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M. Irham Nurwidyanto
Laboratorium Geofisika FMIPA Undip

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INTERPRETASI BAWAH PERMUKAAN DENGAN METODE SELF POTENTIAL DAERAH BLEDUG KUWU KRADENAN GROBOGAN Dwi Indriana, Rina; Nurwidyanto, M. Irham; W. Haryono, Kurnia
BERKALA FISIKA Vol 10, No 3 (2007): Berkala Fisika
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Abstract

The geophysics research to observe the subsurface anomaly in Bledug Kuwu had been done. It was used to analyze and interpret the potential data. The purpose of this research was to interpret the object of subsurface anomaly. The research was used self potential method with base point electrode configuration. Data processed used Surfer 8 software, which result was an isopotential contour map. The modeling processed used curve matching for a spherical model. By using Bhattacharya theory, the depth and polarization angle was founded as the parameter of a spherical model. The research?s result of the depth of anomaly origin is 19,5 m, 23,68m, and 40,8 m. The polarization angle is 70o, 70,38o and 100o.   Keywords: Bledug Kuwu, self potential, spherical model  
ESTIMASI PENYEBARAN SEDIMEN CEKUNGAN JAWA TIMUR DENGAN METODE GRAVITY Adib Hasan, Muhamad; Nurwidyanto, M. Irham
BERKALA FISIKA Vol 11, No 4 (2008): Berkala Fisika
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This research is a reconnaissance study to predict the distribution and depth of the sediment basin in East Java based on Bouger Anomaly data in gravity method.Bouger anomaly is projected to flat plane used by equivalent point mass source method. Upward continuation is used to separate the regional and residual anomaly.  Modeling sub surface in two dimensions are used by polygon Talwani method by help computer program Geomodel.The results of this research can be concluded that in East Java sediment basin has about 6 km in depth. The central basin are reside in mid of East Java, there are around Sragen, Karanganyar, Ngawi, Madiun, Nganjuk, Kediri, Bojonegoro, Jombang and Mojokerto which in the east west direction. In the eastern part of East Java Basin there are Sidoarjo, Pasuruhan, Probolinggo and Maura bay has direction in northwest to southeast. Key words: Basin, basement, sediment, Bouger Anomaly
PEMODELAN TOMOGRAFI CROSS-HOLE METODE GEOLISTRIK RESISTIVITAS (BENTUK ANOMALI SILINDRIS) Prabowo, Riza Eka; Yulianto, Gatot; Nurwidyanto, M. Irham
BERKALA FISIKA Vol 9, No 1 (2006): Berkala Fisika
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Abstract

