Imam Setiadi
Pusat Survei Geologi

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DELINEASI CEKUNGAN SEDIMEN DAN INTERPRETASI GEOLOGI BAWAH PERMUKAAN CEKUNGAN TANIMBAR BERDASARKAN ANALISIS DATA GAYABERAT Imam Setiadi; Arenda Reza Riyanda
Jurnal Geologi dan Sumberdaya Mineral Vol. 17 No. 3 (2016): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v17i3.14

Abstract

Produksi migas Indonesia semakin menurun secara bertahap, untuk kembali meningkatkan produksi migas diperlukan pencarian cadangan-cadangan  baru dengan cara melakukan penelitian pada cekungan-cekungan sedimen frontier. Salah satu metoda geofisika yang dapat digunakan untuk mendelineasi cekungan sedimen adalah metoda gayaberat. Metode gayaberat mengukur variasi percepatan gravitasi yang disebabkan karena perbedaan densitas antar batuan bawah permukaan. Penelitian gayaberat dilakukan di daerah Kepulauan Tanimbar dengan tujuan untuk mengetahui Anomali Bouguer, pola sub-cekungan, pola tinggian, struktur geologi bawah permukaan daerah penelitian melalui pemodelan 2,5D  dan inversi 3D. Pengolahan data yang dilakukan dalam penelitian meliputi : analisis spektral, analisis SVD, pemodelan 2,5D dan pemodelan inversi 3D untuk mengetahui struktur bawah permukaan daerah penelitian dan model/pola sub-cekungan Tanimbar. Hasil penelitian menunjukkan bahwa: (1) Daerah penelitian memiliki rentang anomali Bouguer antara -46,4 mGal hingga 9,6 mGal dengan anomali rendah pada bagian tengah, anomali sedang pada bagian tepi Pulau Yamdena, sedangkan anomali tinggi pada bagian tenggara dan barat laut daerah penelitian. (2) Jumlah sub-cekungan sedimen yang dapat diinterpretasi adalah sebanyak 6 sub-cekungan. (3) Pola tinggian (basement high)  mempunyai arah relatif timur laut-barat daya. (4) Hasil pemodelan bawah permukaan 2,5D menunjukan, a) batuan pengisi dari setiap sub-cekungan adalah batuan sedimen Tersier, yaitu Anggota Napal Formasi Batimafudi (Tmbm) nilai densitas 2,38 gr/cc, Formasi Batimafudi (Tmb) dengan densitas 2,37 gr/cc, Formasi Tangustabun (Tpt) dengan densitas 2,42 gr/cc dan batuan yang mengalasi sub-cekungan adalah batuan pra-tersier yakni batubasalt dengan densitas 2,7 gr/cc dari Kompleks Molu (M), b) Analisis SVD  menunjukkan letak patahan pada model 2,5D relatif sama dengan grafik SVD yang diperoleh dari peta anomali SVD.
INTERPRETASI STRUKTUR GEOLOGI BAWAH PERMUKAAN DAERAH LEUWIDAMAR BERDASARKAN ANALISIS SPEKTRAL DATA GAYA BERAT Imam Setiadi; Ai Diyanti; Nanang D Ardi
Jurnal Geologi dan Sumberdaya Mineral Vol. 15 No. 4 (2014): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v15i4.59

Abstract

Kajian analisis data gayaberat daerah Leuwidamar, Banten telah dilakukan menggunakan metode analisis spektral.Tujuannya adalah memperkirakan kedalaman batuan alas dan menginterpretasi model geologi bawah permukaan. Metode gayaberat dilakukan beralaskan anomali gayaberat yang muncul karena adanya variasi rapat massa dari penyusun material bawah permukaan bumi. Hasil analisis spektral menunjukkan dua nilai kedalaman dengan rata-rata 1,71 km yang merefleksikan kedalaman batuan alas dan 10,66 km yang mencerminkan kedalaman kerak. Berdasarkan pemodelan dua dimensi bawah permukaan diperkirakan batuan alas daerah Leuwidamar adalah andesit yang memiliki densitas sebesar 2,74 g/cc. Evolusi tektonik menyebabkan terbentuknya sesar bawah permukaan dan batuan terobosan seperti granodiorit Cihara yang memiliki densitas 2,68 g/cc di bagian selatan Leuwidamar.Kata kunci : Leuwidamar, gayaberat, analisis spektral
POLA STRUKTUR DAN GEODINAMIKA CEKUNGAN BULA, BERDASARKAN ANOMALI GAYA BERAT Budi Setyanta; Imam Setiadi
Jurnal Geologi dan Sumberdaya Mineral Vol. 20 No. 1 (2010): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v20i1.161

Abstract

Gravity is one of the geophysical methods that can be used to estimate subsurface condition based on the density of rocks. Seram bouguer anomaly map reduced by density 2.67 gr/cc indicates negative anomaly pattern in Bula Basin with anomaly range between ( -50 mgal – 0 mgal). Gravity data analyses were carried out by separating the residual and regional anomalies using moving average filtering and second vertical derivative. The subsurface modeling was done by using gravmag forward modeling software. The results show two regional faults i.e. the norteast-sothwest strike slip fault and the east-west thrust fault. Those faults have different periods. The filtering using moving average and second vertical derivative shows closure areas and fold within Pretertiary rocks that geologically are interesting features.Keywords : Gravity, moving average, second vertical derivative, Bula Basin
DELINEASI CEKUNGAN SEDIMEN SUMATRA SELATAN BERDASARKAN ANALISIS DATA GAYA BERAT Imam Setiadi; Budi Setyanta; Bambang Suci Widijono
Jurnal Geologi dan Sumberdaya Mineral Vol. 20 No. 2 (2010): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v20i2.164

