Seismo-ionospheric perturbations, and the precursors to the 2011 Japan earthquake

The ionospheric perturbations have been found to take place prior to an earthquake (EQ) (with magnitude greater than 5.5 (or so) and with shallow depth), on the basis of the long-term VLF/LF subionospheric propagation. Then, there have been presented the precursors to the recent 2011 Japan EQ. That is, the ionospheric perturbation was definitely found on the basis of two completely different phenomena ((i) subionospheric VLF/LF propagation anomaly and (ii) ULF magnetic field depression). Further, atmospheric ULF/ELF radiation was observed a few days before the EQ.