Bulletin of Scientific Contribution (BSC) Peer-Reviewed • Open Access • Earth Sciences and Applied Geology Journal About the Journal Bulletin of Scientific Contribution (BSC) is a peer-reviewed, open-access journal published by the Faculty of Geological Engineering, Universitas Padjadjaran. The journal aims to provide a platform for scientists, researchers, and academicians to share and discuss breakthrough ideas, innovative methods, and significant findings in the field of Earth Sciences and Applied Geology. BSC accepts original research articles, review papers, and short communications that have not been published previously. The journal is committed to maintaining high ethical standards in publishing and ensuring a rigorous double-blind peer-review process. Scope of the Journal The journal welcomes submissions focusing on a wide range of geological disciplines, including but not limited to: Structural Geology and Tectonics Volcanology, Petrology, and Mineralogy Geochemistry and Geochronology Sedimentology and Stratigraphy Geophysics and Applied Geophysics Petroleum Geology and Energy Resources Hydrogeology and Environmental Geology Geological Engineering and Geohazards Language Policy Bulletin of Scientific Contribution (BSC) accepts original research articles, review papers, and short communications written in either English or Indonesian. However, to ensure broader international visibility and reach a global audience, authors are highly encouraged to submit their manuscripts in English. All accepted articles must include titles, abstracts, and keywords in both languages. Publication Frequency Bulletin of Scientific Contribution is published three times a year: April August December Open Access Policy This journal provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.
Fakultas Teknik Geologi Universitas Padjadjaran
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EVALUASI MORFOTEKTONIK SEBAGAI FAKTOR PENGONTROL LONGSORAN DI KAWASAN SESAR LEMBANG
ABSTRACT The Lembang Fault is recognized as one of the major active fault structures in West Java with significant potential to trigger geological hazards, particularly earthquakes and landslides. The morphology of the area is characterized by steep slopes underlain by volcanic rocks that have undergone intensive weathering, making them highly susceptible to landslide. This study aims to examine the relationship between morphotectonic parameters, geological conditions, and landslide distribution in the northern part of the Bandung Basin. The analysis employs a quantitative geomorphological approach utilizing Digital Elevation Models (DEM) imagery and the calculation of morphotectonic indices, including Assymetric factor (Af), Basin shape index (Bs), Sinuosity of mountain front index (Smf), and valley floor width-to-height ratio (Vf). The findings indicate that most landslide occurrences are concentrated in areas with high Index of Relative Tectonic Activity (IRTA), reflecting both active tectonic deformation and unstable slope conditions. The integration of morphotectonic parameters with landslide data has proven effective in delineating hazard-prone zones with higher accuracy, thereby providing a valuable reference for geological hazard mitigation efforts in the Lembang Fault area. Keywords: Morphotectonic; geomorphology; landslide; Lembang Fault; Bandung Basin ABSTRAK Sesar Lembang dikenal sebagai salah satu struktur patahan aktif di Jawa Barat yang memiliki potensi besar memicu bencana geologi, terutama gempabumi dan gerakan tanah. Morfologi wilayah ini didominasi oleh lereng curam dengan batuan vulkanik yang telah mengalami pelapukan intensif, sehingga