Two-dimensional Sharp Boundary Inversion Of Magnetotelluruc Data

MT (magnetotelluric) was first proposed in 1950th by scientists of Russia and France. This is a frequency domain sounding method using the natural magnetotelluric field of frequency range between 10^-4 to 10⁴ Hz. The method can be used to detect the electrical structures of the underground model according to the distribution of magnetotelluric field, which was caused by the natural source. And this method has the advantage of detecting the electrical structures of crust and upper mantle, and it is the only way besides the seismic exploration whose depth of prospecting can be so deep. MT played an important role in detecting the electrical structures of Qinghai- Tibet Plateau. And it is also used successfully in oil exploration. It can provide the distribution of electrical structures in the detection of gas, metal, and water resource and predication of ore deposit.We did some research of the sharp boundary inversion which was used in MT in this paper. The sharp boundary outlined here means sharp resistivity contrasts between layers. The sharp boundary inversion is similar to the widely used Occam method. It comes from a tenet of modern science known as Occam's razor: a simple solution is preferable to the one which is unnecessarily complicated. Like the Occam method, a Lagrange multiplier is needed as the trade-off between the data misfit and the model roughness. But it is different that we penalize variations in the boundary depths, rather than in resistivity contrasts between a large number of adjacent blocks.Based on these theories and algorithms above, I have learned the knowledge of sharp boundary inversion and Occam's inversion, revised and debugged the program of the 2-d sharp boundary inversion used in MT, which was wrote by Constable etc. and do the 2-d sharp boundary inversion and Occam's inversion of MT data of four models. I want to learn the difference between the two inversions through comparing the inversions'results.