Geomagnetic Data Analysis to Identify Subsurface Condition of Gondang Area, Bojonegoro

The presence of manifestation in the Gondang indicates a specific geological condition. Those manifestations are Banyu Kuning Hot Spring, Selo Gajah Hot Spring, and Jari Mud Burst. The purpose of this study, which was carried out near Mount Pandan, was to identify the distribution of magnetic fields and magnetic anomalies, including the patterns of potential geothermal energy distribution in the region based on its magnetism. It also aimed to explain the rock structure in the manifestation area based on susceptibility values. The survey was conducted using 94 measuring points that were randomly distributed throughout the manifestation area. The data was corrected using IGRF and diurnal correction, and it was examined using Surfer 11 to construct a contour map and Oasis Montaj to visualize 3D models. According to the processed data, the residual anomaly's value ranges from -232.1 nT until 159.4 nT. For the anomaly of residual, 2D and 3D models demonstrated low susceptibility dissemination values ranging from -0.029 until -0.0135 cgs on the manifestation zone. The high susceptibility value, which is considered an intrusion rock, has a value range of 0.011 to 0.046 cgs.