Journal of Geoscience, Engineering, Environment, and Technology
JGEET (Journal of Geoscience, Engineering, Environment, and Technology) (E-ISSN : 2541-5794, P-ISSN : 2503-216X ) is a peer-reviewed and open access journal that publishes significant and important research from area of geological science, related with engineering, environment, and technology. We accept submission from all over the world on English language. Editorial Board members are prominent and active researchers in geological sciences and engineering fields who ensure efficient, fair, and constructive peer-review process. All accepted articles will be published and available to all readers with worldwide visibility and coverage. Our Journal is already indexed in DOAJ, EBSCO, SINTA, GARUDA, Indonesia One Search, Crossref, Index Copernicus, OCLC, BASE, and University Libraries around the world. ACCREDITED SINTA 2 by Ministry of Research, Technology, and Higher Education of the Republic of Indonesia, Nomor 295/C/C3/KPT/2026, January 2nd, 2026 Address Department of Geological Engineering, Fakulty of Engineering, Universitas Islam Riau Jl. Kaharuddin Nasution No 113 Perhentian Marpoyan, Pekanbaru, Riau 28284 e-mail: jgeet@journal.uir.ac.id Submit Your Article Here Jornal Name : Journal of Geoscience, Engineering, Environment, and Technology Initial : JGEET Frequency of Publication : 4 times per year (March, June, September, and December) DOI Prefix : 10,25299 P-ISSN : 2503-216X E-ISSN : 2541-5794 Editor-in-chief : Husnul Kausarian Publisher : PRESS UIR Citation Analysis :SCOPUS | SINTA | Google Scholar
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Relative Age and Depositional Environment of The Limestone Unit of Karangsambung Formation in Jatibungkus Hill, Kebumen Geopark, Indonesia
The Jatibungkus Hill is an isolated karst hill and is one of the olistolith fragments in the Karangsambung Formation deposited as olistostrome deposits. This formation formed above the Luk-Ulo Mélange Complex, one of the geological heritage sites in the Kebumen Geopark. The presence of limestone as a fragment in the olistostrome deposits requires further investigation because its formation history is related to regional geological history. This study aims to determine the relative age and depositional environment of limestone in Jatibungkus Hill based on microfossil analysis through petrographic observations. Of the 39 rock samples obtained during field data collection, 15 rock samples were selected for petrographic analysis. The petrographic analysis is divided into two parts, namely descriptive methods and point counting as the basis for classifying carbonate rocks. Based on the classification results, reef facies analysis was conducted using facies zonation and standard microfacies (SMF) to obtain an overview of the limestone depositional environment. In addition, the types of large foraminifera fossils and algae were also used as a basis for determining the relative age. The lithology found in the research area consist of packstone, rudstone, grainstone, and crystalline limestone. The limestone depositional environment is located in SMF 4, SMF 5, and SMF 6 which are included into FZ 4 (Slope) on a restricted carbonate platform. This facies zone influenced by currents and waves between the storm base wave and the normal base wave. The petrographic analysis showing the domination of large bioclastic grain indicating that the deposition were under a high energy. The influence of waves is also reflected in the mixture of bioclass and lithoclast grains or high-density terrigenous clastics that are observed in most of the samples. This facies contains more quartz clastics and bioclast grains than carbonate mud as consistently observed in the identified samples.The association of large benthic foraminifera fossils and algae indicates that the limestone was formed in Zone Ta1 (Late Paleocene) characterized by the presence of Discocyclina sp., Ranikothalia sp., Nummulites sp., Miscelanea sp., Distichoplax biserialis, and Parachaetes sp. It can be seen that the deposition of the limestone olistolith occured after the initial subduction event which produced the mélange complex in Early Cretaceous.
Preliminary Study of Geo-Magnetic Phenomena at The Arjuno–Welirang Volcano, Indonesia
Mount Arjuno–Welirang is an active volcano in East Java that exhibits volcanic activity in the form of shallow and deep earthquakes, as well as fumarolic emissions. This study aims to monitor the subsurface dynamics of the volcano through the integration of magnetic and seismic methods. Magnetic field measurements were carried out using a proton precession magnetometer to obtain local magnetic anomalies after applying diurnal corrections, IGRF correction, and regional–residual anomaly separation. The RTP and residual maps reveal high-anomaly zones that are interpreted as shallow magma intrusions, as well as low-anomaly zones associated with hydrothermal alteration and fracturing. These interpretations are integrated with the lithology of the Qvaw Formation, which consists of lava, volcanic breccia, and tuff. In addition, MAGDAS data were used to analyze diurnal geomagnetic variations (H, D, Z), which show significant fluctuations during certain periods, indicating local geomagnetic disturbances likely influenced by seismic activity or subsurface geological processes. The combination of magnetic and seismic methods provides a more comprehensive understanding of magma pathways, hydrothermal fluid dynamics, and potential increases in volcanic activity, thereby supporting disaster mitigation efforts in the Arjuno–Welirang region.
