2-DIMENSIONAL MAGNETOTELLURIC INVERSION MODELING USING FINITE ELEMENT METHOD WITH UNSTRUCTURED TRIANGULAR MESH

• Main Author: Herman, Sofiana
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76159
• Institution: Institut Teknologi Bandung

The Magnetotellurik (MT) method is a geophysical method that utilizes the properties of natural electromagnetics fields and telluric currents which are the results of induction from electromagnetic fields. Telluric currents are used to induce material below the earth's surface so that information is obtained about the resistivity structure below the earth's surface. The model response is in the form of apparent resistivity and phase impedance on the surface as a function of frequency. The model response is obtained by solving Maxwell's equations. This makes the magnetotelluric method effective in imaging the subsurface medium which has a different resistivity from the surrounding environment. The numerical method used in solving partial separation equations is the Finite Element Method. Modeling of the two-dimensional magnetotelluric resistivity structure was carried out using the node-based finite element method. In this study forward modeling and magnetotelluric inversion are applied to the transverse electric mode (TE Mode) and the transverse magnetic mode (TM Mode). Inversion modeling uses the GaussNewton Algorithm which is used to minimize the linearized objective function. The program that has been created is validated using the standard two-dimensional model COMMEMI 2D-0 and COMEMMI 2D-1 (Zhdanov, 1997). The inversion program was tested on several synthetic models with different resistivity structures. Then the program was applied to the MT data of Lembang Fault structure. The results obtained from this modeling are two-dimensional resistivity structure models and responses in the form of apparent resistivity values and phase impedance at the surface of homogeneous earth models, layered earth, vertical contact earth, anomalous earth and topographic models with inversion modeling results obtained showing that there is a match with the initial model with variations in RMS values < 2. The inversion program is also applied to field data of the Lembang fault structure with the results of RMS values < 2