Remote reference magnetotelluric impedance calculation method based on correlation detection

Abstract

The invention discloses a remote reference magnetotelluric impedance calculation method based on correlation detection, and belongs to the field of geophysical exploration, for overcoming the disadvantage of low accuracy of conventional magnetotelluric tensor impedance calculation. The method comprises the following steps: electric fields and magnetic fields of a base station and a reference station are respectively acquired, processed and obtained, electromagnetic field coherence degrees of the base station and the reference station are respectively calculated, when the two electromagnetic field coherence degrees are greater than a certain threshold, data segments are reserved and marked, and data segments, free from non-relevant noise interference, of the base station and the reference station are obtained; and then, magnetic field component coherence degrees of the base station and the reference station with the marked data segments are calculated, when the magnetic field component coherence degrees are greater than a certain threshold, data segments, free from noise interference, of these magnetic fields are reserved, otherwise, the data segments are abandoned, participation in subsequent tensor impedance estimation is canceled, tensor impedance estimation is carried out by use of a conventional remote reference magnetotelluric mode based on a Robust method, and apparent resistivity and impedance phase values are calculated by use of tensor estimated values. The method provided by the invention is applied to magnetotelluric exploration.

Description

technical field [0001] The invention belongs to the field of geophysical exploration, and in particular relates to a far reference magnetotelluric impedance calculation method based on correlation detection. Background technique [0002] Magnetotelluric sounding (MT) is to observe the naturally changing and mutually perpendicular electromagnetic field components at one or more points on the ground at the same time to detect the electrical structure inside the earth. Because of its advantages of simple field construction and large detection depth, this method has been widely used in the study of deep geological structures, mineral exploration, oil and gas exploration, etc. However, when measuring magnetotelluric data, it is often disturbed by noise, and the noise sources mainly include the following aspects: (1) Field source noise. This type of noise includes the Schumann resonance and solar wind generated by lightning phenomena. When the Schumann resonance or lightning acti...

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(2) Geological noise

However, the above results are based on the assumption that the reference station is not affected by noise, or the interference is not related to the noise of the base station. However, due to the development of industrial society, electromagnetic interference is becoming more and more serious, and the reference station is generally subject to stronger noise. At this time, if the conventional far reference processing is used, not only the correct sounding curve cannot be obtained, but the "flying spots" will increase; although the conventional far reference can choose to use the magnetic track or the circuit for far reference comparison processing, due to the electromagnetic Interference generally does not exist in the circuit or magnetic track alone, so even if the circuit and magnetic track are used for processing, the correct sounding curve cannot be obtained in many cases; existing studies have shown that even if the noise interference suffered by the remote reference station is not the same as the noise of the base station However, when the interference of the reference station or the base station is extremely strong, a more continuous sounding curve cannot be obtained by using the conventional far reference

Using the existing method will still lead to many "flying points" in the bathymetry curve, which will seriously distort and affect the accuracy of impedance estimation. In addition, this deeply distorted bathymetry curve will bring difficulties to subsequent data inversion and geological interpretation, and even The wrong electrical structure model will be obtained, which directly affects the exploration effect of the magnetotelluric sounding method

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