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Journal : Journal of Aceh Physics Society

The Computation of Residual and Regional Anomaly of Gravity Method Data By Polynomial Filter Using Microsoft Excel Muhajirin Muhajirin; Nazli Ismail; Bukhari Bukhari
Journal of Aceh Physics Society Volume 9, Number 2, May 2020
Publisher : PSI-Aceh

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24815/jacps.v9i2.15745

Abstract

Eksplorasi metode gravitasi umumnya dilakukan untuk mencari objek di bawah permukaan yang dangkal sehingga perlu dilakukan pemisahan anomali residual dan regional dari anomali Bouguer lengkap. Perhitungan anomali residual biasanya menggunakan software khusus untuk pengolahan data geofisika yang berlisensi atau algoritma dengan bahasa pemrograman, sedangkan program Microsoft Excel pada PC dan notebook biasa digunakan untuk perhitungan polinomial pada pengolahan data statistik. Penelitian ini memperkenalkan cara menghitung anomali residual menggunakan Microsoft Excel dengan filter polinomial. Hasil validasi yang menggunakan model sintetik menunjukkan bahwa perhitungan tersebut dapat diaplikasikan pada data metode gravitasi. Aplikasi pada data lapangan diperoleh bahwa anomali residual berfrekuensi tinggi, sedangkan anomali regional berfrekuensi rendah. Nilai anomali regional dipengaruhi oleh trendline anomali Bouguer lengkap dalam domain jarak. Hasil ini relatif sama dengan hasil perhitungan software lainnya. Gravity method exploration was generally conducted to seek the object in shallow underground so that required residual and regional anomaly separation of complete Bouguer anomaly. The residual anomaly separation was usually used by the special softwares for geophysics that require licency or algorithm by programming language, however the program of Microsoft Excel in the PC or notebook was usually applied to compute the polynomial filter for statistic data analysis. This research introduces how to compute residual anomaly using Microsoft Excel through polynomial filter. The validation result of sintetic model shows that the computation using Microsoft Excel can be applied to gravity method data. The application of field data was obtained that residual anomaly has high frecuency, whereas residual anomaly has low frecuency. The value of regional anomaly was influenced by trendline of complete Bouguer anomaly in distance domain. This result relatively equals to the result of other softwares. Keywords: gravity method, residual anomaly, regional anomaly, polynomial filter, Microsoft Excel
Delineation of Gold Prospecting Area Based on Total Magnetic Field Anomalies Reduction to The Pole Alvin Caesar Lesmana Ikramsyah; Nazli Ismail; Ibnu Rusydy; Agus Pajrin Jaman
Journal of Aceh Physics Society Volume 7, Number 3, September 2018
Publisher : PSI-Aceh

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (751.352 KB)

Abstract

Telah dilakukan reduksi ke kutub data anomali medan magnetik total untuk mendelineasikan area prospek emas. Intensitas medan magnetik total dikoreksi dengan nilai diurnal dan IGRF untuk mendapatkan anomali medan magnetik total. Reduksi ke kutub anomali medan magnetik total dilakukan untuk menyederhanakan pola kontur anomali di ekuator. Anomali medan magnetik total reduksi ke kutub telah difilter untuk mendapatkan anomali residual yang merefleksikan target benda anomali pada kedalaman yang dangkal. Hasil yang didapat menunjukkan kontur anomali medan magnetik total reduksi ke kutub terlihat lebih sederhana dan mudah untuk diinterpretasi. Aplikasi kedua metode tersebut pada daerah “C” di Jawa Barat telah berhasil diterapkan. Pada low pass filter anomali yang muncul menunjukkan pola smooth yang merupakan efek dari benda anomali regional. Pada anomali residual menunjukkan pola efek dari benda anomali yang dangkal. Nilai anomali medan magnetik total residual yang rendah pada lokasi penelitian diprediksi sebagai tempat terdepositnya emas yang berasosiasi dengan patahan dan zona alterasi yang berada di bagian selatan dan barat lokasi penelitian.Delineation of gold prospecting area based on the total magnetic field anomalies reduction to the pole have been done. The total magnetic field intensity data were corrected by diurnal and IGRF to obtain the total magnetic field anomalies. The total magnetic field values were reduced to the pole to simplify contour shceme in equator and filtered to obtain the residual anomalies which are reflected as shallow depth anomalies. The results showed that the reduction to the pole contour were more simple and easily to be interpreted. Application of both methods in area "C" at West Java Province has been successfully delineating gold deposit in the area. In low pass filter the anomalies showed smooth pattern which are representated as regional effects. The residual anomalies appear as near surface effects. The low magnetic values in the residual data be expected as gold deposit which associated with fault and alteration zones where located in south and west section of the research field. Keywords: magnetic method, the total magnetic field anomalies, reduce to the pole, low pass  filter, gold potential
2D Modeling of Seulawah Agam Geothermal Field Based on Magnetotelluric (MT) Data irfan Putra; Nazli Ismail; Marwan Marwan
Journal of Aceh Physics Society Volume 8, Number 2, May 2019
Publisher : PSI-Aceh

