Koreksi Statik Resistivitas Magnetotelurik Menggunakan Data TDEM pada Area Panas Bumi Pantar serta Implikasinya Terhadap Model Resistivitas Bawah Permukaan

Kinasih, Ardelia (2025) Koreksi Statik Resistivitas Magnetotelurik Menggunakan Data TDEM pada Area Panas Bumi Pantar serta Implikasinya Terhadap Model Resistivitas Bawah Permukaan. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Static shift pada data Magnetotelurik (MT) merupakan pergeseran statis pada kurva resistivitas semu yang disebabkan oleh heterogenitas near-surface, keberadaan kontak vertikal, serta pengaruh topografi. Fenomena ini dapat mengganggu proses pemodelan dan menurunkan akurasi pemodelan resistivitas bawah permukaan. Area Panas Bumi Pantar, Nusa Tenggara Timur, memiliki potensi mengalami static shift yang signifikan. Penelitian ini menerapkan koreksi static shift menggunakan data Time Domain Electromagnetic (TDEM) yang dikumpulkan pada lokasi yang sama dengan stasiun MT. Tujuannya adalah membandingkan model resistivitas bawah permukaan sebelum dan sesudah koreksi serta memetakan distribusi resistivitas secara lebih akurat. Data MT yang telah melalui proses cross power dikoreksi dengan menyelaraskan kurva resistivitas semu terhadap kurva TDEM. Untuk memperoleh gambaran distribusi resistivitas bawah permukaan secara lebih detail, dilakukan inversi 2D menggunakan algoritma Nonlinear Conjugate Gradients (NLCG), dengan analisis kualitatif dan kuantitatif berdasarkan data pendukung dan nilai root mean square (RMS) error sebagai parameter validasi. Hasil penelitian menunjukkan bahwa model resistivitas bawah permukaan setelah koreksi static shift menjadi lebih akurat dan representatif. Inversi 2D menghasilkan penurunan nilai RMS error secara signifikan, yaitu dari 3,7% menjadi 2,4% pada line 1, dari 2,6% menjadi 1,9% pada line 2, dan dari 2,4% menjadi 1,8% pada line 3. Arah geoelectrical strike dominan di area penelitian adalah NE–SW dengan sudut 74,5°. Distribusi resistivitas mengindikasikan keberadaan clay cap (<10Ωm) di kedalaman sekitar 500 meter, reservoir (±100Ωm) di kedalaman sekitar 1500 meter, serta zona resistivitas tinggi di kedalaman dangkal yang diasosiasikan dengan jatuhan piroklastik. Hasil koreksi TDEM meningkatkan resolusi zona resistivitas rendah, yang berkaitan erat dengan aktivitas hidrotermal dan pola alterasi sistem panas bumi Pantar yang dikontrol oleh aktivitas vulkanik aktif.

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Static shift in Magnetotelluric (MT) data refers to a static shift in the apparent resistivity curve, caused by near-surface heterogeneity, the presence of vertical contacts, and topographic influences. This phenomenon can disrupt the modeling process and reduce the accuracy of subsurface resistivity modeling. The Pantar Geothermal Area, East Nusa Tenggara, has the potential to experience significant static shift. This study applies static shift correction using Time Domain Electromagnetic (TDEM) data collected at the exact location as the MT station. The aim is to compare the subsurface resistivity models before and after correction and to map the resistivity distribution more accurately. MT data that has gone through the cross-power process is corrected by aligning the apparent resistivity curve with the TDEM curve. To obtain a more detailed picture of the subsurface resistivity distribution, 2D inversion is performed using the Nonlinear Conjugate Gradients (NLCG) algorithm, with qualitative and quantitative analysis based on supporting data and the root mean square (RMS) error value as a validation parameter. The results show that the subsurface resistivity model after static shift correction becomes more accurate and representative. 2D inversion resulted in a significant decrease in the RMS error value, namely from 3.7% to 2.4% in line 1, from 2.6% to 1.9% in line 2, and from 2.4% to 1.8% in line 3. The dominant geoelectrical strike direction in the study area is NE–SW with an angle of 74.5°. The resistivity distribution indicates the presence of a clay cap (<10Ωm) at a depth of about 500 meters, a reservoir (±100Ωm) at a depth of about 1500 meters, and a high resistivity zone at shallow depths associated with pyroclastic fallout. The TDEM correction results enhance the resolution of the low-resistivity zone, which is closely related to hydrothermal activity and alteration patterns of the Pantar geothermal system, controlled by active volcanic activity.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Magnetotelurik, Panas Bumi, Resistivitas, Static Shift, TDEM. ============================================================== Magnetotelluric, Geothermal, Resistivity, Static Shift, TDEM.
Subjects:	Q Science > QC Physics > QC610.3 Electric conductivity Q Science > QC Physics > QC665.E38 Electric fields. T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK1318 Geothermal Power Plants
Divisions:	Faculty of Civil Engineering and Planning > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User:	Ardelia Khadar Kinasih
Date Deposited:	29 Jul 2025 06:20
Last Modified:	29 Jul 2025 06:20
URI:	http://repository.its.ac.id/id/eprint/122574

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