Investigation of the Undergmund Electromagnetic Phenomena from the Data Observed at the Undergmund and the Ground surface

点击翻译按钮获取中文摘要

We have installed an underground electromagnetic observation room in the Hosokura mine in Miyagi Prefecture and observed the electromagnetic variation signals at both the underground and the ground surface. Here, we prepared the observation system composed of the following subsystems.1. Subsystem to observe high frequency electromagnetic variation signals. (NS, EW and UD electrostatic capacitive antennas and NS, EW and UD loop antennas)2. Subsystem to observe quasi steady state electromagnetic variation signals. (large plate electrode, field mill type electrometer and NS, EW and UD flux gate magnetometers)3. Data recording subsystem provided with high precision time stamp.We have succeeded to obtain many electromagnetic variation signals at the underground and the ground surface simultaneously throughout 2006 to 2007. The obtained results are followings.1. The data observed at the underground and the ground surface suggests that there could exist electromagnetic surface wave modes beneath the ground surface.2.With the long-term observation ion concentration, space electric field, room temperature and humidity in the underground observation room show the characteristic yearly, monthly, and daily variations.3. The seismic electric field variation signal was observed just after the occurrence of the Nigatakenn Chuetsu-oki Earthquake in 2007.4.We inspected rock electrification using air-dried brocks of igneous rocks in laboratory. The rock samples that were pressed partially showed the positive electrification on the unstressed volume.5. To simulate electromagnetic fields propagating in the underground we examine the recently developed novel CIP method. Various types of CIP method were examined to find out the best type of CIP method. We pointed out the boundary conditions are very important for the electromagnetic or the acoustic simulation using CIP method.