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (141.752 KB) | DOI: 10.24815/jacps.v8i2.12871

Abstract

Telah dilakukan pemodelan 2D data Magnetotellurik (MT) di Gunung Api Seulawah Agam. Penelitian ini bertujuan untuk mendapatkan model konseptual lapangan panas bumi Gunung Api Seulawah Agam berdasarkan model resistivitas 2D. Data fungsi transfer MT yang digunakan yaitu dari rentang frekuensi 2,34 - 320 Hz yang terdiri dari 7 titik stasiun pengukuran. Data titik pengukuran terdiri dari nilai intensitas medan listrik dan intensitas medan magnet yang memiliki 28 frekuensi. Total panjang lintasan pengukuran yaitu sepanjang 27,7 km. Lintasan pengukuran memotong Gunung Api Seulawah Agam dari arah Selatan ke Utara. Data hasil pengukuran yaitu berupa nilai resistivitas semu dan fase yang kemudian dimodelkan menggunakan kode REBOCC. Terdapat 3 model yang dihasilkan dari proses inversi data MT menggunakan REBOCC yaitu mode TE, mode TM dan mode TE+TM. Model mode TE+TM merupakan model yang paling bagus karena menghasilkan model yang lebih jelas dan smooth bila dibandingkan dengan model pada mode TE dan mode TM. Hasil model konseptual menunjukkan bahwa pada lapisan pertama yaitu lapisan top soil (lapisan teratas) memiliki nilai resistivitas sebesar 20 - 60 Ω.m, yang terdapat pada jarak 6 - 23 km. Lapisan kedua yaitu lapisan clay/caprock dengan nilai resistivitas relatif rendah yaitu lebih kecil dari 10 Ω.m, yang berada pada jarak 6 - 27,7 km. Lapisan clay/caprock memiliki sifat impermeabel dan konduktif. Selanjutnya lapisan ketiga yaitu lapisan reservoir dengan nilai resistivitas berkisar antara 10 - 100 Ω.m. 2D modeling of magnetotelluric data has been conducted at Seulawah Agam volcano. This study aims to obtain a conceptual model of Seulawah Agam geothermal field based on 2D resistivity model. The magnetotelluric data were measured in range of frequency from 2.34 to 320 Hz at 7 stations along a profile crossing the Seulawah Agam volcano. The length of the profile is 27.7 km with a direction from north to south. The apparent resistivity and phase of magnetotelluric transfers function were used for the 2D inversion modelling of REBOCC code. The inversion was carried out using TE-mode, TM-mode and TE+TM-mode to obtain a better model. The model inverted of TE+TM-mode has resolved well, resistivity variation of subsurface of the Seulawah Agam volcano area. The inverted model shows the top later has resistivity values from 20-60 Ω.m, which is interpreted as a top soil. The second layer is a layer of clay/caprock with a relatively low resistivity values of less than 10 Ω.m. The third layer is predicted as reservoir with resistivity values ranging between 10-100 Ω.m. Keywords: magnetotelluric method, resistivity, 2D model, REBOCC code and Volcano Seulawah Agam.
Investigation of Shallow Fault Structures Using Ground Penetrating Radar Method in Gampong Pangwa Trienggadeng District, Pidie Jaya Regency Ayu Safrida; Nazli Ismail; Marwan Marwan
Journal of Aceh Physics Society Volume 8, Number 2, May 2019
Publisher : PSI-Aceh

