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Seismic Velocity Structures beneath the Guntur Volcano Complex, West Java, Derived from Simultaneous Tomographic Inversion and Hypocenter Relocation
Andri Dian Nugraha1, Sri Widiyantoro1, Awan Gunawan2 & Gede Suantika3
1Global Geophysical Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia
2Graduate Program of Earth Science, Faculty of Earth Science and Technology, Institut Teknologi Bandung, Jalan Ganesa No. 10, Bandung 40132, Indonesia
3Center for Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro No. 57, Bandung 40122, Indonesia
Email: nugraha@gf.itb.ac.id
Abstract. We conducted travel time tomographic inversion to image seismic velocity structures (Vp, Vs, and Vp/Vs ratio) with simultaneous hypocenter adjustment beneath the Guntur volcano complex that is located in the Garut district, West Java province, Indonesia. The Guntur volcano is one of the active volcanoes in Indonesia, although large eruptions have not occurred for about 160 years. We used volcanic and tectonic earthquakes catalog data from seismic stations deployed by Centre for Volcanology and Geological Hazard Mitigation (CVGHM). For the tomographic inversion procedure, we set grid nodes with a horizontal spacing of 2 x 2 km2 and an average vertical spacing of 2 km. Our results show low Vp, low Vs, and high Vp/Vs ratio regions beneath the Guntur crater and the Gandapura caldera at depths of 6-8 km and 7-9 km, respectively. These features can be associated with amelt-filled pore rock structure. However, a low Vp/Vs ratio and low velocities are exhibited beneath the Kamojang caldera at depths of 2-6 km that may be associated with rock with H2O-filled pores with a high aspect ratio.
Keywords: Seismic tomography; Guntur volcano; Seismic structure; Melt-filled pore; West Java.
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