The Utilization of GGMplus Data Using Derivative Method and 3D Modeling of Subsurface Structure for Trienggadeng Fault Identification in Pidie Jaya, Aceh Region

Abstract

The Pidie Jaya, Aceh earthquake occurred on December 7th, 2016 that caused damage to the northern coastal area. This event was caused by a local fault (Trienggadeng Fault). The existence of this fault is close to settlements so we need the mitigation efforts to reduce the casualties and material loss. One of those efforts is mapping the fault location by using the gravity method that is sensitive to subsurface rock density changes. In this study, we used GGMplus gravity data then processed with derivative analysis (First Horizontal Derivative and Second Vertical Derivative) to determine the location and type of fault. By performing the slices, we found that this fault is oblique with strike-slip dominant tends to reverse fault. The azimuth discovered through fault position traces that the value is 47.5°. Then, we use 3D inversion modeling to obtain a subsurface structure model. The average density is 2.3 g/cm3. The model shows a distribution of limestone and sandstone sedimentary rocks reaches a 4 km depth. The clay sediments follow the river flow. In the southern part, there are andesite and granite igneous rocks. The difference in rock density within 3 km and below indicates the existence of the Trienggadeng Fault.