Volcanic Hazard Implication Based on Magnetic Signatures Study of Seulawah Agam Geothermal System, Indonesia

Geothermal is a natural phenomenon of the Earth. Magma flows from earth crust through thinned and fractured area as lava while trapped magma heats underground rocks and groundwater. Crustal rocks lose their magnetization at the Curie point temperature. Geothermal region is characterized as high temperature gradient with heat flow and the region will be associated with Curie point isotherm. Almost all volcanic rocks are magnetic because they contain small amounts of primary magnetic minerals. Ground magnetic study was conducted at Seulawah Agam (Aceh, Indonesia) and its vicinity where the flow of the geothermal is suspected from south-east to north-west from Seulawah Agam. Ground magnetic data was acquired in line mode consisting of few stations crossing the suspected geothermal flow using GEM-GSM19T system with 30-50 m station spacing and ∼500 m line spacing. Magnetic residual shows the value of 0-110 nT interpreted as hot water, flowing from west to east and south to north while the value of ˃170 nT interpreted as hot mud/fumaroles flowing from north to south. This study shows that magnetic residual of hot water and hot mud/fumaroles generally decreases with depth.