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1338.614 KB) | DOI: 10.24815/jacps.v8i2.11200

Abstract

Wilayah Aceh merupakan wilayah yang sering terjadi gempa bumi dengan skala besar. Salah satu gempa bumi dengan skala besar adalah Gempa Pidie Jaya yang terjadi pada 7 Desember 2016. Setelah terjadi gempa bumi, banyak terjadi pergerakan tanah yang ditemukan di area penelitian. Telah dilakukan serangkaian pengukuran menggunakan Ground Penetrating Radar (80 MHz) untuk mempelajari struktur bawah permukaan setelah terjadinya gempa bumi. Penelitian ini dilakukan di Desa Pangwa, Kecamatan Trienggadeng, Kabupaten Pidie Jaya. Pengukuran dilakukan di sepanjang jalan di Desa Pangwa yang melintasi dua jembatan. Pengukuran dilakukan pada 18 lintasan dengan panjang masing–masing lintasan sepanjang 50 m. Pengolahan data dilakukan dengan menggunakan software GRED. Berdasarkan hasil radargram, kita menemukan struktur pemukaan dangkal berupa patahan di tengah gambaran radargram pada lintasan 13 yang disebabkan oleh terjadinya gempa di Pidie Jaya. The Aceh region is an area of frequent large-scale earthquakes. One of the earthquakes with a large scale is Pidie Jaya Earthquake that occurred on December 7, 2016. After the earthquake, many ground movement evidences were found in the area. The ground penetrating radar (80 MHz) measurement is used to study subsurface structures after the earthquake. This research was conducted in Pangwa Village, Trienggadeng Subdistrict, Pidie Jaya District. Measurements were carried out along the road in Pangwa Village which crossed two bridges. Data measurements were made along 18 profiles with 50 m length of each profile. Data processing were done by using GRED software. Based on processed radargrams, we found a fault trace at the middle of the profile lane 13 caused by the newest earthquake in Pidie Jaya. Keywords: Ground Penetrating Radar, Subsurface structure, electromagnetic wave velocity
Locating of Fault Zone at the Western of Seulawah Agam volcano Using Gravity Method Mieftah Oesanna; Nazli Ismail; Marwan Marwan
Journal of Aceh Physics Society Volume 7, Number 2, May 2018
Publisher : PSI-Aceh

