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

我们在宫城县细仓矿设置了地下电磁观测室，观测了地下和地表的电磁变化信号。在这里，我们准备了由以下子系统组成的观测系统。1.观测高频电磁变化信号的子系统。(NS、EW和UD静电电容天线以及NS、EW和UD环形天线）2.观测准稳态电磁变化信号的子系统。（大极板、场磨式静电计和NS、EW和UD磁通门磁力计）3.数据记录子系统具有高精度的时间戳，在2006年至2007年期间，我们成功地同时获得了地下和地表的多个电磁变化信号。主要研究结果如下：1.地下和地表观测资料表明，地表以下可能存在电磁表面波模式。2.通过长期观测，地下观测室内离子浓度、空间电场、室内温度和湿度呈现出年、月、日变化特征。在2007年新余县地震发生后，观测到了地震电场的变化信号。4.在实验室条件下，利用风干的火成岩岩块对岩石带电进行了检测。部分受压的岩样在无应力体积上表现为正带电.为了模拟电磁场在地下传播，我们研究了最近开发的新CIP方法。对不同类型的CIP方法进行了试验，以找出最佳的CIP方法。指出了边界条件对CIP方法进行电磁或声学模拟的重要性。

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.