Iskara Hadijah Aqila Nasywa Rastramata Athorhab
Influence of weathering on the mechanical strength and factor of safety of andesitic rocks in the Gunung Geulis area, Jatinangor, West Java, Indonesia
Weathering gradually alters the physical character and engineering performance of volcanic rocks, including andesite, which is commonly found and frequently used for construction and slope-related works within the Gunung Geulis region of Sumedang Regency, Indonesia. To examine how these changes affect mechanical behavior, this study compared the estimated uniaxial compressive strength (UCS) and the resulting factor of safety (FOS) of andesite across different weathering grades. Seventy-eight samples were collected from three geological segments, representing slightly to moderately weathered (Grade II–III) and highly weathered (Grade IV). Point Load Tests (PLT) were performed on all samples, and the resulting indices were converted to estimated UCS values using an empirical correlation. Statistical analyses, including descriptive analysis, the Mann–Whitney test, and two-factor analysis, were performed to assess strength differences between weathering grades and geological segments. These estimated UCS values were then converted into shear-strength parameters through the Generalized Hoek–Brown approach, and the corresponding cohesion and internal friction angle were obtained using RocLab 1.0 software for slope-stability modelling in Slide2. The results show a consistent and marked decline in strength as weathering progresses; overall, the estimated UCS decreases by 59.22% across all investigated segments, demonstrating that increasing weathering reduces the rock strength by more than half. This reduction in rock-mass strength is reflected in the slope-stability analyses, where slopes composed of SW–MW andesite produced FOS values ranging from 3.518 to 4.271, indicating relatively stable slope conditions, whereas HW andesite yielded lower FOS values ranging from 1.191 to 1.307, representing comparatively lower and marginally stable conditions. These findings demonstrate that progressive weathering significantly reduces the mechanical performance and slope stability of andesitic rock in the Gunung Geulis area.
Design of Disposal Area Transition and Drainage at Pit 2AA PT Sentosa Laju Sejahtera Site CV Anggaraksa Adisarana Loa Janan
This research discusses the design of the disposal area transition and drainage system in Pit 2AA of PT Sentosa Laju Sejahtera to overcome the limited space of the stockpile due to the use of the backfilling method. The main issues include effective drainage design, selection of alternative disposal sites, and embankment slope stability analysis. The planned rainfall was calculated using the Gumbel distribution with rainfall data for the last 10 years (2014-2023), while the runoff water discharge was calculated using the Rational method, resulting in a discharge of 7.8 m³/second. The open channel was designed with two trenches, Trenches A and B, with capacities of 9.59 m³/sec and 7.92 m³/sec, respectively. The disposal design was placed outside the Life of Mine boundary, using the gradual finger disposal method with three levels from elevation 93 to 105 meters. The slope geometry consists of a tier height of 4 meters, a tier width of 15 meters, a single slope angle of 30°, and an overall slope of 13°. The total disposal capacity reached 441,310 BCM. Slope stability analysis was conducted using the Janbu Simplified method, showing that the factor of safety (FK) value is in the range of 1.308-2.404, meeting the minimum FK ≥ 1.3 according to the Decree of the Minister of Energy and Mineral Resources No. 1827 K/30/MEM/2018. The results show that the drainage and disposal designs are technically feasible and support the sustainability of mine operations.
Eocene Paleoclimatic Implications in the Bayat Basin Based on Nannofossil Distribution
The Middle–Late Eocene represents a critical interval of greenhouse climate evolution following the Early Eocene Climatic Optimum (EECO), yet quantitative paleoclimate records from low-latitude Southeast Asia remain scarce. This study presents a multi-proxy calcareous nannofossil-based reconstruction of surface-water conditions from the Gamping–Wungkal Formation in the Bayat Basin, southern Java. Detailed stratigraphic logging and systematic sampling along a 60 m section were combined with quantitative assemblage analysis and Scanning Electron Microscope validation. Biostratigraphic evaluation assigns the studied interval to the NP17 zone (Middle–Late Eocene). Paleoclimatic reconstruction integrates the Reticulofenestra Size Ratio (RSR), Warm-Water Index (WWI), Discoaster Abundance Ratio (DAR), and total Reticulofenestra abundance. Assemblages are dominated by medium- to large-sized Reticulofenestra and persistent Discoaster occurrences, indicating warm, oligotrophic, and stratified surface-water conditions. Despite global post-EECO cooling trends documented in mid- and high-latitude records, the Bayat data suggest sustained tropical greenhouse conditions during NP17. These findings are consistent with emerging evidence of latitudinal variability in Eocene climate evolution and establish the Bayat Basin as an important low-latitude archive for evaluating Paleogene greenhouse dynamics in Southeast Asia.