rentan terhadap terjadinya longsoran. Penelitian ini bertujuan untuk menelaah keterkaitan antara parameter morfotektonik, kondisi geologi, dan distribusi longsor di bagian utara Cekungan Bandung. Analisis dilakukan melalui pendekatan geomorfologi kuantitatif dengan memanfaatkan citra Digital Elevation Model (DEM) serta penghitungan sejumlah indeks morfotektonik seperti Faktor asimetri DAS (Af), Indeks bentuk DAS (Bs), Indeks sinusitas muka gunung (Smf), dan Rasio dasar lembah berbanding tinggi lembah (Vf). Temuan penelitian mengindikasikan bahwa mayoritas kejadian longsor terkonsentrasi pada area dengan nilai Indeks Aktivitas Tektonik Relatif (IATR) tinggi, yang mencerminkan aktivitas tektonik aktif sekaligus lereng tidak stabil. Integrasi antara parameter morfotektonik dengan data longsoran terbukti efektif dalam memetakan zona rawan dengan tingkat akurasi lebih tinggi, sehingga dapat dijadikan acuan penting bagi upaya mitigasi bencana geologi di kawasan Sesar Lembang. Kata Kunci : Morfotektonik; geomorfologi; longsor; Sesar Lembang; Cekungan Bandung
KARAKTERISTIK GEOMORFOLOGI DAERAH CIMARAGANG DAN SEKITARNYA, KECAMATAN CIDAUN DAN CISEWU, KABUPATEN CIANJUR DAN GARUT, PROVINSI JAWA BARAT
Penelitian ini dilakukan di daerah Cimaragang dan sekitarnya yang secara administratif berada di Kecamatan Cidaun dan Cisewu, Kabupaten Cianjur dan Garut, Provinsi Jawa Barat. Secara regional, daerah penelitian termasuk ke dalam Zona Pegunungan Selatan Jawa Barat yang terbentuk akibat aktivitas subduksi Lempeng Indo-Australia di bawah Lempeng Asia sejak Oligosen Akhir. Kondisi tektonik tersebut menghasilkan keragaman bentang alam yang mencerminkan interaksi antara proses geologi endogen dan eksogen sehingga daerah ini memiliki karakteristik geomorfologi yang menarik untuk dikaji. Penelitian ini bertujuan untuk menganalisis karakteristik geomorfologi daerah penelitian berdasarkan aspek morfografi, morfometri, dan morfogenetik sebagai dasar dalam pengelompokan satuan geomorfologi. Penelitian dilakukan melalui analisis data Digital Elevation Model (DEM), interpretasi citra satelit, serta verifikasi lapangan. Analisis morfografi digunakan untuk mengidentifikasi bentuk lahan dan pola pengaliran, morfometri untuk klasifikasi kemiringan lereng, dan morfogenetik untuk mengkaji proses endogen dan eksogen yang berperan dalam pembentukan bentang alam. Hasil penelitian menunjukkan bahwa daerah penelitian didominasi oleh bentuk lahan perbukitan dengan elevasi 50–675 mdpl dan kemiringan lereng yang bervariasi dari sangat landai hingga sangat curam, dengan dominasi kelas lereng curam yang menunjukkan intensitas proses geomorfologi yang relatif tinggi. Pola pengaliran yang berkembang meliputi subparalel, radial, dan braided yang mencerminkan pengaruh kontrol struktur geologi, morfologi vulkanik, serta suplai sedimen yang tinggi pada segmen sungai tertentu. Secara morfogenetik, bentang alam daerah penelitian terbentuk akibat interaksi proses endogen dan eksogen. Proses endogen meliputi aktivitas vulkanik yang menghasilkan litologi breksi vulkanik dan tuf serta aktivitas tektonik yang mengontrol struktur geologi dan kemiringan lereng. Sementara itu, proses eksogen berupa pelapukan dan erosi berperan dalam memodifikasi bentuk lahan yang telah terbentuk sebelumnya. Berdasarkan integrasi aspek morfografi, morfometri, dan morfogenetik, geomorfologi daerah penelitian diklasifikasikan ke dalam empat satuan, yaitu Perbukitan Vulkanik Curam, Perbukitan Struktural, Perbukitan Vulkanik Landai, dan Lembah Fluvial. Klasifikasi ini memberikan gambaran mengenai pengaruh proses geologi terhadap perkembangan bentang alam di daerah penelitian.
