TEM中心回线中—远带响应特征

近20年来,中心回线观测已进入全域时段,然而有关中—远带响应特征的文章极为少见,致使用户困惑,比如晚延时响应值大于早延时响应值(ε-上凸)、在同一测点2种仪器系统观测结果相差太大等。对此笔者做了详细分析。结果表明,中—远带响应特征基本为4种,ε-上凸只是其中之一,导致所测响应出现差别的主要原因是接收线圈延时。因此,若工作于中—远带,必须确切测定线圈延时,合理选择发射回线边长。

AN ANALYSIS OF THE RESPONSE CHARACTERISTICS OF THE MEDIUM-DISTAL ZONE OF TEM CENTRAL LOOP

Central loop measurement has covered the full zone in the past 20 years. Nevertheless, articles dealing with response features of the medium-distal zone are very insufficient, which has caused perplexity among the users, for example, the late delay response value is larger than the early delay response value (ε-overshoot);the results observed by two sorts of instruments are considerably different from each other at the same measuring point. These problems have been analyzed in detail in this paper, and the results show that there basically exist four basic response features in the medium-distal zone, and the "ε-overshoot" is only one of them. The intensity distortional response is caused by the receiver coil delay. Therefore, the coil character should be exactly known and the transmitter loop length should be carefully selected before the performance of the survey in the field.