ANALYSIS OF GRAVITY AND MAGNETIC ANOMALY RESPONSES FOR GEOTHERMAL POTENTIAL ESTIMATION IN THE SOUTHERN PART OF SUMATRA ISLAND

• Main Author: Prasetyo, Irfan
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/83099
• Institution: Institut Teknologi Bandung

Sumatra Island was formed through a complex tectonic process that resulted in various geological resources, including geothermal potential. Research involving the analysis of gravity and magnetic anomaly responses has been conducted to map the geothermal system in southern Sumatra. Gravity anomaly separation was performed using the moving average method, followed by gradient analysis on the residual anomaly using the Fast Sigmoid-Based Edge Detection (FSED) method. The reduced to pole (RTP) magnetic anomaly was analyzed spectrally to calculate the Curie Point Depth (CPD), thermal gradient, and heat flow. The results of this study indicate that the heat source on Sumatra Island consists of volcanic intrusive rocks with a density of 2.8 gr/cc and a susceptibility value of 0.007, extending from the west to the south in a northwest-southeast pattern. These rocks are part of the Kikim formation (Tpok) from the remnants of Bukit Besar, Bukit Lumut, and Bukit Balai volcanoes, at a depth of more than 7 km. The reservoir layer in the central part is likely caused by the Sumatra Fault Zone or sedimentary rocks, composed of the Hulusimpang and Gumai Formations, with a density of 2.6 gr/cm³ and susceptibility of 0.075, at a depth of 1000-1500 m. The thermal gradient ranges from 21.1°C/km to 31.6°C/km, with heat flow between 55.1-79 mW/m². High thermal gradients are observed beneath volcanic complexes, including the Bukit Barisan Mountain Range area. The northwest-southeast fault structure aligns with the Sumatra Fault (SGF), indicating that the geothermal system on Sumatra Island is controlled by this fault.