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SURVEI METODE SELF POTENTIAL MENGGUNAKAN ELEKTRODA POT BERPORI UNTUK MENDETEKSI ALIRAN FLUIDA PANAS BAWAH PERMUKAAN DI KAWASAN BATURADEN KABUPATEN BANYUMAS JAWA TENGAH Sehah, Sehah; Raharjo, Sukmaji Anom
Jurnal Fisika FLUX Vol 8, No 1 (2011): Jurnal Fisika Flux Edisi Februari 2011
Publisher : Lambung Mangkurat University Press

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.20527/flux.v8i1.3102

Self Potential research has been done in the area of geothermal prospectsof Slamet Volcano, with locations is at around the hot water sources of PancuranTujuh Baturaden, District of Banyumas, Central Java. Tools used in this study wereporous pot electrodes and digital milivoltmeter that have very high input impedance.Dimension of research area are 24 x 24 square meters, with the number ofmeasurement points are 112 point. The electrode configuration used is the fixedmodel that is by keeping one electrode fixed at the reference point, while the otherelectrode moved at any interval in accordance with the direction of trajectory in theresearch area. According to the results obtained is known that the highest potentialdata obtained is -2.20 mV, the lowest data is -40.83 mV, and then the average data is-16.40 mV. According to the contour map of iso-potential obtained is known that thestudy area is a conductive zone, which probably contains of sulfide minerals in thesubsurface hot fluid. This is indicated by the low value of the measured self potential(its value are negative). According to qualitative and quantitative interpretation, knownthat the flow of subsurface hot fluid in following the change of research areatopography and self potential anomalies. The subsurface hot fluid in research area ispredicted flow from southern to northern.

Pengembangan model pelatihan pembuatan peta kontur topografi untuk mengidentifikasi dini zona-zona rawan bencana longsor di Kabupaten Banjarnegara Sehah, Sehah; Aziz, Abdullah Nur; Raharjo, Sukmaji Anom
Jurnal Riset dan Kajian Pendidikan Fisika Vol 3, No 2 (2016): Vol 3: Oktober 2016
Publisher : Universitas Ahmad Dahlan

Pengembangan model pelatihan pembuatan peta kontur topografi untuk mengidentifikasi dini zona-zona rawan bencana longsor telah dilaksanakan di Sekolah Menengah Kejuruan (SMK) Negeri 1 Mandiraja Kabupaten Banjarnegara. Kegiatan bertujuan untuk melakukan sosialisasi teknis dasar pemetaan dan pelatihan teknis pembuatan peta kontur topografi menggunakan perangkat lunak Surfer untuk mengidentifikasi dini zona-zona rawan bencana tanah longsor di Kabupaten Banjarnegara. Metode yang digunakan adalah perpaduan ceramah dan diskusi yang dipadukan dengan praktek. Setelah dilakukan pelatihan, sebagian besar peserta memberikan respon positif dan terdapat keinginan untuk mengimplementasikan dan menyebarluaskan hasil-hasil pelatihan. Indeks capaian rata-rata keberhasilan pelatihan berdasarkan hasil pengisian kuisioner adalah 75,69% dengan indeks capaian tertinggi adalah 92,24% dan indeks capaian terendah adalah 56,90%. Tingkat pemahaman peserta terhadap materi pelatihan cukup baik, meskipun masih perlu ditingkatkan. Hal ini dapat dilihat dari hasil rekapitulasi nilai pre-test dan post-test. Nilai rata-rata pre-test adalah 5,96 dan post-test adalah 6,95. Dengan demikian terdapat kenaikan nilai sebesar 12,14%. Salah satu faktor keberhasilan pelatihan adalah adanya dukungan dari pihak sekolah dan tersedianya fasilitas komputer di Laboratorium Komputer SMK Negeri 1 Mandiraja. Salah satu faktor penghambatnya adalah banyaknya peserta kegiatan yang kesulitan dalam mempraktekkan penggunaan perangkat lunak Surfer untuk membuat peta kontur, sehingga diperlukan bimbingan teknis lanjutan.Â The development of the training model of creating of the topographic contour map to early identify the landslide gristle zones has been done in the First State Vocational Middle School (SMK) of Mandiraja, Regency of Banjarnegara. The purpose of this activity is to do technical socialization of basic of mapping and technical training of creating of the topographic contour map using the Surfer software to early identify the landslide gristle zones in the Regency of Banjarnegara. The method used in the training is combination of lecture, discuss, and practical. After this activities has been done, the largely participant give positive response and there is wish to implement and disseminate the activities results. The successfulness average attainment index of this training based on the quiz inlay result is 75.69%; with highest index is 92.24% and lowest index is 56.90%. The understanding of participant of the training on the training matters have rather good although still need be improved. It can be known from recapitulation results of pre-test and post-test values. The average pre-test value is 5.96 and the average post-test value is 6.95. Thus, there is a ascension from pre-test value to post-test value about of 12.14%. One of the successfulness factors of the activity is supporting from the chairman of school and available of computer in the Computer Laboratory of the First State Vocational Middle School (SMK) of Mandiraja. And one of the resistance factors is many participants which have difficulty to practice how procedure of utilizing of the Surfer software to create a contour map, so required by advanced technical guidance.

