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<![CDATA[Estimasi Struktur Bawah Permukaan Menggunakan Metode Seismik Refraksi Di Kawasan Pantai Padang ]]>
<![CDATA[Windi Jalnadia]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 3 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.3.399-405.2024
<![CDATA[Peristiwa gempa bumi di Sumatera Barat menyebabkan terbentuknya retakan-retakan di atas permukaan tanah.Kondisi tersebut tentu berpengaruh terhadapstruktur bawah permukaan tanahnya. Penelitian mengenai pemodelan strukturbawah permukaan menggunakan metode seismik refraksi telah dilakukan.Penelitian ini bertujuan untuk mendapatkan penampang seismik di kawasanPantai Padang. Jumlah lintasan padapenelitian sebanyak dua lintasan dengan panjang masing-masing lintasan 80 meterdan spasi geophone 1 meter. Data yang diperolehberupa waktu rambat sebagaifungsi jarak dan data diolah menggunakan metodeHagiwara. Hasil penelitianmenunjukkan kecepatan pada Lintasan 1 untuk lapisanpertama (v1) adalah (1111,11-1250) m/s yang diinterpretasikan sebagai batuan alluvial dan lapisan kedua didapatkan nilai kecepatan (v2) berkisar (2000-5000) m/s yang diinterpretasikan kemungkinan sebagai batu gamping, batu pasir dan batu serpih. Kedalaman yang mampu direkam pada Lintasan 1 adalah (2,9-29,53) m. Pada Lintasan 2,besarnya nilai kecepatan lapisan pertama (v1) adalah (263,16-769,23) m/sdiinterpretasikan sebagai batuan aluvial, sedangkan besarnya nilai kecepatan lapisan kedua (v2) adalah (3333,33-5000) m/s diinterpretasikan kemungkinan sebagai batu gamping, batu pasir dan batu serpih. Kedalaman yang mampu direkam pada Lintasan 2 adalah (0,16-29,87) m. Jenis batuan yang didapatkan sesuai dengan peta geologi. Padakedua lintasan terindikasi adanya amblesan atau penurunan struktur bawah permukaankarena struktur lapisan yang tidak sejajar atau horizontal antara lapisan atasdengan lapisan di bawahnya.]]>
<![CDATA[Identifikasi Gerakan Partikel Air Panas Berdasarkan Analisis Mikrotremor di Mata Air Panas Bukit Kili dan Garara, Kabupaten Solok ]]>
<![CDATA[Muhammad Khaikal Marbun]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 2 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.2.177-182.2024
<![CDATA[Di bawah permukaan bumi terdapat energi panas bumi yang mana energinya berasal dari dalam bumi. Energi panas bumi dapat dimanfaatkan baik secara langsung ataupun tidak langsung. Pemanfaatan energi panas bumi secara tidak langsung membutuhkan beberapa tahapan untuk mendapatkan hasilnya. Tahapan tersebut dimulai dengan penelitian awal yang dilaksanakan dengan menggunakan metode geofisika. Tahapan awal ini sangat penting untuk dilakukan karena menentukan layak tidaknya suatu wilayah prospek panas bumi untuk dilakukan tahapan eksplorasi lebih lanjut. Dalam penelitian ini dilakukan penelitian dengan metode geofisika (mikrotremor) di mata air panas Bukit Kili dan Garara untuk mengetahui nilai frekuensi dominan, pola aliran fluida panas, kandungan fluida manifestasi, dan temperatur reservoir. Metode mikrotremor digunakan untuk mengetahui nilai frekuensi dominan yang dapat melihat pola aliran fluida panas. Berdasarkan penelitian yang dilakukan didapatkan nilai frekuensi dominan (f0) di mata air panas Bukit Kili dan Garara berturut-turut yaitu 0,65 Hz dan 0,75 Hz. Gerakan partikel fluida panas di mata air panas Bukit Kili terpusat atau tidak ada arah gerak dominan. Sedangkan di mata air panas Garara, gerak dari partikel tegak lurus ke arah permukaan tanah. Berdasarkan data kandungan mineral fluida panas didapatkan bahwa kedua daerah mata air panas merupakan zona outflow.]]>
<![CDATA[Pemisahan Anomali Regional dan Residual pada Metode Gravitasi Menggunakan Metode Moving Average, Upward Continuation dan Polynomial ]]>
<![CDATA[Iqwal Ramadhan]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 1 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.1.1-7.2024