The Water Chemistry Geothermal of Ranang-Kasimbar Hot Springs, Parigi Moutong Regency, Central Sulawesi, Indonesia
The Ranang-Kasimbar geothermal system in Central Sulawesi is located within the West Sulawesi Mandala, an area significantly influenced by the active tectonic zone of the Palu-Koro Fault that controls the emergence of surface manifestations. This study aims to characterize the water chemistry of the Ranang-Kasimbar hot springs through surface geological mapping and fluid geochemical analysis, which includes cation-anion analysis, stable 18O and 2H (D) isotopes, and geothermometer calculations for subsurface temperature estimation. The geological conditions of the study area are composed of Cretaceous-Eocene metamorphic rocks, Tertiary intrusive rocks, and Quaternary sedimentary rocks, with structural controls in the form of north-south trending strike-slip faults and a normal fault system that forms a central depression zone as controls for the emergence of manifestations. Field data identified hot springs with surface temperatures ranging from 55–61°C and alkaline pH (~9). Geochemical analysis results classify the geothermal fluid as a chloride type indicating a deep reservoir origin, with a Cl/B ratio indicating strong interaction with igneous rocks and partial equilibrium conditions. Isotope analysis indicates a dominant mixing with meteoric water with very low oxygen-18 enrichment. Reservoir temperature estimation using a Na-K geothermometer and a silica-enthalpy mixing model indicates a minimum temperature of 130°C, thus categorizing it as a medium enthalpy system. This geothermal system is controlled by secondary permeability from normal and strike-slip fault structures, with the heat source suspected to originate from residual heat from Plio-Pleistocene andesitic intrusions.
Effectiveness of Vetiver (Vetiveria zizanioides) Application with Modular System in Soil Bioengineering for Soil Reinforcement
Indonesia has a diverse topography characterized by many hilly and mountainous regions, rendering it vulnerable to landslides. BNPB data indicate that, in 2024, there were 207 landslide incidents in Indonesia. Soil bioengineering methods using vetiver plants can improve soil stability. This study aimed to evaluate the effectiveness of vetiver application via a modular soil stabilization system using soil bioengineering. The research was conducted by testing soil properties, followed by planting vetiver in 10-cm-diameter pipes 50 cm high, with a geotextile measuring 10 × 10 × 10 cm on top containing a mixture of soil and planting media. Subsequently, maintenance, soil shear strength testing, and root dimension observations were performed on samples aged 1, 2, and 3 months after planting (MAP). The test results showed that the root growth rate increased by 30–40 cm in vetiver samples in the modular system. The most significant increase in soil shear strength was observed in the cohesion parameter, reaching 19.55 kPa. Therefore, vetiver roots contributed to the greatest increase in cohesion (c), reaching 8.57 kPa. The application of vetiver significantly increases soil shear strength, making it suitable for use as a slope reinforcement method.
Mine Dewatering Design for Re‑Mining in a Mined‑Out Laterite Nickel Pit: Case Study of South Pit, PT NPM, Central Sulawesi, Indonesia
This study aims to design an effective mine dewatering system for the South Pit mined-out area of PT Nusajaya Persadatama Mandiri, supporting re-mining activities. The methods used include hydrological analysis to determine the design rainfall using the Log Pearson Type III distribution, calculation of rainfall intensity using the Mononobe method, and estimation of runoff discharge using the rational method based on the catchment area. The results show that the design rainfall is 72.2 mm/day with a rainfall intensity of 49.9 mm/hr and a catchment area of 13.47 ha. The total inflow into the pit is 0.48 m³/s (1,726 .20 m³/hr), requiring a sump capacity of 7,250.03 m³. The pumping system is designed using a DnD LCC-M 100 pump with a capacity of 300 m³/hr, operated for 14 hours/day. The pumped water is conveyed through a 6-inch diameter HDPE pipe to a trapezoidal open channel, where it is then discharged into a Water Management Pond (WMP) with a total capacity of 11,200 m³, consisting of four compartments. The research results indicate that the designed mine drainage system is capable of effectively controlling mine water, thereby supporting safe and efficient re-mining operations.
