Incorporating Geological Dip Information Into Magnetotelluric Two-dimensional Inversion

The magnetotelluric method is an efficient method of geophysical exploration.After years of development, the theoretical system of the method has been improved gradually, and the new mathematical calculation method has been introduced.Therefore, the application of the magnetotelluric method is more and more extensive.At present, the magnetotelluric method has an important role in oil and gas exploration, geothermal resources exploration and metal mineral exploration. It is proved that this method is an indispensable method of geophysical exploration, and it is necessary to study it more deeply.The objective function of the magnetotelluric method consists of the data fitting term and the model constraint term, where the data fitting term makes the difference between the response of the inversion results and the forward response of the theoretical model within an acceptable range, the model constraint term controls the smooth of the model. In addition, this item can also change the anomalous form in the inversion result, it's flexible, you can add a priori information in it. This paper mainly introduces the idea of introducing the inclination information and interface information by modifying the model constraint term, and make full use of it reach the purpose of improving the inversion results.Geological bodies generally have clear directions or inclination information, and it is necessary to establish a new objective function to add this information to the electromagnetic method inversion. Rotate the horizontal and vertical derivatives with a rotation matrix so that its derivative direction can be changed arbitrarily. This rotation matrix is substituted into the model constraint term to create a new objective function, so that the new objective function can be in the direction of the structure or inclination direction to play the role of stretching. In this paper, the method is discussed in the case of two-dimensional magnetotelluric method, and the theoretical model and the measured data are validated. The validity of the new method is proved by comparing the new method and the general method.In the geophysical exploration method, seismic exploration is more sensitive to the interface information, and the underground interface information can be divided by reflected waves. In this paper,we propose a new objective function to introduce the interface information into the electromagnetic method inversion. We use the method of adding the cross-gradient term to invert the region and modify the laplacian operator to control the boundary derivative. The objective function can be more accurately divided into the stratigraphic interface. In the case of two-dimensional magnetotelluric method, the theoretical model and the measured data are respectively validated by the improved algorithm to prove the correctness of the method.The introduction of inclination information and interface information has achieved good results. It shows that the introduction of a priori information in the inversion is very important. By introducing the a priori information, we can reduce the inversion of multi-solution and improve the inversion result.