水域MT勘探电磁信号分离采集的视电阻率计算

Computation of apparent resistivity for separately acquired electromagnetic signals in MT exploration of water domain

在水域进行大地电磁测深勘探中,因接收磁信号的探头难以在水底精确布设,只能布设在岸上,因而必须电、磁信号分离采集,这势必导致接收的电、磁信号不在同一界面上,由此计算出的视电阻率和阻抗相位需要进行校正。本文通过层状介质不同界面上电磁场及阻抗间的关系,推导出了将实测资料改正到水面或水底的视电阻率和阻抗相位的计算公式。经理论模型试验和实测资料应用,证实所述改正方法的正确性。

When carrying out the magnetotelluric sounding exploration in water domain, because the accurate deployment of probes on water bottom for receiving magnetic signal is difficult,but only on land, therefore, the electromagnetic signals should be separately acquired, which leads received electronic and magnetic signals to be unable to be at same interface and correction of computed apparent resistivity and impedance phase should be carried out. Through the relationship between electromagnetic field and impedance on different interfaces of layered media, the paper deduced the computation formula correcting the real-surveyed data to be apparent resistivity and impedance on water surface or bottom. The tests of theoretical models and application of real data showed the correctness of the corrected approach.