Can Liquefaction Be Repeated? An Electrical Resistivity Study at South Palu, Indonesia
The recurrence of liquefaction remains a significant concern, prompting a resistivity study in South Palu to investigate subsurface condition associated with this phenomenon. A total of eight lines 2D resistivity lines with dipole-dipole configuration and 10m electrode spacing were acquired in the South Palu subdistrict, covering a cumulative length of 1470m. All stages of data processing and modelling were conducted using a regularized inversion algorithm implemented in the Phyton-based ResIPy software. The inversion results revealed three distinct resistivity layers, low-resistivity ranging from 4.1 – 78.5 ohm.m, interpreted as low permeability a sandy shale or clay rich soil with saturated clay layer extending to a depth of approximately 10m, an underlying high-resistivity layer ranging from 78.6 - 201.4 ohm.m, interpreted as a saturated sand or gravel layer with ± 10m of thickness and associated as a good aquifer and the deep layer at ±20 m depth with highest resistivity (> 200 ohm.m) which is interpreted as compacted sand or hard soil and acted as the base soil in this study area. The evidence of sand intrusion features, upward – moderate to high resistivity intrusions, potentially associated with liquefaction events, were observed in six of resistivity sections. These are indicated by the upward penetration of moderate to high-resistivity value through the low-resistivity layer, towards the surface. Additionally, the recurrence of liquefaction is still conceivable since the existence of ±10m of layer-2 which is interpreted as the most potential liquefiable layer and the thickness of low resistivity of layer-1 and in study area, particularly if subjected to strong earthquake motion.
Water Hyacinth Phytoremediation for Reducing COD, BOD, and Pb in Leachate: An Environmental Geoscience Perspective
Leachate generated from landfill disposal sites poses a serious environmental threat due to its high content of organic pollutants and heavy metals. Elevated levels of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and lead (Pb) may contaminate soil and surrounding water bodies if the leachate is not properly treated. Phytoremediation using water hyacinth offers an eco-friendly and low-cost alternative for leachate treatment. This study was conducted to evaluate the effectiveness of water hyacinth in reducing COD and BOD concentrations and removing Pb from leachate. An experimental method with a batch reactor system was applied, using 30 clumps of water hyacinth in each tank and contact time variations of 7, 14, and 21 days. COD, BOD, and Pb concentrations were measured before and after treatment using standard water quality analysis methods. The results showed that the 21-day contact time produced the highest removal efficiency. COD decreased from 1551.21 mg/L to 520.32 mg/L, representing a 66.44% reduction, while BOD decreased from 576.34 mg/L to 150.62 mg/L, equivalent to a 73.88% reduction. Pb concentration also decreased from 0.92 mg/L to 0.18 mg/L, with a removal efficiency of 80.43%. These reductions are attributed not only to the physiological activity of water hyacinth but also to the interactions among hydrological conditions, root zone architecture, and rhizosphere-mediated microbial communities, which collectively facilitate biodegradation, assimilation, and bioaccumulation of pollutants. Overall, the study highlights the critical role of integrating environmental geoscience principles with phytoremediation to optimize leachate treatment. Understanding the geochemical characteristics of leachate, subsurface hydrodynamics, and plant-microbe interactions provides a scientific basis for designing sustainable, low-cost, and efficient treatment systems. The findings indicate that water hyacinth can serve as a practical and geoscience-informed solution for mitigating organic and heavy metal pollution from landfill leachate, with 21 days identified as the optimum contact time.
MCDA-AHP-GIS-Based Site Suitability Assessment for a Multi-Utility Tunnel in Panakkukang Sub-district, Makassar City , Indonesia
This study develops a transparent MCDA–AHP–GIS framework to screen Multi-Utility Tunnel (MUT) corridor suitability in Panakkukang Sub-district, Makassar City, using 2024 baseline datasets and five criteria: utility/network density (C1), road functional class and corridor capacity (C2), flood susceptibility (C3), activity intensity (C4; proxied by kelurahan-level population density), and spatial planning compatibility with RTRW/RDTR (C5). All layers were standardized and reclassified (1–3 or 1–5) and integrated using Weighted Linear Combination (WLC) with AHP-derived weights (CR = 0.028), where C1 (0.26) and C5 (0.24) were highest, followed by C2 (0.19), C4 (0.16), and C3 (0.15). The 2,918.3-ha study area was classified into Very Unsuitable (88.2 ha; 3.0%), Unsuitable (405.8 ha; 13.9%), Moderately Suitable (764.9 ha; 26.2%), Suitable (935.8 ha; 32.1%), and Highly Suitable (723.6 ha; 24.8%). A corridor-focused overlay shows that 436.9 ha fall within the Suitable–Highly Suitable mask, of which 127.3 ha (29.1%) intersect high flood-hazard zones, indicating that some priority segments require attention during detailed planning. Uncertainty mainly arises from buffer distances and reclassification thresholds and from non-differentiating attributes in some utility layers; however, a ±10% weight sensitivity test yields only minor shifts in class areas and preserves the main priority-corridor pattern.
