The 2011 Tohoku-Oki earthquake GCMT solution from the GOCE model of the Earth’s crust

Space gravity missions allow us to make a step ahead in the physics of large earthquakes, Mw higher than 8.5, thanks to the gravity signal from mass rearrangement within the crust and lithospheric mantle and from the ocean water washed away from the epicentral region by co-seismic displacement of the ocean bottom. Although designed to detect the time dependent and static components of the gravity field, the Gravity Recovery And Climate Experiment (GRACE) and the Gravity and steady state Ocean Circulation Explorer (GOCE) space missions play a complementary role in retrieving this new physics by sampling the co-seismic gravity signal and the thickness of the crust, the latter of importance to determine the synthetic expression of the former within realistic, dislocation Earth’s models. We present a novel procedure for estimating the global Centroid Moment Tensor (CMT) solution, which provides the principal seismic source parameters (hypocentre and moment tensor) of the 2011 Tohoku earthquake that relies solely on space gravity data from GRACE and GOCE. Increasing the GOCE crustal thickness from 13.0, to 16.5 and 20.0 km, corresponding to the error bounds, the former and the latter values, of the regional value of 16.5 km, the epicentre for the best model moves by about 20 km roughly in the SE direction and the magnitude Mw decreases from 9.19 ± 0.11 for the thinner crust to 9.07 ± 0.11, the latter concordant with the CMT solution from teleseismic waves.