ANUGRAH, FEBRY (2016) IDENTIFIKASI STRUKTUR GEOLOGI BAWAH PERMUKAAN BERDASARKAN METODE MAGNETOTELURIK PADA DAERAH PULAU BIAK, KABUPATEN BIAK NUMFOR, PROVINSI PAPUA IDENTIFICATION OF SUBSURFACE GEOLOGICAL STRUCTURES BASED ON MAGNETOTELLURIC METHOD AT BIAK ISLAND, BIAK NUMFOR REGENCY, PAPUA PROVINCE. Other thesis, UPN ''VETERAN'' YOGYAKARTA.
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Abstract
Struktur Geologi merupakan salah satu faktor pengaruh karakteristik suatu daerah
yang dapat dihasilkan dari proses tektonik dan vulkanik. Keberadaan struktur dapat
dilihat dengan foto udara dan pemetaan topografi. Pulau Biak merupakan Pulau yang
terbentuk dari aktivitas Lempeng Samudera Pasifik dan lempeng Benua Australia
sehingga membentuk struktur geologi kompleks, Namun, pada bagian timur Pulau Biak
didominasi oleh Gamping Terumbu dengan topografi relatif datar sehingga sangat sulit
untuk mengetahui keberadaan struktur geologi. Untuk mengetahui keberadaan struktur
tersebut dibutuhkan studi geofisika dengan menggunakan metode magnetotelurik yang
dapat merepresentasikan struktur geologi bawah permukaan.
Penelitian dilakukan pada tanggal 26 Juni sampai 26 Juli 2013 dengan cara
pengukuran Single Sounding sebanyak 15 titik pengukuran AMT dan MT, untuk
menghasilkan frekuensi 10-4 Hz hingga 104 Hz. Pada data MT dilakukan peningkatan
kualitas data berdasarkan analisis Time Series untuk mereduksi Noise, tahapan ini
mempengaruhi kualitas data yang mengacu pada peningkatan nilai koherensi. Pemodelan
1D dan 2D dilalukan melalui perangkat lunak WinGlink menggunakan inversi OCCAM
dengan iterasi 30 dan RMS Error kurang dari 5%. Selanjutnya, didapatkan penampang
dengan kedalaman mencapai 10 Km dan panjang penampang 35 km, kemudian dilakukan
interpretasi struktur geologi bawah permukaan berdasarkan variasi nilai tahanan jenis.
Interpretasi dilakukan secara kualitatif dan kuantitatif dengan mengacu pada
informasi geologi dan data variasi nilai tahanan jenis. Dari hasil penampang 1D
digunakan sebagai pengontrol kedalaman dan penampang 2D digunakan untuk
interpretasi keberadaan struktur geologi pada daerah penelitian. Pada Penampang 2D
diintrepretasikan terdapat cekungan sedimen berupa busur depan dengan umur tersier,
sesar normal terbentuk pada Oligosen Akhir hingga Miosen Tengah, dan diidentifikasikan
terdapatnya Intrusi Basalt.
Kata kunci : Geofisika, Magnetotelurik, Audio Magnetotelurik, Analisis Time Series,
Tahanan Jenis, Struktur Geologi, Cekungan Sedimen.
Geological structure is one factor influences the characteristics of an area which
is generated by tectonic and volcanic processes. The existence of the structure can be
seen by Aerial Photographs and Topographic Mapping. Biak Island is formed by the
activity of the Pacific Plate and the Australian Plate generating the Complex Geological
Structure. The eastern part of the island is dominated by carbonate reef with relatively
flat Topography. Therefore, it is difficult to know the existance of Geological Structures.
To know the existence of such structures needed geophysical studies using
Magnetotelluric method that can represent the subsurface geological structure.
The study was conducted from June 26th to July 26th, 2013 in singles Sounding
measurements with 15 AMT and MT measuring points, to generate frequency of 10-4Hz to
104 Hz . The MT data were improved by the analysis of time series to reduce noise. This
stage affects the quality of the data that lead to increase the coherence value. This value
is represented by a better pattern of pseudo resistivity graph and phase versus frequency.
The 1D and 2D modeling was conducted in WinGlink software using Occam inversion
with 30 iterations and RMS error of less than 5%. After the modelling process, the cross
sections obtained with a depth of 10 km and 35 km long cross-section, then carried
interpretation of subsurface geological structures based on variations in resistivity
values.
Interpretation was performed qualitatively and quantitatively with reference to
the geological information and data variations in resistivity value. From the results, the
1D cross sections were used as depth control and the 2D cross sections were used for the
geological structure interpretation in the research area. In the 2D cross-section are
interpreted a fore arc sedimentary basins in tertiary age, normal faults formed in the
Late Oligocene to Middle Miocene, and identified the presence of Basalt intrusions.
Keywords: Geophysics, Magnetotelluric, Audio Magnetotelluric, Time Series
Analysis, Resistivity, Geological Structures, Sedimentary Basin.
| Item Type: | Thesis (Other) |
|---|---|
| Subjek: | Q Science > QE Geology |
| Divisions: | x. Faculty of Engineering, Science and Mathematics > School of Geography |
| Depositing User: | Erny Azyanti |
| Date Deposited: | 09 Nov 2016 03:55 |
| Last Modified: | 09 Nov 2016 03:55 |
| URI: | http://eprints.upnyk.ac.id/id/eprint/8593 |
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