<![CDATA[Pemisahan anomali regional dan residual adalah hal yang harus dilakukan dalam pengolahan data yang berhubungan dengan geologi bawah permukaan. Tidak ada ketentuan khusus tentang metode terbaik yang harus digunakan dalam pemisahan anomali, karena pemisahan anomali bersifat subjektif. Penelitian ini bertujuan untuk mengidentifikasi struktur bawah permukaan pada daerah Kepulauan Mentawai dengan menggunakan persebaran nilai anomali.Dalam penelitian ini, metode yang digunakan adalah metode moving average, upward continuation dan polynomial untuk menginterpretasikan kontur anomali regional dan residual Kepulauan Mentawai. Hasil dari ketiga metode tersebut menunjukkan bahwa upward continuation mencerminkan anomali regional dan residual Kepulauan Mentawai lebih baik dibandingkan metode moving average dan polynomial, karena pada upward continuation memiliki kontur dan nilai anomali mendekati kontur dan nilai anomali Bouguer  lengkap dan kontur struktur geologi. Sebaran nilai anomali yang rendah berada pada sekitar wilayah Padang, Pulau Siberut, Pulau Sipora dan Pulau Pagai, sehingga diidentifikasi wilayah tersebut memiliki struktur bawah permukaan dengan nilai massa jenis yang rendah. Sedangkan anomali sedang berada pada laut dangkal yang diidentifikasi memiliki massa jenis yang sedang, dan anomali tinggi berada pada laut dalam di sekitar wilayah Indian Ocean diidentifikasi memiliki massa jenis yang tinggi.]]>
<![CDATA[Pemodelan 3D Bidang Gelincir Tanah Longsor Menggunakan Metode Geolistrik di Bukit Nobita Padang ]]>
<![CDATA[M. Arif]]>;
<![CDATA[Dwi Pujiastuti]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 1 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.1.15-21.2024
<![CDATA[The surface of rupture investigation has been conducted at Nobita Hill, Kampung Jua, Lubuk Begalung, Padang City using the 3-dimensional resistivity geoelectric method in Wenner configuration. The research was conducted in a hilly area with a slope of up to 40º. Data was collected on three tracks with variations in length lengths of 120 and 240 m. The electrode spacing is 6, 12, 18, and 24 m for current and potential electrodes. Data processing was carried out using Res2dinv software to display a 2-dimensional image of the subsurface layer based on the resistivity values measured in the field. The results of 2-dimensional image processing were then modeled in 3 dimensions using Voxler software. Data interpretation of the results obtained by Track 1 has a resistivity value of 1170-2028 Ωm at a depth of 4.5-19.1m. Track 2 has a resistivity value of 1052-1768 Ωm with a depth of 4.5-19.1 m. Track 3 has a resistivity value of 1492-2937 Ωm at a depth of 1.5-19.1 m. The direction of the sliding plane of Tracks 1 and 2 is to the northwest, while track 3 is to the northeast. The results showed that the sliding plane on each track is granite.]]>
<![CDATA[Indeks Kerentanan Seismik Menggunakan Data Mikrotremor untuk Daerah Perbukitan dan Pemukiman di Bukit Nobita Kota Padang ]]>
<![CDATA[Fani Anjelina]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 4 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.4.511-517.2024
<![CDATA[Research on the seismic vulnerability index on Nobita Hill, Padang City uses the microtremor method. The study was conducted in two areas, namely hilly and residential areas around Nobita Hill. Measurements were carried out using a geophone with three components, a north-south horizontal component, an east-west horizontal component and an up-down vertical component at 7 points in hilly areas and 9 points in residential areas with a recording duration of 30 minutes. The measurement results were then processed using the Horizontal Vertical Spectral Ratio (HVSR) method using Geopsy software and mapped using Surfer 11. The research results show that the Nobita Hill area and the settlements around the hill are not vulnerable to seismicity because both research areas have a small category of seismic vulnerability index. This is characterized by dominant frequency values in the hills ranging from 0.633 - 0.935 Hz, amplification from 0.905 - 1.306, and seismic vulnerability index from 1.234 - 2.622. In residential areas, dominant frequency values were found ranging from 0.645 - 2.983 Hz, amplification from 1.109 - 1.316, and seismic vulnerability index from 0.438 - 1.974. This indicates that both studies are safe in the event of an earthquake. ]]>
