Gravity Gradient Technique to Identify Fracture Zones in Palu Koro Strike-slip Fault

The forces acting upon a rock mass can result in physical changes on either side of the fault plane that are known as fracture zones. This tectonic activity will lead to a difference in the density of fracture zones from the density of surrounding rocks. This condition can be detected using gravity method. The changes of rocks density in contrast to fracture zones are relatively small, so a rigorous technique of gravity data processing to detect its presence is required. This research has developed and implemented the gravity gradient technique as one of the processing and acquisition techniques of gravity data which is found to have a high accuracy to detect the boundaries of rock density contrast changes. For the purposes of analyzing the gravity responses in identifying fracture zones, the characteristics of the gravity and its gradient responses of fracture zones in a strike-slip fault system were analyzed based on the forward and inverse modeling results. Furthermore, the gradient and gravity anomaly inversions were applied to the gravity data towards Palu-Koro strike-slip fault, a segment of the Palu City, Central Sulawesi, Indonesia. The measurement results show that the gravity gradient anomaly has a higher sensitivity compared to its gravity anomaly in detecting the fracture zones. In addition, the inversion result of the gravity gradient anomaly shows that the boundaries of lateral changes in the distribution of density contrast of fracture zones can be identified more accurately.