Optimalisasi Data Gayaberat untuk Pemodelan Struktur Geologi Bawah Permukaan Daerah Kepulauan Sabu-Raijua, Nusa Tenggara Timur, Indonesia
DOI:
https://doi.org/10.26418/positron.v12i1.54321Keywords:
Gayaberat, prisma akresi, sabu "“ raijua, struktur, uplift.Abstract
Kawasan Timur Indonesia (KTI) yang merupakan daerah frontier meliputi sepertiga luas cekungan sedimen di Indonesia. Namun sampai dengan saat ini hanya beberapa cekungan sedimen yang berproduksi. Kendala yang dihadapi di daerah frontier adalah ketersediaan dan kualitas data yang kurang memadai. Data gayaberat dapat dijadikan solusi alternatif dalam memberikan gambaran awal kondisi bawah permukaan di daerah frontier. Analisis lanjut dilakukan dengan mengkompilasi land gravity data (onshore) dengan topex free air gravity data yang dikoreksi menjadi anomali bouguer untuk mengungkap daerah offshore, penerapan metode Second Vertical Derivative (SVD) untuk mendelineasi struktur geologi dan metode Euler 3D Deconvolution dalam memperkirakan kedalaman sumber anomali gayaberat yang umumnya dilakukan dengan analisis spektral. Hasil penelitian menunjukkan adanya anomali gayaberat tinggi yang diinterpretasikan sebagai prismatic body di bawah Pulau Sabu "“ Raijua. Prismatic body diduga terbentuk karena terdapat dua arah tegasan yang hampir saling tegak lurus, yaitu arah baratdaya "“ timurlaut dan arah tenggara "“ baratlaut di sekitar Scott Plateau. Tegasan baratdaya "“ timurlaut mensesarkan Savu Thrust di sebelah timurlaut daerah penelitian. Metode Euler 3D Deconvolution memberikan informasi kedalaman yang mendekati hasil estimasi kedalaman analisis spektral dengan disertai informasi posisi lateralnya. Kedalaman sumber berdasarkan Euler bervariasi dari 2.4 Km "“ 7 Km, sedangkan kedalaman berdasarkan analisis spektral pada kisaran 2 Km "“ 6 Km. Pemodelan 2.5D dilakukan berdasarkan data gayaberat dengan 3 unit lapisan yaitu air laut (seabed), lapisan sedimen, dan lapisan batuan alas yang diduga berupa Thrust Fold Australian Continental Margin. Pemodelan struktur geologi bawah permukaan memperlihatkan pola struktur naik yang mendorong lapisan di atasnya (uplifted) hingga memunculkan daratan Pulau Sabu "“ Raijua.
Kata kunci: Gayaberat, prisma akresi, sabu "“ raijua, struktur, uplift.
References
Extract XYZ Grid – Topography and Gravity, http://topex.ucsd.edu/cgibin/get_data.cgi.
Badan Geologi, “Peta Cekungan Sedimen Indonesia Berdasarkan Data Gayaberat dan Geologi Skala 1:5.000.000â€. Badan Geologi. 2010.
L. L. Nettleton, “Determination of Density For Reduction of Gravimeter Observations†Annu. Meet. Oklahoma City, Oklahoma, pp. 176–193, 1939.
Kadir, W. G. A. “Eksplorasi Gayaberat dan Magnetikâ€. Jurusan Teknik Geofisika, Fakultas Teknik Pertambangan dan Perminyakan, ITB. 2000.
Thompson, D. T. “EULDPH: A New Tehcnique for Making Computer-Assisted Depth Estimation from Magnetic Dataâ€. Geophysics, Vol. 47, pp. 31 – 37. 2004.
Reid, A. B., Allsop, J. M., Granser, H., Milett, A. J., Somerton, I. W., “Magnetic Interpretation in Three Dimensions using Euler Deconvolutionâ€. Geophysics, Vol. 55, pp. 80 – 91. 1990.
Yudistira, Tedi., Grandis, H. “Interpretasi Gravitasi dan Magnetik Menggunakan Metode Sinyal Analitik dan Dekonvolusi Euler-3Dâ€. Prosiding HAGI, Yogyakarta. 1998.
Lilie, R. J. “Whole Earth Geophysics, An Introductory Textbook for Geologist & Geophysicistâ€. Prentice – Hall, pp. 223 – 283. 1999.
Handyarso, A., Padmawidjaja, T. “Struktur Geologi Bawah Permukaan Cekungan Bintuni Berdasarkan Analisis Data Gayaberatâ€. Jurnal Geologi dan Sumberdaya Mineral, Vol. 18, pp. 53 – 66. 2017.
