Fundamental Study on the Effective Observation Method and the Propagation Mechansm of Anomalous Radio Wave Noise Occurring Just Prior to Earthquakes

1.参考文献调查：从1970年开始，对可能与地震有关的电磁辐射异常进行了实验观测。观测点几乎都在地表附近，接收频率都在几MHz以下。由于观测到的数据还很少，这些数据在一般情况下是不能完全接受的。没有找到假定震源在深部的理论研究或数值算例的参考文献.近似理论方程的推导和数值计算的结果：我们把这个问题看作由两层（地面和空气）均匀介质组成的最简单模型，假定震源位于震源处。利用几何光学理论，得到了近地面电场强度和源强度的计算公式。将其他研究机构的观测数据应用于方程，进行了数值估计。这些结果导致下文第4.3节所述的结论。室内小尺度地气模型实验：实验试图验证计算的正确性。测量是在有限的空间内进行的，包括由一些无线电波吸收器封闭的干沙。但由于吸收体的反射和接收天线的不稳定性，观测到的数据并不令人满意.有效观测的考虑：观测点应位于较深的地下，以消除来自地面上方的另一种噪声，并在低电导率的地面，以较低的观测频率，以降低传播损耗。

1. Survey of references : The experimental observations of the anomalous electromagnetic emissions possibly related to earthquakes have been carried out from the years of 1970. The observation points are almost near the ground surface, and the receiving frequencies are less than several MHz. As the observed data are few as yet, these data are not entirely acceptable in general. The references of the theoretical investigations or numerical examples assuming the wave source at the deep ground were not found.2. Derivation of the approximately theoretical equations and the results of the numerical calculations : We treated this problem as the simplest model consisted of two-layred (ground and air) homogeneous media, assuming the source was located at the focus of an earthquake. Equations of the electric field intensity near the ground surface and of the strength of the source were obtained, using the geometrical optics theory. Applying the observed data by other research institution to the equations, numerical estimations were carried out. These results lead to the conclusion described later section 4.3. Experiments with the small-sized ground-air model in a room : The experiments were attempted to verify the validity of the calculations. The measurements were done in the limited space including dry sand enclosed by some radio-wave absorbers. But we observed the unsatisfied data because the reflection occured from absorber and the instability of a receiving antenna.4. Consideration for the effective observation : The observation point should be located in the deep ground to remove another noise coming from above the ground, and in the low conductivity ground at lower observation frequency for lower propagation loss.