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MODELING OF THREE-DIMENSIONAL SUBSURFACE STRUCTURES BASED ON GRAVITY ANOMALY IN SOUTHWEST SUMBA INDONESIA Novitri, Adinda; Margiono, Relly; Pevriadi, Anggi; Zakariya, Hilmi; Segoro, Yan Adi
Indonesian Physical Review Vol. 8 No. 1 (2025)
Publisher : Universitas Mataram

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29303/ipr.v8i1.388

Abstract

Modeling subsurface conditions using gravity anomaly data, focusing on density contrasts, provides critical insights into subsurface structures and supports identifying rock types. This study aims to define residual gravity anomalies in the Sumba region and utilize them to develop a three-dimensional subsurface model of Southwest Sumba, characterizing density contrasts and associated rock formations. Gravity data from the TOPEX dataset were employed in this research. The Airy isostasy model was applied to separate regional and residual anomalies, followed by a three-dimensional inversion using the Generalized Cross-Validation (GCV) method. The results reveal residual gravity anomalies range from -170 mGal to 211 mGal, with the Java Trench exhibiting the highest anomaly. The 3D modeling shows a relatively homogeneous density contrast at shallow depths, transitioning to more erratic variations at greater depths, extending to 15 km beneath Southwest Sumba Island. Furthermore, the calculated densities are consistent with the region's known geological background. The Java Trench, located south of Sumba, notably demonstrates a consistently high-density contrast from shallow to deeper depths, highlighting its tectonic complexity.
Identifikasi Sesar Segmen Ketahun Berdasarkan Metode First Horizontal Derivative (FHD) dan Second Vertical Derivative (SVD) Data Anomali Gaya Berat GGMplus Syaputra, Edo Win; Refrizon, Refrizon; Zakariya, Hilmi
Jurnal Fisika Unand Vol 12 No 4 (2023)
Publisher : Universitas Andalas

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25077/jfu.12.4.598-607.2023

Abstract

Daerah Bengkulu merupakan daerah yang dilalui oleh jalur subduksi Indo-Australia dan Eurasia. Jalur subduksi dapat teridentifikasi dengan metode gravitasi yang dapat menggambarkan bentuk bawah permukaan berdasarkan variasi medan gravitasi yang dapat dilihat oleh perbedaan rapat masa anatar batuan. Penelitian ini bertujuan untuk mengidentifikasi karakteristik Sesar Segmen Ketahun dengan menggunakan data anomali gayaberat GGMplus. Wilayah penelitian adalah daratan Lebong-Rejang Lebong. Metode First Horizontal Derivative (FHD) dan Second Vertical Derivative (SVD) digunakan untuk melihat posisi dan karakteristik sesar. Dari analisis FHD dan SVD, daerah Sungai Lisai dan Ketenong merupakan sesar turun, sedangkan Pinang Berlapis, sekitar Pungguk Pedaro dan Rimbo Pengadang merupakan sesar naik. Talang Ulu dan sekitar Lubuk Pedaro merupakan sesar naik, Daerah Mangkorajo merupakan sesar geser, serta Danau Tapak Kaki merupakan sesar turun. Berdasarkan pemodelan data anomali diperoleh wilayah Kabupaten Lebong–Rejang Lebong memiliki sebaran densitas antara 1,97 gram/cm3-2,00 gram/cm3 yang merupakan batuan sedimen (debu bersisipan pasir,bongkahan lepas, kerakal, gambut dan kaolinit).
3D MODELING AND DERIVATIVE ANALYSIS OF THE KETAHUN SEGMENT BASED ON GGMPLUS AND SRTM2 DATA FOR DISASTER MITIGATION Ulandari, Clora; Halauddin, Halauddin; Refrizon, Refrizon; Zakariya, Hilmi; Suhendra, Suhendra; Farid, Muchammad; Sulistiani, Alda; Raihana, Hana; Apriyanti, Nurul
Jurnal Geosaintek Vol. 12 No. 2 (2026)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25023659.v12i2.9106

Abstract

interaction between the Sumatra subduction zone and the Sumatra Fault, resulting in high seismic activity. One of the important segments with the potential to cause earthquakes is the Ketahun Segment in Lebong Regency, Bengkulu Province. This study aims to map the three-dimensional (3D) fault structure and identify lithological density contrasts to support disaster mitigation efforts. The methods used include processing GGMPlus and SRTM2gravity satellite gravity data, complete Bouguer correction, regional-residual anomaly separation, first horizontal derivative (FHD) and second vertical derivative (SVD) analysis, and 3D inversion modeling using Grav3D software. The CBA analysis results show anomaly values of –8 to 50 mGal with sharp gradations indicating the presence of major fault structures. SVD and FHD analyses show the dominance of dip-slip faults with significant density contrasts. The 3D inversion modeling shows a density range of 1.02–3.52 g/cm³ with an average value of 2.27 g/cm³, where the low-density zone is at a shallow depth (0–1500 m) and the high-density zone is at a depth of 500–2000 m. The sharp boundary between the two zones indicates an active fault plane at a depth of 1000–2500 m. These findings provide a more representative picture of the fault geometry and can be used as a basis for developing earthquake mitigation strategies and spatial planning based on actual geological conditions in the Bengkulu region.