Reservoir Magnetic Anomaly at Geothermal Area of Mount Pandan, East Java, Indonesia

The magnetic method has been applied to identify the geothermal reservoir in the mount Pandan East Java, Indonesia. The magnetic survey was performed using PPM G-856 and measured on 80 magnetic stations that cover an area of 9 x 10 km². The magnetic stations cover two hot springs, Jari and Banyukuning in the mount Pandan. The magnetic data were processed by 2D and 3D data modeling. The results showed that total magnetic intensity ranged from -446.7 nT to 526.3 nT. The residual anomaly of contour map revealed that geothermal reservoir was suspected in an area with the low magnetic intensity value around the hot spring and identified as the volcanic breccia and tuffaceous sandstone. The tentative model from magnetic residual anomaly can show location, depth, and the thickness of the geothermal reservoir. The flow pattern the reservoir to manifestation, show the alleged presence of a secondary structure. This indicates that Jari and Banyukuning manifestation have different reservoirs