COSEISMIC AND POSEISMIC GRAVITY CHANGES OBTAINED FROM GRACE SATELLITE DATA DURING THE POWERFUL TOHOKU-OKI EARTHQUAKE OF 11 MARCH 2011

In this paper, we study the gravitational gradient changes induced 11 March 2011 Mw 9.0 Tohoku-Oki earthquake using data gathered by Gravity Recovery and Climate Experiment (GRACE) satellite. Previous studies have demonstrated the capability of GRACE data for observing the coseismic gravity change concerning the Tohoku earthquake. However, we show for the first time that changes of the coseismic and postseismic gravitational gradient components are detectable without doing any post-processing and filtering. It can be seen that the derivative of gravitational potential amplify the high-frequency components of the earth gravity field. Therefore, gravitational gradient changes delineate more clearly the rupture lines and reveal refined mass redistribution features caused by the studied earthquake