半航空瞬变电磁探测能力及影响因素研究

半航空瞬变电磁法通过在地面布设发射源，在空中使用无人机搭载接收线圈获取二次场信号实现对地下结构的探测，然而在实际应用过程中其探测能力会受到接收高度、水平偏移距等因素的影响。针对这一问题，开展半航空瞬变电磁响应空间分布特征研究。首先通过均匀大地模型和层状大地模型的正演计算，采用控制变量的方法分析不同因素对半航空瞬变电磁响应的影响；其次通过含异常体模型的正演计算，分析异常体埋深、电阻率等参数等对半航空瞬变电磁勘探地下目标体能力的影响。研究结果表明：接收高度和水平偏移距对半航空瞬变电磁响应的影响主要集中在早期，随着接收高度或者水平偏移距的增加，早期垂直感应电动势幅值逐渐降低，且回线源外响应出现极性反转现象；半航空瞬变电磁响应曲线在不同电阻率地层中表现出不同的衰减速率，这表明其对地层电阻率变化有着较好的识别作用；半航空瞬变电磁响应曲线中可以体现出地下目标体的埋深及电阻率变化，证明了半航空瞬变电磁对不同异常体的分辨能力。

Research on the response of semi-airborne transient electromagnetic

The semi-airborne transient electromagnetic realizes the detection of underground structures by arranging loop source on the ground and using UAV equipped with receiving coils to get signals. However, the response will be affected by the flight height and reception offset in the actual application. Aiming at this problem, the research on the spatial distribution of semi-airborne transient electromagnetic response is carried out. Firstly, the influence of different factors on the electromagnetic response is analyzed by using the method of control variables with the forward calculation of the uniform earth model and the layered earth model; Secondly, through the forward calculation of the model with abnormal body, the influence of parameters such as the buried depth and resistivity of the abnormal body on the ability of the semi-airborne transient electromagnetic exploration underground target body is analyzed. The results show that the effects of flight height and offset on the semi-airborne transient electromagnetic response are mainly concentrated in the early stage. With the increase of the flight height or the offset, the amplitude of the early vertical induced electromotive force gradually decreases, and the polarity reversal phenomenon occurs in the external response of the loop source. The response curve shows different decay rates in different resistivity formations, which indicates that it has a good identification effect on the formation resistivity change. The response curve can reflect the buried depth and resistivity of underground target body, which proves the ability of semi-airborne transient electromagnetic to distinguish different objects.