Tobing, Kevin Christiardi (2020) Aplikasi Metode Combined Inversion pada Data Geolistrik Resistivitas 2D Konfigurasi Wenner-Schlumberger untuk Identifikasi Sungai Bawah Permukaan Kawasan Karst, Pacitan. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Perkembangan celah-celah atau rekahan pada kawasan karst Pacitan secara perlahan bertambah lebar akibat proses pelarutan sehingga membentuk rongga atau terowongan yang baik. Adanya manifestasi luweng-luweng yang tersebar di beberapa daerah tersebut diduga saling terhubung dan membentuk sistem perguaan atau sungai bawah permukaan. Metode resistivitas 2D adalah salah satu metode geofisika dapat digunakan untuk mengidentifikasi sungai bawah permukaan karena memiliki kemampuan yang baik dalam pemetaan distribusi nilai resistivitas sungai bawah permukaan. Akan tetapi kompleksitas struktur karst menjadi permasalahan dalam pengolahan dan interpretasi data resistivitas 2D. Maka dari itu, penelitian ini bertujuan untuk menganalisis kinerja metode combined inversion untuk identifikasi sungai bawah permukaan dan menganalisis distribusi nilai resistivitas 2D berdasarkan metode combined inversion terhadap dugaan sungai bawah permukaan di kawasan karst Desa Sekar, Pacitan. Metode akuisisi yang dilakukan penelitian ini adalah Metode Geolistrik Resistivitas 2D Konfigurasi Wenner-Schlumberger. Akuisisi data dilakukakan sebanyak empat lintasan dengan tiap panjang lintasan adalah 170m, 170m, 130m dan 145m dengan a = 5m. Uji kinerja combined inversion menggunakan variasi damping factor antara lain 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 0.8, 1, dan 1.5. Secara kuantitatif combined inversion menghasilkan lintasan 1 damping factor yang optimal adalah 0.25 dengan nilai abs error 8.67% dan perubahan persentase error sebesar 45.71%. Lintasan 2 damping factor yang optimal adalah 0.05 dengan nilai abs error 5.08% dan perubahan persentase error sebesar 71%. Lintasan 3 damping factor yang optimal adalah 0.05 dengan nilai abs error 5.08% dan perubahan persentase error sebesar 54.16%. Lintasan 4 damping factor yang optimal adalah 0.25 dengan nilai abs error 5.58% dan perubahan persentase error sebesar 56.3%. Secara kualitatif, sungai bawah permukaan di Desa Sekar Kecamatan Donorojo, Pacitan teridentifikasi dengan nilai resistivitas antara 1.55-10 Ohm.m dengan orientasi hubungan indikasi sungai bawah permukaan berarah NE-SW.
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The development of cracks or fissures in the Pacitan karst region is slowly widening due to the dissolution process so as to form a good cavity or tunnel. The existence of luweng-luweng manifestations scattered in some of these areas is thought to be interconnected and form a subsurface system or river surface. 2D resistivity method is one of many geophysical methods that can be used to identify subsurface rivers because it has good ability in mapping the distribution of resistivity values of subsurface rivers. However, the complexity of karst structures is a problem in processing and interpreting 2D resistivity data. Therefore, this study aims to analyze the performance of the combined inversion method for identification of subsurface rivers and analyze the distribution of 2D resistivity values based on the combined inversion method on the alleged subsurface rivers in the karst area of Sekar Village, Pacitan. The acquisition method used in this research is the 2D Geoelectric Resistivity Method with Wenner-Schlumberger Array. Data acquisition was carried out as many as four lines with each line measures 170m, 170m, 130m and 145m in length respectively with 5m of spacing between electrodes. The combined inversion performance test uses variations of damping factor values of 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 0.8, 1, and 1.5. Quantitatively, combined inversion in line 1 produce the most optimal result with damping factor value 0.25, with 8.67% abs error value and a change in error percentage of 45.71%. In line 2 the most optimal damping factor is 0.05 with an error value of 5.08% and a change in error percentage of 71%. In line 3 the most optimal damping factor is 0.05 with an abs error value of 5.08% and a change in error percentage of 54.16%. In line 4 the most optimal damping factor is 0.25 with an abs error value of 5.58% and a change in error percentage of 56.3%. Qualitatively, the subsurface river in Sekar Village, Donorojo Subdistrict, Pacitan was identified with a resistivity value between 1.55-10 Ohm.m with the connected orientation of subsurface river leads from NE (North-East) to SW (South-West).
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Uncontrolled Keywords: | karst, combined inversion, resistivitas 2D, sungai bawah permukaan, karst, combined inversion, 2D resistivity, underground river |
| Subjects: | G Geography. Anthropology. Recreation > GB Physical geography > GB600 Karst conservation. |
| Divisions: | Faculty of Civil, Environmental, and Geo Engineering > Geophysics Engineering > 33201-(S1) Undergraduate Theses |
| Depositing User: | Kevin Christiardi Tobing |
| Date Deposited: | 20 Aug 2020 03:59 |
| Last Modified: | 16 May 2023 15:00 |
| URI: | http://repository.its.ac.id/id/eprint/78800 |
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