants of the separated viscoelastic relaxations were reported. The main reason is probably that the 2004 Sumatra earthquake was the only earthquake for which long-term changes in post-seismic gravity changes have been clearly evident today.
In this study, I applied principal component analysis (PCA) to the gravity time series around the Tohoku region based on the GRACE-FO satellite data from 2002 to the end of 2023. As a result, the signal of the post-seismic gravity change of the 2011 Tohoku-oki earthquake was extracted as the first principal component (55.8%), and its principal components were approximated by a linear function in 2024 (PC1 in Figure). The time variable gravity (TVG) at (144E, 36N) is also showed in the figure. The figure also show a clear trend at the end of the time series. Furthermore, a similar trend appeared in the post-seismic gravity change of the 2010 Maure earthquake, suggesting that as of January 2024, the short-term components of viscous relaxations of the three M9-class earthquakes have already been indominant and the long-term components are dominant. Therefore, I will estimate the time constants of the short-term components of viscoelastic relaxations and the amounts of gravity changes caused by the short-term components, and consider their scaling based on the magnitudes of the earthquakes in this presentation.
Co- and post-seismic gravity changes are easily seen, for example, in the GRACE Plotter ( https://thegraceplotter.com/ ). Those caused by three M9-class earthquakes after the launch of the GRACE satellite, the 2004 Sumatra earthquake (Mw 9.2), the 2010 Maule earthquake (Mw 8.8), and the 2011 Tohoku earthquake (Mw 9.0), appeared clearly. However, no detailed investigations of the time constants of the separated viscoelastic relaxations were reported. The main reason is probably that the 2004 Sumatra earthquake was the only earthquake for which long-term changes in post-seismic gravity changes have been clearly evident today.
In this study, I applied principal component analysis (PCA) to the gravity time series around the Tohoku region based on the GRACE-FO satellite data from 2002 to the end of 2023. As a result, the signal of the post-seismic gravity change of the 2011 Tohoku-oki earthquake was extracted as the first principal component (55.8%), and its principal components were approximated by a linear function in 2024 (PC1 in Figure). The time variable gravity (TVG) at (144E, 36N) is also showed in the figure. The figure also show a clear trend at the end of the time series. Furthermore, a similar trend appeared in the post-seismic gravity change of the 2010 Maure earthquake, suggesting that as of January 2024, the short-term components of viscous relaxations of the three M9-class earthquakes have already been indominant and the long-term components are dominant. Therefore, I will estimate the time constants of the short-term components of viscoelastic relaxations and the amounts of gravity changes caused by the short-term components, and consider their scaling based on the magnitudes of the earthquakes in this presentation.