Optimization of Bench Width and Vertical Bench Position for Claystone Slopes Using the Limit Equilibrium Method under a Safety Factor Constraint
One important aspect of open pit mine planning is slope geometry design, which affects the stability of the slope and the efficiency of overburden removal. This study aims to investigate the influence of vertical bench position and bench width on slope stability and their effect on stripping volume. The limit equilibrium method was used for slope stability analysis, with the assistance of Rocscience Slide2 software. The stripping volume estimate was obtained from pit shell simulations using GEOVIA Surpac software. The vertical bench positions analyzed were ¼, ½, and ¾ of the total slope height, which was 60 m. The bench width variations tested were 0, 5, 10, 15, 20, and 25 m, while maintaining a minimum safety factor requirement of 1,3. The analysis indicated that the optimal configuration is achieved by placing the bench at the vertical position of ½ of the overall slope height with a bench width of 10 m, which results in an overall slope angle of 44°. The result is steeper than the no-bench scenario, with an overall slope angle of 42°. This geometry produces an estimated overburden volume of 195,123,000 m3, which is smaller than the no-bench scenario of 196,559,500 m3. Therefore, the reduction in stripping volume is 1,436,500 m3 or approximately 0.73%. This study shows that optimizing the bench configuration enables the implementation of steeper overall slope angles while reducing the required stripping volume in open pit mine planning.
Effect of Sand Pretreatment on Bio-Stabilization Using Rhizopus oligosporus
Ottawa sand is a type of sand widely used in geotechnical research for its uniformity and high silica content. However, Ottawa sand is classified as a non-cohesive soil, lacking intergranular bonds, resulting in low shear strength. Therefore, a soil improvement method that enhances the material's mechanical stability is needed. This study aims to analyze the effect of Ottawa sand pretreatment on increasing soil shear strength through a bio-stabilization method using the fungus Rhizopus oligosporus. The research method used is a laboratory experimental method with an unconfined compression test. Ottawa sand samples were divided into three treatments: normal treatment (S-0), washed sand treatment (S-1), and washed and oven-dried treatment (S-2). Each sample was mixed with tempeh yeast containing Rhizopus oligosporus and distilled water, each at 5% of the sand weight. The curing process was conducted in a closed container, with temperature, humidity, and mycelium development monitored during incubation. The results showed that sand pretreatment increased the soil's unconfined compressive strength. The samples treated with washing and oven drying (S-2) had the highest unconfined compressive strength of 9.72 kPa and shear strength of 4.86 kPa at 12 days of curing. Meanwhile, the samples without pretreatment showed lower unconfined compressive strengths. Visually observed mycelial growth showed a more even distribution in the samples with sand pretreatment. The results of this study indicate that bio-stabilization using Rhizopus oligosporus has the potential to be a more environmentally friendly soil-improvement method for increasing the stability of sandy soil.
A Preliminary Assessment of the Reliability of a Personal Weather Station for Urban Flood Monitoring in a Tropical Coastal Urban Area: A Case Study from Kendari, Indonesia
This study conducted a preliminary assessment of the PWS reliability compared to the official BMKG reference station in a tropial coastal urban area of Kendari, Indonesia, particularly for urban flood monitoring. Daily rainfall obtained from the PWS and the BMKG station were compared over February to December 2024, using rainy days where both stations recorded rainfall exceeding 10 mm on the same day. For statistical tests, there were statistical metrics implemented in this study including Pearson correlation (r), coefficient of determination (R²), mean bias error (MBE), percent bias (PBIAS), mean absolute error (MAE), and root mean square error (RMSE). The rainfall data was also compared to flood-confirmed dates. The rainfall data analysis showed that there was moderate agreement between the PWS and the BMKG (r = 0.66, R² = 0.40, MBE = 1.83 mm, PBIAS = 4.91%, MAE = 17.12 mm, RMSE = 23.87 mm). Moreover, the PWS recorded the same rainfall category as BMKG on three flood events, particularly for heavy and very heavy rainfall category. However, the PWS showed moderate rainfall category for two flood events when the BMKG recorded heavy rainfall category. This difference could be attributed to climate background of Kendari and the device environment settings. Moreover, it is suggested that the PWS can be a useful tool for urban flood monitoring, especially during large and spatially widespread rainfall events.