LANDSLIDE VULNERABILITY ZONE USING ANALYTICAL HIERARCHY PROCESS (AHP) METHOD IN BANYURESMI VILLAGE, SUKASARI DISTRICT, SUMEDANG, WEST JAVA
Landslides are a common natural disaster in Indonesia, especially in Banyuresmi Village, Sukasari District, Sumedang Regency, which is a research area covering 9.58 . This study aims to identify landslide vulnerability zones using the Analytical Hierarchy Process (AHP) method. This method is used in decision making by compiling a process hierarchy structure, a pairwise comparison matrix, class and subclass weighting analysis, and a consistency ratio (CR) test. The method was applied to evaluate and spatially overlay the controlling factors of landslide vulnerability, namely slope gradient, lithology, aspect (slope direction), land cover, and distance from streams. The results showed that the study area was predominantly classified as having moderate to high vulnerability, with the high vulnerability zone covering 60.94% of the area, the moderate vulnerability zone covering 38.38%, and the low vulnerability zone covering only 0.68%. Slope gradient was identified as the dominant factor, followed by lithology and aspect. Field validation confirmed a strong spatial correlation between the mapped high-risk zones and the actual locations of reported landslides, demonstrating the reliability of the method through field validation. Overall, this study provides a scientific basis and recommendations for land use planning, minimizing the risk of landslides, and mitigation strategies, especially in residential areas in Banyuresmi Village. Keywords: Analytical Hierarchy Process, Banyuresmi, Landslide, Sumedang, Slope
Dinamika Tutupan Hutan pada Lanskap Penyangga Karst Sangkulirang 1990–2020 dan Implikasinya terhadap Pengelolaan Karst
ABSTRACT The Sangkulirang–Mangkalihat Karst in East Kalimantan represents one of the largest karst landscapes in Southeast Asia, characterized by complex carbonate formations, extensive cave systems, and significant ecological and archaeological values. The sustainability of this karst system is not only controlled by its carbonate lithology but also strongly influenced by the surrounding buffer landscape, which functions as a recharge area regulating hydrological processes. This study aims to analyze the spatiotemporal dynamics of forest cover within the karst buffer landscape during the period 1990–2020 and to evaluate its implications for karst management. The analysis was conducted using multitemporal Landsat imagery processed through the Google Earth Engine (GEE) platform, including cloud masking, median composite generation, and Normalized Difference Moisture Index (NDMI)–based classification. Forest cover was identified using a NDMI derived from near-infrared (NIR) and shortwave infrared (SWIR) bands, and spatial extent was calculated for each observation year. The results indicate that forest cover experienced significant fluctuations over the study period. Forest area decreased from 438,259 ha in 1990 to 419,807 ha in 1995 and reached its lowest extent of 181,608 ha in 2000, indicating a period of intensive deforestation. Subsequently, forest cover gradually recovered to 330,405 ha in 2005, remained relatively stable at 313,495 ha in 2010, and increased to 354,042 ha in 2015 and 445,208 ha in 2020, surpassing its initial condition. Spatial analysis reveals that forest loss was predominantly concentrated in non-karst areas located in the southern and southeastern parts of the study area, which are characterized by sedimentary lithology, gentler morphology, and higher accessibility. In contrast, forest cover within carbonate karst areas remained relatively stable due to steep topography, high permeability, and limited land-use suitability. These findings highlight the critical role of buffer landscapes in maintaining karst system stability, particularly in regulating infiltration processes and protecting hydrological balance. The study emphasizes that effective karst management should adopt an integrated landscape approach that includes both core karst zones and surrounding buffer areas. This is consistent with the designation of the Sangkulirang–Mangkalihat region as geological heritage under Ministerial Decree No. 187.K/GL.01/MEM.G/2024, which provides a regulatory framework for sustainable karst conservation and geopark development. Keywords: Sangkulirang Karst, forest cover change, buffer landscape, Google Earth Engine, karst management ABSTRAK Kawasan Karst Sangkulirang–Mangkalihat di Kalimantan Timur merupakan salah satu bentang alam karst terbesar di Asia Tenggara yang memiliki kompleksitas geologi tinggi, sistem gua yang luas, serta nilai ekologis dan arkeologis yang penting. Keberlanjutan sistem karst tidak hanya ditentukan oleh litologi karbonat, tetapi juga sangat dipengaruhi oleh kondisi lanskap penyangga yang berfungsi sebagai daerah imbuhan air dan pengontrol proses hidrologi. Penelitian ini bertujuan untuk menganalisis dinamika spasial