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Bulletin of Geology
Published by Institut Teknologi Bandung
ISSN : 25800752     EISSN : 25800752     DOI : 10.5614/bull.geol.
Core Subject : Science, Engineering,
Earth & Planetary Sciences Energy Engineering
Bulletin of Geology is a research-based periodical scientific open access journal published by Faculty of Earth Sciences and Technology, Institut Teknologi Bandung (ITB). The published article in Bulletin of Geology covers all geoscience and technology fields including Geology, Geophysics, Geodesy, Meteorology, Oceanography, Petroleum, Mining, and Geography. The submitted abstract must be written in English and Bahasa Indonesia, but the article content is English or Bahasa Indonesia.
Arjuna Subject : Ilmu Bumi dan Planet (semua kategori) - Geologi
Articles 100 Documents
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LANDSLIDE SUSCEPTIBILITY ZONATION BASED ON FREQUENCY RATIO METHOD, IN KARAHA BODAS GEOTHERMAL FIELD, WEST JAVA Giva Havirgus Zahara
Bulletin of Geology Vol 5 No 4 (2021): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Abstract – Indonesia has the potential for geothermal energy which is quite unique because of the location of geothermal sources in mountainous areas with fairly steep slopes and quite complex geological structures. In general, high temperature geothermal fields are located in volcanic areas with high relief, steep morphology, thermal alteration rocks that produce thick soil, and high rainfall. This is a threat in geothermal development that causes landslides. This study aims to map the landslides susceptibility in the Karaha Bodas geothermal area using the Frequency Ratio (FR) method and evaluate the parameters that have a strong influence on landslides in the study area. Based on the inventory of landslides, there were 538 landslides in the study area. The landslide event data is then divided randomly into two groups, namely 70% training data (377 landslides) and 30% test data (161 landslides). There are 16 parameters used to determine their effect on landslides, including elevation, slope, aspect slope, curvature, lithology, flow direction, distance from the road, lineament density, distance to lineament, drainage density, distance to drainage, stream power index (SPI), topographic wetted index (TWI), rainfall, normalized differential vegetation index (NDVI) and Land Use and Land Cover. The value of the area under curve (AUC) of the parameters causing landslides that affect landslides is ≥ 0.6. Based on the AUC value, the parameters that affect the occurrence of landslides in the study area using the FR method are the slope, LULC, drainage density, elevation, distance to road, lithology, distance to drainage, rainfall, TWI, NDVI, and curvature. The results of the evaluation of the AUC success rate value show the FR method (0.786) and the evaluation results of the AUC prediction rate value show the FR method (0.793). Based on the results of the study, it was concluded that the FR method has an accurate AUC value which affects the landslide susceptibility zoning in the Karaha Bodas geothermal area and its surroundings. Key words: Karaha Bodas, landslide, frequency ratio
APLIKASI KLASIFIKASI TERBIMBING UNTUK MEMETAKAN PRODUK GUNUNG AGUNG DENGAN LANDSAT 8-OLI/TIRS DAN VERIFIKASI GEOLOGI LAPANGAN Yudhistira Adika Nugraha; Asep Saepuloh
Bulletin of Geology Vol 3 No 2 (2019): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2019.3.2.4

