抄録
In order to confirm that earth-origin electromagnetic (EM) pulses could be excited by dynamical stress impacts onto earth crusts, we have been developing a method of pointing source locations of EM pulses on real-time basis, using a highly sensitive direction finding sensor system installed in deep boreholes at geographically different observation sites. Source locations of EM pulses can be determined by intersected points of arrival direction lines obtained at the observation sites. Through test measurements, we found that many detected EM pulses were unnecessary ones radiated from electric power lines on the ground and their related earth currents. It tells us a most important remark to beware in measurements of natural electromagnetic phenomena. By taking the preventive measures against noise, we obtained a preliminary result of source locations of EM pulses which are concentrated in an area of off-shore of Tou-Nan-Kai where is an area of potential earthquake occurrences in the future. Through the present developing process, we have proceeded to another stage toward the establishment of an observation network for accurately pointing source locations of earth-origin EM pulses on real-time basis.
