Two-Dimensional Magnetotelluric Resistivity Correlation For Estimating The Depth and Distribution of The Geothermal Top Reservoir In Babakan Bogor, Kepahiang
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Abstract
Kepahiang Regency, Bengkulu Province, hosts an active hydrothermal system on the flank of the Mount Kaba volcanic complex, marked by hot springs and fumaroles around Babakan Bogor and Air Sempiang, yet subsurface information on the depth and lateral extent of its geothermal top reservoir remains limited. This study estimates the depth and spatial distribution of the top reservoir in Babakan Bogor by correlating three new magnetotelluric (MT) soundings (T1, T2, T3), spaced 0.8–1.3 km apart along a west–east line, into a two-dimensional resistivity cross-section. Data were acquired across low (128 Hz), medium (1024 Hz), and high (4096 Hz) frequency bands, processed using a robust, remote-reference-based approach, and interpreted following a three-layer conceptual model of cap rock, reservoir, and hot rock calibrated against previous Kepahiang and Bogor-segment MT studies. The resulting cross-section reveals two shallower reservoir compartments flanking a markedly thickened cap rock beneath the central station, with a resistive hot-rock body rising toward the surface beneath the western reservoir. The top reservoir shallows to about 0.5–2 km near the western station, closest to the surface manifestation, and deepens beyond 4 km toward the centre and east of the line. This geometry mirrors the neighbouring Bogor-segment section reported in earlier work and is independently supported by gravity modelling of the same area. These findings indicate that reservoir accessibility along the Bogor Fault segment is governed by structural position rather than by a uniform regional depth, and they provide a spatial framework to guide the siting of subsequent exploration lines and wells in the Kepahiang geothermal system.
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Copyright (c) 2026 Melly Angglena, Fhandy Pandey, Mey Chyntia Yesaya
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