Joint Inversion of 2011 Mw 9.0 Tohoku-Oki Earthquake Source Parameters with GRACE Gravity Data and GPS Data

Tuesday, 16 December 2014
Zheng Gong and Caijun Xu, School of Geodesy and Geomatics - Wuhan University, Wuhan, China
As modern geodesy technologies, both GRACE and GPS are used for observing the earthquake activities nowadays. While GPS can obverse the surface deformation continuously and accurately, GRACE satellites can measure the global gravity changes especially for those inaccessible areas. This shows that the GRACE satellites have the potential to supplement the unique information in those great offshore earthquakes. In the case of 2011 Mw 9.0 Tohoku-Oki earthquake, many scientists have been using GPS measurement data to inverse the earthquake parameters. Because the GPS observations are all on one side of the fault, it should be more accurate when combined with the coseismic gravity changes measured by GRACE data which can provide the information of the other side of the fault. In this study, we firstly used the Slepian function method to extract coseismic gravity change caused by Tohoku-Oki earthquake from GRACE data and then combined this coseismic gravity change with the coseismic deformation data measured by GPS. As these two data sets are quite different in space resolution and time spans, variance component estimation (VCE) was then used to determine the weights of gravity data and deformation data in joint inversion. At last a simulated Annealing method was used to inverse the earthquake source parameters. As a result, we found the fault geometry and source location are similar to previews studies which were derived from GPS data or seismic data but with differences. It shows that the GRACE data can play an important role in a joint inversion for source parameters of great earthquakes.