Pre- and after-sign detection of earthquake through ELF radiation

A highly sensitive geomagnetic field detection system of order 0.01 pT at the ELF frequency of 225 Hz has been developed and set up in Ito city, Shizuoka prefecture, over four years and at Mt. Fugen, Nagasaki prefecture, over two years. From the ground ELF radiation, the authors detected precursors and after-signs of the advent of the tenth and eleventh lava domes and further even precursors of the fall of the eleventh lava dome at Mt. Fugen. Taking these observations into account, the authors propose a model of radiation due to volcanic activity. At Ito-city, they also detected precursor and after-signs of geomagnetic variations for five earthquakes out of six which occurred during August 30 to October 17, 1992, whose magnitudes were M=4.7, 6.6, 4.7, 4.6, 3.9, 5.1, excepting the case of M=3.9. The radiation showed a positive and negative correlation with the seismometer for the sequence of the earthquakes; the authors consider the reason for this and model the electromagnetic radiation