Abstract
The ionospheric anomaly prior to the 2007 SouthernSumatra earthquake (M8.5) was observed by GPS receivers around Sumatra islands. In this paper, to investigate the three-dimensional structure of electron density in Ionosphere, a tomographic approach (Residual Minimization Training Neural Network; RMTNN) has been performed. The results of the tomographic approach are consistent with those of total electron content (TEC) approaches. We found that the significant decreases take place in the heights of 250-400 km, especially at 330 km height. But the height which gives the maximum electron density is not changed. The obtained structure is that the decreased region exists in the southwest side of Integrated Electron Content (IEC) (400-550 km altitudes) and in the northern side of IEC (250-400 km altitudes). Global tendency of the decreases area is expanded to the east with an altitude and it is concentrated in the southern hemisphere of over the epicenter. These resultsshow that the high capability of RMTNN method for the estimation of the ionospheric electron density distribution possibly associated with earthquake.
