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Abstrak :
Kondisi reservoir pada lapangan karbonat sangat jauh berbeda dengan kondisi reservoir pada lapangan batu pasir, dan ketika masuk kedalam ranah interpretasi geofisika, analisa sifat intrinsik dari batuan karbonat itu sendiri tidak dapat diabaikan atau bahkan diasumsikan sama dengan reservoir jenis batuan lain. Dalam beberapa kasus nyata terjadi misinterpretasi dalam mendeskripsikan reservoir migas yang ada dibawah permukaan karena kekurangan informasi sifat intrinsik reservoir, untuk menghindari kasus yang merugikan tersebut, studi mengenai kondisi dan sifat intrinsik reservoir batuan karbonat itu sendiri perlu diperhatikan lagi baik dari komposisi tipe pori, jenis mineralnya hingga fluida yang terkandung didalam reservoir tersebut. Pada reservoir batuan karbonat itu sendiri terdapat 3 jenis tipe pori yaitu Crack, Stiff dan Interparticle yang mana sangat berpengaruh merubah kecepatan gelombang-P hingga 30 ketika merambat dan direkam oleh receiver. Begitu pula dengan mineral penyusunnya, terdapat Calcite, Dolomite, Quartz dan Clay yang mana sangat mempengaruhi rigiditas dan sifat elastik batuan karbonat itu sendiri. Fluida yang terkandung didalam reservoir karbonat ini turut menyumbangkan pengaruh yang signifikan terhadap respon perambatan gelombang-P pada reservoir. Dengan menggunakan metode Simultaneous DEM-Rockphysics Reservoir Accurate Modelling dapat diketahui dengan akurat sifat elastik dan kondisi reservoir karbonat dengan mengkalkulasi secara simultan inklusi tipe pori, fluida dan mineral penyusun yang terdapat dalam reservoir serta dengan memprediksi kondisinya se-akurat mungkin seperti kondisi yang sesungguhnya agar dapat membantu meningkatkan interpretasi respon seismik yang ada se-optimal mungkin.

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The condition of reservoir in carbonate base fields is significantly different compared to the sandstone base reservoir, and when enhance forward into the geophysical interpretation domain, the intrinsic nature of carbonate stone analysis itself cannot be ignored or evenmore being assumed as slightly coherent with any other reservoir rock type. In some real cases the misinterpretation happened while describing the oil and gas reservoir beneath due to insufficient information of the intrinsic nature of reservoir, to avoid the misleading and disadvatageous case happens, advance studies for the intrinsic nature and condition of the carbonate base reservoir rock need to be concern more specifically in terms of porosity type composition, minerals type, and also the fluids contained in the reservoir. There are 3 types of porosity classification for carbonate reservoir itself, viz. Crack, Stiff and Interparticle which affecting the P velocities significantly for almost 30 change while propagating and recorded by receivers. Likewise as the minerals composition, occur to be Calcite, Dolomite, Quartz or Clay also affecting the rigidness and the carbonate rock elastic properties. The fluids content in the carbonate reservoir also contribute an effect that significantly changing the P velocities response upon the reservoir. By using the Simultaneous DEM Rockphysics Reservoir Accurate Modelling method, the elastic properties and the condition of reservoir will be able to determined more accurately by simultanly calculating the inclusion of pore type, fluids, and minerals composition contained in the reservoir also to predict the condition as accurate as possible to the real condition beneath the surface, so the information could be used to improve the seismic interpretation understanding optimally.

