Spatial and temporal characteristics of long-term satellite gravity change in the epicenter of M_W9.0 Japan earthquake and its surrounding regions

Considering the contribution of terrestrial water storage from global land data assimilation system to gravity changes, we use the temporal gravity filed models of GRACE from April 2002 to April 2015 to calculate regional gravity changes in the epicenter of M_W9.0 Japan earthquake and its surrounding regions. Then we present annual accumulated gravity changes, differential gravity changes and co-seismic gravity changes in the M_W9.0 source region and its surrounding regions. Meanwhile empirical orthogonal function method is applied to study the contribution of the earthquake to regional gravity changes. The results show that GRACE is able to reveal the evolution of regional gravity field accompanied with the M_W9.0 earthquake, the gravity changes reached about 2×10^-8 m/s² in the studied area three years before the M_W9.0 earthquake. Furthermore, the change in coseismic gravity and post-seismic regional gravity field are significant. The results from empirical orthogonal function method indicate that the coseismic effect with temporal and spatial gravity characteristics are presented in the first mode, which fully demonstrates that the Japan earthquake had significant influence on the regional gravity field.