The article analyzes the amplitude spectra of audio magnetotelluric sounding (AMTs) data. Particular attention is focused on the frequency range from 1 to 5 kHz, which is called dead band. We analyzed the data of base stations used in the fieldwork during the summer and autumn seasons in 2013, 2014, and 2017. The area of work is located in the Chukotka Autonomous Area beyond the Arctic Circle. Previous researchers noted that a reliable signal in the dead band can only be obtained at nighttime. The authors of the article found that in Chukotka region in the daytime against the minimum signal within the dead band there is a local maximum at a frequency of 2.4 kHz. When registering a field for more than 3 hours during daytime, in most cases, it is possible to restore the frequencies of 2.2 and 2.6 kHz. These frequencies are reliable benchmarks, allowing in some cases to restore the AMT curve using the correlation between amplitude and phase. We have proposed ways to improve data quality in the dead band when measured during the daytime.
The problem of estimating the effect of anomalous bodies situated away from the profile line occurs in magnetotelluric data interpretation, as well as in other geophysical methods. In this case using of magnetic-variation profiling (MVP) data is important. MVP method can be used together with magnetotelluric sounding (MTS) method. It is done by adding a channel for measuring a vertical magnetic component (Hz). MTS and MVP methods can be applied together due to the use of precise tripods. MTS and MVP methods together increase the possibility of es-timating the effect of anomalous bodies situated away from the profile line. The research target is to determine parameters of an anomalous conductive body situated away from and parallel to the profile line. This work shows how the depth of a 2D conductive body situated away from the station can be determined by tipper frequency responses (on condition the distance between the station and the body is specified). The step-by- step method for determining the depth of an anomalous body has been used in this work. The introduced method allows avoiding gross mis-takes in interpretation, as well as constructing a valid 3D model.
The regularities of the amplitudes and phases connections of magnitotelluric (MT) impedance tensor components for 1D, 2D and 3D geoelectrical synthetic models have been considered. The amplitude-phase correction allows to improve the quality of data processing results both for the main and for the additional impedances. It also gives a possibility to suppress biased data for noise pollution data. Recommendations on accuracy rising of determination of tensor impedance components in the MT-data processing have been defined on the base of found regularities. Examples of processing of field MT-data received on the basis of MTU equipment by «Phoenix Geophysics Ltd» (Canada) have been considered.
The regularities of the amplitudes and phases connections of MT-impedance tensor components for 2D geoelectrical synthetic models have been considered. The amplitude-phase correction (APC) allows to improve the quality of data processing results both for the main and for the additional impedances. It also gives a possibility to suppress biased data for noise pollution data. Recommendations on accuracy rising of determination of tensor impedance components in the MT-data processing have been defined on the base of found regularities.
The relation between parameters of 2D anomaly body and features of vertical sections of tipper amplitude are considered in this paper. According to investigations the depth of center, top and bottom of conductive body is connected with geometrical distance between two symmetrically located positive extremes in tipper pseudo-sections. In addition the tipper amplitude in extremes decreases on account of increasing depth of anomalous body. The described regularities can be used for MT projects planning and quantitative estimation of anomalous body parameters using tipper pseudo-section constructed from field data.