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Abstract

Telah dilakukan survey metode gravitasi di sebelah barat Gunung Api Seulawah Agam, Aceh Besar, provinsi Aceh. Distribusi data percepatan gravitasi diukur dengan menggunakan alat Scrintrex CG-5. Pengukuran dilakukan pada satu lintasan dengan Jarak 27 km dan jumlah stasiun 52 buah. Nilai anomali Bouguer didapatkan setelah dilakukan beberapa standar koreksi data yaitu koreksi apungan, koreksi pasang surut, koreksi lintang, koreksi udara bebas, koreksi Bouguer, dan koreksi medan. Hasil interpretasi kualitatif data anomali Bouguer bahwa terindikasi pada jarak 36 - 37 km terdapat zona patahan. Lokasi ini sangat berhubungan dengan keberadaan manifestasi mata air panas Ie Ju di Lamteuba, Aceh Besar.Gravity survey has been done at the western part of Seulawah Agam volcano, Aceh Besar, Aceh Province. Variation of gravitational field data were measured using Scrintrex CG-5 instrument. The data were colected along 27 km lenght of profile with 52 stations but irregularly in spacing. The Bouguer anomaly values were obtained by drift, tide, latitude, free-air, Bouguer, and terrain corrections. Qualitative interpretation of Bouguer anomaly data show that the profile is crossed by a fault at distance of 36 - 37 km along the profile, i.e in between Lamteuba and Lampanah.Keywords: Gravity, Bouguer anomaly, fault, Seulawah AgamREFERENSIBennet, J. D et al. 1981. Peta Geologi Lembar Banda Aceh, Sumatera. Pusat Penelitian dan Pengembangan Geologi, Bandung.Caine, J. S., Evan J. P., Foster C. B. 1996. Fault Zone Architecture and Permeability Structure. Geology 24, 1025-1028Lillie, R. J. (1999). Whole earth geophysics. An Introductory Textbook for Geologists.Marwan, M., Rusydy, I., Nugraha, G. S., Asrillah, A. 2014. Study of Seulawah Agam’s Geothermal Source Using Gravity Method. Jurnal Natural, 14(2).Sieh, K., Natawidjaja, D. 2000. Neotectonics of the Sumatran fault, Indonesia. Journal of Geophysical Research: Solid Earth, 105(B12), 28295-28326.
Quantitative Interpretation of Gravity Anomaly Data in Geothermal Field Seulawah Agam, Aceh Besar Aprillino Wangsa; Nazli Ismail; Marwan .
Journal of Aceh Physics Society Volume 7 Number 1, January 2018
Publisher : PSI-Aceh

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Abstract

Survei metode Gravitasi telah dilakukan di lapangan panas bumi Seulawah Agam, Aceh Besar, Provinsi Aceh untuk menentukan struktur bawah permukaan daerah tersebut. Distribusi percepatan gravitasi telah diukur dengan menggunakan instrumen Gravitimeter Scintrex CG-5. Pengukuran dilakukan pada dua lintasan. Lintasan pertama sepanjang 10 km dan lintasan kedua sepanjang 5,5 km dengan total panjang lintasan 15,5 km. Data diukur secara berturut-turut pada 33 titik dan 21 titik untuk lintasan pertama dan kedua. Untuk mendapatkan nilai Anomali Bouguer Lengkap, beberapa standar koreksi data diterapkan termasuk koreksi drift, koreksi pasang surut, koreksi lintang, koreksi udara bebas, koreksi Bouguer, dan koreksi medan. Data nilai Anomali Bouguer Lengkap sepanjang