3-D inversion of gravity data to determine the Tulehu geothermal prospect zone, Maluku

The Gravity method is a geophysical method that is widely used for geothermal exploration. The use of gravity data is commonly limited to interpretation of geological structure using 2-D modeling. In this study, 3-D inversion of gravity data conducted to improve 3-D conceptual model of geothermal system. This method was applied in Tulehu geothermal prospect area, which is located in Maluku Province. In 2019, gravity survey was conducted for geothermal exploration in Tulehu by gridding measurement of 130 stations with 500 m spacing. The geological condition of the area is dominated by quaternary volcanic rocks, limestone, alluvial, and metamorphic rocks. The result of CBA and residual gravity indicate the existence of medium gravity anomaly at the Mt. Eriwakang, the high gravity anomalies are found around several structures obtained from Remote Sensing. In the section of gravity 3-D inversion, it shows that the low-density contrast can be seen at 2000-3500 meter and 4500-7000 meter, while high density contrast can be seen at 0-5000 meters and 6500-8000 meters. The low and high-density contrast is associated with the presence of Huwe Fault, Banda Fault, and Banda Hatuasa Fault in the prospect area which is correlated to the geological condition. 2-D forward modeling has a good correlation to confirm the results of 3-D inversion of gravity data.