After the occurrence of the October 25 2010 Mentawai tsunami earthquake on the Sunda megathrust in Indonesia, a following September 14 2012 earthquake occurred right on the east of the 2010 event with a deeper focal depth. Although the damages caused by this 2012 event was not significant, it is important to understand the seismic hazard of the Mentawai seismic gap and its relationship with the 2010 earthquake. In this study, we collected GPS observations during two weeks before and after the earthquake from 17 SuGAr stations to compute the coseismic displacements of these two earthquakes. The GPS data was processed using GAMIT/GLOBK 10.7 software. The time series of the 2007-2010 and 2010-2012 data show an exponential pattern which means that there are no interseismic phase before the 2010 and 2012 earthquakes.
The two earthquakes show similar displacement patterns, and the biggest displacements are found at BSAT, SMGY, and SLBU stations. The orizontal displacement of the coseismic phase is moving towards southwest, while the vertical displacements are upward at the Mentawai Islands and downward at the Sumatra Island. The coseismic source model has been completed using the kinematic model. From that, the energy accumulation released in 2010 and 2012 earthquakes are Mw 7.9 and Mw 6.2, respectively. These two earthquakes have filled the seismic gap area and are highly correlated.

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