profil digunakan untuk pemodelan maju (forward modeling) 2D menggunakan software Grav2DC. Model menunjukkan bahwa struktur bawah permukaan daerah penelitian terdiri dari tiga lapisan. Lapisan paling atas ditafsirkan sebagai lapisan tufa pasiran (ρ = 2,09 g/cm3), dan diikuti oleh lapisan lempung dibawahnya (ρ = 2,02 g/cm3). Lapisan terbawah diduga sebagai breksi vulkanik (ρ = 2,17 g/cm3). Breksi vulkanik dapat dianggap sebagai lapisan reservoir dan lapisan clay sebagai lapisan penutup (cap rock) pada sistem panas bumi di Gunung Api Seulawah Agam.Kata Kunci: Metode Gravitasi, Densitas, Grav2DC, Sistem Panas Bumi, Seulawah AgamSurvey on gravity method has been done in Seulawah Agam geothermal field, Aceh Besar, Aceh Province to determine the subsurface structure of the area. We have measured distribution of acceleration gravity using Gravitimeter Scintrex CG-5 instrument. The measurements were carried out along two profiles. Length of the first profile is 10 km and the second profil is 5,5 km with the total profile length is 15,5 km. The data were measured at 33 and 21 stations for the first and the second profile respectively. In order to obtain a Complete Bouguer Anomaly value, some standard data corrections were applied including drift correction, tidal correction, latitude correction, free air correction, Bouguer correction and terrain correction. Complete Bouguer Anomaly value data along the profile were use for 2D forward modeling using Grav2DC software. The models show that subsurface structure of the area consist of 3 layers. The upper most layer is interpreted as sandyceous tuffastones (ρ = 2,09 g/cm3), and followed by underlaying clay layer (ρ = 2,02 g/cm3). The lowest layer is expected as volcanic breccias (ρ = 2,17 g/cm3). The volcanic breccias can be considered as reservoir and the clay layer as a cap rock in geothermal system of Seulawah Agam vulcano.Keywords: Gravity Method, Density, Grav2DC, Geothermal System, Seulawah AgamREFERENSIBennett, J.D., dkk. 1981. Peta Geologi Lembar Banda Aceh, Sumatera. Bandung: Pusat Penelitian dan Pengembangan Geologi.Hidayat, N dan Basid, A. 2011. Analisis Anomali Gravitasi Sebagai Acuan Dalam Penentuan Struktur Geologi Bawah Permukaan dan Potensi Geothermal, Jurnal Neutrino, 4.1,p-36.Muzakir. 2014. Investigasi Struktur 2D Lapangan Panasbumi Seulawah Agam Berdasarkan Data Pengukuran Magnetotellurik. Skripsi. Universitas Syiah Kuala, Banda Aceh.Saptadji, N. M. 2001. Teknik Panas Bumi. Departemen Teknik Perminyakan Fakultas Ilmu Kebumian dan Teknologi Mineral. Institut Teknologi Bandung: Bandung.Yu, G., He, Z. X., Hu, Z.Z., borbergsdottir, I. M., Strack, K. –M., dan Tulinius, H.2009. Geothermal Exploration Using MT and Gravity Techniques at Szentlorinc Area in Hungary - SEG 2009 International Expoloration and Annuad Meeting. Houston. P-4333
Design of Inversion Modeling 1-D Gravity Data Using a Method of Singular Value Decomposition (SVD) Based on Matlab Irwansyah .; Teuku Khairuman; Nazli Ismail
Journal of Aceh Physics Society Volume 2 Number 1, March 2013
Publisher : PSI-Aceh

