Research related to the identification of slip surfaces was conducted on the Trans Seram Road section in the Sugiarto area, Kariele Hamlet, Haruru Village, Amahai District, Central Maluku Regency. This area is fairly steep and hilly, so landslides often occur. This can disrupt activities and endanger the community, as the area hosts several community settlements and serves as an important route for commodity distribution in the Central Maluku region. This research aimed to assess landslide potential by identifying the slip surface using the ERT (Electrical Resistivity Tomography) method. ERT measurements were carried out using the Wenner-Schlumberger configuration at four locations within a narrow area adjacent to a relatively deep ravine. At each location, one survey line was established parallel to the road, spanning 200 meters and with an electrode spacing of 5 meters. The results of the measurements and data processing revealed indications of slip surfaces at each location, with varying depths reaching up to 18 meters. To achieve optimal results, it is necessary to validate drilling data on rock layers below the surface and to conduct further geotechnical research . In addition, the results of the research are expected to have a positive impact on the community and local government in designing future policies related to regional development and can serve as a reference to encourage further research.
Galunggung volcano (7°15′S, 108°3′E) in West Java, Indonesia, is an active stratovolcano with a significant history of eruptions and widespread impacts on the surrounding area. One major eruption occurred around 4,200 years ago, causing a sector collapse in the southeastern part of the mountain and forming a caldera that shaped the landscape known as the Thousand Hills of Tasikmalaya. Previous studies explained the cause of this collapse as triggered by a massive eruption or by the steep-slope control to the southeast. However, both suggest a tectonic role that may have contributed to the flank collapse. The distribution of hot springs around Galunggung, which forms a lineament toward the caldera, may provide a clue regarding the factors controlling the sector collapse event. We analyzed 117 legacy gravity measurements collected in 2000 and reprocessed them using advanced techniques to examine the subsurface structure and investigate the possibility of a subsurface weak zone. Bouguer anomaly separation using a Butterworth Band-pass Filter and derivative analysis (FHD, FVD, TDX) revealed a linear NW-SE trending low-gravity anomaly (32.5–39.4 mGal) extending ~6 km southeast of Galunggung, indicating the presence of a subsurface fault. This interpretation is supported by the alignment of the distribution of geothermal manifestations and the orientation of the caldera's morphology, which opens in the same direction. This NW-SE inherited fault structure is interpreted to have played a dual role in the volcano dynamics, serving both as a pathway for the migration of hot fluid, which may decrease rock strength, and as a structural weakness intruded by magma. Thus, we propose that this pre-existing fault was a controlling factor in the collapse of Galunggung through a fault-parallel breaching mechanism. These findings have important implications for volcanic hazard assessment in densely populated areas around Galunggung.
Bauxite, the primary ore of aluminium, forms through intense weathering of alumina-rich rocks, typically in tropical climates. In Gunung Kijang, bauxite deposits were commercially mined until 2009, and remnants of these deposits are still observed in the region. This study aims to investigate the bauxitization process in the Gunung Kijang area of Bintan Island, Indonesia, with a focus on geochemical aspects. Samples from stockpile and test pits were analyzed using X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS). Geochemical results show a high concentration of gibbsite (Al(OH)3). Al₂O₃ content ranged from 40.41% to 55.29%, while other oxides, such as SiO₂ and Fe₂O₃, were found in moderate concentrations. Loss on ignition (LOI) values confirmed the weathering intensity of the samples, with higher values indicating more hydroxyl-bearing minerals. Weathering indices, including the Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW), showed that all samples experienced intense chemical weathering. Rare earth element (REE) analysis indicated Light-REE enrichment and a significant positive cerium anomaly, suggesting reductive conditions during bauxitization. The study concludes that the bauxite deposits are highly weathered and exhibit geochemical characteristics typical of tropical bauxite formation.
Mineralogical and geochemical characterization of bauxite ore in stockpile, alumina, and red mud in Kendawangan, Ketapang Regency, West Kalimantan, are conducted to determine the mineral composition, chemical composition, analyze the correlation between mineralogy and geochemistry, and identify the potential of vanadium (V) elements at each stage of the processing of bauxite ore in stockpiles using the X-Ray Diffraction (XRD) and X -Ray Fluorescence (XRF) methods. The results shows that the three types of samples, such as bauxite ore in stockpile, alumina, and red mud. The highest gibbsite mineral and Al₂O₃ content is found in the alumina sample, with >95% gibbsite and 98.74% Al₂O₃, followed by the washed sample from the bauxite ore in stockpile with gibbsite at 92.60% and Al₂O₃ at 56.17%, while the lowest content is found in the red mud sample with gibbsite <1% and Al₂O₃ at 8.11%. Correlation analysis reveals a positive relationship between the main minerals (gibbsite, quartz, kaolinite, and hematite) and the three main oxide compounds (Al₂O₃, SiO₂, and Fe₂O₃). In addition, another correlation analysis exhibits a very strong negative relationship between Al₂O₃ and SiO₂ (R²=0.78), confirming that the alumina enrichment process occurs through the removal of silica in the washing and Bayer processes. Furthermore, the enrichment of vanadium (V) in the form of V₂O₅ is found in red mud, reaching a maximum concentration at 0.19%.
