Three-dimensional Magnetotelluric Inversion Effect Evaluation

The deep crust exploration, not only could uncover the secrets of the evolution ofcontinental crust, but also could effectively find the resources, disaster mitigation andenvironmental protection. The "mainland experimental study of electromagneticparameters of the standard network" project which taken by the China University ofGeosciences (Beijing) has been completed the standard array of magnetotelluric dataacquisition works in north china. A large number of the north china standard networkmagnetotelluric data is needed the appropriate inversion method. Now magetotellurictwo-dimensional inversion is already matured and widely used. Three-dimensionalinversion method has just started in recent years, however, limited by current computerhardware, processing efficiency is not high. In this thesis, several models in differenttypical and parameters will be under the three-dimensional numerical simulation, thenusing the forward data to two-dimensional and three-dimensional inversion and comparethe results, analysis the differences on the performance of different models. And discussthe impact of different parameters on the inversion results, makesure which type ofinversion fit the specific geology, in order to provide guidance to the north china andtibet magnetotelluric data processing.The thesis compares the layered media model, fault model, columnar structuremodel, low resistance coating, the typical model of the cube model and severalparameters of themodel's two inversion results, and draw a conclusion that: 1. the twokinds of inversion results of one-dimensional and two-dimensional structures is lookedthe same, but three-dimensional inversion's resolution is better than two-dimensionalinversion's. 2. Three-dimensional anomalous along the direction perpendicular to theprofile extension will greater impact on the two kinds of inversion, when the extensionlimit enough, abnormal decreases rapidly, and the false anomalies easily comes to thethree-dimensional inversion result. 3. Low-resistance covering layer will have a greaterimpact on the two kinds of inversion,the most intuitive performance is false anomalyusually appear. In two-dimension inversion, under the low-resistance covering layer there usually is a high-resistance false anomaly, and reduce its real high-resistanceanomaly. However, In three-dimension inversion, false anomaly comes to horizontalbanded. 4. On sideways measuring line, the signal of anomalous in three-dimensioninversion results is bigger than two-dimension inversion results, and the abnormal bodyboundary is more clear. 5. Processing the real magnetotelluric data, the abnormaldistribution of the two inversion results are basically the same. However, in twodimensioninversion, abnormal tend to describe the details. Besides, abnormal tend todescribe macro-regional electrical information in three-dimension inversion.