Electronic Theses and Dissertation

Penelitian untuk mengidentifikasi struktur Sesar Sumatra telah dilakukan pada kawasan Pidie-Nagan Raya berdasarkan data gaya berat. Nilai percepatan gravitasi telah diukur menggunakan instrument Gravitimeter Scintrex CG-5 sebanyak 83 titik dengan total panjang lintasan ± 156 km. Nilai percepatan gravitasi juga didapatkan dari satelit GGMPlus yang memiliki resolusi spasial 230 m/px hingga diperoleh 160.626 grid data yang mencakup seluruh lokasi penelitian. Untuk mendapatkan nilai anomali Bouguer lengkap pada data lapangan diterapkan beberapa koreksi standar yaitu koreksi apungan, koreksi pasang surut, koreksi lintang, koreksi udara bebas, koreksi Bouguer dan koreksi medan sedangkan untuk data gravitasi satelit GGMPlus yaitu koreksi Bouguer dan koreksi medan. Nilai anomali Bouguer lengkap pada data lapangan dan data gaya berat GGMPlus sepanjang profil digunakan untuk pemodelan maju 2D menggunakan software Grav2DC dan dilihat perbandingan dari kedua model. Hasil model menunjukkan bahwa struktur Sesar Seulimeum, Sesar Aceh dan sesar Minor dapat diidentifikasi dengan kontras nilai anomali percepatan gravitasi yang menurun ataupun meningkat. Kontras kenaikan dan penurunan nilai anomali percepatan gravitasi pada data GGMPlus lebih tajam dibandingkan data lapangan. Hasil interpretasi kuantitatif dari data lapangan dapat diidentifikasi keberadaan Sesar Seulimeum, Sesar Aceh dan sesar minor secara berturut-turut berada di sekitar Glumpang Tiga sampai Mane, Mane dan Sungai Mas sedangkan berdasarkan data GGMPlus dapat diidentifikasi keberadaan Sesar Seulimeum, Sesar Aceh dan sesar minor secara berturut-turut berada di sekitar Glumpang Tiga sampai Tangse, Mane dan Sungai Mas. Pemodelan data lapangan dan pemodelan data GGMPlus dapat diidentifikasi keberadaan Sesar Seulimeum, Sesar Aceh dan sesar minor dengan jenis sesar oblique yaitu kombinasi sesar mendatar dan sesar normal. Keberadaan sesar lebih akurat pada hasil lapangan berdasarkan jarak pergeseran sesar terhadap sesar dugaan.

Kata kunci: Gaya berat, GGMPlus, Pidie-Nagan Raya, Anomali Bouguer Lengkap, Software Grav2DC, Sesar Sumatra

A research to identify the structure of the Sumatran Fault has been carried out in the Pidie-Nagan Raya area based on gravity data. The value of the acceleration of gravity has been measured using the Scintrex CG-5 Gravitimeter at 83 points with a total track length of ± 156 km. The value of the acceleration of gravity was also obtained from the GGMPlus satellite which has a spatial resolution of 230 m/px to obtain 160,626 grid data covering all research locations. To get the complete value of the Bouguer anomaly in field data, several standard corrections are applied, namely drift correction, tidal correction, latitude correction, free air correction, Bouguer correction and terrain correction while for GGMPlus satellite gravity data, namely Bouguer correction and terrain correction. The complete Bouguer anomaly values in the field data and GGMPlus gravity data along the profile were used for advanced 2D modeling using Grav2DC software and a comparison of the two models is shown. The model results show that the structures of the Seulimeum Fault, Aceh Fault, and Small Fault can be identified by contrasting the decreasing or increasing gravitational acceleration anomaly values. The contrast between the increase and decrease in the value of the gravitational acceleration anomaly in the GGMPlus data is sharper than in the field data. The results of quantitative interpretation of field data can identify the presence of the Seulimeum Fault, Aceh Fault and minor faults around Glumpang Tiga to Mane, Mane and Sungai Mas respectively, while based on GGMPlus data their presence can be identified. The Seulimeum Fault, Aceh Fault and Small Fault are respectively located around Glumpang Tiga to Tangse, Mane and Sungai Mas. Field data modeling and GGMPlus data modeling can identify the existence of the Seulimeum Fault, Aceh Fault and minor faults with oblique fault types, namely a combination of horizontal faults and normal faults. The presence of faults is more accurate in field results based on the distance of the fault displacement to the suspected fault. Keywords: Gravity, GGMPlus, Pidie-Nagan Raya, Complete Bouguer Anomaly, Grav2DC Software, Sumatra Fault