A magnetotelluric multi-scale and multi-period exploration method

The magnetotelluric method (MT) realizes according to the principle that electromagnetic waves of different frequencies have different skin depths in the earth medium. The attenuation of electromagnetic waves has the same effect not only along the depth direction, but also in the horizontal lateral direction, which causes the volume effect in MT method. The resolution decreases sharply with the increase of depth. For low frequency range, the too dense observation sites have no benefits on improving the resolution and strengthening detection constraints. During field observation, with the increase of data period, both the cost of acquisition time and field construction increase exponentially and greatly. Therefore, it is more economical to use the distribution of different density observation sites to constrain the depth structure separately. In this paper, a magnetotelluric multi-scale and multi-period exploration method is proposed. Among the method, observation sites are divided into groups with different density according to the detection depth. To the sites in the small spacing group, a short observation time is designed getting the data in high frequency range, while for the sites in the large spacing groups, a long observation time is used for the low frequency data. Through the test of synthetic and real data, a equivalent detection result can be obtained under the new method with much lesser observation time totally compared to traditional observation method. This paper expounds the principle and implementation steps of the multiscale and multi-period exploration method in detail. Meanwhile, the validity of the method is verified by the inversion of 2D and 3D synthetic data and real data.