Interpretation of 2D-Subsurface Resistivity Data in The Iron Ore Prospect Area of Eastern Binangun Coastal, Regency of Cilacap, Central Jawa Sehah, Muhammad; Raharjo, Sukmaji Anom; Destiani, Fajar
Journal of Geoscience, Engineering, Environment, and Technology Vol 3 No 4 (2018): JGEET Vol 03 No 04 : December (2018)
Publisher : UIR PRESS

Interpretation of 2D-subsurface rock resistivity data has been carried out in the iron ore prospect area of Eastern Binangun Coastal in Cilacap Regency, Central Java. The background of this research is the potential for abundant iron sand in this area that prospects to be exploited. The research was conducted using a magnetic method in 2017 to map the distribution patterns of the local magnetic anomalies that were interpreted to originate from the distribution of iron ore in the subsurface. In 2018, the research continued using the 2D-resistivity method to find out the lithology section in the subsurface of research area. 2D-resistivity data acquisition is carried out on four tracks consisting of Bng-01 to Bng-04. The resistivity data modeling have produced the true resistivity value for each track in the form of the subsurface resistvity section, which including the Bng-01 track is 2.27 – 44.1 Ωm; the Bng-02 track is 4.5 – 58.6 Ωm; the Bng-03 track is 6.37 – 63.4 Ωm; and the Bng-04 track of 4.98 – 83.3 Ωm. After interpretation process, some models of subsurface rocks lithology section is obtained under the four trajectories. The rocks resulted from interpretation process consists of sand which inserted with gravel (> 58.6 Ωm); sand containing iron ore grains (28.2 – 83.3 Ωm), clayey sand (11.1 – 32.9 Ωm), sandy clay (4.98 – 13.5 Ωm), and fine sand which intruded by saltwater (<6.49 Ωm). Sand containing iron ore grains is main part of the coastal aquifer so that exploitation of iron sand has the potential to reduce aquifer function in storing and flowing of groundwater and causing of abrasion in the Eastern Binangun Coastal area.

Pemetaan Anomali Magnetik dan Log Resistivitas Batuan di Pesisir Timur Kecamatan Nusawungu Kabupaten Cilacap Siti Amalia Fahrunnisa, Sehah, Sukmaji Anom Raharjo, Azmi Risyad,
Risalah Fisika Vol 3, No 2 (2019): Risalah Fisika ISSN 2548-9011
Publisher : Physical Society of Indonesia (PSI)