<![CDATA[Perbandingan Koreksi Medan (Terrain Correction) Konvensional dan Modern pada Metode Gravitasi Menggunakan Data DEM ERTM2160 dan SRTM2gravity pada Wilayah Cianjur ]]>
<![CDATA[Afikatul Awaliyah]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 5 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.5.651-657.2024
<![CDATA[A study has been conducted to compare the distribution of anomaly values obtained through conventional and modern terrain correction to identify the subsurface structure of the Cianjur region, especially around the location of the Cugenang Fault. The data used are gravity disturbance data equivalent to Free Air Anomaly (FAA) from GGMplus, ERTM2160 DEM data as topographic data, and modern terrain correction data from SRTM2gravity. Data is processed using Microsoft Excel, Oasis Montaj, and Surfer software. Based on the results of the CBA contour map obtained, the application of SRTM2gravity data as a modern terrain correction provides better results so that subsurface structure modeling will provide more accurate results. The CBA contour map produced from modern terrain correction provides clearer topographic results than conventional terrain correction using ERTM2160 DEM topographic data. Furthermore, using SRTM2gravity modern terrain correction data provides clearer rock density contrast results along the active path of the Cugenang Fault.]]>
<![CDATA[Identifikasi Sesar Gorontalo Dengan Memanfaatkan Data Gravitasi Satelit Resolusi Tinggi ]]>
<![CDATA[Aina’ul Mardiyah]]>;
<![CDATA[Ahmad Fauzi Pohan]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 5 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.5.658-664.2024
<![CDATA[The Gorontalo fault is an active fault and is the main source of earthquakes in Gorontalo Province. A strong and destructive earthquake that has occurred in Gorontalo Province was on November 16, 2008 with a magnitude of 7.4 Mw. As one of the disaster mitigation efforts, a research was conducted to identify the type of Gorontalo fault. Data used from global gravity model plus (GGMplus) as free air anomaly data and shuttle radar topography mission (SRTM2Gravity) as modern terrain correction data that rely on full-scale topographic gravity data. These data are used to calculate the complete Bouguer anomaly data. The complete Bouguer anomaly data was subjected to spectrum analysis to obtain the depth of regional and residual anomalies and to separate regional and residual anomalies using the upward continuation method. On the residual anomaly, second vertical derivative (SVD) analysis was conducted to determine the type of Gorontalo fault. The inversion result of 3D model of gravity anomaly shows Gorontalo fault with medium and low density contrast. Based on the SVD analysis, the Gorontalo fault is a turun fault. This geological structure is considered to be a potential source of natural disasters in the Gorontalo region.]]>
<![CDATA[Pemodelan Struktur Bawah Permukaan Kabupaten Rejang Lebong dengan Metode Inversi 3D Data Gravitasi Satelit Menggunakan Koreksi SRTM2gravity ]]>
<![CDATA[Puja Kasmailen Putri]]>;
<![CDATA[Ahmad Fauzi pohan]]>;
<![CDATA[Marzuki Marzuki]]>
<![CDATA[ Jurnal Fisika Unand Vol 13 No 6 (2024) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.13.6.799-805.2024
<![CDATA[Rejang Lebong is a tourism area in Bengkulu Province, Indonesia, which is located close to the active Ketaun and Musi faults which are segments of the Sumatran Fault System (SFS). This research uses 3-D analysis and modeling of Earth's gravity anomaly inversion data obtained from the high-resolution Global Gravity Model (GGM). The aim of this research is to identify subsurface geological structures such as faults, active volcanoes and sedimentary layers that have the potential to pose a danger to the Curup Rejang Lebong tourism area. The Complete Bouguer Anomaly (CBA) in the study area was calculated using