Development of ionospheric tomography using neural network and its application to the 2007 Southern Sumatra earthquake

Abstract

AbstractAn ionospheric anomaly prior to the 2007 Southern Sumatra earthquake (M8.5) was observed by GPS receivers around the Sumatra islands. In this paper, to investigate the three‐dimensional structure of electron density in the ionosphere, a tomographic approach (Residual Minimization Training Neural Network; RMTNN) has been used. Results of the tomographic approach are consistent with those of the total electron content (TEC) approach. We found that a significant decrease of electron density takes place at altitudes of 250 to 400 km, especially at an altitude of 330 km. But the altitude at which the maximum electron density has been observed remains unchanged. The obtained structure has a region of decreased density of Integrated Electron Content (IEC) in the southwest area (at altitudes of 400 to 550 km) and in the northern area (at altitudes of 250 to 400 km). The global tendency of the decreased electron density expands to the east with higher altitudes and it is concentrated in the southern hemisphere over the epicenter. These results show that the high capability of the RMTNN method can be used for estimation of the ionospheric electron density distribution possibly associated with earthquake. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 181(4): 9–18, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22298