            Cross-hole method using an amount of electrode were placed downhole is one of tomography method. Cross-hole tomography method delineate the geological conditions of the earth surface therefore it takes an important rule in the case of anomaly monitoring. The buis concrete planted in subsurface with deepness of about 1 m were used as the source of anomaly. Tomography cross-hole data with configuration such as pole-pole, pole-bipole, bipole-pole and bipole-bipole array were taken with the depth of the borehole is 1,2 m. The space variation of one electrode to another in the hole of drill is 0,2 m, 0,4 m, 0,6 m and 0,8 m for the configuration of pole-bipole, bipole-pole and bipole-bipole. Res2Dinv program obtained the images of bipole-bipole better than the images of other configuration. While the pole-pole configuration had the worst images compared to others. It is caused by two remote electrode of pole-pole array while bipole-bipole array do not have ones. Key words: cross-hole, tomography, borehole, remote electrode
INTERPRETASI DATA SEISMIK REFRAKSI MENGGUNAKAN METODE RECIPROCAL HAWKINS DAN SOFWARE SRIM (STUDI KASUS DAERAH SIOUX PARK, RAPID CITY, SOUTH DAKOTA, USA) Wahyuningrum, Sri; Yulianto, Gatot; Nurwidyanto, M. Irham
BERKALA FISIKA Vol 9, No 4 (2006): Berkala Fisika
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Data processing of seismic refraction has been done. This data processing was the secondary data from seismic measurement result in the Sioux Park area, Rapid City, South Dakota, USA using EG refraction & G Geometrics Model ES-1210 seismic refraction instrument made in America with 12 geophones. The seismic refraction data processing was to determined the velocity and the deepness of eachs layer, and make geology under surface model then to interpreted the the data processing result using Reciprocal Hawkins method and SRIM software. On the seismic data processing used Reciprocal Hawkins method and SRIM (Seismic Refraction Inverse Modelling) software. Reciprocal Hawkins method used time depth concept and SRIM software used delay time concept. The time depth value or the delay time value was same with a half value of intercept time.The result from the data processing using Reciprocal Hawkins method was obtained threes layer, that are the seismic wave velocity of the first layer is 1013 ft/s, the second layer is 4007 ft/s and the third layer is 6887 ft/s. While the result of the deepness calculation obtained the deep of first layer range is 0,93 ft ? 11,24 ft, the second layer ranging is 8,72 ft ? 19,38 ft and from data processing the result using SRIM software obtained seismic wave velocity of the first layer is 970 ft/s, the second layer is 3485 ft/s and the third layer is 6150 ft/s, while the result of deepness calculation of the first layer range is 0,10 ft ? 7,20 ft, the second layer range from 3,40 ft ? 27,00 ft. From the under surface image model can be interpreted that the first layer is mouldy  layer which represent cover layer, the second layer is clay stone layer, sand ( dry, having the pass character) and third layer is napal stone at Spearfish formation which has impermeable characteristic or waterproof. Key words: delay time, intercept time, Reciprocal Hawkins method, seismic refraction
PEMODELAN ZONA SESAR OPAK DI DAERAH PLERET BANTUL YOGYAKARTA DENGAN METODE GRAVITASI Nurwidyanto, M. Irham; Dwi Indriana, Rina; Thaha Darwis, Zukhrufuddin
BERKALA FISIKA Vol 10, No 2 (2007): Berkala Fisika
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A gravity research was done in Pleret, Bantul, Yogyakart.It?s covering 55 measurements points. This research aims to estimated subsurface structure  fault zone of the area, correctly along Opak River?s. Type of Gravitymeter La Coste & Romberg G-1118 using electronics feedback system with accuracy 0.005 miligal was used to measure gravitational field. Interpretation result from kualitative and kuantitative  are  estimated the structure in the research area consist of tree layer that arre  limestone, breccia, and alluvial sediment and Opak sediment?s
ANALISIS ATRIBUT SEISMIK UNTUK IDENTIFIKASI POTENSI HIDROKARBON Maulana Hadi, Johan; Nurwidyanto, M. Irham; Yulianto, Gatot
BERKALA FISIKA Vol 9, No 4 (2006): Berkala Fisika
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Abstract

Rms amplitude and spectral decomposition attribute have been extracted for hydrocarbon potential identification in Amandah area, Talangakar Formation, North West Java Basin. Purpose of rms amplitude extractions is to see the change of lithology which is extreme. Example is like reservoir existence. Spectral decomposition has been used to see reservoir at thin thickness. The seismic attributes has been extracted from seismic data 3D Pre Stack Time Migration (PSTM). Log data has been taken from a well (AMD-01) to interpret and determine reservoir thickness in interest zone. Seismic attribute analysis has been used to see existence and shape of channel?s geometry spreading. The result of rms amplitude attribute extraction is reservoir which can be detected clearly at 10 ms, 20 ms, 30 ms and 40 ms window analysis. Whereas the result of spectral decomposition attribute extraction is reservoir which can be detected at 15 Hz ? 25 Hz frequency with 30 ms and 40 ms window analysis. The result of rms amplitude and spectral decomposition attribute analysis shows hydrocarbon in Amandah area, Talangakar Formation is potential in channel depositional facies with depositional direction at north-south (N-S) and north nort east ? south south west (NNE-SSW) and  thickness high of channel is concern at 36-60 m.   Key words: Seismic attribute, rms amplitude, spectral decomposition, reservoir,
PENENTUAN KEDALAMAN DAN KETEBALAN AKUIFER MENGGUNAKAN METODE SEISMIK BIAS (STUDI KASUS ENDAPAN ALLUVIAL DAERAH SIOUX PARK, RAPID CREEK, SOUTH DAKOTA, UNITED STATE OF AMERICA) Listiyani, Fenti; Nurwidyanto, M. Irham; Yulianto, Gatot
BERKALA FISIKA Vol 9, No 3 (2006): Berkala Fisika
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Abstract