Abstrak – Pesisir Timur Kecamatan Nusawungu merupakan rangkaian kawasan di Pesisir Kabupaten Cilacap bagian timur yang disinyalir masih mengandung pasir besi. Survei magnetik dan geolistrik telah dilakukan pada bulan April hingga Oktober 2017 untuk mengetahui sebaran pasir besi di kawasan tersebut. Survei magnetik dilakukan di daerah penelitian dengan posisi 109,34619° – 109,37183°BT dan 7,69581° – 7,70978° LS. Hasil yang diperoleh dari survei magnetik adalah peta kontur anomali magnetik lokal, dengan nilai anomali berkisar -498,66 – 201,73 nT. Berdasarkan peta kontur yang diperoleh, terdapat beberapa closure anomali magnetik yang membentuk arah kelurusan 7,73° yang mengindikasikan adanya endapan pasir besi di bawahnya. Survei geolistrik dilakukan di kawasan yang diindikasikan mengandung pasir besi untuk memperkirakan potensinya. Berdasarkan hasil pemodelan diperoleh log resistivitas yang menunjukkan 4 – 5 lapisan batuan bawah permukaan. Pada setiap titik sounding terdapat lapisan yang diinterpretasi sebagai pasir yang mengandung butiran bijih besi yang berselingan dengan lanau dan lempung. Lapisan pasir besi ini tersebar pada titik sounding Sch-1 pada posisi 109,347722° BT dan 7,701611° LS hingga titik sounding Sch-5 pada posisi 109,362750° BT dan 7,703472° LS; dengan kedalaman berkisar 1,03 – 9,27 meter dan nilai resistivitas berkisar 2,51 – 75,55 Ωm. Berdasarkan hasil eksplorasi ini, kawasan pesisir timur Kecamatan Nusawungu Kabupaten Cilacap diperkirakan memiliki potensi pasir besi. Kata kunci: anomali magnetik, log resistivitas, pasir besi, batuan bawah permukaan, Pesisir Timur NusawunguAbstract – The Eastern Coastal of Nusawungu District is a series of areas in the Eastern part of the Cilacap Regency Coastal which allegedly still contains iron ore. The magnetic and geoelectric surveys have been conducted in April up to October 2017 to determine the distribution of iron sand in this area. Magnetic survey has been done in the research area at position of 109.34619° - 109.37183°E and 7.69581° – 7.70978°S. The results that obtained from the magnetic survey are local magnetic anomaly contour map, with anomalies values ranging of -498.66 – 201,73 nT. Based on the contour map that obtained, there are several magnetic anomalous closures with 7.73° strike that indicate the presence of iron sand deposits in its subsurface. The geoelectric survey has been carried out in the zone which indicated to contain iron sand to estimate its potential. Based on the results of modeling, several log resistivities have been obtained which show the existence of 4 - 5 lithologic layers. At each the sounding point, there is a layer which is interpreted as sand containing iron ore grains which alternating with silt and clay. This iron sand deposits are distributed at the sounding point of Sch-1 with position of 109.347722°E and 7.701611°S to the sounding point of Sch-5 with position of 109.362750°E and 7.703472°S; a depth ranging of 1.03 – 9.27 meters and resistivity values ranging of 2.51 – 75.55 Ωm. Based on the results of this exploration, the Eastern Coastal area of Nusawungu is estimated to have the potential of iron sand.Keywords: magnetic anomaly, log resistivity, iron sand, subsurface rocks, Eastern Coastal of Nusawungu

PENDUGAAN MODEL ANOMALI MAGNETIK BAWAH PERMUKAAN DESA DARMAKRADENAN, KECAMATAN AJIBARANG, KABUPATEN BANYUMAS Sehah, Sehah; Raharjo, SUkmaji Anom
BERKALA FISIKA Vol 16, No 3 (2013): Berkala Fisika
Publisher : BERKALA FISIKA

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (410.292 KB)

Magnetic survey has been carried out to estimate the subsurface magnetic anomaly model inDarmakradenan Village, Ajibarang District, Banyumas Regency. After the data processing whichincludes some corrections and reductions, then obtained the residual magnetic anomaly data in theresearch area. Then this magnetic anomaly data was modeled use Mag2DC for Windows software,thus obtained four subsurface anomalous objects, which are interpreted as coarse grained sandstones,Â conglomerates, and andesitic breccias from Tapak Formation (Ï‡ = 0.0055 cgs units), lava depositionof Slamet Volcano; with boulder of basaltic-andesite from old Slamet Volcano eruption (Ï‡ = 0.0175Â cgs units), andesitic sandstone, tuff conglomerate, and marl which insert of sandstone from HalangFormation (Ï‡ = 0.0015 cgs units), and limestones from Tapak Formation (Ï‡ = 0.0035 cgs units). TheÂ research areas have natural resources of limestone that is being cultivated mining now. While thepresence of gold minerals can not be determined, but is expected in the old alluvial deposits of TapakFormation and Halang Formation.Keywords: Magnetic anomaly, subsurface, Darmakradenan Village

