Tektono-Sedimen Segmen Subduksi Aceh Andaman: Akumulasi Nicobar Fan pada Sumatera Wedge terhadap Zona Seismogenik

Saputra, Bayu (2025) Tektono-Sedimen Segmen Subduksi Aceh Andaman: Akumulasi Nicobar Fan pada Sumatera Wedge terhadap Zona Seismogenik. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Zona subduksi Aceh–Andaman, bagian utara dari sistem subduksi Sunda, merupakan wilayah dengan dinamika tektonik tinggi yang ditandai oleh gempa megathrust besar seperti peristiwa Mw 9,2 tahun 2004 dan Mw 8,6 tahun 2005. Akumulasi sedimen tebal dari Nicobar Fan, yang mencapai lebih dari 5 km, memberikan pengaruh signifikan terhadap geometri prisma akresi, kekuatan geser antarmuka, serta segmentasi zona seismogenik. Penelitian ini bertujuan untuk mengungkap keterkaitan antara akumulasi sedimen fan dengan deformasi prisma akresi dan mengkarakterisasi struktur basement sebagai lempeng masukan pada segmen Aceh–Andaman. Analisis geomorfologi dilakukan dengan mengintegrasikan peta isobase, indeks diseksi vertikal, Stream Length–Gradient Index (SL > 350 pada beberapa kanal), Steepness Index (kₛₙ) yang bervariasi antara 34,12–198,63, serta nilai Hypsometric Integral (HI = 0,501) yang menunjukkan fase geomorfik transien akibat uplift tektonik. Data batimetri multibeam, backscatter (intensitas -12 dB pada zona keras), dan profil seismik dangkal mengindikasikan adanya zona décollement yang aktif di bawah prisma akresi, tercermin dari kombinasi uplift morfologi dan anomali litologi. Temuan ini menegaskan bahwa sedimen Nicobar Fan berperan dalam memperluas prisma, mengatur segmentasi tektonik, serta memengaruhi potensi asperitas dan tsunami di pesisir barat Sumatra. Pendekatan integratif ini menjadi kontribusi penting dalam pemahaman tektono-sedimen dan mitigasi risiko kebencanaan berbasis karakterisasi zona seismogenik.
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The Aceh–Andaman subduction zone, forming the northern part of the Sunda subduction system, exhibits high tectonic activity, highlighted by major megathrust events such as the Mw 9.2 earthquake in 2004 and Mw 8.6 in 2005. Thick sediment accumulation from the Nicobar Fan, exceeding 5 km in places, plays a critical role in shaping the accretionary wedge geometry, controlling shear strength at the plate interface, and influencing the segmentation of the seismogenic zone. This study aims to explore the relationship between fan sedimentation and wedge deformation while characterizing the basement structure as the incoming plate in the Aceh–Andaman segment. Geomorphological analysis integrates isobase mapping, vertical dissection indices, Stream Length–Gradient Index (SL > 350 along certain channels), Steepness Index (kₛₙ) ranging from 34.12–198.63, and a Hypsometric Integral (HI = 0.501), all indicating a transient geomorphic phase under active tectonic uplift. Multibeam bathymetry, backscatter intensity (peaking at -12 dB in hardened zones), and shallow seismic profiles collectively reveal an active décollement zone beneath the accretionary wedge, expressed through uplifted morphology and lithological anomalies. These findings highlight that Nicobar Fan sedimentation significantly contributes to wedge growth, tectonic segmentation, and the potential for asperity formation and tsunami hazards along the west coast of Sumatra. The integrative approach presented here provides key insights into tectono-sedimentary dynamics and supports disaster risk mitigation through refined seismogenic zone characterization.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Tektonik Lempeng, Akresi Sedimen, Megathrust, Nicobar Fan, Seismogenik; Plate Tectonics, Sediment Accretion, Megathrust, Nicobar Fan, Seismogenic
Subjects:	G Geography. Anthropology. Recreation > G Geography (General) G Geography. Anthropology. Recreation > G Geography (General) > G70.217 Geospatial data
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geomatics Engineering > 29101-(S2) Master Thesis
Depositing User:	Bayu Saputra
Date Deposited:	27 Jul 2025 13:57
Last Modified:	27 Jul 2025 13:57
URI:	http://repository.its.ac.id/id/eprint/121786

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