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All Journal Journal of Mathematical and Fundamental Sciences Journal of Engineering and Technological Sciences Jurnal Ilmu Fisika Jurnal Geofisika
Widodo Widodo
Teknik Geofisika, Institut Teknologi Bandung, Indonesia
Astronomy Chemistry Earth & Planetary Sciences Energy Engineering Materials Science & Nanotechnology Mathematics Physics

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Magnetic Characterization of Sand and Boulder Samples from Citarum River and Their Origin Sudarningsih Sudarningsih; Luki Maulana; Satria Bijaksana; Abd Hafidz; Aditya Pratama; Widodo Widodo; Irwan Iskandar
Journal of Mathematical and Fundamental Sciences Vol. 49 No. 2 (2017)
Publisher : Institute for Research and Community Services (LPPM) ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.math.fund.sci.2017.49.2.2

Abstract

The Citarum River is a nationally strategic river located near Bandung, the capital city of West Java Province. The feasibility of using magnetic methods for monitoring pollution level is currently being tested in the river. Due to its location in a volcanic area, the sediments from the river are expected to be highly magnetic. In this study, sand and boulder samples from Balekambang, a relatively pristine upstream area of the river, were subjected to magnetic and geochemical characterizations to establish the baseline for unpolluted sediments. Such baseline is important for future magnetic monitoring of sediments in the river. The mass-specific magnetic susceptibility of boulder samples was found to be varied from 819.2 to 2340.5 × 10-8m3 kg-1 while that of sand samples varied from 2293.9 to 3845.3 × 10-8m3 kg-1. These high magnetic susceptibility values infer that river sediments are highly magnetic even before being contaminated by industrial and household wastes. The predominant magnetic mineral in sand samples was multi-domain magnetite while that in boulder samples was single to pseudo-single domain magnetite. These differences were supported by the results from petrographic and XRF analyses, implying that the sand and boulder samples originated from different geological formations.
Pemodelan Inversi Data Vertical Electrical Sounding Dengan Menggunakan Algoritma Modified Symbiotic Organism Search (mSOS Mohammad Rheza Zamani; Widodo Widodo
Jurnal Geofisika Vol 20 No 1 (2022): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v20i1.533

Abstract

Vertical Electrical Sounding (VES) dengan konfigurasi sclumberger merupakan salah satu teknik dalam metode geolistrik untuk mengetahui model struktur bawah permukaan bumi secara 1D melalui variasi vertikal resistivitas terhadap kedalaman dengan resolusi vertikal yang tinggi. Pemodelan data hasil akuisisi lapangan VES dilakukan menggunakan teknik inversi, inversi data VES merupakan permasalahan non-linier sehingga diperlukan algoritma dengan pendekatan global untuk mendapatkan solusi yang optimum. Pada penelitian ini digunakan algoritma berbasis populasi dengan pendekatan global untuk melakukan pemodelan inversi data VES yaitu modified Symbiotic Organism Search (mSOS) yang terinspirasi dari simbiosis yang terjadi di suatu ekosistem. Algoritma yang digunakan pada penelitian ini terdiri dari 3 tahapan optimasi yaitu mutualisme, komensalisme, dan parasitisme yang masing-masing memiliki peranan dalam peningkatan kapasitas eksplorasi yang berkaitan dengan akurasi solusi dan eksplotasi yang berkaitan dengan kecepatan konvergensi algoritma. Pengujian algoritma mSOS dilakukan pada data sintetik dan data lapangan. Hasil dari pemodelan inversi data sintetik kemudian dibandingkan dengan algoritma damped least-square (DSLQR), Flower Pollination Algorithm (FPA), dan Symbiotic Organism Search (SOS) untuk mengetahui kemampuan eksplorasi dan eksploitasi solusi dibandingkan algoritma lain yang ditinjau dari kesesuaian dari parameter model sintetik dan data sintetik dengan hasil perhitungan, sedangkan pada data lapangan hasil pemodelan inversi dibandingkan dengan perangkat lunak IP2WIN meliputi kesesuaian data observasi dengan data perhitungan inversi dari keduanya dan kesesuaian dengan data lubang bor. Hasil inversi pemodelan data sintetik menunjukan algoritma mSOS memiliki keseimbangan dalam kapasitas eksplorasi dan eksplotasi dibandingkan dengan algoritma lain yang diujikan dibuktikan dengan kemampuan algoritma mSOS yang berhasil mendapatkan kembali model data sintetik dengan tingkat kesesuaian yang paling tinggi dengan waktu konvergensi yang relatif cepat, untuk hasil pemodelan inversi data lapangan juga menghasilkan model yang representatif dengan kondisi bawah permukaan karena bersesuaian dengan data lubang bor serta memiliki tingkat kecocokan data lapangan dan data perhitungan inversi yang lebih baik dari perangkat lunak IP2WIN.
Study of Aquatic Sedimentation Using Electromagnetic Modeling in Flood Hazard Mitigation Scheme Widodo Widodo; M. Rheza Zamani; Sindi Hajah Patimah; Elis Agustiana
Journal of Engineering and Technological Sciences Vol. 55 No. 3 (2023)
Publisher : Directorate for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2023.55.3.1

