时域航空中心回线源三维异常体的电磁响应探测分辨率

RESEARCH ON DETECTION RESOLUTION OF 3-D ANOMALY' S ATEM RESPONSE BY CENTRAL LOOP

采用时域有限差分法,计算不同埋深和电导的三维典型地质体在中心回线方式下的航空电磁响应,讨论其探测分辨率,并结合实际航空电磁探测系统的工作参数进行计算。结果表明,对于70 m×70 m×70 m的异常体,当异常体与围岩的电导比值为200时,探测深度最大范围为180 m,当合理提高接收机的前端放大倍数,可以有效提高勘探深度;当异常体埋深为135 m时,可以检测的异常体与围岩电导的比值最小为1.5。时间域航空电磁探测三维异常体的分辨率研究,对于电磁数据解释时异常体的识别、精细化处理等方面具有理论指导意义。

Airborne time-domain electromagnetic （ATEM）system has some advantages, such as high-speed, economy and deep-explo- ration depth. ATEM is one of effective methods to explore water resources and minerals. Study on the detection resolution of three - di- mensional （3-D） geological body has great importance in ATEM detection in China. The article using finite-difference time-domain method （FDTD） and Central loop mode calculates the airborne electromagnetic response of 3-D typical geologic body. We had dis- cussed the detection resolution of 3-D targets which were in different depth or electrical conductance. Combine with the reality operating parameters of ATEM system, and we calculated 3-D anomalous body of 70 m × 70 m × 70 m. Numerical calculation results indicate that, when the ratio of electrical conductance of abnormal and background is 200, the maximum range of detecting depth is 180 meters. When reasonable improve the magnification of the receiver front-end, you can effectively enhance the exploration depth. When anoma- lous body is buried 135m depth, can detect the minimum ratio of electrical conductivity of anomalous body and the surrounding rock is 1.5. Using ATEM methods to study 3-D anomalous body~ resolution has great guiding significance of the theory in recognition of anom- aly and precise processing for electromagnetic data interpretation.