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Accepted manuscripts

Identification of Areas at Risk of Abrasion Application of Electrical Resistivity Tomography (ERT) Method on Nangai Beach, North Bengkulu

Bayu Saputra, Suhendra*, Halauddin, Liza Lidiawati, and Shyaira Marcelina

Abstract: A study of the underground structures in areas prone to abrasion of Nangai Beach, North Bengkulu Regency. In this study, 2D images of the subsurface structure at the Nangai Beach site were obtained using the Wenner-Schlumberger configuration, while 3D representations were obtained using the Electrical Resistivity Technique (ERT). To protect coastal materials, the main objective of this research is to identify rock types that are resistant to seawater erosion and measure the resistivity of rocks that can be eroded. In addition, software (ERT LAB 64, View Lab 3D and Res2Dinv) was used to analyze the data by processing it and displaying an image of the resistivity value. The interpretation results show that the coastal zone of the study area is dominated by clays with resistivity (> 34 m). The shoreline of Nangai beach consists of shale clay (>> 437 m). Rocks having a resistivity value (437 m) are not easily eroded by erosion in shale clay. This is because the rocks known as shale clay have low porosity, resulting in compact rock density. Restoring damaged soil and planting trees near the coast are two ways to slow down the abrasion process.

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Effect of Carbonization Temperature on Pore Formation and Adsorption Ability of Coconut Shell Activated Carbon with KOH Activator

Arinda Yukashima Putri Prahesti, Sheilla Rully Anggita*, and Hamdan Hadi Kusuma

Abstract: Activated carbon derived from coconut shells has great potential as an adsorbent for water purification due to its high porosity. This study investigates the effect of carbonization temperature on pore formation and adsorption capacity of coconut shell activated carbon. Carbonization was conducted at temperatures rang-
ing from 500◦C to 700◦C for 2 hours, followed by chemical activation using 3M KOH solution. The activated carbon was then filtered, washed until neutral pH (± 7), and dried. Characterization was carried out using the BET method to analyze surface area and pore volume, while adsorption capacity was determined using a UV-Vis spectrophotometer with methylene blue as the adsorbate. The results show that increasing the carbonization temperature enhances pore development, as indicated by higher surface area and pore volume. The highest surface area and pore volume were obtained at 700◦C, reaching 426.692 m2/g and 2.414 cc/g, respectively. Correspondingly, the highest adsorption capacity was also observed at 700◦C, with a value of 3957.15 mg/g. These findings suggest that carbonization temperature plays a critical role in optimizing the physical characteristics and adsorption performance of coconut shell-based activated carbon.

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Estimation Earthquake Source Parameters in Mentawai Island Region Using Moment Tensor

Fahmia Zuwidhatul Husna, Sungkono, Muhammad Nurul Fahmi, Eko Minarto, and Saifuddin

Abstract: The Mentawai Islands is a seismically active zone that often experiences earthquakes due to the interaction of tectonic plates, so it is necessary to analyze the earthquake source parameters to understand its characteristics. This study aimed to determine earthquake source parameters for events of M w ≥ 5.5 that occurred in 2023 using moment tensor inversion. Three-component waveform data from the GEOFON network were analyzed in the time domain, filtered within a frequency range of 0.01 to 0.025 Hz. The inversion yielded variance reduction (VR) values above 70% (88.24%, 81.98%, 94.05%, and 73.16%), indicating a good fit between observed and synthetic waveforms. The results of waveform data analysis show that the earthquake in the study area was caused by tectonic activity characterized by the percentage of Double-Couple (DC) more dominant than Compensated Linear Vector Dipole (CLVD), at shallow depths. Comparison with earthquake catalogs (GCMT, USGS, and GFZ) showed agreement, supported by Kagan angle values below 60◦. In addition, the focal mechanism of the waveform data analysis indicated that the type of fault that causes the earthquake in the study area was a reverse fault.

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Lithological Identification using Geoelectric Method in Landslide Area in Bengle Village

Icha Khaerunnisa, Andi, Nugroho Budi Wibowo, and Thaqibul Fikri Niyartama

Abstract: Dlepih Village, specifically in Bengle Hamlet, is an area that experienced a landslide disaster on November 28, 2017. This landslide disaster occurred in a residential area, resulting in the death of 2 people, necessitating mitigation measures. One of the initial steps in mitigation is to identify the lithology in the landslide area. This study aims to determine the lithology in the landslide area using the Dipole-Dipole resistivity geoelectric method. The resistivity method is used to investigate the subsurface structure of the earth by measuring the resistivity of rock or soil. The mechanism of this method relies on the flow of electric current and the measurement of potential difference, and is calculated based on a certain electrode configuration to obtain a picture of underground resistivity. Data was acquired using a set of Naniura Resistivity Meter instruments on four measurement lines. The measurement paths are located in the Semilir Formation, which consists of sedimentary rocks. The research results show that the landslide area consists of soil layers with a resistivity value of 2.32 Ωm 6.69 Ωm and a thickness of 1.26 m - 11.39 m, claystone layers with a resistivity value of 6.69 Ωm - 160 Ωm and a thickness of 11 m - 40.5 m, and andesite rock layers with a resistivity value of more than 160 Ωm and a thickness of 5.25 m - 37.71 m.

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