Transit Oriented Development (TOD) Development in Senen Area, Central Jakarta, Indonesia
Senen area, Central Jakarta, is a strategic area that faces various problems, such as traffic congestion, lack of integration between modes of transportation, and minimal facilities for pedestrians and public transportation users. This study aims to evaluate the application of the TOD concept in the Senen area based on principles such as transportation integration, mixed land use, and pedestrian connectivity. This study uses a qualitative descriptive method approach , where the data used is secondary data obtained through literature studies. Literature studies are conducted by referring to previous studies and relevant institutional reports. The data collected includes spatial information, such as maps and geographic data, as well as non-spatial information, such as planning documents and policies. The results of the study indicate that the Senen area has great potential to be developed as a TOD area. Some steps that can be taken include improving connectivity between modes of transportation, improving public facilities, and adding green open spaces. In conclusion, the implementation of TOD in the Senen area can reduce the use of private vehicles, increase the efficiency of public transportation, and create a more comfortable and environmentally friendly city environment.
Quantifying the Effect of Natural Consolidation and Fluid Discharge on Land Subsidence of the Sidoarjo Mud Volcano, East Java, Indonesia
Land subsidence in the Sidoarjo Mud Volcano (SMV) area has been widely recognized as a consequence of sustained mud discharge and progressive subsurface consolidation. Earlier geodetic studies using GPS and InSAR, combined with geological and geomechanical investigations, have demonstrated persistent long‑term ground deformation, widespread flooding, and severe infrastructure damage linked to these processes. This study aims to (1) quantify spatial and temporal subsidence rates, (2) identify the dominant controlling mechanisms, and (3) estimate the relative contributions of fluid discharge and natural consolidation to total subsidence. Surface deformation was derived through time‑series analysis of Sentinel‑1A SAR data using the pair‑wise logic technique differential interferometric synthetic aperture radar (PLT‑D‑InSAR). These results were integrated with one‑dimensional (1D) consolidation modeling based on lithological coring data and mud discharge records. The PLT‑D‑InSAR analysis successfully captured detailed subsidence patterns over a wide area and shows good agreement with GPS observations (R² ≈ 0.82). The combined D‑InSAR, consolidation, and discharge analysis reveals a very strong correlation (R² ≈ 0.97), indicating that subsidence is mainly governed by fluid discharge and consolidation processes. Fluid discharge accounts for approximately 72.2% of the total subsidence, while natural consolidation contributes about 16.5%. The highest subsidence rates are concentrated near the mudflow center and are structurally influenced by the Watukosek and Siring faults. These findings highlight the dominant role of discharge‑induced deformation and provide important constraints for long‑term hazard assessment and land‑use planning in the SMV region.
Analysis of Subsurface Hardness during the Wet and Dry Seasons in the Rice Fields of Semarang Village, Bengkulu City, Using the MASW Seismic Method
The mechanical properties of soil in agricultural land are greatly influenced by seasonal changes, which can affect productivity and food security. This study aims to analyze the effects of wet and dry seasons on the mechanical properties of subsoil in the rice fields of Semarang Village, Bengkulu City, and their implications for land management that supports food security. The method used was Multichannel Analysis of Surface Waves (MASW) with data acquisition at 24 points using 24 geophones (2 m spacing, 5 m offset). The data was then processed using WinMASW Professional 5.0 software to obtain a 2D model of shear wave velocity (Vs) and Poisson's Ratio to a depth of 30 m. The results showed that during the wet season, the soil was dominated by low Vs values (< 350 m/s) and high Poisson's Ratios (0.4 0.45), indicating saturated and soft conditions. Conversely, during the dry season, Vs values increased (600–1200 m/s) with lower Poisson Ratios (0.35–0.4), indicating a denser and stiffer subsurface medium. These findings confirm that seasonal variations in water content greatly affect the mechanical properties of the soil. Therefore, MASW-based analysis can be used as a basis for planning adaptive water and agricultural land management to support food security in tropical climates.