Semeru, one of Indonesia’s most active volcanoes, generated significant pyroclastic density current (PDC) events in December 2020, 2021, and 2022, resulting in varying societal impacts. This study reconstructs the spatial extent and temporal evolution of these PDCs by integrating open-access satellite imagery, official reports, and crowdsourced data from social media and video platforms. Deposits mapping reveals that PDCs primarily affected the southeast sector, with deposits emplacement controlled by topography and prior ravines infilling. Chronological reconstruction shows distinct eruption styles: 2020 and 2022 events developed progressively over several hours, initiated by incandescent rockfalls and culminating in large PDCs, while the 2021 event was abrupt, coinciding with heavy rainfall, exhibiting a shorter duration but greater runout. Crater morphology indicates that all three events were preceded by active lava coulee growth and followed by increased lava extrusion suggesting gravitational collapse as the primary trigger, with meteorological factors potentially enhancing explosivity in 2021. The integration of multi-source open data addresses gaps in official records and enhances eruption documentation, particularly for well-observed volcanoes with persistent activity. However, challenges remain due to diverse variable data quality and the need for careful validation. This approach supports improved hazard assessment and underscores the value of open and citizen-generated data in volcanic crisis response.
Geotourism in Waluran District, part of the Ciletuh–Palabuhanratu UNESCO Global Geopark (UGGp), is exposed to potential degradation and safety risks if its management remains inadequate. This study assesses the sustainability of three geosites, including Taman Batu Cukcrukan, Taman Batu Sarongge, and Lorong Tengah, through an integrated approach combining Degradation Risk Assessment and Hazard Identification, Risk Assessment, and Determining Control (HIRADC). The first method was applied to evaluate site vulnerability to several factors using standardized scoring criteria, while the latter was applied to recognize hazards by considering their likelihood and severity, followed by determining control measures in line with the ISO 45001 framework. The results indicate that none of the sites can yet be categorized as threatened. Nevertheless, Taman Batu Cukcrukan attained the highest risk score (4.25), largely linked to its relative accessibility and proximity to problematic areas. Field observations also revealed recurring safety concerns, such as steep and slippery trails, unsafe bridges, deep river holes, and unstable rocks, with 60% of hazards in Taman Batu Cukcrukan categorized as high risk. The methodological strength lies in combining degradation assessment with HIRADC, which not only highlights governance and conservation weaknesses but also converts them into practical safety measures. This integrated approach provides structured prioritization of risk control and management. The findings underscore the importance of targeted mitigation measures, including infrastructure improvements, slope stabilization, routine maintenance, and visitor education. Overall, this study demonstrates that proactive risk management is essential to preserve geodiversity, enhance visitor safety, and secure the long-term sustainability.
Squeezing refers to large, time-dependent deformations that happen around the tunnel perimeter. This phenomenon commonly occurs in tunnel excavations with poor rock mass class and very great depth. In many cases, squeezing exerts considerable pressure, which can damage the installed tunnel support system. In this study, numerical modeling was carried out on 10 tunnels in both squeezing and non-squeezing conditions based on data from the literature, using actual support pressure values to obtain modeled convergence values that match the observed ones. The results showed a difference between the numerical and actual convergence values that were due to additional pressure from squeezing. This squeezing pressure was then modeled by increasing the horizontal and vertical stresses until the numerical convergence matched the actual convergence. The effectiveness of this approach was confirmed by plastic zone validation in a selected case using the 2D FEM method. The final model successfully reflected real tunnel behavior, particularly in squeezing-prone zones. These results emphasize the importance of accurately modeling squeezing pressure to determine realistic deformation levels and develop appropriate support design.