Abstract

The accumulation of sediment in aquatic environments can lead to an increase in flood risk due to raised floodplains and water levels. Electromagnetic modeling techniques, such as Time Domain Electromagnetic (TDEM) resistivity or lithological conductivity contrast, can be utilized to detect changes in the subsurface. In this study, we investigated the use of TDEM in flood hazard mitigation schemes by developing a 1-D forward modeling program for the central loop configuration in an aquatic environment using the Adaptive Born Forward Mapping (ABFM) method. The program was tested in various environmental conditions, i.e., freshwater, brackish water, and saltwater, to determine its response. The objective is to prevent natural disasters, particularly flooding caused by sedimentation. The TDEM models can generate images of sediment thickness, providing a sensitive response in saltwater environments and enabling the detection of changes in depth compared to other aquatic environments. Overall, this study demonstrated the potential of TDEM as a valuable tool in flood hazard mitigation schemes.
Quasi-3D Geoelectrical Imaging as A New Application for Landslide Investigations: A Tunnel Case Induced by Blasting Activity Cahyadi, Rudi; Widodo, Widodo
Jurnal Ilmu Fisika Vol 16 No 2 (2024): September 2024
Publisher : Jurusan Fisika FMIPA Universitas Andalas

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25077/jif.16.2.177-186.2024

Abstract

Landslides are a significant hazard in mountainous regions, especially when influenced by construction activities such as tunnel excavation. In this paper, we aim to conduct a slope stability analysis as a result of tunnel blasts using quasi-3D subsurface models based on resistivity values. The study site is a construction area for the Jakarta-Bandung High-Speed Train tunnel, located in a mountainous region undergoing drill-and-blast excavation. This excavation method makes the area susceptible to landslides, which pose a threat to settlements in the Padalarang subdistrict, West Bandung Regency, Indonesia. Data was collected along four lines in 2D, and the dipole-dipole array was used to enhance resolution. Data modeling was carried out using ResIPy v3.2.3 software to create 2D and quasi-3D subsurface models based on resistivity values. The study findings indicate that the study area exhibits three resistivity ranges: low resistivity (0-30 Ωm), medium resistivity (31-49 Ωm), and high resistivity (>50 Ωm). Utilizing quasi-3D imaging, we were able to identify the dimensions and presence of slip surfaces, which can be categorized as shallow (1.5-5 m) and deep (5-20 m) criteria. This study successfully applied the quasi-3D geoelectrical approach in a susceptible environment to detect potential landslide zones.
Co-Authors Abd Hafidz Aditya Pratama Elis Agustiana Irwan Iskandar Luki Maulana M. Rheza Zamani Mohammad Rheza Zamani Rudi Cahyadi Satria Bijaksana Sindi Hajah Patimah Sudarningsih Sudarningsih