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Ogara, Evan Rosyadi
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Earth & Planetary Sciences

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IDENTIFICATION OF AQUIFER LAYERS USING THE ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) METHOD IN GUNUNG KASIH AREA Alviyanda, Alviyanda; Farduwin, Alhada; Nugraha, Purwaditya; Widiatama, Angga Jati; Natalia, Happy Christin; Ogara, Evan Rosyadi; Piqri, Hafidz
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 3 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i3.491

Abstract

The varied physiographic conditions of Lampung, from the west to the center and east, are the main factors in determining the geological field campus as a suitable learning environment. Gunung Kasih is one of the areas located on the Bukit Barisan Range, which has unique geological conditions with exposed basement rocks on the surface, making it a key factor in determining the geological field campus. However, the presence of crystalline basement rocks in Gunung Kasih prevents water from penetrating below the surface, thereby affecting the availability of groundwater for the local community. This study aims to identify aquifer layers around the Gunung Kasih area, using the Electrical Resistivity Tomography (ERT) method. Stratigraphically, based on field observations of rocks, the study area has lithology consisting of schist, marble, and sandstone in the western part, with a landscape characterised by structural hills. On the eastern side, volcanic deposits such as tuff and andesitic lava were found, with a denudational plain landscape. The geophysical survey was conducted using Wenner-Schlumberger configuration, with four survey lines oriented relatively west to east and north to south. Low resistivity anomalies are indicated by layers with resistivity values of 0–20.7 Ωm, while moderate-to-high anomalies have resistivity values of 29.9–89.9 Ωm. Very high resistivity anomalies are indicated by layers with resistivity values of 61.9–128 Ωm. In comparison with observations of rock outcrops and rock resistivity values, the aquifer layer is interpreted as being indicated by low resistivity anomalies in the relatively eastern part of the study area, which is near the surface to a depth of 15 metres and 25 metres. This layer is interpreted as tuffaceousrock comparable to the Hulusimpang Formation. The aquifer layer in the study area is interpreted as a shallow unconfined aquifer.
THE EFFECT OF INTRUSION ON THE PHYSICAL AND CHEMICAL PROPERTIES OF COAL Ogara, Evan Rosyadi; Tri Wahyuni; Al Hussein Flowers Rizqi
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 3 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i3.495

Abstract

Coal is a deposit of organic matter derived from plant remains that have undergone diagenesis process to form a coal seams. This study aims to determine the impact of intrusion on the physical and chemical characteristics of coal. The location of this research is in the Air Laya mining area, PT Bukit Asam Tbk, Tanjung Enim, South Sumatra and is part of the South Sumatra Basin which is well known as one of the coal bearing formation areas. Four (4) coal samples were analysed including proximate analysis, total sulphur content, and calorific value to measure moisture content, volatile matter, fixed carbon, ash content, and calorific value of the coal. Petrology and well log analysis was used to determine lithology and regression analysis was used to assess the effect of intrusion on coal characteristics. The results of the coal analysis in the research area reveal significant differences between coal samples located near the intrusion and those farther away. Coal located near the intrusion exhibits black colour, vitreous and conchoidal fracture. In contrast, coal farther from the intrusion shows a dull, blackish-brown, brownish streak, and uneven fracture. Coal near the intrusion shows lower moisture (1.5–1.7%) and volatile matter (17–25%), but higher ash content (7.9–8.2%), fixed carbon (67–73%), calorific value (7700–7968 kcal/kg), and sulphur (0.7–0.8%). In the other hand, coal farther from the intrusion has higher moisture and volatile matter, but lower fixed carbon, calorific value, and sulphur. The findings conclude that proximity to intrusion increases fixed carbon and calorific value but also raises sulphur levels, which may pose environmental and operational concerns.
Co-Authors Al Hussein Flowers Rizqi Alviyanda, Alviyanda Farduwin, Alhada Natalia, Happy Christin Nugraha, Purwaditya Piqri, Hafidz Tri Wahyuni Widiatama, Angga Jati