Coastal areas support diverse human activities such as fishing, aquaculture, salt farming, and tourism, but are increasingly vulnerable to plastic pollution. This study investigates microplastic contamination in beach sediments of Cirebon, Indonesia—a densely populated coastal city with intense trade and tourism. Fifteen sediment samples were collected from five sites, representing both fishermen settlements and tourist beaches. The average microplastic abundance was 583.33 ± 166.09 particles·kg⁻¹ dry weight. Although particle abundance did not significantly differ among sites, significant variation was observed in microplastic size. Films were the dominant morphotype (84%), with white being the most common color (48%). Smaller particles (<1 mm) comprised 51% of total microplastics. Fourier Transform Infra-Red analysis of microplastics sized 2–5 mm identified polyethylene as the most abundant polymer (50%), commonly used in packaging and household products. Raman spectroscopy also revealed organic pigments potentially containing metal-based fouling agents. The dominance of plastic films, especially near settlements, suggests direct household waste discharge into the ocean. These findings highlight the role of human activity and inadequate waste infrastructure in driving coastal microplastic pollution. Effective waste management strategies and public awareness are essential to mitigate further contamination and protect coastal ecosystems
Folding and subsequent pinching out are common geological features in geologically active areas. This gives layers a non-uniform thickness, especially for a multilayer slope with a weak interlayer. Thickness non-uniformity is often disregarded in stability analysis to simplify slope models. However, the geometrical variability of rock masses always exists, and the impact is inevitable; therefore, it is not to be discounted. This research systematically established a geometric correlation framework to understand how tapering configurations in weak interlayer influence slope stability in layered rock masses. Analytical and numerical methods are implemented using the RocScience code. Statistical analysis was also performed to assess the significance and correlation of tapering configurations to slope stability conditions. It was found out that Tilting Intensity (ρ≥0.736) and Thickness Gradient (ρ≥0.743) consistently exhibited the strongest (α=0) negative correlation with critical strength reduction factors and slip surface radius, confirming that taper steepness and vertical irregularity are the dominant geometrical destabilizers in non-uniform weak layers. Moreover, stratigraphic unevenness not only exerts a direct destabilizing influence but also modulates the sensitivity of other geometrical parameters, such as the aspect ratio, by a factor of 2 units ΔFS recorded at the highest elevation. The findings of this study carry several practical and scientific implications for slope design, geomechanical modeling, and geological interpretation in complex stratified rock masses.
In general, liquefaction occurs in areas with high seismic activity and saturated, loose, sandy soil. The Soekarno-Hatta International Airport is situated in an area with a medium to high potential for earthquake occurrence. This paper aims to predict the liquefaction potential around the third runway of Soekarno-Hatta International Airport. The liquefaction potential analysis was conducted using the Idriss-Boulanger method, calculating the liquefaction safety factor to a depth of 20 m. There are 54 locations for which N-SPT bore log data and soil laboratory tests were used in this analysis. The variation of Peak Ground Acceleration used in the analysis was obtained from the earthquake risk map of Indonesia. Furthermore, the liquefaction potential zone was mapped using QGIS, considering the Liquefaction Potential Index (LPI), Liquefaction Severity Index (LSI), and Liquefaction Severity Number (LSN). The results show that there is no significant difference between LSI and LSN, and a slight difference in favor of LPI. Several locations have the potential to experience liquefaction, especially in the central, northeastern, and slightly southwestern parts of the runway construction area.
This study was conducted to investigate the hydrogeochemical features and sources of pollution in Cirasea River located in the highly polluted Citarum Watershed, Indonesia. Field sampling was performed during the dry season to provide insight into the water quality during its most critical period. The water quality of river water and groundwater samples was evaluated and the natural geological controls and anthropogenic impact were compared using integrated hydrogeochemical methods (Gibbs, Stiff, and Piper diagrams) and statistical analyses (Pearson’s correlation). Gibbs analysis showed that the main factor controlling the composition of water was water-rock interaction. Stiff diagrams revealed an evolutional trend of water chemistry from upstream to downstream, controlled by lithology (upstream) and land use (downstream). Piper diagrams showed that the dominant hydrochemical facies for both river and groundwater was Ca2+–Mg2+–HCO3− which is typical for volcanic rock weathering. Statistical analysis confirmed that the lithological types (Qgpk and Qmt) significantly affected the hydrogeochemical parameters (TDS, EC, Na⁺, K⁺, HCO₃⁻). The study also showed the impact of land use, especially dryland agriculture (TDS, EC, K+, SO42−) and residential areas (Na+, Cl−, Mg2+, HCO3−) on groundwater chemistry. The results provide a scientific basis for targeted monitoring and sustainable management strategies for reduction of water quality degradation in the Cirasea River sub-watershed considering both geological and anthropogenic pressures.