Blakely, R. J. “Potential Theory in Gravity and Magnetic Applicationâ€. Cambridge University Press. 1996.
Elkins, T. A. “The Second Derivative Method of Gravity Interpretationâ€. Geophysics, Vol. 16 (1), pp. 29 – 50. 1951.
Nabighian, M. N. “The Analytic Signal of Twi Dimensional Magnetic Bodies with Polygonal Cross Section: Its Properties and Use for Automated Anomaly Interpretationâ€. Geophysics, Vol. 37, pp. 507 – 517. 1972.
Rigg, J. W. D., Hall, R. “Structural and Stratigraphic Evolution of the Savu Basin, Indonesiaâ€. Geological Society of London, Special Publication, Vol. 355, pp. 255 – 240. 2011.
Satyana, A. H., Armandita, C., Tarigan, R. L. “Collision and Post Collision Tectonics in Indonesia: Role for Basin Formation and Petroleum Systemsâ€. Proceeding, Indonesia Petroleum Association (IPA), IPA08 – G – 140. 2008.
Carter, D., Charles, M. A., Barber, A. “Stratigraphical Analysis of Island Arc – Continental Margin Collision in Eastern Indonesiaâ€. Journal of the Geological Society, Vol. 132, pp. 179 – 198. 1976.
Bowin, C., Purdy, G. M., Johnston, C., Shor, G., Lawver, L., Hartono, M. S., Jezek, P. “Arc – Continent Collision in Banda Sea Region: REPLYâ€. AAPG Bulletin, Vol. 65, pp. 868 – 915. 1981.
Hamilton, W. “Tectonics of the Indonesian Regionâ€. U.S. Geological Survey Professional Paper 1078. 1979.
Richardson, A. N., Blundell, D. J. “Continental Collision in the Banda Arcâ€. Geological Society Special Publication, Vol. 106, pp. 47 – 60. 1996.
Chamalaun, F., Grady, A. E. “The Tectonic Development of Timor: A New Model and its Implications for Petroleum Explorationâ€. Australian Petroleum Exploration Association (APEA) Journal, Vol. 18, pp. 102 – 108. 1978.
Harris, R., Sawyer, R., Charles, M. A. “Collisional Melange Development: Geologic Associations of Active Melange-Forming Processes with Exhumed Melange Facies in the Western Banda Orogen, Indonesiaâ€. Tectonics, Vol. 17 (3), pp. 458 – 479. 1998.
Harris, R., Vorkink, M. W., Prasetyadi, C., Zobell, E., Roosmawati, N., Apthorpe, M. “Transition from Subduction to Arc – Continent Collision: Geologic and Neotectonic Evolution of Savu Island, Indonesiaâ€. Geosphere, Vol. 5 (3), pp. 152 – 171. 2009.
Rosidi, H. M. D., Tjokrosapoetro, S., Gafoer, S. “Peta Geologi Lembar Kupang – Atambua, Timor Skala 1:250.000â€. Pusat Penelitian dan Pengembangan Geologi Bandung. 1996.
Bachri, S., Permana, A. K. “Tectonostratigraphy of Timor Basin in Western Timorâ€. Jurnal Geologi dan Sumberdaya Mineral (JGSM), Vol. 16, pp. 79 – 91. 2015.
Sawyer, R. K., Sani, K., Brown, S. “The Stratigraphy and Sedimentology of West Timor, Indonesiaâ€. Proceedings: Indonesian Petroleum Association – 22nd Annual Convention Proceedings, Vol. 1, pp. 533 – 574. 1993.
Bachri, S., Partoyo, E. “Geology of the Eastern Timorâ€. Pertamina – Mobil Oil – GRDC East Indonesia Project, East Timor. Unpublished.
Roosmawati, N., Harris, R. “Surface Uplift History of the Incipient Banda Arc – Continent Collision: Geology and Synorogenic Foraminifera of Rote and Savu Islands, Indonesiaâ€. Tectonophysics, Vol. 479, pp. 95 – 110. 2009.
Fullea, J., Fernandez, M., Zeyen, H. “FA2BOUG – A Fortran 90 Code to Compute Bouguer Gravity Anomalies from Gridded Free – Air Anomalies: Application to the Atlantic Mediterranean Transition Zoneâ€. Computer and Geosciences, Vol. 34 (12), pp. 1665 – 1681. 2008.
Downloads
Published
Issue
Section
License
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).
This work is licensed under a Creative Commons Attribution 4.0 International License.
