JURNAL GEOCELEBES

Identification Lithology of Geothermal Potential Areas Using the Electrical Resistivity Tomography (ERT) Method

Hana Raihana — 2024-10-01

The rock lithology of the potential hydrothermal area has been studied using Electrical Resistivity Tomography (ERT) in Pungguk Pedaro Village, Bingin Kuning District, Lebong Regency. Field data acquisition uses a stretch length of 480 meter with the MAE X612-EM Geoelectric tool that forms a straight line. ERT method, using Res2dinvx64 software. The study aims to determine the subsurface conditions of the potential hydrothermal area and the characteristics of the rocks that make up the hydrothermal area. The results of this study can be concluded that Pungguk Pedaro Village is dominated by clay, sandstone, sandy gravel, andesite, basalt, and granite rocks. In this study, measurements were taken with six lines to see variations in resistivity values as a reference for identifying potential geothermal lithologies. There is 1 line that cuts to five lines to validate the resistivity value of each line. Line 1 has no potential for hydrothermal distribution because there has been a mixture of hydrothermal water with mountain water, so this line will only provide groundwater.

Identification of Sub-Fault Zone Using Magnetotelluric Inversion (Case Study: Ketaun Fault, Lemeu Village, Lebong Regency)

Nurul Ilmi Rahmawati — 2024-10-01

Lemeu Village, Lebong Regency, borders the Bukit Barisan Mountain range and is crossed by the Ketaun Fault, which causes a high level of seismic activity, so it is necessary to conduct research on the potential existence of the Ketaun sub-fault as one of the efforts to mitigate natural disasters such as earthquakes. The Magnetotelluric method utilises the earth's natural electromagnetic field, which is used to determine the distribution of resistivity in the subsurface using the ADU-07e Magnetotelluric tool with two horizontal electrical sensors (Ex, Ey) and three horizontal (Hx, Hy) and vertical (Hz) magnetic sensors and uses seven research points with an interval of 1 km. Data processing uses MAPROS software to convert data from the time domain to the frequency domain and ZONDMT2D to obtain subsurface resistivity values. The results obtained from this study are 2D magnetotelluric cross sections showing a zone with low resistivity values between research points P4 and P5 which is thought to be a new fault zone with resistivity values ranging from 1.3 – 6.1 Ωm from a depth of 2.5 km to a depth of 10 km. The zone is assumed to be a new fault that is a branch of the Ketaun fault.

Study of the Digital Geological Compass in Increasing the Effectiveness and Efficiency of Measuring Geological Structure Data in the Field

Rezki Naufan Hendrawan — 2024-10-01

This study compares the use of analog geological compasses and digital geological compasses in measuring fracture planes on crystalline rocks at the Lampung region. The measurement results demonstrate that using digital compasses yields higher time efficiency than analog compasses, with a reduction in measurement duration of over 50%. Although the dominant directions of the fracture planes were similar between the two methods, the inclination values and accuracies of each plane were not always consistent. Data processing using rose diagrams and stereonets indicates that the RockD application provides comparable results to measurements obtained using analog compasses. Therefore, the use of digital compass applications such as RockD can serve as an efficient alternative for geologists in collecting field data related to rock fractures, particularly in the context of quantitative data. However, analog geological compass is still recommended for measuring planes with on single-plane characteristics, such as rock bedding and fault mirrors. This study demonstrates the potential for development and transformation from analog geological compasses to digital geological compasses, and further research is needed to investigate the minimum number of fractures that can be measured with a digital geological compass to be considered statistically valid.

Drought Analysis in Ketapang District using the Keetch-Byram Drought Index Method

Lusyndatul Massuro — 2024-10-10

Ketapang Regency is one of the areas in West Kalimantan that is prone to drought. Drought can trigger forest and land fires. In this research, the Keetch-Byram Drought Index (KBDI) method was used to determine the level of drought in Ketapang Regency. The KBDI method relies on annual rainfall accumulation, daily rainfall, and maximum air temperature. The KBDI values obtained were correlated with the number of hotspots using Pearson correlation. This research was conducted throughout 2018-2022. Based on the monthly average KBDI value, the highest drought in Ketapang Regency occurred in August and September, while the lowest drought occurred in December and January. In terms of the annual average, the highest drought occurred in 2019. During the ENSO phenomenon in 2019, the El Niño phase experienced higher drought than the La Niña phase and normal years. In the El Niño phase, drought levels reach high to extreme categories. The correlation value between annual KBDI and the number of hotspots is 0.88, indicating a solid relationship. An increase in the KBDI value will be followed by an increasing number of hotspots.