Coseismic gravity gradient change caused by the Japan Tohoku-Oki 2011 earthquake based on the GOCE observations

Abstract:

We use the GOCE gradiometry data spanning from November 2009 to May 2012 to detect the coseismic gravity gradient change caused by the Japan Tohoku-Oki 2011 earthquake event. Two global gravity field models up to degree and order 220 before and after this event are determined based on the least-squares method with the bandpass ARMA filter applied to the gradiometry data along the orbit. Because of the low accuracy in the low frequency of the gravity field model caused by the colored noises in SGG (Satellite Gravity Gradient) data, only the tailored SH coefficients of the models are used to compute the coseismic changes of gravity gradient components Vxx, Vyy, Vzz, Vxzin space domain. Considering the polar gap problem of GOCE satellite orbit, the zonal and near-zonal coefficients are excluded. The Gaussian filter is also applied to the model coefficients. The calculated gravity gradient changes based on the GOCE observations are compared with the corresponding modeled coseismic signal based upon the given fault slip model parameters. The results show that the coseismic gravity gradient signal could be recovered from the GOCE observations.