Abstract

Geological mapping for volcano products that has just erupted will give important basic information to understand the eruption characteristic and the hazard mitigation that can be done. Difficult terrain and high danger around active volcano cause geological mapping hard to be done using direct observation method. To give another solution for the problem, we try to explain digital volcano products mapping using supervised classification method from field data that still be reached. Image data selection with atmospheric correction is the important factor to get high map accuracy. Supervised classification method that used in this research is Minimum Distance Classification. This method uses average vector for each ROI and calculates Euclidean distance from every pixel for each class, so every class can be distinguished well and precisionly. Geological observation is done before classification process by choosing 140 observation point that spread in the east of Agung Volcano. Geological data consists of lithology, correlation, and the mechanism of the rocks that used as the reference in the determination of class for classification from Landsat 8-OLI/TORS image. The research area is located on the east of Agung Volcano which has 60 km2. It is located between Kubu District, Abang District, and Bebandem District, Karangasem Regency, Bali Province. Supervised classification can map products of Agung Volcano for area that can’t be reached around 324 km2. Verification process is done by comparing supervised classification result in research area with observation point at the field using Classification Accuracy Assessment method with result reaching 90%.
Multi-Sensor Data Acquisition at Bukit Pawon (West Java) to Support Sustainable Conservation of Cultural Heritage Gusti Ayu Jessy Kartini
Bulletin of Geology Vol 6 No 2 (2022): Bulletin of Geology Special Issue: International Seminar on Earth Sciences and Te
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Currently, the survey and mapping technologies for data acquisition are rapidly developing. One can obtain thousands to millions of points in a single measurement using a variety of sensors. Additionally, this rapid development also applies to image-based data acquisition. The development of these technologies is very beneficial for various purposes, one of which is the cultural heritage conservation. This study aims to describe the data acquisition using multi-sensors to support the conservation of cultural heritage at Bukit Pawon West Java. This study was conducted in the Bukit Pawon, West Java, and the laser-based and image-based geospatial data were utilized, e.g., Terrestrial Laser Scanner (TLS), Handheld Laser Scanner (HLS), UAV (Unmanned Aerial Vehicle) photogrammetry, and Airborne Laser Scanner (LiDAR) to obtain point clouds representing the Earth’s surface of the interest area along with their corresponding true colors and intensities. The combination of TLS and HLS technologies is complimentary, providing a complete image for subsequent analysis. Combining these multi-sensors will be beneficial for geospatial analysis and support cultural heritage conservation at Bukit Pawon, West Java. In the future study, a multi-sensor data integration algorithm will be created and will be used to detect geological fractures and classify cave materials using a deep learning approach.
NUMERICAL SIMULATION OF THE 2018 KRAKATAU TSUNAMI GENERATED BY FLANK COLLAPSE AND ASESSMENT OF TSUNAMI HEIGHT IN PANDEGLANG REGENCY Hamzah Latief; KHOLILLAH YUDICIA ISNAENI; MUTIARA RACHMAT PUTRI; HAEKAL YUSRIL FAIZIN; HANIF DIASTOMO; Iwan Pramesti Anwar
Bulletin of Geology Vol 7 No 1 (2023): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

This study aims to reconstruct the tsunami event on December 22, 2018, due to the eruption of Mount Anak Krakatau which caused flank collapse generated an underwater landslide. Then this landslide caused a tsunami that impacted along the coast of the Sunda Strait, especially on the coast of Pandeglang Regency. Based on satellite imagery, it is known that the source of the landslide came from the southwestern part of Anak Krakatau's wall moving down the former caldera wall of the 1883 Krakatau volcanic eruption. The mount grew again and was known as Mount Anak Krakatau and appeared above sea level in 1929 and continued to grow. Subsequently, several eruptions spewed sediment deposits that had accumulated on the edges and foot of the mount. These sediments increased and become unstable, causing flank collapse and triggering underwater landslides. Several simulation scenarios have been carried out, in order to obtain the best model that can represent the 2018 Anak Krakatoa Tsunami with landslide parameters, namely: the volume of the landslide is 0.276 km3, the duration of propagation is 410 seconds, the inclination angle is 8.2°, and the length of the landslide trajectory is 3435 meters. The waveform generated as a tsunami source is in the form of wave peaks in the direction of the slide and wave valleys on the back of the slide. Furthermore, this wave propagated to all directions however mostly focused towards the southwest i.e. Panaitan Island and Pandeglang Regency. Tsunami simulations show that the tsunami reached: Panaitan Island and Pandeglang Regency at 58-60 minutes, Kota Agung (Lampung) at 42 minutes, and Ciwandan (Banten) at 46 minutes after the landslide with a tsunami height of 5.01m, 0.9 m and 0.7 m respectively, with a maximum tsunami wave height of 18.6 m on Panaitan Island. Furthermore, it is known that there are 5 areas in Pandeglang Regency that fall into the high tsunami hazard category with a tsunami height of more than 3 m, namely Panaitan Island, Ujungkulon District, Sumur, Panimbang, and Labuhan. By knowing the distribution tsunami height and estimate time arrival of the tsunami in the affected area, as well as the inundation area accurately, an early warning system and mitigation efforts can be planned such as spatial planning and other efforts
METODE SEISMIC PORE PRESSURE UNTUK PENYEBARAN TEKANAN LUAP DI BLOK ARU, CEKUNGAN SUMATRA UTARA Jihan Cessar H. Gurning; Agus Mochamad Ramdhan
Bulletin of Geology Vol 1 No 2 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.2.5