dan temporal tutupan hutan pada lanskap penyangga karst selama periode 1990–2020 serta implikasinya terhadap pengelolaan kawasan karst. Analisis dilakukan menggunakan citra Landsat multitemporal berbasis Google Earth Engine (GEE) melalui tahapan masking awan, komposit median, dan klasifikasi berbasis Normalized Difference Moisture Index (NDMI). Identifikasi tutupan hutan dilakukan menggunakan NDMI yang sensitif terhadap kandungan air berbasis kanal near-infrared (NIR) dan shortwave infrared (SWIR), kemudian luas tutupan hutan dihitung untuk setiap periode pengamatan. Hasil penelitian menunjukkan bahwa tutupan hutan mengalami dinamika fluktuatif selama periode pengamatan. Luas hutan menurun dari 438.259 ha pada tahun 1990 menjadi 419.807 ha pada tahun 1995, dan mencapai titik terendah sebesar 181.608 ha pada tahun 2000 yang mencerminkan fase deforestasi intensif. Setelah periode tersebut, tutupan hutan mengalami pemulihan bertahap hingga mencapai 330.405 ha pada tahun 2005, relatif stabil pada 313.495 ha pada tahun 2010, dan meningkat menjadi 354.042 ha pada tahun 2015 serta 445.208 ha pada tahun 2020 melampaui kondisi awal. Analisis spasial menunjukkan bahwa perubahan tutupan hutan lebih dominan terjadi pada wilayah non-karbonat di bagian selatan dan tenggara yang memiliki morfologi lebih landai dan aksesibilitas tinggi. Sebaliknya, kawasan karst berbatuan karbonat menunjukkan tutupan hutan yang relatif stabil akibat topografi terjal dan keterbatasan pemanfaatan lahan. Temuan ini menegaskan bahwa lanskap penyangga memiliki peran penting dalam menjaga stabilitas sistem karst, terutama dalam mengontrol proses infiltrasi dan keseimbangan hidrologi. Oleh karena itu, pengelolaan kawasan karst perlu dilakukan secara terpadu dengan mempertimbangkan keterkaitan antara zona inti karst dan lanskap penyangganya. Hal ini sejalan dengan penetapan kawasan sebagai warisan geologi melalui Kepmen ESDM No. 187.K/GL.01/MEM.G/2024 yang menjadi dasar dalam pengelolaan karst secara berkelanjutan. Kata Kunci : Karst Sangkulirang, tutupan hutan, lanskap penyangga, Google Earth Engine, pengelolaan karst
ANALISIS PERSEBARAN SEISMISITAS DAN MEKANISME FOKAL DI WILAYAH TIMUR PULAU JAWA
Pulau Jawa merupakan wilayah dengan aktivitas seismotektonik kompleks akibat interaksi antara subduksi Lempeng Indo-Australia dan Lempeng Sunda serta keberadaan sejumlah sesar aktif di daratan. Penelitian ini bertujuan untuk menganalisis persebaran seismisitas dan mekanisme fokal gempa bumi di kawasan Jawa Timur sebagai kajian awal untuk memahami pola tektonik regional. Data yang digunakan meliputi katalog ISC-EHB (1964–2021), BMKG (2009–2021), serta data moment tensor dari GCMT (1976–2022). Setelah proses penyaringan dan penggabungan, sebanyak 13.782 kejadian gempa dianalisis berdasarkan distribusi spasial, kedalaman, serta penampang vertikal per interval 1° bujur. Hasilnya menunjukkan pola seismisitas yang mengikuti geometri subduksi Indo-Australia, membentuk zona Wadati–Benioff dengan kemiringan slab curam ke arah utara–timur laut hingga kedalaman ~600 km. Variasi seismisitas antar lintasan mengindikasikan adanya kemungkinan slab tear dan zona seismic gap pada segmen tengah. Mekanisme fokal memperlihatkan dominasi thrust fault di zona megathrust, sementara wilayah daratan didominasi sesar strike-slip dan oblique-slip yang berkaitan dengan Sesar Kendeng Timur, Probolinggo, dan Blitar. Temuan ini mengonfirmasi bahwa deformasi tektonik di Jawa Timur dipengaruhi oleh kombinasi proses subduksi dan aktivitas sesar lokal, yang penting untuk pemodelan bahaya seismik dan mitigasi bencana gempa bumi di wilayah ini.
GEOCHEMISTRY OF VOLCANIC ROCKS OF THE BALEENDAH AREA AND SURROUNDINGS, BANDUNG REGENCY, WEST JAVA
The Baleendah area, Baleendah District, Bandung Regency, West Java, contains andesitic-dacitic volcanic rocks produced during the second eruptive phase of Baleendah Volcano (~2.8–3.2 Ma). Major-oxide XRF analyses of four representative samples (ESR 02, ESR 14, ESR 18, ESR 22) yield SiO2 contents of 57.6–63.3 wt.%, classifying the rocks as andesite on the Total Alkali–Silica diagram. The FeOt/MgO vs. SiO2 diagram and AFM ternary diagram both place the samples within the tholeiitic series field; ESR 14 is transitional with the highest FeOt/MgO ratio of 9.45. Harker variation diagrams reveal systematic decreases in Al2O3, CaO, MgO, and FeOt with increasing SiO2, consistent with fractional crystallisation of plagioclase, pyroxene, and Fe–Ti oxides. Compared to the older Pliocene calc-alkaline suite from the Southern Bandung area (samples KRM and CPN), the ESR samples show lower MgO, CaO, Sr, V, and Co concentrations alongside higher FeOt/MgO ratios, indicating a more iron-enriched, more evolved magma. The tholeiitic character, elevated FeOt/MgO, and depleted compatible element concentrations collectively point to advanced fractional crystallisation under relatively low oxygen fugacity within a shallow crustal magma chamber beneath the Baleendah volcanic system.
