[S-GD02] Crustal Deformation

[SGD02-P08] Postseismic gravity change after the 2011 Tohoku earthquake observed by superconducting gravimeters at Mizusawa, Japan (part 2)

*Yuichi Imanishi¹, Yoshiaki Tamura², Takahito Kazama³, Ryuichi Nishiyama¹, Koji Matsuo⁴ (1.Earthquake Research Institute, The University of Tokyo, 2.National Astronomical Observatory of Japan, 3.Graduate School of Science, Kyoto University, 4.Geospatial Information Authority of Japan)

Keywords:2011 Tohoku earthquake, superconducting gravimeter, viscoelastic relaxation, satellite gravity observation

Tamura et al. (2022, JpGU) presented preliminary analysis results of long-term gravity changes recorded by superconducting gravimeters at Mizusawa, Japan, after the 2011 Tohoku earthquake. The postseismic gravity changes (increases) retrieved from the ground observations by means of superconducting gravimeters were much different from those derived from satellite observations (GRACE/GRACE-FO) with respect to the time scale and magnitude. Tamura et al. (2022) presented qualitative interpretation of the difference in the magnitude on the basis of the different spatial resolutions of the ground-based and satellite-based methods of gravimetry. In this paper, we will present physical interpretation on the difference in the time scale from the viewpoint of viscoelastic relaxation, based on the results of numerical simulations by Suito (2017) as well as the results of theoretical calculations by Takagi (2018).