2025-12-24
Volvariella Volvacea, Adi Susilo, Wa Ode Sumartini
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 utilized to acceess the resistivity values of soil layers and to generate a 2D 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 0.3g 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.
2025-12-24
Ulfa Ambarwati, Agus Hendratno
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.
2025-12-24
Qi Adlan, Eric Aldo Tanuwijaya
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.
2025-12-24
Wira Cakrabuana, Imam Achmad Sadisun, Adrin Tohari, Indra Andra Dinata, Mudrik Rahmawan Daryono, Rendy Dwi Kartiko, Antonina Pri Martireni, Koko Hermawan, Hasan Tri Atmojo
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.
2025-12-24
Aminah Rahmadani Lubis, Lindung Zalbuin Mase, Khairul Amri, Rena Misliniyati, Fepy Supriani
This research presents a unique microzonation map based on shear wave variations, specifically Vs10, Vs20, Vs30, Vs40, and Vs50. Microzonation is dividing a region into smaller zones based on specific characteristics, such as soil resistance to seismic waves. The method used in this research includes secondary data collection of shear wave velocity values and soil layers in the District of Kampung Melayu, then producing shear wave velocity distribution at various depths, soil site class distribution map, and Ground Amplification Factor (GAF) distribution map. The results of this study indicate that the variation in shear wave velocity at different depths provides an overview of the soil type resistance in Kampung Melayu District, Bengkulu City. The resulting microzonation map, a novel approach in this context, indicates an increase in the Vs value with increasing depth. Additionally, the Ground Amplification Factor (GAF) distribution reveals that areas with low soilspecific resistance exhibit higher amplification values, thereby increasing their susceptibility to seismic vibrations. These findings provide valuable and novel information for earthquake risk mitigation and the planning of safer infrastructure in this area, significantly contributing to civil engineering and urban planning.