modern terrain correction methods that utilize full-scale topographic gravity data from the SRTM2gravity model. Separating regional and residual anomalies using an upward continuity filter with a height of 10 km. The 3D inversion model of satellite gravity data has succeeded in modeling the subsurface of the Rejang Lebong district where the presence of the Mount Kaba magma chamber is characterized by low negative density contrast, and the Ketaun and Musi fault lines are characterized by low and high contrast boundaries which have the potential to cause natural disasters in the region. Analysis of gravity anomalies and rock density contrasts provided results that are in line with the regional geological conditions of the Bengkulu region, including the pattern of intrusion of igneous rocks with high density contrasts and sedimentary rocks with lower density contrasts.]]>
<![CDATA[Suseptibilitas Magnetik, pH dan Kandungan Mineral untuk Uji Tingkat Kesuburan Tanah pada Lahan Perkebunan Kemiri di Kecamatan IX Koto Sungai Lasi ]]>
<![CDATA[Oktavia, Geby Sri Ayu]]>;
<![CDATA[Pohan, Ahmad Fauzi]]>
<![CDATA[ Jurnal Fisika Unand Vol 14 No 3 (2025) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.14.3.263-269.2025
<![CDATA[Research has been conducted on the value of magnetic susceptibility, pH and mineral content to test the level of soil fertility in Nagari Indudur, District IX Koto Sungai Lasi. Samples were taken at the location of candlenut plantations in two different locations that were suspected of experiencing a decrease in soil fertility. Sampling was taken at 6 points with three depth variations, 30 cm, 60 cm and 90 cm so that 36 samples were obtained. The distance between sampling points is 2 m. Magnetic susceptibility measurements using the MS2B Bartington Susceptibility Meter using two frequencies, namely 0,47 kHz LF (Low Frequency) and 4.7 kHz HF (High Frequency). At location 1, the average value obtained is 181.2089 x10-8 m3/kg, while the average χHF value obtained is 170.5870x10-8 m3/kg. At location 2 the average χLF value obtained is 487.6539x10-8 m3/kg, while the average χHF value obtained is 480.5271 x10-8 m3/kg. with an average pH in both locations of candlenut plantations is acidic. This occurs because of the excess of Si and Al elements that make the plantation soil acidic, as well as the deficiency of Magnesium (Mg) and sulfur, minerals that make candlenut plants experience a decrease in production. Besides that deposition on plantation land is also one of the triggers for soil in the plantation location to experience a decrease in soil fertility.]]>
<![CDATA[Indonesia IDENTIFIKASI PERCEPATAN TANAH MAKSIMUM MENGGUNAKAN METODE MIKROTREMOR DI KOTA PADANG ]]>
<![CDATA[Illona giovanni, Vannessa]]>;
<![CDATA[Pujiastuti, Dwi]]>;
<![CDATA[Pohan, Ahmad Fauzi]]>
<![CDATA[ Jurnal Fisika Unand Vol 14 No 1 (2025) ]]>
Publisher : <![CDATA[Universitas Andalas ]]>
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DOI: 10.25077/jfu.14.1.1-7.2025
<![CDATA[The position of Padang City on the coast and close to the subduction zone makes it very vulnerable to the impact of earthquakes, therefore mitigation efforts against potential disasters are very important to reduce the risk of such events. This study was conducted to map ground acceleration using the microtremor method as one of the efforts in earthquake disaster mitigation. The calculation of the maximum ground acceleration (PGA) value uses dominant frequency data (f0), amplification factor (A0 ) and soil vulnerability (kg) as input data obtained from microtremor data analysis using the Horizontal to vertical spectral ratio (HVSR) method. The microtremor data processed were 33 measurement points in 11 sub-districts in Padang City with a distance between points of 1-5 km. The dominant frequency, amplification, vulnerability and maximum ground acceleration values were then mapped to determine areas prone to earthquake disasters. Areas of Padang City with a high level of vulnerability can be seen in Bungus Teluk Kabung District and Padang Barat District.]]>