INTERPRETASI MODEL ANOMALI MAGNETIK BAWAH PERMUKAAN DI AREA PERTAMBANGAN EMAS RAKYAT DESA CIHONJE, KECAMATAN GUMELAR, KABUPATEN BANYUMAS Sehah, Sehah; Raharjo, Sukmaji Anom; Prasetyo, Chandra Adi
BERKALA FISIKA 2015: Berkala Fisika Vol. 18 No. 2 Tahun 2015
Publisher : BERKALA FISIKA

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (798.889 KB)

Measurement of magnetic data has been done in the area of â€‹â€‹the gold mining in the village of Cihonje, the district of Gumelar, the regent of Banyumas in May to June 2013. Based on the modeling that has been conducted on the local magnetic anomalies along cross section of AB obtained six models of subsurface rock, while for along cross section of AB obtained five models. Based on the modeling results, rock formations that developed in the research area are Tapak formation, Halang formation, andesite-basaltic, and the alternating formation of the sandstones with some other rocks. The magnetic susceptibility of subsurface rock in the research area are interpreted ranged from 0.0039 to 0.0174 cgs units with the average magnetic susceptibility of rocks is estimated equal to 0.0099 cgs units that interpreted as the alternating formation of sandstone and claystone from Halang formation. The mineralization of gold ore is estimated to occur in almost of all subsurface rocks, but the most dominant mineralization is estimated to occur in the Halang formation especially on the alternating formation of sandstone and claystone. The gold ore mineralization occurs in the form of veins of pyrite, chalcopyrite, galena, and the others, that fill the cracks and the pores of the rocks. Keywords: magnetic anomaly, gold mining, Village of Cihonje

APPLICATION OF MAGNETIC SURVEY TO EXPLORE THE IRON ORE DEPOSITS IN THE NUSAWUNGU COASTAL REGENCY OF CILACAP CENTRAL JAVA Sehah, S; Raharjo, Sukmaji Anom
Jurnal Penelitian Fisika dan Aplikasinya (JPFA) Vol 7, No 2 (2017)
Publisher : Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/jpfa.v7n2.p79-88

The research aiming to explore the iron ore deposits in the Nusawungu coastal Regency of Cilacap has been conducted using the magnetic survey. The acquisition of magnetic data was conducted in April ? Mei 2017, covering the area in the ranges of 109.314° ? 109.345°E and 7.691° ? 7.709°S. The obtained magnetic field strength data were corrected, reduced, and mapped to obtain the contour map of local magnetic anomaly. The modeling process was carried out along the path extending over the map from the positions of 109.314°E and 7.695°S to 109.335°E and 7.699°S, so that some subsurface anomalous objects are obtained. The lithological interpretation was performed to identify the types of subsurface rocks and their formations based on the magnetic susceptibility value of each anomalous objects and supported by the geological information of the research area. Based on the interpretation results, three rocks deposits of alluvium formations were obtained, which are estimated to contain iron ore. The first deposit has a length of 164.85 m, a depth of 0.57 ? 8.43 m, and a magnetic susceptibility value of 0.0097 cgs. The second deposit has a length of 376.28 m, a depth of 2.56 ? 19.66 m, and a magnetic susceptibility value of 0.0108 cgs. The third deposit has a length of 1,306.26 m, a depth of 3.70 ? 58.69 m, and a magnetic susceptibility value of 0.0235 cgs. Out of the whole rocks deposits, the third rock deposit is interpreted to have the most prospective iron ore. This interpretation based on its high magnetic susceptibility value, which indicates the presence of many magnetic minerals (i.e. iron ores) in the rock.

Coastal Hydrogeological Model in the Iron Ore Prospect Area of Widarapayung Coastal, Cilacap Regency Based on 2D-Resistivity Data Sehah, Sehah; Raharjo, Sukmaji Anom; Aziz, Abdullah Nur
Jurnal Penelitian Fisika dan Aplikasinya (JPFA) Vol 8, No 2 (2018)
Publisher : Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/jpfa.v8n2.p71-83