Evaluation of Matrix Acidizing Using Formation Water Parameters in Hilal Well, Arqom Field, Indonesia
Formation damage due to scale deposition is a common production problem that reduces reservoir permeability and decreases oil and gas well productivity. One effective remediation technique is matrix acidizing. This study evaluates the effectiveness of matrix acidizing in a sandstone reservoir with carbonate mineral content in Hilal well, Arqom Field, by analyzing production rate changes and formation water characteristics before and after treatment. Formation water analysis plays a critical role in evaluating acid compatibility and revealing mineral dissolution mechanisms during the treatment. The Stiff method was used to characterize formation water, followed by matrix acidizing planning through optimal injection volume and pressure calculations. The treatment involved preflush, main acid injection, and displacement, along with an Injectivity Rate Test (IRT). The effectiveness was evaluated using Productivity Index (PI) and Inflow Performance Relationship (IPR) analysis. The results demonstrate that matrix acidizing significantly increased the PI of Hilal well from 1.62 bbl/psi to 3.15 bbl/psi, resulting in a 102% increase in production. Key technical parameters, including formation breakdown pressure (BHFP), acid hydrostatic pressure (pH), and surface treating pressure (STP), aligned with the designed injection volume of 46 bbl. These results demonstrate that matrix acidizing is an effective method for enhancing well productivity.
Optimizing Tsunami Evacuation Route with GIS and Network Analysis: Case Study of Barus City, Central Tapanuli, Indonesia
A tsunami is a natural disaster triggered by the vertical displacement of the seafloor following a major earthquake along a megathrust zone. Barus District lies within the active Sumatran megathrust, making it highly vulnerable to large earthquakes that could generate tsunamis. This study aims to map tsunami hazard and risk zones under a 16-meter wave scenario and to model evacuation routes using Geographic Information Systems (GIS) and Remote Sensing approaches. The research employs a descriptive quantitative method, integrating spatial data through overlay and network analysis techniques. The analysis revealed that high-hazard and high-risk zones each cover 0.64 km² out of the total 2.27 km², primarily located in Pasar Terandam and Pasar Batu Gerigis villages. Evacuation route modeling showed estimated travel times ranging from 25.06 to 65.73 minutes, assuming an average walking speed of 1.2 m/s. Among the designated shelters, the Catholic church offers a more efficient route, whereas evacuation to the HKBP church requires more than 60 minutes exceeding the ideal time limit. These findings highlight the urgent need to prioritize disaster mitigation strategies to ensure the effectiveness of tsunami evacuation systems in high-risk coastal areas.
Hydrothermal Alteration and Geochemical Signatures of High-Sulfidation Epithermal Gold Mineralization in Petai Patah, West Kalimantan, Indonesia
High-sulfidation epithermal systems are an important source of precious metals in volcanic-arc settings, yet detailed studies of these systems in the Schwaner Mountains of western Borneo remain scarce. This study investigates the hydrothermal alteration and geochemical signatures of high-sulfidation epithermal gold mineralization in the Petai Patah area, Ketapang District, West Kalimantan, Indonesia, hosted within the Cretaceous Sukadana Granite and the Paleogene Kerabai Volcanic Complex. An integrated analytical approach was employed, combining reflectance spectroscopy, petrographic analysis, X-ray diffraction (XRD), and whole-rock geochemistry on 15 representative rock samples from surface outcrops and drill cores. Results reveal a well-defined hydrothermal alteration zonation, comprising an advanced argillic core (alunite, pyrophyllite, dickite) in Pit Lokma, surrounded by a phyllic zone (dominant muscovite/sericite–illite–pyrite assemblage) extending into Pit Limun. Gold mineralization (maximum 1.61 ppm Au in sample DC 347, Pit Limun) is spatially correlated with these alteration zones and occurs in association with sulfide minerals, suggesting a structurally controlled fluid pathway. Elevated As concentrations in gold-bearing samples from Pit Limun, together with the diagnostic mineralogical assemblage, support the interpretation of a high-sulfidation epithermal system. This study provides new insights into the spatial relationship between alteration zonation and gold enrichment within a high-sulfidation epithermal system, offering implications for mineral exploration in similar magmatic arc settings across Southeast Asia.
