Design And Implementation Of Two-dimensional Magnetotelluric Forward Software System

Magnetotelluric sounding method is widely used as an important geophysical exploration method in groundwater exploration, engineering exploration and other fields. It uses natural alternating electromagnetic field as source field and observes the electromagnetic field on the ground to gain the ground resistivity distribution at different depth of underground media.With the development of computer technology and the breakthrough of theory about MT, the instrument of magnetotelluric sounding data processing and interpretation experienced from "Manual Stage" to "Digital Stage," and "Visualization Stage". Forward modeling and forward computation are effective ways and means to recognize the ground electromagnetic response characteristics in the various ground conditions for us. This dissertation begins with two-dimensional screen modeling to establish a forward calculation software system of two-dimensional magnetotelluric modeling and visualization. By establishing different geological precise models and comparing forward results of different geologic-al models, the distribution of the earth under different geological conditions is concluded with electromagnetic field, which can be a positive guidance for data processing, inversion and interpretation.A two-dimensional magnetotelluric forward modeling software system framework is presented with the main function of achieving its systematic approach and analyzing response characteristics of two-dimensional model of MT method. The MT2D forward software system consists of four sub modules: data management module, two-dimensional screen modeling module, forward modeling module and mapping module. Data management module uses the database management technology instead of the traditional mode of using hierarchical directory management, which can more easily manage the data of each module, and this module provide data service for other modules of the system; The means of the traditional Geological Modeling has transferred from drawing to use test editor with computer modeling, to manually using the keyboard, mouse to visual modeling, This paper has actualized two-dimensional visual screen modeling interact with human-machine, which using the way of combine with representation of polygon and curve to achieve fault, abnormal body and other complex geological models, And providing the manner of curved quadrilateral mesh to simulate terrain and encrypted partition of the grid that can better simulate the complex geological model for the two-dimensional forward calculation to provide accurate forward model, forward screen modeling module provides accurate two-dimensional forward model; The forward procedure choose the finite element mesh within the two-dimensional quadratic interpolation algorithm, the Forward calculation of the algorithm fast, effective, high resolution; mapping module has the function for drawing maps of the complete forward calculation results .In this paper, Visual C + + 6.0 as a development tool to complete the system interface, two-dimensional screen modeling and mapping module; Using SQLite micro-database management technology to achieve data management module; Using FORTRAN language to program the procedure of forward algorithm of a finite element grid quadratic interpolation; And achieve the two-dimensional modeling of the relevant details of the forward calculation in using VC++ language and FORTRAN language mixed-programmed technology, which increasing the flexibility of the system development and improving the efficiency of the system. A visualization system based on Windows MT2D forward software system has been developed, the interface of system is friendly, and is easy to operate; the comparison of the result of the same model with the previous confirms the system is correct. This system has greater value in use.