EM Precursor Phenomena of Off-West-Fukuoka M7 .0 Earthquake

Abstract

. We have been studying an earthquake precursor of environmental electromag netic waves (EM) at ELF band of 30-300Hz for the last twenty years. In this paper, a new approach to extract precursor radiation out of noisy ELF environmental signal by making use of Linear Predicting Coefficient, LPC signal model is introduced. For the case of Off- West Fukuoka earthquake with M7.0, an anomalous magnetic flux radiation of about lOpT /VHZ with lpT / VHZ background noise was detected about four days before the event at Tijiwa town Nagasaki Prefecture, 120km south of the epicenter, and five aftershocks exceeding M5.0 also followed respectively the anomalous radiations within one day's delay. The radiation area was determined near the epicenter for both the main and aftershocks, by direction finding of the detected anomaly signal from two sites of Tijiwa and Tomochi through the signal amplitude ratio of EW to NS of sensing loop coils. These two facts may confirm the existence of EM precursor.