Electromagnetic Radiations from Shallow Earthquakes Observed in the LF Range

In order to observe anomalous electromagnetic radiations associated with occurrences of earthquakes, a simple system was adopted for a continuous observation in the LF range using a radio receiver as a sensor. The frequency of 163kHz was chosen as a monitoring frequency based on the result of a careful survey of spectra of artificial radio signals. The accumulated number of pulse type noises was continuously recorded by this system.Anomalous LF noises have been observed before and after shallow earthquakes which occurred in the inland area or in the shallow sea region. They appeared for a few hours to several days before and after the main shocks. The total number of them depends on the magnitude of the main shock. No significant increments of noises have been observed in the case of earthquakes whose epicenters were located in the deep sea region.These results suggest that electromagnetic noises are emitted from the focal region of shallow earthquakes and this phenomenon is important for the study of focal processes and the earthquake prediction.