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

研究结果总结如下：1。我用样条近似研究了波场变换。我特别注意了样条近似中的项数和采样间隔。经过这种变换后，伪波场的初始部分有时会出现奇特的振荡现象。这似乎是数值拉普拉斯逆变换的结果。振荡取决于近似中的采样间隔。计算了层状地球模型的瞬态垂直磁场及其伪波场。在波场中探测到直接波的时间与波理论的预期时间一致。但是，由于折射波和反射波的振幅远小于直接波的振幅，因此在预期的时间内没有清晰地检测到折射波和反射波。在大分县玉湖地区进行了实地测试调查，使用的磁通门磁强计附有四个传感器和发射机。结果表明，这种仪器对信号的检测和噪声的抑制是有效的。结果表明，在多个站点的数据中使用信号参考来抑制噪声是可行的。调查结果表明，以玉富盆地为界的玉富断裂带垂直磁场瞬态响应变化明显。

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.