Nonlinear Conjugate Gradients Algorithm For 2-D Seafloor Magnetotelluric Inversion

Expatiate the character of magnetotelluric(MT) and analyzing the source, this Master’s thesis discuss both the numerical feature of land MT and the seafloor one.From the Maxwell’s functions and the basic of algorithm of forwarding in land which uses finite-differences method, we derivate the forwarding algorithm of seafloor using finite-differences method, afterwards, complete the forwarding program in FORTRAN, and verificate the correctness of it. Therefore, from the basic of 2-D inversion of magnetotelluric in land, we study the thesis of seafloor inversion of MT. We deduce the nonlinear conjugate gradients algorithm of seafloor MT inversion on the basic of Rodi(2001), and improve the program to achieve seafloor condition. And verificate the correctness of the program.For studying the possibility of tipper inversion, study tipper forwarding algorithm using finite-differences method, and make the forwarding program, and verificate the correctness of it. On the basic of the function of tipper, we deduce the Jacobian matrix of tipper, and the calculation method of the product of Jacobian matrix and other vector without computing Jacobian matrix.We get some conclusions from the study of forwarding and inversion of MT(land & seafloor). 1.The result of TP forwarding has the same characters with TE mode, and it can reflect the boundary of abnormal areas accurately.2.Because of the impaction of the sea, the forwarding of the same geological condition with sea or not is different, and the difference is relative with the depth of the sea. 3.In TE mode, the sea intense the forwarding difference of abnormal of high apparent resistivity and low one. In TM mode, the sea decrease the forwarding difference of abnormal of high apparent resistivity and low one. In the inversion part, we get the same result as forwarding. And there is some proliferation phenomenon on the result of inversion.