BZ参数瞬变电磁法的优势及在沿海滩涂区的验证试验

Superiority of BZ-based transient electromagnetic method and verification test in coastal tidal regions

随着我国一系列发展战略的实施,在沿海滩涂区等低阻环境下开展电磁法深部探测工作的需求越发迫切.传统瞬变电磁法(TEM)一般观测感应电动势(dBz/dt)参数,其响应函数复杂,数据解译难度大,且衰减极快,勘探深度较小,不能满足深部探测的需求.而瞬变电磁法的感应磁场(Bz)参数具有响应函数单调、衰减速度慢等优点,深部探测应用前景广阔.本文首先从理论上讨论了TEM的Bz参数相比dBz/dt参数在响应曲线形态、探测深度等方面的优越性,然后在某沿海滩涂区开展了野外验证工作.理论分析计算和野外试验结果表明,TEM的Bz参数相较于dBz/dt参数有诸多优势,基于Bz参数的瞬变电磁法在滩涂区的极低阻条件下仍具有较强的分层能力、较大的探测深度和较强的适用性.

With the implementation of national development strategies,it is urgent to carry out electromagnetic prospecting work in particular areas such as the coastal tidal regions to take rather depth.The traditional Transient Electromagnetic Method(TEM)using induced electromotive force(dBz/dt)parameter has complex response functions and a rapid decay,which limit its detection depth and easily leads to distortions of the interpretation profile.However,the TEM induced magnetic field(Bz)parameter has monotonic response functions and a much slower decay,which give it a good application prospects of deep exploration.In this paper,the theoretical advantages of TEM Bz parameter over dBz/dt parameter are discussed firstly,and experimental TEM work using Bz parameters is arranged in the tidal regions.Theoretical analysis,calculation and experimental results show that the Bz parameter have many advantages compared with dBz/dt parameter.Even under extremely low resistance conditions in the tidal region,the TEM using Bz parameter has still stronger layered ability,larger detection depth and a high efficiency.