Abstract:The application of finite element method to 2-D forward solution of magnetotelluric sounding is discussed,and the mesh dissection scheme adopted in present literatures is reviewed in this gaper. The rectangle mesh scheme makes formula easier to normalize and convenient for calculation, but it loses good adaptability to geometric shapes of interfaces. Forthermo re,because bilinear interpolation is used over rectangle elements the partial derivative of the field respect to z is only a function of y, and a constant in z direction, thus decreasing the accuracy of auxiliary field values.Proceeding from this thesis, the author adopts a combination of triangle and rectangle dissection schemes, which includes the following steps: first, on the surface and interfaces (particularly inclined snterfaces),each rectangle element is divided into two right triangles by a diagonal; second, a functional is obtained by using lagrange's quadric interpolaton formula; finally, a resultant stiffness matrix is made up of ones which consist of rectangle elements. Thus this combination not only makes a good adaptability to various interfaces but also helps to raise the field value accuracy of the fields near interfaces and the auxiliary field at ground surface. In this case, the expression of auxiliary field values is a linear function of y and z; besides, it can be expressed as a simple linear combination of functional values at interpolation points, which is very helpful to inversion.Corresponding calculating formulae are given in this paper.
引用本文:
陈乐寿, 孙必俊. 有限元法在大地电磁场二维正演中的改进[J]. 石油地球物理勘探, 1982, 17(3): 69-76.
Chen Leshou, Sun Bijun. Improvement on the application of finite element method to 2-D forward solution of magnetotelluric field. OGP, 1982, 17(3): 69-76.