Seabed Morphology and Geohazard Assessment for Subsea Pipeline Routing based on MBES and Seismic Data: A Case Study of Teluk Palabuhanratu, Indonesia
To support the development of subsea pipeline infrastructure across Java, there is a need to assess geohazard potential in Teluk Palabuhanratu. The aim of this study is to characterize seabed morphology and evaluate its implications for geohazard potential for subsea pipeline routes. The method employed consists of morphometric analysis based on digital bathymetric model (DBM) that is derived from multibeam echosounder (MBES), delineation of seabed morphological units by integrating DBM with seismic interpretation, and geohazard assessment based on morphometric parameters and morphological units. Seabed morphology is predominantly characterized by very gentle to gentle slopes, near-planar curvature, and low roughness, while localized zones of steep slopes, complex curvature, and high roughness are associated with faults, submarine landslides, and mud volcanoes. Ten morphological units were identified, including slopes, ridges, knolls, channels, basin floors, sand ridges, mounds, valleys, gullies, and landslides. The geocost-based geohazard assessment indicates a spectrum of hazard potential ranging from low to high for subsea pipeline. High hazard levels are associated with steep slopes, high roughness, and morphological units influenced by erosion and mass-transport processes, such as gullies, valleys, and fault-associated ridges.
Use of the Diffuse Field Assumption (DFA) Method to Determine The Condition of The Subsurface Layer in The Government Office Area of Bengkulu City, Indonesia
Bengkulu City lies in an earthquake-prone region because of tectonic activity along the Sumatra subduction zone. Subsurface characterization is critical for safe infrastructure planning. This study identifies subsurface conditions in the Bengkulu City Government office area using microtremor data analyzed with the Diffuse Field Assumption (DFA) approach. Researchers recorded 52 measurement points to determine key seismic parameters: dominant frequency (f0), amplification factor (A0), seismic vulnerability index (Kg), and shear wave velocity (Vs30). The results show that f0 values range from 3.57 to 14.8 Hz, A0 from 1.62 to 7.18, Kg from 0.30 to 6.35, and Vs30 from 189.29 to 740.48 m/s, indicating significant spatial variation in subsurface conditions. Areas characterized by low f0, high A0, and low Vs30, particularly at points T33 and T41, are identified as zones with higher seismic vulnerability. The application of the DFA approach enables a more reliable estimation of subsurface shear wave velocity and enhances the interpretation of site effects compared to conventional analysis. These findings highlight the importance of integrated seismic parameter mapping to support earthquake hazard mitigation and urban spatial planning in tectonically active regions.
Estimation of Subsurface Structure Using Euler Deconvolution and SVD Methods of Geomagnetic Data in the Non-Volcanic Geothermal Area of Tahi Ite Village, Bombana, Southeast Sulawesi, Indonesia
This study aims to estimate the presence of subsurface structures in the geothermal area of ​​Tahi Ite Village, Bombana Regency, Southeast Sulawesi by using geomagnetic data collected in the field at 656 measurement points using a PPM unit divided into nine survey lines oriented N0oS, with distances between measurement points and between survey lines of approximately 50 m and 180 m, respectively. Based on the research results, the Total Magnetic Intensity (TMI) values for the study area ranged from 42,375.605 to 42,817.045 nT. A value range of 441.44 nT indicates the presence of rock magnetic heterogeneity in the geothermal manifestation area. After applying Diurnal Correction and IGRF Correction, the Total Magnetic Anomaly (TMA) values were found to be approximately -136.89 to 200 nT. The Local Magnetic Anomaly (LMA) was obtained after performing an upward continuation process through four continuation stages up to an altitude of 1,700 m from the reference surface, The Local Magnetic Anomaly (LMA) was obtained after performing an upward continuation process through four continuation stages up to a height of 1,700 m from the reference surface, and was found to be within a range of approximately -120 to 60 nT. Subsequently, Reduced to the Pole (RTP) processing was applied to transform the magnetic response so that it lies above its causative source and exhibits a monopolar nature. On the RTP results, the Euler Deconvolution (DE) method with a Structural Index of N=0 and the Second Vertical Derivative (SVD) method were applied to infer the presence of subsurface structures. The results show the presence of magnetic anomaly patterns suggesting strong structural control with a dominant North–South orientation. It is estimated that there are approximately five to nine minor faults with depths ranging from <15 m (Very Shallow) to >55 m (Deep), and it is known that approximately two minor faults intersect the Tahi Ite hot spring. The existence of these minor faults is thought to act as thermal conduction pathways and channels for the migration of hydrothermal fluids to the surface with the water source in the reservoir originating from surface or meteoric water. These findings are also supported by the presence of outcrops, further confirming that the Tahi Ite Village geothermal system is non-volcanic in nature and controlled by secondary structures in the form of minor faults.