INTERPRETATION OF GEOTHERMAL SYSTEM IN DOLOK MARAWA, SIMALUNGUN DISTRICT, NORTH SUMATERA USING MAGNETOTELLURIC DATA

• Main Author: Dwi Utami, Zullinira
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/52007
• Institution: Institut Teknologi Bandung

The Magnetotelluric (MT) method is a geophysical method that is widely used for geothermal exploration because it has a deep penetration of up to hundreds of kilometres. The MT method can describe a 2Dimensional (2D) geothermal system by utilizing the relationship between the magnetic field and the electric field which produces a model in the form of resistivity to depth. The MT method is applied to the Dolok Marawa area by using 43 sound points. This method is used to determine the resistivity structure beneath the earth's surface and interpret the geothermal system in the region. In this study, the quality of MT data has been improved by rotating the data as well as static correction using co-kriging. The results showed that the geoelectric strike was NW-SE (northwest southeast). The 2D MT modelling results in the Dolok Marawa area show a thin layer with a resistivity of 10-100 ohm.m near the surface. In the next layer, there is a conductive layer with a small resistivity value of 10 ohm.m which is interpreted as a clay cap. In the lower layer, there is a layer with a resistivity of 10-100 ohm.m which is interpreted by the reservoir zone. In the next layer, there is a resistive zone with a large resistivity of 100 ohm.m which is interpreted to be associated with limestone rock and the heat source of the Mount Bahtopu area. The heat source in the Dolok Marawa area is indicated by andesite intrusion. There is a low resistivity zone that is not continuous in the study area which is indicated to be related to the geological structure which is the way for the emergence of the geothermal system manifestations.