Abstrak :
Indonesia merupakan negara yang memiliki potensi sangat besar dalam bidang panas bumi. Salah satu daerah yang berpotensi panas bumi yaitu berada di Kabupaten Brebes, Jawa Tengah. Penelitian ini berfokus dalam memperkirakan persebaran daerah prospek panas bumi di daerah Brebes dengan melakukan analisis dan integrasi beberapa metode penginderaan jauh yang meliputi LST, NDVI, dan FFD. Metode ini diolah pada data citra Landsat-8 dan DEM serta didukung oleh data lapangan berupa data geologi dan manifestasi permukaan. Selain itu, dilakukan juga evaluasi daerah prospek panas bumi untuk mengetahui kondisi sistem panas bumi dan kondisi permukaannya yang ditentukan berdasarkan analisis aspek 3G (Geologi, Geofisika, dan Geokimia) dari penelitian terdahulu, sehingga dapat ditentukan tingkat kelayakan daerah tersebut untuk di eksplorasi. Hasil dari penelitian ini menunjukan bahwa terdapat dua daerah prospek panas bumi di daerah Brebes, yaitu prospek A yang terletak pada koordinat UTM 269690 – 271040 mE, dan 9197903-9199163 mN serta luas 165 Hektar, dan prospek B yang terletak pada koordinat UTM 280224-281083 mE, dan 9188823-9190237 mN serta luas 115 Hektar. Evaluasi daerah prospek panas bumi menunjukkan kondisi sistem panas bumi sudah lengkap dan terletak dekat dengan daerah prospek serta kondisi permukaan dengan akses yang mudah dan tidak mengganggu daerah hutan. Secara keseluruhan, daerah prospek ini sudah cukup layak untuk eksplorasi panas bumi lebih lanjut. ......Indonesia is a country that has enormous potential in the geothermal sector. One area that has geothermal potential is located in Brebes Regency, Central Java. This research focuses on estimating the distribution of geothermal prospect areas in the Brebes area by analyzing and integrating several remote sensing methods which include LST, NDVI, and FFD. This method is processed on Landsat-8 and DEM image data and is supported by field data in the form of geological data and surface manifestations. In addition, an evaluation of the geothermal prospect area was also carried out to determine the condition of the geothermal system and surface conditions which were determined based on an analysis of the 3G aspects (Geology, Geophysics and Geochemistry) from previous studies, so that the level of feasibility of the area for exploration could be determined. The results of this study indicate that there are two geothermal prospect areas in the Brebes area, namely prospect A which is located at UTM coordinates 269690 – 271040 mE, and 9197903 – 9199163 mN and an area of 165 hectares, and prospect B which is located at UTM coordinates 280224-281083 mE, and 9188823-9190237 mN and an area of 115 hectares. Evaluation of the geothermal prospect area shows that the condition of the geothermal system is complete and is located close to the prospect area as well as surface conditions with easy access to the area and does not disturb forest areas. Overall, this prospect area is quite feasible for further geothermal exploration.

 

Abstrak :
Soil erosion is a crucial environmental problem in the Manjunto watershed, Bengkulu Province, Indonesia. It has economic implications and environmental consequences. Assessment of potential soil erosion rate is useful in designing soil conservation strategies within the framework of integrated watershed management. Information obtained from Remote Sensing (RS) and Geographic Information System (GIS) framework supports decision makers in preparing more accurate spatial maps in less time and cost. The aim of this research is to assess the average annual rate of potential soil erosion in Manjunto watershed for each soil mapping unit using remote sensing data, namely Normalized Difference Vegetation Index (NDVI) and Slope. The NDVI value obtained from satellite imagery processing while slope value obtained from Digital Elevation Model-Shuttle Radar Topographic Mission (DEM-SRTM) processing. The results showed that the eroded catchment area increased significantly. The average annual rate of potential soil erosion in Manjunto watershed in the year 2000 amounted to 3.00 tons ha- 1 year-1, while in the year 2009 there was a significant increase to 27.03 ton ha-1year-1. The levels of erosion hazard in soil mapping unit numbers 41, 42 and 47 are classified in the very heavy category. Soil mapping unit numbers 41, 42 and 47 should be a first priority in soil and water conservation activities.