Abstract

The North Sumatra Basin is one of the Tertiary back-arc basins which has been explored since the colonial era. The existence of overpressured zone has already been recognized. This is due to the existence of shale or claystone sequence that is capable to generate overpressure condition. Therefore, the understanding and knowledge of pore pressure and the mud weight used to counter the pressure are of paramount importance. The approach used to define pore pressure value with Eaton empirical method is generally done on wells only. In this research, determination of lateral pore pressure distribution is done with the seismic image and seismic interval velocity data. Wireline log and seismic interval velocity data are both being integrated to generate the pore pressure estimation and the distribution of overpressured zone in the North Sumatra Basin. The overpressure in this research area is caused by non-loading mechanism with the transformation of smectite into illite. The top of overpressure generally follows stratigraphic layer and sometimes it crosses the stratigraphic layer.
ANALISIS TEKANAN LUAP DAN MEKANISME PEMBENTUKANNYA MENGGUNAKAN DATA SUMUR DAN KECEPATAN SEISMIK PADA LAPANGAN “SKW”, CEKUNGAN JAWA TIMUR UTARA FASIH KAZAINULLAH; Perdana Rakhmana Putra; Agus Mochamad Ramdhan
Bulletin of Geology Vol 5 No 3 (2021): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

The drilling in the North East Java Basin, known as one of the prolific hydrocarbon basins in Indonesia, is often experiencing several problems due to the presence of overpressure. This study aims to predict overpressure and analyze the generating mechanism using well and seismic data in SKW field in the basin, so that overpressure-related drilling problems could be avoided. Based on pore pressure analysis, we found that there are 5 pressure zones in the study area, i.e: hydrostatic pressure in Zone A and C, occurring in Lidah to the upper of Mundu formation and Ledok Formation; first appearance (top) of overpressure at Zone B occurring in the middle to lower Mundu Formation; moderate overpressure in Zone D occurring in upper – middle Wonocolo Formation; high overpressure in Zone E occurring in middle Wonocolo – Ngrayong formations. Our analysis also shows that sediment thickness controls overpressure magnitude in the study area, indicating that overpressure is due to loading mechanism. The interpretation of loading mechanism as the main generating mechanism of overpressure in the study area is also supported by constant effective stress behaviour as observed in wells analysed in this paper. Burial history analysis also shows that rate of sedimentation in the study area is about 113 m/mY, in favour of supporting the loading mechanism interpretation. We also found that starting at the depth of 4000 ft, smectite starts to transform into illite, however, this transformation does not give substantial impact to overpressure magnitude in the study area.
Karakteristik Hidrogeokimia dan Isotop Air Tanah di Pesisir Kota Balikpapan, Kalimantan Timur Irsyadulhaq Irsyadulhaq; Arifin Arifin; Agus Muhammad Ramdhan; Rima Rachmayani; Irwan Iskandar; Kemala Wijayanti
Bulletin of Geology Vol 8 No 1 (2024): Bulletin of Geology Vol. 8 no. 1
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Daerah studi meliputi wilayah pesisir Kota Balikpapan yang memiliki jumlah penduduk sekitar 733 ribu, dengan persentase pemanfaatan air tanah untuk keperluan domestik diperkirakan sebesar 70%. Sebagai kota penyangga bagi Ibu Kota Nusantara (IKN), diperkirakan akan terjadi peningkatan jumlah penduduk di Balikpapan pada masa yang akan datang yang dapat berdampak terhadap meningkatnya jumlah pemanfaatan air tanah dan perubahan kualitas air tanah. Studi ini mengkaji karakteristik hidrogeokimia dan isotop air tanah, mengidentifikasi keberadaan dan penyebab fenomena intrusi air laut, serta merekonstruksi model konseptual hidrogeologi menggunakan data sampel air tanah, litologi, seismik, muka air tanah, dan pasang surut air laut. Hasil studi ini menunjukkan nilai Total Dissolved Solids (TDS) air tanah berkisar antara 141 – 11.023 mg/l dan pH sampel air tanah berkisar antara 4,49 hingga 9,29. Fasies air tanah terdiri dari mixed cation/HCO3-, Na+/Cl-, Na+/HCO3-, Ca2+/HCO3-, dan Na+/mixed anion. Komposisi isotop 18O dan 2H mengindikasikan evolusi kimia air tanah melalui proses evaporasi dan interaksi air tanah dengan batuan. Indikasi intrusi air laut ditemukan pada satu sampel air tanah (titik M-2.1) pada akuifer di kedalaman 30 – 33 m. Intrusi air laut tersebut diperkirakan terjadi secara alamiah. Perhitungan rasio pencampuran menunjukkan komposisi air tanah tawar sekitar 60% dan air laut sebesar 40%. Adapun model konseptual hidrogeologi di daerah studi menunjukkan perselingan batupasir dan batulempung atau perselingan akuifer dengan akuitar, dimana akuifer pada kedalaman 30 hingga 33 m di titik M-2.1 diinterpretasi terhubung dengan laut.
STUDI DIAGENESIS BATUPASIR PADA ASOSIASI FASIES CHANNEL-FILL FORMASI HALANG Yan Rizal; Ricky Adrian Tampubolon; Wahyu Dwijo Santoso
Bulletin of Geology Vol 3 No 1 (2019): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2019.3.1.2

