The Seismic Electromagnetic Emissions During the 2010 Mw 7.8 Northern Sumatra Earthquake Revealed by DEMETER Satellite

Abstract

The abnormal electromagnetic emissions recorded by DEMETER (the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite associated with the April 6, 2010 Mw 7.8 northern Sumatra earthquake are examined in this study. The variations of wave intensities recorded through revisiting orbits from August 2009 to May 2010 indicate that some abnormal enhancements at Extremely Low Frequency range of 300–800 Hz occurred from 10 to 3 days before the main shock, while they remained a relatively smooth trend during the quiet seismic activity times. The perturbation amplitudes relative to the background map which were built by using the same-time seasonal window (February 1 to April 30) data from 2008 to 2010 further suggest strong enhancements of wave intensities during the period prior to the earthquake. We further computed the wave propagation parameters for the electromagnetic field waveform data by using the Singular Value Decomposition method, and results show that there are certain portions of the Extremely Low Frequency emissions obliquely propagating upward from the Earth toward outer space direction at 10 and 6 days before the main shock. The potential energy variation of acoustic-gravity wave suggests the possible existence of acoustic-gravity wave stability with wavelengths roughly varying from 5.5 to 9.5 km in the atmosphere at the time of the main shock. In this study, we comprehensively investigated the link between the electromagnetic emissions and the earthquake activity through a convincing observational analysis, and preliminarily explored the seismic-ionospheric disturbance coupling mechanism, which is still not fully understood at present by the scientific community.