Abstrak :
Gerakan tanah merupakan bahaya geologi utama di dunia yang menyebabkan tingginya jumlah korban manusia hingga kerugian harta benda yang sangat besar, serta mengakibatkan kerusakan pada sumber daya alam, ekosistem, dan infrastruktur. Selama periode Januari 2020 hingga Desember 2021, bancana gerakan tanah telah menjadi bencana yang paling rawan terjadi di Kabupaten Wonosobo, yakni sebanyak 238 kejadian. Bahkan, beberapa dari kejadian tersebut memakan korban jiwa yakni satu orang meninggal dunia di Kecamatan Kaliwiro, satu orang meninggal dunia di Kecamatan Kepil, dan dua orang meninggal dunia di Kecamatan Watumalang. Oleh karenanya, penelitian ini dilakukan agar dapat menentukan zona kerentanan gerakan tanah yang berguna dalam membantu proses mitigasi risiko sehingga segala bentuk kerugian dapat diminimalisasi. Zona kerentanan gerakan tanah pada Kabupaten Wonosobo divisualisasikan dengan peta kerentanan gerakan tanah. Sebanyak 242 titik gerakan tanah dikumpulkan untuk menghasilkan peta inventori. Titik tersebut kemudian dibagi menjadi 168 (70%) sebagai data training dan 74 (30%) sebagai data testing. Parameter yang dipertimbangkan terdiri dari berbagai parameter penyebab seperti aspek lereng, curvature, elevasi, kemiringan lereng, jarak dari sungai, litologi, tata guna lahan dan satu parameter pemicu, yaitu curah hujan. Selain itu, dilakukan pengurangan resolusi terhadap turunan data DEM seperti aspek lereng, curvature, elevasi, kemiringan lereng menjadi 8, 17, 25, dan 40 m untuk melihat pengaruhnya terhadap akurasi model. Semua parameter diolah menggunakan piranti ArcGIS untuk mengasilkan peta parameter. Peta parameter selanjutnya digabungkan dan dianalisis menggunakan metode frequency ratio dan weight of evidence untuk menghasilkan peta kerentanan gerakan tanah. Hasil penelitian menunjukkan bahwa Kabupaten Wonosobo memiliki kecenderungan terhadap kerentanan gerakan tanah dengan tingkatan rendah, sedang, hingga tinggi. Berdasarkan data resolusi DEM 8 m dan 17 m, tingkatan kerentanan didominasi oleh kelas sedang. Namun pada data resolusi DEM 25 m dan 40 m, tingkatan kerentanan didominasi oleh kelas rendah. Peta kerentanan masing-masing resolusi kemudian diuji nilai AUC nya menggunakan success rate curve untuk melihat keberhasilan model dan prediction rate curve untuk mengukur akurasi prediksi model. Setelah dilakukan validasi, resolusi tinggi ternyata tidak berbanding lurus dengan kualitas akurasi model. Akurasi success rate mengalami puncaknya pada resolusi DEM 25 m sedangkan prediction rate pada resolusi DEM 17 m. ......Landslide is a major geological hazard in the world that causes a high number of human casualties to enormous property losses, as well as causing damage to natural resources, ecosystems and infrastructure. During the period from January 2020 to December 2021, landslide disasters have become the most prone to disasters in Wonosobo Regency, with 238 incidents. In fact, some of these incidents claimed lives, namely one person died in Kaliwiro District, one person died in Kepil District, and two people died in Watumalang District. Therefore, this research was conducted in order to determine the susceptibility zones of landslide which are useful in assisting the risk mitigation process so that all forms of losses can be minimized. The landslide vulnerability zone in Wonosobo Regency is visualized with a landslide susceptibility map. A total of 242 landslide points were collected to produce an inventory map. These points are then divided into 168 (70%) as training data and 74 (30%) as testing data. The parameters considered consist of various causal parameters such as slope aspect, curvature, elevation, slope, distance from river, lithology, land use and one trigger parameter, namely rainfall. In addition, the resolution of the DEM data derivatives was reduced, such as slope aspects, curvature, elevation, slope to 8, 17, 25, and 40 m to see the effect on model accuracy. All parameters are processed using the ArcGIS tool to produce a parameter map. Then the parameter maps are combined and analyzed using the frequency ratio and weight of evidence methods to produce a landslide susceptibility map. The results of the study show that Wonosobo Regency has a tendency towards low, moderate and high susceptibility to landslide. Based on DEM 8 m and 17 m resolution data, the susceptibility level is dominated by the moderate class. However, in DEM 25 m and 40 m resolution data, the susceptibility level is dominated by the low class. Then the susceptibility map of each resolution is tested for AUC value using a success rate curve to see the success of the model and a prediction rate curve to measure the accuracy of model predictions. After validation, it turns out that high resolution is not directly proportional to the quality of the model accuracy. Success rate accuracy peaks at DEM 25 m resolution while prediction rate at DEM 17 m resolution.

Abstrak :
The internal erosion is a common mode of failure in earth dams. The phenomenon of filtration process corresponds to a transport over long distances of fine particles under the effect of seepage forces. The filters arranged by both sides of the clay core are supposed to be dimensioned so to stop this transfer. In a granular material, the constriction is very important in the filtration process. It is the narrowest path linking pores. If there is a fluid flow and the constriction size is larger than the diameter of particle, the particle follows its route. On the other hand, if the constriction size is smaller than the diameter of particle, the particle is stopped. Then, the curve of cumulative size constrictions for a granular material is identified as the key characteristic of the filtration process. This characteristic depends on the density and size distribution curve of the filter. The objective of this research is to find and compare the curve with three different approaches by using periodic conditions. These three approaches are MEDTD (Discrete Element Method Triangulation Delaunay), the probabilistic approach and the inverse approach by experiment.

