Seismo – Ionospheric Induced Perturbations Prior to the September 28, 2007 M7.5 Northern Mariana U.S.A. Geoquake From Gps, Tec and Demeter Data

Data from DEMETER (IAP and ISL sensors) and GPS (TEC), were used to decipher variations of electron density, electron temperature and ion density within the seismogenic zone of a seismic event that occurred on September 28, 2007 at Northern Mariana U.S.A, through statistical analysis. The study revealed both pre and post ionospheric perturbations from both sets of data. The observed anomalous variations were screened for false alarm using the geomagnetic indices of kp and Dst. It was observed that the abnormal TEC on -10, – 7, -3 and -2 days occurred under quiet geomagnetic conditions while all pre-seismic (-15, -10, – 9 -7 days) ionospheric variations from the DEMETER data were also obtained during quiet geomagnetic conditions suggesting them to be seismo-ionospheric induced perturbations. Interestingly, the perturbations on -10 and -7 days were simultaneously observed from both GPS and DEMETER datasets under quiet geomagnetic ionospheric conditions offering a strong pointer to the impending geo-quake.