MODELING OF SUBSURFACE STRUCTURE BASED ON MAGNETIC AND GRAVITY DATA IN MOUNT LAWU, KARANGANYAR REGENCY AND MAGETAN REGENCY

• Main Author: Brilliandi, Octaviano
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/81052
• Institution: Institut Teknologi Bandung

Indonesia is one of the countries that is passed by the Pacific Ring of Fire. This makes Indonesia the country with the largest geothermal potential in the world. One of the mountains that is a geothermal prospect area in Java is Mount Lawu. The mountain is located on the border of Karanganyar Regency, Central Java, and Magetan Regency, East Java. The mountain has an estimated resource of 195 MW and a hypothetical resource of 137 MW. Unfortunately, the data in previous studies has not been properly processed. In addition, the modeling performed was limited to each method. Therefore, this research aims to reconstruct magnetic and gravity observation data and model the subsurface structure related to the location of geothermal reservoirs on Mount Lawu. The methods used in this research are magnetic and gravity methods. The magnetic and gravity data used were obtained from the Integrated Geophysical Survey Team Report of Mount Lawu in 2009. Before modeling, the gravity data were first re-corrected. This correction consists of drift correction, free air correction, Bouguer correction, and terrain correction. Then, forward modeling was carried out with the help of Oasis Montaj software. In this study, the susceptibility value used has a value range of 000034 - 0.049 ????????3/????, while the density value has a value range of 1.6 - 2.82 ????/????????3. Modeling is done by making three sections with the error range of the magnetic method ranging from 11.597 - 16.712% and the gravity method ranging from 1.587 - 2.909%. From the modeling that has been done, it resulted in a subsurface structure that allign with the geological conditions. Geothermal reservoir rocks are identified in the area around Candradimuka Fumarol with a depth of 1500 m from the surface and the rock is Lava Jobolarangan 1.