Lineament Extraction using Gravity Data in the Citarum Watershed Gumilar Utamas Nugraha, Karit Lumban Gaol, Lina Handayani and Rachmat Fajar Lubis Research Center For Geotechnology, Indonesian Institute of Sciences, Indonesia Abstract. Lineament is one of the most important features showing subsurface elements or structural weakness such as faults. is study aims to identify subsurface lineament patterns using automatic lineament in Citarum watershed with gravity data. Satellite gravity data were used to generate a sub-surface lineament. Satellite gravity data corrected using Bouguer and terrain correction to obtain a complete Bouguer anomaly value. Butterworth ĕlters were used to separate regional and residual anomaly from the complete Bouguer anomaly value. Residual anomaly gravity data used to analyze sub-surface lineament. Lineament generated using Line module in PCI Geomatica to obtain sub-surface lineament from gravity residual value. e orientations of lineaments and fault lines were created by using rose diagrams. e main trends observed in the lineament map could be recognized in these diagrams, showing a strongly major trend in NW-SE, and the subdominant directions were in N-S. Area with a high density of lineament located at the Southern part of the study area. High-density lineament might be correlated with fractured volcanic rock upstream of the Citarum watershed, meanwhile, low-density lineament is associated with low-density sediment. e high- density fracture might be associated with intensive tectonics and volcanism. 1. Introduction Area of approximately Seven thousand four hundred square kilometers, divided into three parts; the upper part (1771 squared kilometer), the middle part (4242 km2), the lower part (1387 square kilometer) (Juwana et al., 2016a). e average watershed rainfall is 2300 mm/year, and the Citarum Ęow measured by the Saguling Dam is around 5.7 billion m3/ year (Juwana et al., 2016b). In 2008, there were just over 11 million people in the watershed. Most live on the Riverbanks and have used it directly in different domestic applications (Juwana et al., 2016b). e river runs through Jakarta and West, two central provinces. Water companies in the watershed also use the river as the raw water source for their water treatment plants(Juwana et al., 2016b). A lot of Citarum researchers (Agaton et al., 2016; Djuangsih, 1993; Harashina et al., 2003; Herawati et al., 2016; Juwana et al., 2016a; Nastiti et al., 2015; Parikesit et al., 2001; Sunardi et al., 2012). None of them concerns the mapping of sub-surface geological structures. e mapping of geological structures in the area, particularly in areas with insufficient outcrop exposures, can take time and are difficult (Yeomans et al., 2019). Moreover, partial exposure and subtle topographic variation structures such as severe defects can be complicated to map a geologist on the ĕeld. Lineament detection can aid the mapping of geological structures (Yeomans et al., 2019). A lineament is a mappable rectilinear or curvilinear linear feature of a surface, distinct from adjacent patterns, representing a subsurface phenomenon (O'Leary et al., 1976). Lineaments are linear features evident at the land surface that express the underlying geological structure (Ibrahim & Mutua, 2012). It is a linear or curvilinear mappable feature on a surface whose parts are aligned in a straight or somewhat curved relation due to a defect or other line defect (Ibrahim & Mutua, 2012). e surface characteristics that form a lineament can be geomorphological, i.e., relief or tonal differences i.e. (Hung et al., 2005, Haryono et al., 2016). Remotely sensed data, including satellite imaging, and airborne geophysical data, are usually used to map regionals (Yeomans et al., 2019). In addition, these lineaments may be used as a basis to infer the region's structural geology, with implications for mineral exploration (Moore and Camm, 1982; James et Moore, 1985; Ni et al., 2016; Verdiansyah, 2019), oil exploration (Peña and Abdelsalam, 2006). (Rutzinger et al., 2007). e conventional techniques of linear extraction include manual scanning of linear features. In addition, optical images are commonly used, but they take time, are subjective, and are reproductive inadequate (Masoud and Koike, 2006; Scheiberet al., 2015). There are various applications for potential field methods (Zhdanov, 2002; Mehanee and Zhdanov, 2002; Abdelrahman et al., 2004; Zhdanov et al., 2004; Essa et al., 2008; Mehanee et al., 2011; Mehanee, 2014, Mehanee, 2015; Biswas, 2017; Zhang et al., 2018, Essa and Elhussein, 2018). In many geophysical prospect areas, particularly in the determination of the crystalline basement depth (Abdelrahman and Essa 2015a; Yangfan Deng et al., 2016), which define structural environments, gravity and magnetic processes have been presented as beneficial results (Abdelrahman and Essa, 2015b; Gabtni et al., 2016), Exploring and delineating gravity and magnetic resources on minerals, hydrocarbons and geothermals (Eseas, 2007 and 2011; Khazri and Gabtni, 2018) ISSN 2354-9114 (online), ISSN 0024-9521 (print) Indonesian Journal of Geography Vol.53 , No. 1, 2021 (87– 94) DOI: http://dx.doi.org/10.22146/ijg.52402 website: https://jurnal.ugm.ac.id/ijg ©2021 Faculty of Geography UGM and e Indonesian Geographers Association Received: 2020-02-03 Accepted: 2021-04-04 Keywords: Citarum Watershed; Lineament; Gravity Correspondent email: g.utamas.n@gmail.com RESEARCH ARTICLE ©2021 by the authors. Licensee Indonesian Journal of Geography, Indonesia. is article is an open access article distributed under the terms and conditions of the Creative Commons Attribution(CC BY NC) licensehttps://creativecommons.org/licenses/by-nc/4.0/.