HYDROGEOLOGICAL CONDITIONS USING AN INTEGRATION OF AQUIFER GEOMETRY MODEL AND GROUNDWATER CHARACTERISTICS IN THE BANDUNG CITY AREA
ABSTRACT The rapid population and economic growth in Bandung City has driven increased groundwater use, necessitating an understanding of hydrogeological conditions to prevent negative consequences. This study aimed to identify the distribution of subsurface rocks, hydrostratigraphy, and groundwater characteristics in shallow aquifer systems through aquifer geometry modeling and ground-based observations. The model was developed by integrating regional geological data, 22 one-dimensional geophysical points, 7 well logging points, and previous research results, and analyzed using modeling software and GIS software. Resistivity interpretation reveals aquifer lithology consisting of coarse tuff, lapilli, and tuffaceous sandstone (21–103 Ohm.m), aquiclude lithology consisting of fine tuff, tuffaceous claystone (0–30 Ohm.m), and volcanic breccia (101–350 Ohm.m), and aquifug lithology in the form of lava (>350 Ohm.m). The model shows the dominance of tuff sandstone in the northwest, fine tuff in the northeast, and tuff claystone in the southeast. The model revealed two types of developed aquifers, unconfined aquifer at a depth of 0–34.08 m (shallow aquifer system) and confined aquifer at 41.75–68.5 m (deep aquifer system). The characteristics of groundwater in the shallow aquifer system are categorized as fresh groundwater with EC values of 183–897 µS/cm, TDS 92–447 mg/l, and pH 5.4–6.86. Spatial distribution analysis of EC, TDS, and pH values is influenced by lithology, topography, and land cover. Vegetation in the upstream area preserves groundwater quality, while the dominance of built-up land and plantations increases EC, TDS, and pH to close to neutral levels. The results of this study emphasize the need for vegetation conservation in the upstream area, control of land use change, and urban spatial planning based on recharge to maintain the sustainability of groundwater resources in shallow aquifer system in the Bandung City area. Keywords: Groundwater, Hydrostratigraphy, Model, Aquifer, Groundwater Characteristic
Geomorphological Characteristics and Their Implications for Development Planning in the Muaro Kalaban Area, West Sumatra, Indonesia
Understanding geomorphic units and expressions is essential for development planning in areas undergoing tectonic deformation and active surface processes. Several factors such as variations in slope, landform type, and fluvial dynamics strongly influence the occurrence of possible geomorphic hazards such as landslides, erosion, and flooding. Muaro Kalaban area that is located in Sawahlunto City, West Sumatra, Indonesia, exhibits diverse geomorphic conditions that require detailed analysis to support sustainable development area planning. This study integrates field-based geomorphological observations with remote sensing analysis. Then followed with geomorphological mapping that was conducted through morphological and geomorphic process observation, focusing on erosion, weathering, geological structures, fluvial activity, and slope measurement and calculation. DEM derived parameters, including elevation and slope gradient, were used to delineate and validate geomorphic units and their spatial distribution. The results indicate that the study area consists of four main geomorphic units: denudational hills with moderate to steep slopes, denudational hills with gentle slopes, the Kepalakoto floodplain, and a meandering river channel. This study found that each geomorphic unit exhibits distinct surface processes and hazard potentials. The results revealed that denudational hills that are mostly associated with surface erosion and slope instability, while the floodplain and meandering river channel geomorphic units are characterized by fluvial processes and are prone to flooding and channel migration. This study inferred that geographical distribution and features of these geomorphic units emphasize significant limitations and challenges for development planning in Muaro Kalaban. By integrating geomorphological data into landuse planning perhaps can assist in identifying hazardprone areas, and also beneficial to promote sustainable development solutions which can reduce geomorphic risk..