Analisa anisotropi struktur mantel atas di Sumatra berdasarkan shear-wave splitting

Candra, Arya Dwi (2015) Analisa anisotropi struktur mantel atas di Sumatra berdasarkan shear-wave splitting. Masters thesis, Institut Teknology Sepuluh Nopember.

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Abstract

Struktur geologi dari pulau Sumatra berada pada pertemuan dua lempeng besar, yaitu lempeng Indo-Australia dan lempeng Eurasia. Hal ini menyebabkan Sumatra menjadi salah satu wilayah dengan gejala seismik paling aktif di dunia. Analisis shear-wave splitting dilakukan untuk mengamati anisotropi struktur lapisan mantel atas wilayah Sumatra. Data pengamatan diperoleh dari 35 stasiun BMKG dari jaringan GFZ (Geo Forschungs Zentrum) yang berada di Pulau Sumatra dengan besar magnitude lebih dari 6.3 Mw dan rentang jarak episentral 85̊- 140̊. Pengukuran shear-wave splitting dilakukan dengan menggunakan program Splitlab berdasarkan tiga metode secara simultan, yaitu metode minimum energy (SC), rotation-correlation (RC) dan eigenvalue (EV). Dari hasil pengukuran shearwave splitting di wilayah forearc (kepulauan Mentawai) dan sesar Sumatra menunjukkan dua lapisan anisotropi. Pada lapisan pertama, arah polarisasi cepat dominan adalah sejajar dengan palung/sesar dengan waktu delay berkisar antara 0.5-0.9 s yang diduga disebabkan oleh shear-strain akibat dari sesar Mentawai dan sesar Sumatra. Pada lapisan kedua, arah polarisasi cepat dominan adalah tegak lurus palung/sesar dengan waktu delay berkisar antara 1.1-1.9 s yang diperkirakan disebabkan oleh pergerakan lempeng subduksi pada lapisan mantel. ============================================================================================== The geological structure of Sumatra island is located at the confluence of two large plates, the Indo-Australian and the Eurasian plate. This makes Sumatra become one of the regions with the most active seismic phenomenon in the world. Analysis of shear-wave splitting conducted to observe the anisotropy of upper mantle structure in the Sumatra. Data obtained from 35 BMKG stations from GFZ network (Geo Forschungs Zentrum) on the Sumatra with magnitude more than 6.3 Mw and epicentral distance range 85̊-140̊. Shear-wave splitting measurements were performed using Splitlab based on three methods simultaneously, the Minimum Energy (SC), the Rotation-Correlation (RC) and the Eigenvalue (EV) methods. From the results of shear-wave splitting measurements in the forearc region (Mentawai islands) and the Sumatra fault zone exhibit two layers of anisotropy. In the first layer, the predominant fast direction polarization is parallel to the trench/fault with the delay time ranges between 0.5-0.9 s are suspected to be caused by shear-strain as a result of the Mentawai fault and Sumatra fault zones. In the second layer, the predominant fast direction polarization is perpendicular to the trench/fault with the delay time ranging between 1.1-1.9 s are estimated to be caused by the movement of plate subduction on the mantle wedge.

Item Type: Thesis (Masters)
Additional Information: RTFi 551.220 287 Can a
Uncontrolled Keywords: Shear-wave splitting; Anisotropi seismik; Splitlab; Sumatra
Subjects: Q Science > QE Geology > QE538.5 Seismic waves. Elastic waves
Divisions: Faculty of Mathematics and Science > Physics > (S1) Undergraduate Theses
Depositing User: - Taufiq Rahmanu
Date Deposited: 23 Oct 2019 05:49
Last Modified: 23 Oct 2019 05:49
URI: http://repository.its.ac.id/id/eprint/71356

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