Simulation of 3-D Effect in Magnetotelluric (MT) Data and Its Influence on Inversion Modeling

Magnetotelluric (MT) data can be affected by 3-D effect especially in geothermal area which has a complex geological condition. This phenomena is caused by complex lateral variation of subsurface resistivity structure. It has been learned by simulation using 3-D MT forward modeling. Several resistivity model were built as representation of 1-D, 2-D, and 3-D earth model. In 1-D earth model, resistivity varies only with depth. In case of 2- D earth, resistivity changes with depth and in one horizontal direction. For 3-D earth model, resistivity is varies in all direction. MT response, represented by apparent resistivity & phase curve in frequency domain was then calculated & analyzed in every station for each model. The MT response from each model clearly shows the effect to the MT data. Moreover, the research was continued to learn the influence of 3-D effect in MT inversion modeling. All of MT inversion algorithm was developed under certain assumption. Dimensionality of the model is the most important assumption that must be considered. 1-D, 2-D, and 3-D inversion were then applied to all MT data whichis derived from MT forward modeling. The inversion result show that 3-D approach give more reliable model and can be overcome the 3-D effect. Accordingly, MT data in complex geological structure like in geothermal area should be approached by 3-D inversion.