长距离远参考大地电磁测深试验研究

Study for long-distant and far-referential MT

远参考大地电磁测深法（MT）能明显地改善常规MT观测资料的质量,已见报道的远参考MT的参考点设在距离常规MT观测点4.8km处。短距离的远参考不便于进行大面积的MT勘探。为了了解长距离远参考MT方法的可行性,文中利用V5-2000仪器系统进行了一次长距离远参考试验;同时还进行了距离仅2km的近参考和距离达1000km的长距离远参考观测,并分别利用近距离和远距离参考资料对常规MT测点资料进行了参考处理。 处理结果表明,长距离远参考能有效地压制常规MT观测点的局部噪声。利用近距离和长距离参考点的磁场对常规MT测点进行远参考处理获得的视电阻率资料一致性很好,说明了远参考点可以设置在相当大的区域范围内,而且与纬度差没有关系。因此在进行大面积勘探或在利用近距离参考无法压制区域性噪声时,可将参考点设在1000km之外。

Far-referential MT can obviously improve the quality of ordinary MT surveying data. The reference points of reported far-referential MT are located at a distance 4. 8 km from ordinary MT survey points. The short-distant,far-reference is unsuitable for MT survey in a large area. In order to clarify the feasibility of long-distant and far-referential MT method,there is a long distance and far-referential test by using V5-2000 apparatus system in the paper. The surveys which near-referential distance is only 2.0km and far-referential distance is 1000 km are carried out at the same time. The referential processing of ordinary MT data is carried out separately by near-distant and far-distant reference data.The processing results show that the long-distant and far-referential MT method has same role as short-distant and far-referential MT method that can effectively suppress local noise produced in ordinary MT survey points. The apparent resistivity data received from far-referential processing of ordinary MT surveying data separately by using magnetic field of short-distant reference points and long-distant reference points are almost same,which shows the reference points can be located at fair-sized area and no relation with latitude difference,so that the reference points can be located at 1000km and beyond when large-areal prospecting is carried out or it can't suppress regional noise by short-distant reference.