Rabbani, Muhammad Rifqi
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HVSR Microtremor Analysis to Assess Subsurface Fault Characteristics and Geothermal Potential in Kepahiang Rabbani, Muhammad Rifqi; Hadi, Arif Ismul; Harlianto, Budi; Farid, Muchammad; Raihana, Hana; Anggi, Arya Putra
JURNAL GEOCELEBES Vol. 9 No. 2: October 2025
Publisher : Departemen Geofisika, FMIPA - Universitas Hasanuddin, Makassar

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.70561/geocelebes.v9i2.43347

Abstract

Kepahiang, Bengkulu, is an area with considerable geothermal potential, especially in the Air Sempiang and Babakan Bogor areas. This study aims to analyze subsurface fault characteristics and assess geothermal potential using the Horizontal-to-Vertical Spectral Ratio (HVSR) microtremor method. This passive seismic method is used to determine key geophysical parameters, including dominant frequency (f0), amplification factor (A0), shear wave velocity (vs), and primary wave velocity (vp), which are essential for characterizing subsurface geological structures and identifying geothermal reservoir zones. The results show that dominant frequency values in Kepahiang range from 1.24 Hz to 20.45 Hz, while the amplification factor varies between 1.29 and 7.22. vs values range from 121.61 m/s to 3251.79 m/s, and vp values range from 214.91 m/s to 6469.79 m/s. These findings suggest that the surface layer consists mainly of alluvium and hard sandy gravel, with thicknesses varying between 10 and 50 meters. The 3D subsurface model constructed from the data indicates the presence of fault-controlled geothermal manifestations, mainly influenced by the Babakan Bogor Fault and Bogor Fault. These faults facilitate the upward migration of geothermal fluids, forming surface manifestations such as hot springs, fumaroles, and altered rocks. The geothermal system in the study area is classified as a low-temperature geothermal system, mainly caused by residual magmatic heat from Kaba Mountain and Bukit Hitam Crater. This research provides important insights for geothermal energy exploration and geotourism development in Kepahiang. These findings serve as a scientific basis for future geothermal resource assessment, land use planning, and sustainable energy utilization.
Estimate Sediment Thickness in Air Sempiang Village, Kepahiang Using the HVSR Method and the f0 and A0 Values Hafiza, Belliya; S, Vionita; Rabbani, Muhammad Rifqi; Suhendra, Suhendra; Sihombing, Yezra Tariza; Valennita, Valennita; Febriansyah, Gian Ori
Jambura Geoscience Review Vol 8, No 1 (2026): Jambura Geoscience Review (JGEOSREV)
Publisher : Universitas Negeri Gorontalo

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.37905/jgeosrev.v8i1.31789

Abstract

Microtremor-based site characterization provides rapid constraints on near-surface stratigraphy where borehole or geotechnical data are limited. This study estimates relative sediment-thickness variation and site response in Air Sempiang Village (Kabawetan District, Kepahiang Regency, Bengkulu Province, Indonesia) using the horizontal-to-vertical spectral ratio (HVSR) method and the derived dominant frequency (f₀) and amplification factor (A₀). Ambient-vibration data were acquired at 13 measurement points (30 min per site) using a PASIGemini-2 three-component geophone. HVSR processing was performed in Geopsy 3.2.2, including time-window selection, spectral smoothing, and peak identification to obtain f₀ and A₀. The resulting parameters were interpolated using inverse distance weighting in ArcGIS to generate spatial distribution maps. The estimated dominant frequencies are predominantly high (approximately 7–20 Hz), indicating generally shallow sediment cover and relatively stiff near-surface conditions, with localized lower-f₀ zones interpreted as thicker sediment accumulations. Amplification factors vary from 2 to 8, with moderate-to-high amplification concentrated in areas inferred to contain softer or thicker sediments, whereas lower A₀ values coincide with zones interpreted as being closer to competent bedrock. The combined f₀–A₀ patterns delineate subareas that are more susceptible to medium- to high-frequency ground-motion amplification and provide a first-order basis for local-scale seismic microzonation and earthquake risk mitigation planning in the study area.