This study provides a morphological and mineralogical characterization of sands from the dunes at El Hadjeb, near Biskra, southeastern Algeria. At the transition between Saharan and steppe environments, these dunes are of growing environmental and tourism significance. Representative sand samples from three distinctly different geomorphological positions were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. XRD indicated quartz-dominated composition (up to 92.28 wt.%), with subordinate levels of calcite, indicating high mineralogical maturity, characteristic of well-developed aeolian systems. SEM analysis revealed sub-angular to sub-rounded grains with conchoidal fractures, micro-scarps, and pitting, typical of high-intensity mechanical weathering and long-distance transport in winds. The absence of clay coatings, gypsum phases, and biological material further confirms the arid, high-energy deposition setting. These results improve the understanding of the mineralogical maturity and textural characteristics of Saharan dune sands, which is essential for evaluating their suitability in soil rehabilitation, their integration into building materials, and their relevance to regional planning for ecotourism. The combined use of XRD and SEM illustrated how complementary geoscientific methods can provide detailed mineralogical and textural information essential for supporting sustainable management strategies in the studied region.
This study investigates the liquefaction potential in Tambak Wedi Subdistrict, Surabaya, employing the electrical resistivity geophysical method with a dipole-dipole configuration and the Cone Penetration Test (CPT). The electrical resistivity method is employed to assess the resistivity values of soil layers and to generate a two-dimensional subsurface profile. The CPT method is applied to confirm the soil layer types and to compute the safety factor (SF). The soil data from both methods are subsequently analyzed to evaluate the liquefaction potential based on the soil resistivity and SF values. The analysis incorporates a Peak Ground Acceleration (PGA) of 0.3 g and considers an earthquake magnitude of 7.5 Mw. The findings from this study reveal that the soil layers ranging from sandy to organic soil, with dominant silt-sandy and clay-silt layers present up to a depth of 10 meters, and clay-silt and clay layers from 11 to 20 meters. Except in the first 2 meters depth, the calculated SF is less than 0.6, indicating a high liquefaction potential in the region. The assessment of liquefaction potential in this study involved the calculation of N-SPT, Liquefaction Potential Index (LPI), and Liquefaction Severity Index (LSI). These findings underscore the importance of incorporating sitespecific geotechnical evaluations into disaster risk reduction strategies, as they provide critical input for the development of effective mitigation plans aimed at minimizing potential loss of life and economic impact.
Rock strength is a fundamental parameter in rock mechanics, serving as the basis for predicting rock behavior under various loading conditions. Among the various approaches to characterizing rock strength, shear testing of discontinuities plays a crucial role. The Joint Roughness Coefficient (JRC) provides an empirical link between joint surface roughness and shear strength parameters. In this study, joint surface profiles were reconstructed statistically based on JRC parameters and subsequently reproduced using three-dimensional (3D) printing technology. The printed molds were employed to cast laboratory specimens with pre-formed shear surfaces, which were then tested under direct shear conditions. The shear strength parameters obtained from the tests were analyzed in relation to their corresponding JRC values. The results demonstrate that the reconstructed and 3D-printed surfaces were successfully fabricated and accurately replicated joint roughness geometries. Direct shear tests confirmed the expected trend, with shear strength increasing alongside JRC. These findings indicate that shear surfaces can be prefabricated and manipulated with controlled roughness, providing a reliable and reproducible platform for investigating the mechanical behavior of rock joints.
Earthquakes and rainfall can trigger landslides in many regions of Indonesia. Rock slopes of andesite outcrops in Gunung Batu and Graha Puspa areas coincide with the Lembang active fault zone in West Java. The region is also subjected to high-intensity rainfall. Thus, the rock slopes are prone to failure during earthquake shaking and heavy rainfall. To mitigate the hazards associated with slope failure in residential areas close to the rock slopes, it is necessary to assess the slope failure hazard at the andesite hill slopes. The study presented in this paper aims to analyse the stability of the andesite slopes using the pseudostatic limit equilibrium method and evaluate the effect of variations of regional seismicity and water content on the stability of the slopes. Pseudostatic analysis considered the peak ground acceleration (PGA) and the calculated horizontal seismic coefficient (kh). The limit equilibrium method was focused on toppling and wedge failure cases. Based on the analysis, the andesite slopes in Gunung Batu and Graha Puspa are stable (FoS >= 1.1) in factual conditions (dry-static). In contrast, all slopes have the lowest FoS values (less stable-unstable) under the saturated-pseudostatic conditions. The threshold values of kh and %w (percent water fill) for the slopes' instability were obtained by varying the regional seismicity and water content conditions. It is recommended that numerical slope stability modeling (i.e., finite element method) be conducted to improve the accuracy of the models.