The coastal hydrogeological model of iron ore prospect area in Widarapayung coastal, Cilacap Regency, has been designed and performed based on the 2D-resistivity data. The background of this research is potentiality of iron sand in this area and its prospect to be mined. Mining activities in large-scale may lead into surface decreasing, triggering damage to the aquifer, abrasion, and saltwater intrusion in the coastal area. The acquisition of 2D-resistivity data has been performed on five trajectories including of WP-01 up to WP-05. Based on the modeling results, it can be concluded that the sub-surface rocks resistivity profile consists of WP-01 with the values of 1.93-114.00 Î©m; WP-02 with the values of 3.67-121.00 Î©m; WP-03 with the values of 3.86-78.40 Î©m; WP-04 with the values of 1.79-100.00 Î©m; and WP-05 with the values of 2.61-86.20 Î©m. After interpretation, it is found that the hydrogeological profile of sub-surface rocks consists of sand inserted with gravels (topsoil); sand containing iron ore granules inserted with silt (topsoil and shallow aquifer); clayey sand (semi-aquifer layer); sandy clay (semi-impermeable layer); and sand (deep aquifer which is intruded by salt water). Based on the analysis, the sand containing iron ore is part of the shallow aquifer, so the mining activities of iron sand is potential to damage and reduce aquifer function in storing and flowing the groundwater in the research area.

Interpretation of Magnetic Anomaly Data in the Andesitic Rock Prospect Area of Kutasari Subregency, Purbalingga Regency, Central Java, Indonesia Sehah, Sehah; Raharjo, Sukmaji Anom; Prabowo, Urip Nurwijayanto; Sutanto, Dwi Setiawan
Indonesian Journal on Geoscience Vol 8, No 3 (2021)
Publisher : Geological Agency

Interpretation of magnetic anomaly data has been carried out in the andesitic rock prospect area, Kutasari Subregency, Purbalingga Regency, Central Java, Indonesia. Geographically, this area is located within 109.2788Â° - 109.3072Â°E and 7.3032Â° - 7.3319Â°S. The study has been done in April â€“ September 2019 with the purpose to map the distribution of andesitic rocks based on the local magnetic anomaly data. The data that are acquired in this study have the values ranging between -1,238.13 - 1,892.40 nT. The results of qualitative interpretation on the local magnetic anomaly data having been reduced to the pole show the distribution of strong anomalous sources in the northwest area interpreted as massive andesitic rocks. Whereas the results of quantitative interpretation through 2D-forward modeling on the local magnetic anomaly data show six anomalous bodies, with magnetic susceptibility values ranging from 0.0025 to 0.0350 cgs and depths range between 7.16 - 505.97 m. The highest magnetic susceptibility is 0.0350 cgs interpreted as a massive andesite intrusion forming a very dense dike; whereas the lowest magnetic susceptibility is 0.0025 cgs interpreted as undifferentiated igneous rocks, volcanic breccias, lava, and tuff. Based on the study results, the correlation between the results of qualitative and quantitative interpretations occurs.

Interpretation of Magnetic Anomaly Data in the Andesitic Rock Prospect Area of Kutasari Subregency, Purbalingga Regency, Central Java, Indonesia Sehah, Sehah; Raharjo, Sukmaji Anom; Prabowo, Urip Nurwijayanto; Sutanto, Dwi Setiawan
Indonesian Journal on Geoscience Vol 8, No 3 (2021): in-press
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.3.345-357

Interpretation of magnetic anomaly data has been carried out in the andesitic rock prospect area, Kutasari Subregency, Purbalingga Regency, Central Java, Indonesia. Geographically, this area is located within 109.2788Â° - 109.3072Â°E and 7.3032Â° - 7.3319Â°S. The study has been done in April â€“ September 2019 with the purpose to map the distribution of andesitic rocks based on the local magnetic anomaly data. The data that are acquired in this study have the values ranging between -1,238.13 - 1,892.40 nT. The results of qualitative interpretation on the local magnetic anomaly data having been reduced to the pole show the distribution of strong anomalous sources in the northwest area interpreted as massive andesitic rocks. Whereas the results of quantitative interpretation through 2D-forward modeling on the local magnetic anomaly data show six anomalous bodies, with magnetic susceptibility values ranging from 0.0025 to 0.0350 cgs and depths range between 7.16 - 505.97 m. The highest magnetic susceptibility is 0.0350 cgs interpreted as a massive andesite intrusion forming a very dense dike; whereas the lowest magnetic susceptibility is 0.0025 cgs interpreted as undifferentiated igneous rocks, volcanic breccias, lava, and tuff. Based on the study results, the correlation between the results of qualitative and quantitative interpretations occurs.

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