Citation: Zhou, X., W. Sun, B. Zhao, G. Fu, J. Dong, and Z. Nie (2012), Geodetic observations detected co-seismic displacements and gravity changes caused by the Tohoku-Oki earthquake (Mw=9.0), J. Geophys. Res., doi:10.1029/2011JB008849
Absrtact: This paper reports co-seismic displacements and gravity changes caused by the Tohoku-Oki earthquake (Mw 9.0), as observed respectively by GPS in Japan and China and its surrounding area, and observed by GRACE. To interpret geodetic observation data, we must choose a reasonable model among those slip models presented for the event. For this purpose, we first calculated the displacements using these slip models with different dislocation theories and compared the results with the displacements observed in Japan and China. Results show that the modeled co-seismic displacements calculated using the slip model of Shao et al. [2011] and the spherical dislocation theory of Sun et al. [2009] agree well with the observed ones, indicating that the earth's layer structural and curvature effects should be considered. Then, we computed the coseismic geoid and gravity changes on the earth surface and at a space-fixed point using the slip model of Shao et al. [2011] and the dislocation theory of Sun et al. [2009]. Results show that the maximum coseismic geoid change reaches 5 cm and that the coseismic gravity changes are about -2500 - 800 μgal. Furthermore, we processed GRACE data to extract co-seismic changes with decorrelation and a Gaussian filter of 350 km. The gravity changes observed by GRACE were dominated by a decrease over the back-arc region, with -5 μgal reflecting coseismic crustal dilatation of the landward plate, which agrees well with the theoretically modeled values. After the 2004 Sumatra-Andaman and 2010 Central Chile (Maule) earthquakes, this study presents the third case of clear detection of coseismic gravity changes by GRACE.
