跡津川断層と阿寺断層における電磁気観測

Abstract

The electro-magnetic studies have been conducted on the Atera fault and Atotsugawa fault which are known as the conjugating faults in the central part of Japan.The survey of total magnetic intensity at the Atotsugawa fault shows the magnetic anomalies of about 100 nT around the Amo area, the western part of fault and around the Suganuma area, the middle part of the fault. Around the Norimasa area of the Atera fault, the magnetic anomalies of about 70 nT were observed, which is a little smaller than those of Atotsugawa fault.Nakayama et al. (1989) indicate that the principal direction (PD) exists in the electric potential induced at the geomagnetic storm and/or the lightning. They showed that the PD directions, measured at the observation stations around the Atotsugawa fault zones, direct at right angle to the strike of the fault.The study of the PD around the Kashimo area of the Atera fault showed the existence of two PD directions in the data obtained at several series of lightning.That is, the direction which intersects with the main fault at right angle, and the direction which agrees with the strike of the main fault. The observed two principal directions may have the relation with the facts that many faults and/or fracture zones conjugating with the main fault are present around the Kashimo area (Yamada, 1978). These results suggests that the PD studies may become a useful technique to know the differencies between the Atera and Atotsugawa fault system.