This study evaluates four numerical methods-Euler, Heun, Runge-Kutta 4th order (RK4), and Adams-Bashforth-in terms of their accuracy and computational efficiency for solving the Horton infiltration model, which is crucial for hydrological studies. The methods were applied to simulate soil infiltration and cumulative recharge, with a focus on determining the most suitable method for practical applications in water resource management, agriculture, and soil conservation. An ANOVA (Analysis of Variance) test was conducted to assess the statistical significance of differences in the results obtained from the methods. The test revealed no significant differences between the methods (p-value = 0.9995), indicating that despite differences in computational complexity and accuracy, the methods produced similar results. The Euler method, being the simplest and fastest, provided acceptable results for shorter simulations or less critical applications, while RK4 and Heun, though more computationally expensive, yielded more accurate estimates. Adams-Bashforth offered a reasonable balance between accuracy and efficiency. This study highlights the importance of selecting the appropriate numerical method based on both accuracy and computational cost, particularly for real-time applications and large-scale simulations in hydrology. The findings suggest that simpler methods like Euler can be used for less critical tasks, while more accurate methods like RK4 should be employed for high-precision modeling in complex hydrological scenarios.
Investment decisions in upstream oil and gas sector of Indonesia often involve acquiring stakes in existing Production Sharing Contract (PSC) areas. Such decisions require careful assessment of geological uncertainty, economic viability, and regulatory constraints. For investors evaluating PSC blocks, a robust understanding of regional geological risk within the petroleum system is critical. This study introduces a practical and scalable geological risk quantification framework to support upstream investment decisions in the LNG sector in Indonesia. The framework is designed for application under the current fiscal regime and can be effectively implemented even when data availability is limited, such as when relying on information from the Migas Data Repository (MDR). Recognizing that early-stage opportunities often involve significant geological uncertainty, we developed a tailored petroleum system risk metric comprising five parameters: source rock, trap, dynamic factors, reservoir conditions, and subsurface issues. The framework was applied to five PSC blocks using Multi-Attribute Utility Theory (MAUT), integrating operator-specific economic indicators (Net Present Value, Internal Rate of Return, Payout Time, and Profitability Index) alongside CO2 emission intensity. Monte Carlo simulations were conducted to evaluate investment rankings under uncertainty. A key finding is that the proposed risk quantification approach is simple enough to be implemented with limited MDR data, yet robust enough to support investment strategy. Furthermore, the framework builds upon and complements existing standardization efforts by the regulator, SKK Migas, offering a practical tool for upstream investors in an evolving regulatory landscape.
The purpose of this study is to determine the type and distribution of volcanic rocks both laterally and vertically and to analyze the potential hazards of the Karaha-Sadakeling Volcanic Complex. Volcanostratigraphically, the volcanic evolution from old to young is Cakrabuana Crown, Sadakeling Crown, Ewaranda Crown, and Talagabodas Crown. The recognizable landforms are crater traces, volcanic cones, lava flow ridges, and alluvial plains. The north-south oriented volcanic cone morphology of the study area parallels an approximate major fault that passes between the Cakrabuana Complex to the northeast, and the Karaha-Sadakeling Complex. The northern part is dominated by Sadakeling Crown volcanic deposits, the central part is composed of Ewaranda Crown deposits, and the southern part is dominated by Talagabodas deposits. The magmatic evolution shows the process of magma assimilation and mixing with primitive magma. Potential volcanic disasters can include pyroclastic fall, pyroclastic flows, and lava flows. Primary eruptions are inferred to originate from Karaha Crater, which exhibits ongoing volcanic activity.
This study aims to analyze the rock mass quality of Soko Cave, located in Temayang District, Bojonegoro Regency, East Java, as a basis for evaluating geotechnical stability for tourism purposes. Three rock mass classification methods were used: Q-System, Rock Mass Rating (RMR), and Geological Strength Index (GSI). Data were obtained through field surveys, geological mapping, cave geometry measurements, and observation of discontinuities using the scanline method at 11 observation stations. The rock mass quality was generally classified as good to very good, with the Q-System method producing the highest score, followed by GSI and RMR. The differences in results were due to the different parameters used by each method. Based on these findings, the rock mass in Soko Cave was considered naturally stable and did not require additional support structures, making it safe for geological tourism development. This study not only compares methods but also emphasizes the importance of using the three systems complementarily to provide a realistic and applicable picture of the stability of rock masses in carbonate caves. The GSI method shows potential as a reliable approach for this environment, although further validation with a broader data coverage is needed.