Abstrak :
Bencana alam merupakan fenomena alam yang dapat mengakibatkan kerugian. Berdasarkan data IRBI, Kab. Garut berada di posisi ke-12 dari 514 kabupaten/kota dengan indeks risiko tanah longsor tertinggi. Terdapat enam faktor utama penyebab longsor, yaitu curah hujan, kemiringan kelerengan, tanah jenis, jenis tutupan lahan, geologi, dan adanya getaran. penentuan zona patahan yang berpotensi menjadi sumber getaran atau gempa dapat diidentifikasi menggunakan data gravitasi.  Dengan memanfaatkan data gravitasi yang bersumber dari GGMplus, data gravitasi diolah hingga analisis derivatif untuk menentukan zona patahan. Data lain yang juga diolah adalah DEM serta data curah hujan. Peta hasil pengolahan kemudian dilakukan overlay dengan data tutupan lahan, geologi, dan jenis tanah untuk dilakukan pembobotan berdasarkan standar dari DVMBG yang telah dimodifikasi. Keberadaan zona patahan yang banyak terdapat di daerah selatan telah berhasil diidentifikasi dari data gravitasi dan dikonfirmasi dari Peta Geologi Lembar Garut. Hasil dari penelitian menunjukan bahwa daerah utara Kab. Garut memiliki tingkat kerawanan longsor yang lebih rendah dibandingkan daerah selatan dimana zona patahan yang telah teridentifikasi tersebar di bagian selatan Kab. Garut. ......Natural disasters are natural phenomena that can occur anywhere and anytime, so that they can result in material and non-material losses. Based on IRBI data, Kab. Garut is in the 12th position out of 514 districts/cities with the highest landslide risk index. There are six main factors that cause landslides, rainfall, slope level, soil density, type of land cover, geology, and vibration. the determination of fault zones that have the potential to be a source of vibration or earthquake can be identified using gravity data. By utilizing gravity data sourced from GGMplus, gravity data is processed to derivative analysis to determine fault zones. Other data that is also processed is DEM and rainfall data. The processed map is then overlaid with data on land cover, geology, and soil type for weighting based on the modified DVMBG standard. The existence of a fault zone that is mostly found in the southern area has been identified from the gravity data and confirmed from the Geological Map of the Garut Sheet. The results of the study show that the northern area of ​​Kab. Garut has a lower level of landslide susceptibility than the southern area where the fault zones that have been identified are scattered in the southern part of Kab. Garut.

Abstrak :
Wilayah Panas Bumi “X” merupakan bagian dari Busur Banda bagian Vulkanik Dalam. Busur Banda ini merupakan hasil dari subduksi antara Lempeng Indo-Australia dengan Lempeng Eurasia sehingga menghasilkan zona vulkanik yang menguntungkan terbentuknya sistem panas bumi. Identifikasi struktur geologi penting untuk memetakan zona permeabilitas tinggi di Wilayah Panas Bumi “X”, Nusa Tenggara Timur. Identifikasi struktur geologi pada penelitian ini menggunakan metode gravitasi dan pemetaan kelurusan berdasarkan Digital Elevation Model (DEM). Data anomali Bouguer lengkap dipisahkan menjadi anomali residual dan anomali regionalnya menggunakan filter Moving Average (MVA). Berdasarkan analisis spektrum, kedalaman rata-rata dari zona anomali gravitasi regional adalah 49,44 km, sedangkan kedalaman zona anomali gravitasi residual rata-rata adalah 3,612 km. Berdasarkan pemetaan kelurusan berdasarkan DEM, teridentifikasi kelurusan struktur geologi yang sebagian besar menunjukkan orientasi timur laut-barat daya. Hal ini cocok dengan sesar yang teridentifikasi dari data anomali residual berdasarkan analisis derivatif yang sebagian besar menunjukkan orientasi yang hampir sama. Orientasi ini juga cocok dengan sesar yang dilaporkan pada peta geologi yang menunjukkan orientasi yang mirip. Selain itu, pemetaan kelurusan berdasarkan DEM mampu menunjukkan keterkaitan antara keberadaan mata air panas dengan zona yang memiliki nilai Fault and Fracture Density (FFD) tinggi serta keterkaitan antara zona FFD sedang hingga tinggi dengan keberadaan sesar yang dilaporkan oleh peta geologi. Penelitian ini juga menghasilkan informasi mengenai zona permeabilitas tinggi yang berpotensi untuk diteliti lebih lanjut. ......The "X" Geothermal Area is part of the Inner Banda Volcanic Arc. This Banda Arc is the result of subduction between the Indo-Australian Plate and the Eurasian Plate, creating a favorable volcanic zone for the formation of geothermal systems. The identification of geological structures is crucial for mapping high-permeability zones in the "X" Geothermal Area, East Nusa Tenggara. In this study, the identification of geological structures was conducted using gravity methods and lineament mapping based on Digital Elevation Model (DEM). The complete Bouguer anomaly data was separated into residual and regional anomalies using a Moving Average (MVA) filter. Based on spectrum analysis, the average depth of the regional gravity anomaly zone was found to be 49.44 km, while the average depth of the residual gravity anomaly zone was 3.612 km. Based on lineament mapping from DEM, geological structures were identified predominantly showing a northeast-southwest orientation. This is consistent with the identified faults from the residual anomaly data through derivative analysis, which also exhibited a similar orientation. This orientation is also in agreement with reported faults on the geological map showing a similar orientation. Furthermore, lineament mapping from DEM was able to indicate the correlation between the presence of hot springs and zones characterized by high Fault and Fracture Density (FFD) values, as well as the correlation between moderate to high FFD zones and the reported faults on the geological map. This research also provides information regarding high-permeability zones that have the potential for further investigation.