On the study of high resolution electromagnetic prospecting using the wave field transfomation

本文的研究成果总结如下：1.研究了基于样条法的波场变换。特别注意了样条法中的项数和采样间隔。这种变换后，伪波场的初始部分有时会出现一种奇特的振荡。这似乎是数值反拉普拉斯变换的结果。振荡取决于近似中的采样间隔。计算了分层地球模型的瞬变垂直磁场及其伪波场。根据波动理论，在波浪场中检测到了直达波。但是，由于折射波和反射波的幅度远小于直达波，所以在预期的时间内没有检测到清晰的折射波和反射波。使用带有4个传感器的磁通门磁力仪和赠款购买的变送器在大分县育惠地区进行了野外试验调查。结果表明，该仪器对信号的检测和噪声抑制是有效的。结果表明，利用多个站点的数据中的信号参考进行噪声抑制的可能性。测量结果表明，在以玉符盆地为界的玉符断裂上，垂直磁场的瞬变响应变化明显。

The summary of results of the study is as follows ;1. I have studied the wave field transfomation with the spline approximation. I specially paid attention to number of terms and sampling interval in the spline approximation. A peculiar oscillation was sometimes appeared in initial part of the pseudo wave field after this transformation. It seems this was result in the numerical inverse Laplace transformation. The oscillation depends on the sampling interval in the approximation.2. I have computed transient vertical magnetic field for layred earth model and its pseudo wave field. The direct wave was detected in the wave field at the time expected from the wave theory. But, the refractive and reflective waves were not clearly detected at expected time because amplitude of these waves are much less than that of direct wave.3. A field test survey was carried out at Yuhuin area, Oita prefecture using the flux gate magnetometer attached with four sensors and the transmitter purchased by the grant. It was clear that this type of instrument was effective to detect the signal and reject of noise. The result was suggested that possibility of noise rejection using signal reference among the data at several sites. The result of survey showed that transient response of vertical magnetic field varied clearly at the Yufuin fault bounded by the Yufuin basin.