地震予知のための自然電位集中連続観測 A Study of Earthquake Prediction Method by Electric Self-potential Measurements
Whether or not the geoelectric potential field exhibits anomalous changes before earthquakes that can be used for prediction is a matter of long-standing debate. Recently, a number of positive results have been reported for Greek earthquakes. In order to test if such is possible in Japan also, similar observation has been carried out. In Ishikawa Prefecture, central Japan facing the Japan Sea, two long span geoelectric potential monitoring systems have been in operation since March, 1991. During the observation period, three M>5 earthquakes (focal depth <50km) have occurred in central Japan. Anomalous geoelectric potential changes were recorded before each of these events. Moreover, an anomalous change was recorded from June 13 to 25, 1993. This last anomalous change could have been precursory to the devastating M=7.8 Southwest Off Hokkaido Earthquake of July 12, 1993. Although it is quite uncertain at this point if these anomalous changes are causally related to the earthquakes or not, it appears worthwhile to continue the observation, hopefully in a more expanded form.
防災科学技術研究所研究資料 166, 131-148, 1995-03-31