Abstract
The analysis of energetic electron observations made by the DEMETER satellite reveals that radiation belt electron precipitation (RBEP) bursts are observed in general several (~1-6 days) before a large (M > 6.5) earthquake (EQ) in the presence of broad band (~1-20 kHz) VLF waves. The EBs show in general a relative peak-to-background flux increase usually < 100, they have a time duration of ~0.5 – 3 min, and their energy spectrum reach up to energies <~500 keV. The RBEP activity is observed as one, two or three EBs throughout a semi-orbit, depended on the magnetic field structure above the EQ epicenter. A statistical analysis has been made for earthquakes in Japan, which reveals a standard temporal variation of the number of EBs, which begins with an incremental rate several days before major earthquakes, and after a maximum, decreases so that the electron precipitation ceases above the epicenter. Some earthquake induced EBs were observed not only in the nightside ionosphere, but also in the dayside ionosphere.
Highlights
1.1 Electromagnetic methods of earthquake precursory signals researchOver the last few decades, significant efforts have been made to detect and interpret electromagnetic phenomena that are related to seismic activity
The main results of our study are the following: (1) Earthquake precursory radiation belt electron precipitation (RBEP) events show flux-time profiles with: (a) two electron bursts (EBs) at middle latitudes, with one burst above the future epicenter and a conjugate one in the other hemisphere (Japan, Chile); (b) only one EB at north middle latitudes, when the South Atlantic Anomaly (SAA) affects the south hemisphere; (c) one EB above an earthquake epicenter at low latitudes (Haiti); and (d) one EB above an earthquake epicenter at low latitudes and two symmetric EBs at north and south latitudes (Sumatra)
(2) For earthquakes in Japan, a standard temporal variation of the number of EBs was found, which begins with an incremental rate several days before major earthquakes, and which after a maximum, decreases so that electron precipitation ceases above the region of the future epicenter a few hours before the occurrence of the earthquake
Summary
Over the last few decades, significant efforts have been made to detect and interpret electromagnetic phenomena that are related to seismic activity. Sidiropoulos et al [2011] demonstrated that the North West Cape (NWC) transmitter (in western Australia) is the most powerful military transmitter (1 MW), in that it produces the strongest electron precipitation effects compared with all of the other transmitters over the globe, NWC-induced EBs are observed during only ~2.1% of the Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite passes above the transmitter-influenced region (25 ̊-30 ̊S, 114 ̊-167 ̊E), with the NWC-associated EBs (including the conjugate EBs) as low as
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