Abstract

Diagenesis pada asosiasi fasies channel-fill menunjukkan adanya proses kompaksi, sementasi, rekristalisasi, dan pelarutan. Proses kompaksi pada channel-1 dan channel- 2 ditandai dengan adanya kontak antarbutir berupa kontak point, long, dan suture. Derajat kompaksi semakin meningkat pada sampel yang diambil pada dasar channel. Pada channel- 1 terjadi rekristalisasi gelas menjadi mineral lempung dan rekristalisasi kuarsa, sedangkan pada channel- 2 hanya rekristalisasi gelas menjadi mineral lempung. Pelarutan yang terjadi pada channel- 1 berupa pelarutan mineral piroksen, plagioklas dan cangkang foraminifera, dan pada channel- 2 hanya pelarutan mineral piroksen. Adanya penambahan mineral lempung selama diagenesis berlangsung mengurangi nilai porositas, karena mineral lempung dapat mengisi ruang antar butiran pembentuk batuan, sehingga batupasir Formasi Halang memiliki potensi rendah sebagai reservoir hidrokarbon. Kata kunci: Diagenesis, channel-fill, foraminifera, Formasi Halang, hidrokarbon
SAFETY FACTOR ANALYSIS(SF) SAFETY FACTOR ANALYSIS (SF) OF SEDAYU MOUNTAINOUS AREA USING LIMIT EQUILIBRIUM METHOD 2D Arif Setio Wibowo
Bulletin of Geology Vol 6 No 2 (2022): Bulletin of Geology Special Issue: International Seminar on Earth Sciences and Te
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

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Abstract

Landslides and floods that occur in Sedayu Village are disasters that often occur. Both disasters were strongly influenced by rainwater. The area of ​​flow and distribution of surface water is poor resulting in flooding at the location which causes frequent landslides on the slopes. To express the stability value of a slope, a term is known as the value of the safety factor, which is the result of the comparison between the magnitude of the resisting force and the driving force of the avalanche. Slope stability analysis determines the safety factor of the landslide field. The safety factor value for safe soil or rock slopes is in the FK 1.25 – 1.5 according to SNI 8460 2017. This study aims to estimate the slope safety factor around the Mount Sedayu area using the 2-dimensional boundary equilibrium method. The boundary equilibrium method is a very popular method and is often used in slope stability analysis for translational and rotational slip types. The condition of slope stability in the boundary equilibrium method is expressed in the value of the factor of safety. Slope stability analysis is generally carried out using the 2-Dimensional Boundary Equilibrium Method because it is simpler. In the 2D slope stability analysis, the landslide that occurs is assumed to have an unlimited or continuous length. This method uses the principle of balance of forces. The concept of this method is to calculate the ratio between thrust and resistance forces based on the assumption of a potential landslide area and divide the slope into several slices. This method is useful for calculating the safety factor on slopes. From the results of a 2-dimensional slope stability analysis in the Sedayu Mountains area, the safety factor value is 0.91 and it can be concluded that the slope is considered unstable where the value of the FK factor of safety < 1. The smaller value a safety factor, slope is considered to be disturbed or unstable.
KARAKTERISTIK TEKANAN LUAP DAN PENYEBABNYA PADA DAERAH LEPAS PANTAI SELAT MADURA Yudha Risnandar Sinulingga; Agus Mochammad Ramdhan
Bulletin of Geology Vol 1 No 1 (2017): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2017.1.1.2

Abstract

The East Java Basin is known as one of the prolific Tertiary hydrocarbon basin. This basin is also well known for its overpressure characteristic which occurs as a problem in drilling activity. Overpressure in East Java Basin generally occurs in Plio-Pleistocene interval which deposited in depression by rapid sedimentation rate. Wireline logs, pressure direct measurements, drilling mudweight and drilling events from four offshore exploration wells in Madura Strait are analysed to study overpressure characteristics and its mechanism. Eaton’s and Swarbrick’s Method are used to estimate the magnitude of pore pressure in research area. The location of research area within Kendeng Trough that physiographycally is a continuation of Kendeng-Randublatung Depression to the east might cause rapid sedimentation of thick sediment that would led to the generation of overpressure.

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