Abstract

South Sumatra Basin is one of large sedimentary basins in Indonesia which has been proven to produce hydrocarbon energy. Several literatures mention different amount of subbasin with this basin. Gravity is one of geophysical methods that is used to interpret lateral and vertical basin configuration based on rock density parameter. The gravity analysis is conducted by using spectral analysis method in order to estimate shallow and depth anomaly sources, and then to separate regional and residual anomaly using moving average method. The result of spectrum analyses show two discontinuity density plans, located at 3.05 km reflecting the average depth of Tertiary sedimentary basement, and at 15.98 km reflecting Moho discontinuity plane. Meanwhile, the residual anomaly shows that there are two lineament patterns trending northwest-southeast and southwest- northeast. The main fault is Sumatra Fault indicating northwest-southeast lineament, and the subsidiary faults trending southwest-northeast. Azimuth of shallow basement and rifting patterns are northwest-southeast, while the number of identified subbasin are 10. The result of two dimensional modeling shows that the basement in South Sumatra is metamorphic rock having the density contrast 0.12 gr/cc and the average density contrast of the sedimentary rocks filling the basin is -0.22 gr/cc.Keywords : gravity, spectral analyses, moving average, South Sumatra Basin
DELINEASI CEKUNGAN BUSUR MUKA SIMEULUE BERDASARKAN DATA ANOMALI GAYA BERAT Lauty Dwita Santi; Imam Setiadi; Hermes Panggabean
Jurnal Geologi dan Sumberdaya Mineral Vol. 20 No. 3 (2010): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v20i3.169

Abstract

The study of hydrocarbon potential at the fore-arc basins of west offshore Sumatra has been done by many writers. Recently, Simeulue basin, has been put at the spotlight as the Germany's BGR research team published several latest seismic lines showing great sediment accumulation in this basin. Although many new information and speculation emerge by the result of that research, until now the exact basin boundary itself has never been discussed. Delineation process of Simeulue basin in this study is done by applying gravity anomaly data that covers a wide area enough to determine the apparent boundary of sediment distribution within the basin. A gravity anomaly profile is produced using forward modeling method, showing the geometry of the basin, with maximum length of 418 km. The northward and southward of this basin is bounded by hightopographies that separate Simeulue basin with the other adjacent basins.Keywords : Basin delineation, Gravity anomaly
MODEL GEOLOGI BAWAH PERMUKAAN DAERAH MUARAWAHAU HASIL ANALISIS ANOMALI GAYA BERAT BERDASARKAN ESTIMASI KEDALAMAN DENGAN METODE ANALISIS SPEKTRAL Budi Setyanta; Imam Setiadi; W.H. Simamora
Jurnal Geologi dan Sumberdaya Mineral Vol. 18 No. 6 (2008): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v18i6.258

Abstract

A Study about a depth estimation on a gravity model in Muarawahau quadrangle, East Kalimantan, by using a Spectral Analysis method is very helpful to reduce ambiguity that appears in each modeling. The qualitative analysis shows that high anomalies lay at the eastern part of  the research area with values between  10 - 55 mgal, while low gravity anomalies between  -60 to 9 mgal lay at the western area. Two groups of anomaly in this area reflect a basin and basement high which is separated by a regional strike slip fault . A Model resulted  from  East to West  profiling and supported by a Spectral Analyses Method shows that the basin is constructed by PreTertiary rocks with density of about 2.6 gr/cc and thickness approximately 5 km, experiencing tectonic deformation. The eastern high anomaly block is the reflection of ultramafik rocks and mélange with the density of about 2.65 gr/cc. Rocks in this block is partly covered by volcanic sediments abaut 500 meter thich (2.3 gr/cc). However based on the values of anomaly, those two blocks are still underlined by the same granitic continent, meanwhile the existing ultramafic rocks are only ophiolite fragmen of oceanic crust. Keywords : Gravity anomaly, depth estimation, geological model.
ANOMALI GAYA BERAT DAN TATAAN TEKTONIK SEKITAR PERAIRAN LAUT BANDA DAN PULAU SERAM Budi Setyanta; Imam Setiadi
Jurnal Geologi dan Sumberdaya Mineral Vol. 17 No. 6 (2007): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v17i6.319

Abstract

Bouguer and free air gravity anomalies  of the  Banda Sea and Seram Island are divided into southren, central and northern parts. Gravity analyses based on land measurement  combined  with ftee air anomaly data of the sea produce crust structure model which close related to rock composition and tectonic position.  Crust structure at Banda Sea is mainly composed of basaltic crust of  Banda Sea as a base and folded occurrence, collision with granitic crust border (Australian continent fragment  ?).  Banda Sea basaltic  crust is underlying volcanic sediment  Banda  Island, while granitic crust is underlying Pre-Tertiary sediment rock at Seram Island. Collision which happened since early Pliocene of two different crust has caused many things such as material from many sources in Seram Island mad melange  rock and thrust fault that appeared in the surface. Tectonic intensity has also caused some granitic crust borders to get fragmentation which reduces value of the anomaly. Further-more, it appears volcanic rock of  Banda Sea has caused gravity tectonic  toward equilibrium process basaltic  crust. This geodynamic crust   model has an implication  to geological Potency product, both in economic or disaster risk.Keywords: gravity, tectonic, evolution, geological potency