Analisis dan Inversi 3D Data Gravitasi untuk Mencitrakan Bawah Permukaan Sektor Runtuhan Gunung Galunggung

Naufaldi, Muhammad (2025) Analisis dan Inversi 3D Data Gravitasi untuk Mencitrakan Bawah Permukaan Sektor Runtuhan Gunung Galunggung. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Metode gravitasi merupakan salah satu metode geofisika yang mampu mencitrakan distribusi densitas bawah permukaan secara tiga dimensi, sehingga sangat efektif untuk menginvestigasi struktur geologi tersembunyi di wilayah gunung api, seperti rekahan, sesar, dan zona lemah. Penelitian ini dilakukan di Gunung Galunggung, Jawa Barat, yang pernah mengalami peristiwa keruntuhan sektor besar sekitar 4.200 tahun lalu. Peristiwa tersebut membentuk morfologi khas berupa Bukit Seribu Tasikmalaya dan diperkirakan melibatkan struktur bawah permukaan seperti sesar atau rekahan sebagai jalur lemah. Penelitian ini menggunakan data anomali Bouguer lengkap dari BRIN, yang kemudian diproses melalui tahapan koreksi gravitasi standar serta pemisahan anomali regional–residual menggunakan filter Butterworth. Analisis spektral digunakan untuk estimasi kedalaman, sedangkan tilt derivative digunakan untuk menyoroti batas kontras densitas. Model bawah permukaan kemudian dibangun melalui inversi 3D menggunakan perangkat lunak Grablox 2.1. Hasil interpretasi anomali regional menunjukkan zona densitas tinggi di barat dan timur yang diasosiasikan dengan batuan beku padat, serta zona densitas rendah di utara dan tenggara yang berkaitan dengan batuan vulkanik ringan. Anomali residual mengungkap adanya kelurusan berarah tenggara dari kawah Galunggung, yang berimpit dengan manifestasi panas bumi Cipanas dan Citiis. Analisis tilt derivative dan keberadaan lineament morfologis mendukung indikasi rekahan bawah permukaan di arah tersebut. Inversi 3D menghasilkan model densitas dengan rentang 2,44–2,78 g/cm³ hingga kedalaman 5 km. Zona berdensitas rendah (~2,50 g/cm³) memanjang ke arah tenggara hingga kedalaman ±1000 meter, memperkuat dugaan adanya zona lemah. Temuan ini mengindikasikan bahwa keruntuhan sektor Gunung Galunggung kemungkinan besar dipicu oleh keberadaan struktur bawah permukaan berupa rekahan atau sesar, yang berperan sebagai jalur fluida panas dan sebagai bidang lemah struktural.
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The gravity method is one of the geophysical techniques capable of imaging the three-dimensional distribution of subsurface density, making it highly effective for investigating hidden geological structures in volcanic regions, such as fractures, faults, and weak zones. This study was conducted at Mount Galunggung, West Java, which experienced a major sector collapse event approximately 4,200 years ago. The event formed a distinctive morphology known as the Bukit Seribu Tasikmalaya and is thought to have involved subsurface structures such as faults or fractures acting as zones of weakness. This research uses complete Bouguer anomaly data from BRIN, which were processed through standard gravity corrections and regional–residual anomaly separation using the Butterworth filter. Spectral analysis was used to estimate depth, while tilt derivative was applied to highlight density contrast boundaries. A 3D subsurface model was then constructed through inversion using Grablox 2.1 software. Interpretation of the regional anomaly revealed high-density zones in the west and east associated with compact igneous rocks, and low-density zones in the north and southeast correlated with lighter volcanic deposits. The residual anomaly revealed a southeast-trending linear feature from the Galunggung crater, coinciding with geothermal manifestations such as the Cipanas and Citiis hot springs. Tilt derivative analysis and the presence of surface lineaments further support the indication of a subsurface fracture in that direction. The 3D inversion produced a density model ranging from 2.44 to 2.78 g/cm³ down to a depth of 5 km. A low-density zone (~2.50 g/cm³) was found extending southeastward to a depth of approximately 1,000 meters, reinforcing the hypothesis of a weak zone. These findings suggest that the sector collapse of Mount Galunggung was likely triggered by the presence of subsurface structures such as fractures or faults, which acted as both pathways for hydrothermal fluid migration and structural zones of weakness.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Gunung Galunggung, Anomali Gravitasi, Zona Lemah, Inversi 3D, Mount Galunggung, Gravity Anomalies, Weak Zone, 3D Inversion
Subjects:	G Geography. Anthropology. Recreation > G Geography (General) > G70.212 ArcGIS. Geographic information systems. G Geography. Anthropology. Recreation > G Geography (General) > G70.217 Geospatial data Q Science > Q Science (General) > Q180 Gravitation. Q Science > QC Physics > QC20.7.F67 Fourier transformations Q Science > QE Geology > QE471 Sedimentary rocks. Sedimentology Q Science > QE Geology > QE601 Geology, Structural Q Science > QE Geology > QE604 Deformation T Technology > TN Mining engineering. Metallurgy > TN269 Prospecting--Geophysical methods
Divisions:	Faculty of Science and Data Analytics (SCIENTICS) > Physics > 45201-(S1) Undergraduate Thesis
Depositing User:	Muhammad Naufaldi
Date Deposited:	05 Aug 2025 07:59
Last Modified:	05 Aug 2025 07:59
URI:	http://repository.its.ac.id/id/eprint/127459

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