ANALYSIS OF SUBSURFACE STRUCTURE USING MODELING RESULTS FROM GEOMAGNETIC AND GRAVITATIONAL DATA IN BRATAN CALDERA, BALI

• Main Author: Syah Al Basyarah, Wisandie
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76851
• Institution: Institut Teknologi Bandung

Indonesia is one of the countries traversed by the ring of fire, which makes the existence of volcanic activity in this country possible. The island of Bali is one proof of this activity. Bratan caldera is one of the calderas on the island of Bali that was formed due to a strong eruption by the ancient Mount Bratan. The caldera, which has an area of about 11x6 km, has several volcanic lakes (Lake Bratan, Buyan, and Tamblingan) and there are several stratovolcanoes (Mount Tapak, Lesong, Pohen, Adeng, and Sengayang and Catur). This caldera still has a magma chamber located under the areas of Mount Lesong, Pohen, and Sengayang. The existence of magma chamber is also reinforced by the presence of geothermal manifestations. The manifestation is in the form of the emergence of warm springs in the areas of Angseri, Belulang, and Penatahan. The Bratan Caldera magma chamber can be known through subsurface models obtained from the processing of total magnetic anomaly and complete Bouger anomaly. From the three models of subsurface structures made, the presence of magma chambercan be determined at 3–7 km below the surface of the Bratan Caldera. The intrusion of the magma chamber did not reach the surface because it was blocked by the Buyan-Bratan and Batur volcanic rock layers (Qpbb) whose age is relatively younger than the Southern Formation layer (Tmps) and Magma. The magma chamber can be used as a heat source because of the geothermal potential in the area.