Log-periodic modulation to power law of change in the geoelectric potential difference observed on Niijima Island prior to volcanic and seismic activation in the Izu island region, Japan 2000

摘要

Anomalous changes in the geoelectric potential difference between electrodes on Niijima Island first appeared at the end of April 2000 about two months before the onset of a major volcanic and seismic activity in the Izu island region. They ceased at the end of August 2000 simultaneously with the decline of the volcanic and seismic activity. The temporal change in the magnitude of 0.01Hz Fourier coefficient of the geoelectric potential difference was analyzed on the basis of a critical“time-to-failure”model. It was found that the temporal change was well explained by a power-law decorated with a log-periodic oscillation. This indicates that the possible generation mechanism of the electric potential changes was related to a critical phenomenon. Several possible mechanisms that may cause this phenomenon are suggested.