Seismic Velocity Structures beneath the Guntur Volcano Complex, West Java, Derived from Simultaneous Tomographic Inversion and Hypocenter Relocation

Andri Dian Nugraha; Sri Widiyantoro; Awan Gunawan; Gede Suantika

doi:10.5614/j.math.fund.sci.2013.45.1.2

Authors

Andri Dian Nugraha Global Geophysical Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung,
Sri Widiyantoro Global Geophysical Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung,
Awan Gunawan Graduate Program of Earth Science, Faculty of Earth Science and Technology, Institut Teknologi Bandung
Gede Suantika Center for Volcanology and Geological Hazard Mitigation (CVGHM)

DOI:

https://doi.org/10.5614/j.math.fund.sci.2013.45.1.2

Keywords:

Seismic tomography, Guntur volcano, Seismic structure, Melt-filled pore, West Java

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.

References

Matahelemual, J., Gunung Guntur, Berita Berkala Vulkanologi Edisi Khusus, Direktorat Vulkanologi Bandung (in Indonesian), 1989.

Kusumadinata, K., Data Dasar Gunungapi Indonesia, Direktorat Vulkanologi Bandung (in Indonesian), 1979.

Kusumadinata, K., Hadian, R., Hamidi, S. & Reksowirogo, L.G., Catalogue of References on Indonesian Volcanoes with Eruptions in Historical Time, Direktorat Vulkanologi, Direktorat Jenderal Pertambangan Umum, Departemen Pertambangan dan Energi, Republik Indonesia (in Indonesian), 1979.

Eberhart-Phillips, D., Local Earthquake Tomography Velocities and Vp/Vs Theory, in Seismic Tomography: Theory and Practice, pp. 563-583, H.M. Iyer & K. Hirahara (Eds), CRC Press, Boca Raton, Fla, 1993.

Evan, J.R., Eberhart-Phillips, D. & Thurber, C.H., User's Manual for SIMULPS12 for Imaging Vp and Vp/Vs: Derivative of The "Thurber" Tomographic Inversion SIMUL3 for Local Earthquakes and Explosions, U.S. Geol. Surv. Open File Rep., pp. 94-431, 1994.

Thurber, C.H., Earthquake Locations and Three-Dimensional Crustal Structure in The Coyota Lake Area, Central California, J. Geophys. Res., 88, pp. 8226-8236, 1983.

Thurber, C.H., Local Earthquake Tomography Velocities and Vp/Vs Theory, in Seismic Tomography: Theory and Practice, pp. 563-583, H.M. Iyer & K. Hirahara (Eds), CRC Press, Boca Raton, Fla, 1993.

Nugraha, A.D. & Mori, J., Three-Dimensional Velocity Structure in The Bungo Channel and Shikoku Area, Japan, and Its Relationship to Low-Frequency Earthquakes, Geophys. Res. Lett., 33, L24307. doi: 10.1029/2006GL028479, 2006.

Um, J. & Thurber, C.H., A Fast Algorithm for Two-Point Seismic Ray Tracing, Bull. Seismol. Soc. Am., 77, pp. 972-986, 1987.

Nugraha, A.D., Suantika, G. & Widiyantoro, S., Relocation of Earthquake Hypocenter at Mt. Guntur Area Using Three Dimensional Velocity Model, Jurnal Geofisika Indonesia, I, pp.1-6. (in Indonesian with abstract in English), 2006.

Priyono, A., Suantika, G., Widiyantoro, S., Priadi, B.& Surono, Three dimensional P-and S-wave Velocity Structures of Mt. Guntur, West-Java, Indonesia, from Seismic Tomography, International Journal of Tomography & Statistic, 16(W11), pp. 1-11, 2011.

Menke, W., Geophysical Data Analysis: Discrete Inverse Theory, Univ. Calif. San Diego, 1989.

Nakajima, J., Hasegawa, A., Horiuchi, S., Yoshimoto, K., Yoshida, T. & Umino, N., Crustal Heterogeneity Around The Nagamachi-Rifu Fault, Northeastern Japan, as Inferred from Travel-Time Tomography, Earth Planets Space, 58, pp. 843-853, 2006.

Takei, Y., Effect of Pore Geometry on Vp/Vs: from Equilibrium Geometry to Crack, J. Geophys. Res., 107(B2), 2043. doi:10.1029/2001JB000522, 2002.

Priyono, A., Suantika, G., Widiyantoro, S. & Nugraha, A.D., Three-Dimensional Seismic Attenuation Structure of Mt. Guntur, West Java, Indonesia, International Journal of Tomography and Statistics, 17(S11), pp. 17-28, 2011.