Data processing of refraction Seismic has been done by using the secondary data in area of Sioux Park, Rapid Creek, South Dakota, United State of America with the trajectory of seismic SP#1 which  has geology structure of alluvial sediment. The sediment Alluvial has a form of water carrier rock precipitated by Rapid Creek Tthe data processing of refraction Seismic usedin this experiment is  Reciprocal Hawkins methode that  represent a method that develop concept of time depth recognition. The time Depth from the refractor is  equal for the travel of critical time from the aspect of between refractor and surface less than time required for the ray path of projection of area refractor at a speed of refractor. Results   of  the seismic refracted obtained: first layer consist of clay  functioning as covering laye, the second layer lapped over from clay, sand, and gravel functioning as carrier coat irrigate or coat acquife and the   third layer lapped over from stone napal, functioning as waterproof coat ( impermeable). Deepness of layer acquifer vary from 0.93 ft - 12.01 ft ( 0.28 m ? 3.66 m), and their thickness vary from 0.86 ft ? 14.43 ft ( 0.26 m ? 4.40 m). The geometry of these  acquiferare in the form of free acquifer  or unconfined aquifer. Keywords: seismic refraction, ground water
PENGARUH UKURAN BUTIR TERHADAP POROSITAS DAN PERMEABILITAS PADA BATUPASIR Nurwidyanto, M. Irham; Yustiana, Meida; Widada, Sugeng
BERKALA FISIKA Vol 9, No 4 (2006): Berkala Fisika
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It has been done a research to know the influence of grain size to permeabiality and porosity on sandstones from Ngrayong Formation, Ledok Formation, Kerek Formation and Selorejo Formation. The Permeability is measured by RUSKA Permeameter Gas, while the porosity is measured by  Porosimeter Gas A-9756 series. The grain size is then determined  using grain size analysis method. After the calculation, the grain size is attributed to permeability and porosity of sandstones with the analysis regresi method. Results obtained indicate that the influence of grain size significant at six sandstones. Based on the statistic calculation it has been obtained the relation  with Linear regression  equation Log k= -5.7 Log d + 15 with r2=0.7, for the grain size to permeability and = -1.9x102d +75 with  r2=0.7,  for the relation of grain size to porosity.   Key Word: sandstone, grain size, porosity, permeability
PEMETAAN SEBARAN AIR TANAH ASIN PADA AQUIFER DALAM DI WILAYAH SEMARANG BAWAH Nurwidyanto, M. Irham; Widodo, Sugeng; T. Achmad, Refyana
BERKALA FISIKA Vol 9, No 3 (2006): Berkala Fisika
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A research to mapping of saline groundwater spreading at deep aquifer in SEMARANG Awash  area, exactly at 49 zone, coordinate X(422000-445000), Y(9222100-9232000) is carry out. Electrical conductivity used in this research as approximation to saline value of groundwater. Then, the isoconductivity contour map made based on that?s conductivity value using surfer 7 to see the mapping of saline groundwater spreading. After that, a hydrochemistry analyze method resemble to Trilinier Piper diagram and Chlorida-Carbonat Ratio (R) used to analyze caused factor of saline from groundwater. Base on the groundwater saline grade clasification from PAHIAA, Jakarta, the groundwater at deep aquifer of Semarang bawah area come in insipid that spread out almost in all Semarang bawah area and insipid-saltish groundwater clasification that just found in two area, are central Pedurungan (Tlogosari) and Tugu Muda direct to Pemuda street area. Base on Trilinier Piper diagram and Chlorida-Carbonat Ratio (R) analyze,  the saline of groundwater at deep aquifer in  Semarang Awash area is the effect from the sea water intrusio, except in central Semarang area the salted of groundwater it?s not caused by the sea water intrution, may be couse by dilution of salt mineral which imbedded in the groundwater..
INTERPRETASI BAWAH PERMUKAAN DAERAH MANIFESTASI PANAS BUMI PARANG TRITIS KABUPATEN BANTUL DIY DENGAN METODE MAGNETIK Indratmoko, Putut; Nurwidyanto, M. Irham; Yulianto, Tony
BERKALA FISIKA Vol 12, No 4 (2009): Berkala Fisika
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Abstract                 Acquisition of geomagnetic field has been done at Kretek, Sanden, Pundong, Bantul and Panggang, Gunung Kidul, Yogjakarta Province on 14 s/d 17 October and  7,8,9,12 November 2009 in orde to interpreted the subsurface structure. Data has been collected by Proton Precession Magnetometer (PPM) to measured  the total  intensity of magnetic field, Global Positioning System (GPS) to determine the position and geology compass to the direction of north pole.                 The raw data has been processed and performed using IGRF (International Geomagnetics Reference Field) correction to obtain total field magnetic anomaly. Upward continuation was performed at 300 meters heigh by Magpick. Qualitative interpretation was done by analyzing regional and local anomaly maps. Quantitative interpretation was done 2 ½ D modelling cross-sectionanomaly maps using Mag2DC for Windows Software.     The result of 2-D modeling produces anomaly objects was susceptibility value (0,0405) in cgs unit  for the first object, susceptibility value (0,0425) in cgs unit  for the second object, susceptibility value (-0,0085) in cgs unit for the third object. The anomaly objects had depth in +580 meters from the surface and was considered the rock which had been experience demagnetitation proses.    Key word: magnetic anomaly, Parangtritis, susceptibilities.