Identification of Geological Structures in Sigi Regency, Central Sulawesi Based on Derivative Analysis of Gravity Data

Abstract

Sigi Regency is part of the tectonic zone in Central Sulawesi which is crossed by an active transform fault, the Palu Koro Fault. The northern region of Sigi Regency has a depression zone that forms a graben by a couple of Palu Koro Faults. The study area is prone to earthquakes and has fairly high geothermal potential. Therefore, it is necessary to control the dynamics of the structure here to mitigate earthquake disasters that may occur and may also affect the surrounding geothermal system. To identify the presence and characterization of the fault structures, derivative analysis of gravity data is used, including analysis of FHD (First Horizontal Derivative), SVD (Second Vertical Derivative), and MS-SVD (Multi Scale-Second Vertical Derivative). From this analysis, 4 normal oblique fractures and 1 normal fracture were identified. Faults derived from the derivative analysis have greatly improved the fault mapping reported on geological maps, including the shifting fault position from the geological map. And significant improvement was found on a shear fault causing the fault to be separated into 2 segments, changing the direction of the strike fault, and generating a new fault due to the created weak zone.