The Study Of 2D MT Forward And Inversion Interactive Interpretation System

For two-dimensional MT forward and inversion procedure not only cockamamie in the editing of geological model, such as manually edit the grid and give the resistivity of underground geological model and so on, but also is due to the model editing and the results of forward and inversion show in different systems, so we would be expend correspondingly longer cycle to get the results of forward and inversion, That would be serious impact the efficiency of the interpretation.In this paper, through research two-dimensional forward and inversion of MT and two-dimensional model of the image editing techniques ,to use the VB and Fortran mixed programming technique developed the two-dimensional MT interpretation system based on OCCAM inversion, provided the prior model parameters to reduce the multiple solutions of the inversion results. Speed up the efficiency of the interpretation.Two-dimensional MT forward imitated by using simplified Maxwell equations export two wave equations, that is, Helmholtz equation. Using Finite element method to solve this equation, First, differential equations and boundary conditions will be transformed into functional extremum problem, then gridded the solving regional and using the linear interpolation method to indicate the value in functional by node value, take a very small value on the nodes of the system of linear equations, solving the linear equations obtained the value of each node, and then calculate the value of auxiliary field, which has been lucania resistivity.In this paper, written in Fortran geoelectric model of the two-dimensional magnetotelluric forward OCCAM inversion process and procedures, and compile dynamic link library for use VB language to explain the design of interactive interaction system interface, by calling the dynamic link library to VB and Fortran language combination. In the dynamic library calls to use the disk version of transmission, a parameter to overcome the shortcomings of red tape, reducing the demand for memory, saving system resources. Fortran procedures for calculation of input and output all the way to adopt the text, graphical interface from VB to provide the input parameters, also stored in the text, read for the forward calculation, the end results of the calculation stored in the text, by VB read the results in the form of image rendering display.OCCAM principle method is to find structure in the sense of the minimum possible consistent with the data model, a model defines the roughness, in order to suppress data from non-model construction, model of the roughness must be minimized. Method is characterized by OCCAM at each iteration in the parameterλ, not only as a step size control parameter, but also as a smoothing parameter. At each iteration of the single variableλsearch to find the smallest difference data fitting the model, as the next iteration of the model, poor fitting until it reaches the level of expectations. OCCAM law for the use of finite element forward modeling, with an increase in the scale model, the matrix inversion will occupy most of the time, and increase the frequency of measurement than increasing the number of points on the inversion of time a greater impact, but to increase their forward little impact on computing time. OCCAM law and the use of Cholesky decomposition of positive definite symmetric matrix in the inversion, it is not the fastest speed, but very stable.Inversion method by comparing the RRI, OCCAM inversion approach requires that the input parameters small, high efficiency, high precision, stability and inversion algorithm staff do not ask for much and so on. From the calculation speed and convergence of circumstances, the appropriate limit of the model can achieve better results. OCCAM simulation in the pursuit of the original measurement data and fitting curve of the largest at the same time, the most requested model data or the most sleek smooth and stable convergence can be achieved. Results from the inversion, OCCAM inversion to better reflect the bodies of the underground geological features of electricity distribution, in order to explain the results to provide more reliable reference information, is a better tool to explain the inversion.In the Interactive Interaction system development processing, the solution including the dynamic library calls, coordinate transformation technology, mesh generation technology, the graphical model display and editing techniques, the results of the mapping curve, etc.. The realization of the model zoom, pan, a single unit and regional resistivity assignment functions. VB procedure of the functional definition of the subroutine, when necessary to call these routines to increase the utilization rate of the code at the same time enhancing the capacity of the secondary development of the system. Interactive interaction system is mainly explained by the menu bar, toolbar, model and curve areas, tab, select the color box with the resistivity value of these parts. The system functions mainly through the operation to achieve the mouse, the menu bar and toolbars to provide conversion between the various functions as well as the model to open and save. The system functions mainly through the mouse operation to achieve, to the various functions in mouse operation, determine the need to address the issue of function, various functions of the code used to that in operation when the mouse to determine the function of the need to implement the code, so to solve a variety of functions to achieve through the mouse problem.To use interpretation system editing the model is valid, simple and quick, solve the problem that manual input would be cumbersome and error-prone shortcomings, when the model was changed, the corresponding c calculated results will be displayed real-time, so the data processing cycle was shorten, improve the work efficiency. In the system different colors shows different resistivity , editing the model could choose the depth and horizontal position corresponds to a single unit, you can select multiple unit volume editor, intuitive to understand, and convenient. Model can pan and zoom, the overall resistivity of the model distribution and the local resistivity can edit the details, the scaling curve can make the overall curve shape and the local details can be a good show. Another advantage of this system is that the second development ability, are independent of each functional module, as long as other means to provide positive and added new inversion method to the system.