The development of a measuring system for the electromagnetic phenomena caused by volcanic activity of Mount Sakurajima

In order to examine the relationship between volcanic explosions and electr omagnetic phenomena, we constructed the continuous extremely low frequency (ELF) band measuring system, which is composed of geoelectric potential dif ferences (GPD's) and geomagnetic fields (GF's) at the foot of NIL Sakurajim a, Kyushu Island, Japan. The results of the measurements show that the meas uring system is able to measure the natural phenomena properly and the GPD' s in the horizontal direction are observed which are assumed to be associat ed with the volcanic activity of Mt. Sakurajima when the seismometer was ac tive.