浅层瞬变电磁法中全程瞬变场的畸变研究  

Analysis of distortion in all-time transient electromagnetic filed based on inducing of ramp switch-off current for shallow survey

作　　者：嵇艳鞠[1] 林君[1] 王忠[1] 于生宝[1] 王静[1] 

机构地区：[1]吉林大学地球信息探测仪器教育部重点实验室,吉林长春130026

出　　处：《电波科学学报》2007年第2期316-320,共5页Chinese Journal of Radio Science

基　　金：国家高科技发展计划(2002AA615030);国家自然科学基金项目资助(400127003)

摘　　要：浅层瞬变电磁法中,由于发射线圈为感性负载,实际激励信号是斜阶跃波,采用常规的后沿校正方法,探测时近地表仍然存在盲区,直接影响浅层探测的精度和分辨率。针对这一问题,研究了全程瞬变电磁场与斜阶跃波的关断时间与接收探头频率特性之间的关系,揭示了早期瞬变电磁场信号发生畸变和影响浅层瞬变电磁探测的根本原因,提出了当瞬变电磁测量系统在电流关断开始时刻记录全程瞬变响应和发射电流波形时,并且接收探头的位置和谐振频率已知,就可以通过数值计算方法从根本上剔除接收探头对早期瞬变信号的影响,从而实现浅层近地表探测,缩短探测盲区。通过对浙江舟山连岛工程的野外勘探数据进行数值剔除,验证算法的有效性。Since inductive load transient electromagnetic method for shallow survey adopts ramp switch-off current as inducing source, a blind zone near ground surface will exist even though the ramp correcting method is used, and will result in low resolution and precision for shallow detection. The relationship among ramp time of switch-off current, resonance frequency of receiver device and all-time transient e- lectromagnetic filed was analyzed and the essential reason causing the distortion in early period of transient signal was presented. The effect of distortion in shallow survey was analyzed. If the total process of transient response and the waveform of switch-off current are recorded at the beginning of transmitter switch-off, and the position and resonance frequency of receiver sensor are known, the effect of distortion in early period of transient process can be numerical removed. The validity of this algorithm has been proven in Zhoushan field work.

关 键 词：浅层探测 斜阶跃波 探测盲区 接收探头 二次瞬变电磁场 数值剔除 

分 类 号：P631[天文地球—地质矿产勘探]