Pemodelan struktur bawah permukaan daerah prospek panasbumi di Gunung Ungaran sisi utara dengan metode magnetik

REFRIZON, Dr. Wahyudi

2005 | Tesis | S2 Fisika

Telah dilakukan penelitian dengan metode magnetik di daerah Gunung Ungaran sebelah utara yang memiliki dua buah mata air panas. Daerah penelitian meliputi area sekitar 8 km2. Pengukuran medan magnetik total menggunakan PPM dengan spasi sekitar 150 m dan posisi titik ukur dengan GPS Trimble 4600 LS. Data lapangan terlebih dahulu dilakukan koreksi variasi harian dan koreksi IGRF untuk mendapatkan anomali medan magnet total di topografi. Kemudian dilakukan reduksi ke bidang datar dan reduksi ke kutub di berbagai ketinggian. Untuk menghilangkan pengaruh medan regional selanjutnya dilakukan koreksi anomali regional. Interpretasi kualitatif dilakukan terhadap kontur anomali hasil reduksi ke bidang datar dan reduksi ke kutub. Interpretasi kuantitatif dengan pemodelan benda anomali menggunakan bantuan program Mag2DC for Windows. Hasil dari interpretasi kualitatif memperlihatkan bahwa posisi benda penyebab anomali berada di sebelah selatan mata airpanas Nglimut. Mata air panas Nglimut dan Medini di interpretasi muncul melalui bidang batas batuan. Hasil interpretasi kuantitatif berupa penampang lintang model struktur geologi bawah permukaan memperlihatkan bahwa batuan dasar berupa andesit dengan penutup batuan basal dan endapan piroklastik. Andesit dengan suseptibilitas magnet 0,015 emu, endapan piroklastik dengan suseptibilitas magnet 0,025 emu dan basalt dengan suseptibilitas magnet 0,006 emu.

A geophysical research with magnetic method has been done in north Ungaran area that has two hot springs. The research area was about 8 km2. PPM was used to measure total magnetic field with space about 150 m and GPS Trimble 4600 LS to measure its position. Magnetic data processing started by diurnal variation and IGRF corrections to achieve total magnetic anomaly. Then, the data was reduced to a horizontal plane and to pole on several elevations. In order to minimize the regional field, the data was corrected with regional field anomaly. A qualitative interpretation has been done with analyzing the contour map of reduced data. A quantitative interpretation has been done by modeling geological structure using Mag2DC for Windows program. The result of qualitative interpretation is the position of the anomaly resources located on south side of the survey area. Nglimut and Medini hot springs are interpreted as a flow up between rock boundary contact. The result of quantitative interpretation is geological structure model that the formation was formed by bedrock and covered rock. The bedrock were formed by andesit with magnetic susceptibility of 0,015 emu. The covered rocks were pyroclastic deposits with susceptibility of 0,025 emu and basalt with susceptibility of 0,006 emu.

Kata Kunci : Energi Panas Bumi,Metode Magnetik