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Abstract

The study about design of Inversion Modeling 1-D Gravity Data using a method of Singular Value Decomposition (SVD) based on Matlab has been done. This study is aimed to design the modeling program of 1-D gravity data using SVD method based on Matlab and than apply the program for subsurface investigation based on contras density of the target body. The SVD method was used to solve the inversion code by applying truncation method of the data into some eigen values in order to resolve a better model. Gravity data used for inversion modeling is data generated from the forward modelling code. Inversion modeling program has been tested for several models such as with variation depth and its contrast density vertical fault. The result mostly show  a small data error is equal to 0,9908 mGal.
Reduced to the Pole of Total Magnetic field Anomaly of Seulawah Agam Volcano, Aceh Besar Masyithah Masyitah; Nazli Ismail; Marwan Marwan
Journal of Aceh Physics Society Volume 7, Number 3, September 2018
Publisher : PSI-Aceh

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Telah dilakukan penelitian dengan menggunakan metode magnetik pada kawasan Gunung Api Seulawah Agam, Aceh Besar untuk mempelajari respon anomali medan magnetik total berdasarkan hasil transformasi reduksi ke kutub. Akuisisi data medan magnetik total digunakan peralatan GEM System Proton Precission Magnetometer (PPM). Data diukur dalam bentuk lintasan, dengan panjang lintasan 16 km dan banyaknya titik pengukuran berjumlah 33 titik. Untuk mendapatkan anomali medan magnetik total dilakukan koreksi diurnal dan koreksi IGRF (International Geomagnetic Reference Field). Data anomali medan magnetik total dilakukan pengolahan lanjutan dengan transformasi reduksi ke kutub untuk memudahkan dalam interpretasi. Berdasarkan hasil interpretasi kualitatif, didapat pola anomali medan magnetik total reduksi ke kutub dengan respon anomali maksimum dan minimum yang langsung menunjukkan posisi sumber penyebab anomali dan kesesuaian dengan struktur patahan yang ada pada kawasan penelitian.Survey of magnetic method has been done at Seulawah Agam volcano, Aceh Besar. The survey is aimed to analysis reduction to the pole of total magnetic field anomaly. The total magnetic field data were acquired using GEM System Proton Precission Magnetometer (PPM) unit. The Measurements were performed along a profile with 16 km length and 33 stations. Total magnetic field anomaly data were calculated from the measured data by diurnal and IGRF (International Geomagnetic Reference Field) corrections. The total magnetic field anomaly data reduced to the pole for a better interpretaion. The reduced to the pole of total magnetic field anomaly data show a good agreement with geological structures and existence of faults in the area of study.Keywords: Magnetic method, total magnetic field anomaly, reduction to pole, Seulawah Agam
River Water Quality Spatial Analysis Based On Physical Parameter Throughout Krueng Daroy In Banda Aceh Mulyani .; Marwan .; Nazli Ismail
Journal of Aceh Physics Society Volume 1 Number 1 March 2012
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Water quality research has been done along Krueng Daroy in Banda Aceh. The research is aimed to observe water quality based on physical parameters and to identify the sources of pollutant spatially. We measured temperature, turbidity, color, pH, odor, TDS and electrical conductivity, where the data were collected using thermometer, turbidity meter, spectrophotometer, pH meter, TDS meter and conductivity meter, respectively. The physical parameters of water in the upstream area fulfilled the standard of the Health Minister of Republic Indonesia according to law Number 907/ MENKES/ SK/VII/2002 and it is suitable for household needs. However, the water at the downstream area are mostly polluted
Investigation of Shallow Paleochannel in Banda Aceh based on Electrical Resistivity Tomography Muzakir Zainal; Muhammad Yanis; Umar Muksin; Nazli Ismail
Journal of Aceh Physics Society Volume 6 Number 1, March 2017
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Pembentukan daratan pesisir sangat dipengaruhi oleh proses sedimentasi dari material hasil rombakan. Proses sedimentasi pada masa lampau dapat dikaji dengan mempelajari sungai purba sebagai media transportasi material. Survey geofisika metode electrical resistivty tomography dilakukan untuk investigasi sungai purba di Ulee Kareng Banda Aceh. Untuk memetakan sedimen dan geometri sungai purba, pengukuran electrical resistivity dilakukan di sepanjang dua lintasan dengan panjang 240 meter dan spasi elektroda 2 meter. Proses inversi model resistivitas 2D telah dilakukan pada masing – masing lintasan data yang terukur. Hasil electrical resistivity tomography mampu membedakan batas – batas antara setiap lapisan sedimen yang terendapkan di lokasi paleochannel. Sedimen paleochannel secara jelas diidentifikasi dari distribusi nilai resistivitas yang lebih tinggi (15.2–31.6 Ω.m). Berdasarkan interpretasi dari metode electrical resistivity tomography area persawahan merupakan lokasi sungai purba pada masa lampau. The formation of coastal area is influenced by sedimentation process. The sedimentation process along the coastal line in the past one can be explained by studying existence of paleochannels located around the area. Deposition of the sediment along the coast is carried by river activities in the past. We have investigated paleochannel structure in Ulee Kareng, Banda Aceh using electrical resistivity tomography survey. The measurements were performed along two profiles with 240 meters and 2 meters spacing between electrodes crossing the paddy. The method measured apparent resistivity data along the profiles. The 2D resistivity models were inverted from the apparent resistivity data using Res2Div program. The inverted models clearly show indication of paleochannel structure based on distribution of resistivity values within the subsurface. The paleochannel area was characterize by high resistivity i.e. 15.2–31.6 Ω.m.