- Open Access
Reexamination of moment tensors for initial motion of explosion earthquakes using borehole seismograms at Sakurajima volcano, Japan
Earth, Planets and Space volume 53, pages 63–68 (2001)
We estimated the seismic moment tensor for the initial phase of explosion earthquakes associated with Vulcanian explosions at the andesitic volcano Sakurajima. We applied a waveform inversion method to 24 events observed with borehole seismometers at 6 stations assuming a single triangular source time function. The three diagonal components representing volumetric change were dominant in the estimated moment tensors. The three diagonal components were positive and had almost the same values with the difference among them less than 10% for most of the explosion earthquakes, while non-diagonal components were negligibly small compared with the diagonal ones. Durations of source time functions had a range of 0.2–0.5 s and seismic moments were 1011 ∼ 1012 Nm. We conclude that the explosion earthquakes are initiated by an isotropic expansion.
Aki, K., Evidence for magma intrusion during the Mammoth Lakes earthquakes of May 1980 and implications of the absence of volcanic (harmonic) tremor, J. Geophys. Res., 89, 7689–7696, 1984.
Bouchon, M., A simple method to calculate Green’s functions for elastic layered media, Bull. Seismol. Soc. Am., 71, 959–971, 1981.
Iguchi, M., A vertical expansion source model for the mechanisms of earthquakes originated in the magma conduit of an andesitic volcano: Sakurajima, Japan, Bull. Volcanol. Soc. Jpn., 39, 49–67, 1994.
Iguchi, M., Source mechanisms of volcanic earthquakes and tremors and their field of origin, Bull. Volcanol. Soc. Jpn., 40, S47–S57, 1995 (in Japanese).
Ishihara, K., Geophysical evidences on the existence of magma reservoir and conduit at Sakurajima volcano, Japan, Ann. Disast. Prev. Res. Inst. Kyoto Univ., 31B-1, 59–73, 1988 (in Japanese with English abstract).
Kennett, B. L. N. and N. J. Kerry, Seismic waves in a stratified half space, Geophys. J. R. Astron. Soc., 57, 557–583, 1979.
Kikuchi, M. and H. Kanamori, Inversion of complex body waves-III, Bull. Seismol. Soc. Am., 81, 2335–2350, 1991.
Minakami, T., Seismology and volcanoes in Japan, in Physical Volcanology, edited by L. Civetta, P. Gasparini, G. Luongo, and A. Rapolla, pp. 1–27, Elsevier, 1974.
Nishi, K., On the explosion earthquake of Sakurajima volcano, Ann. Disast. Prev. Res. Inst. Kyoto Univ., 19B, 69–73, 1976 (in Japanese with English abstract).
Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, Volcanic activity of Sakurajima volcano (February-May, 1999), Rep. Coord. Comm. Prediction Volcanic Eruption, 74, 111–117, 1999 (in Japanese).
Takeo, M., Near-field synthetic seismograms taking into account of the effects of anelasticity—The effects of anelastic attenuation on seismograms caused by a sedimentary layer, Pap. Meteorol. Geophys., 36, 245–257, 1985 (in Japanese with English abstract).
Uhira, K. and M. Takeo, The source of explosive eruption of Sakurajima volcano, Japan, J. Geophys. Res., 99, 17775–17789, 1994.
Uhira, K., S. Ikeda, and M. Takeo, Source process of explosion earthquakes deduced from short-period records at Sakurajima volcano, Bull. Volcanol. Soc. Jpn., 40, 295–310, 1995.
Yamasato, H., Distribution of the initial motions of explosion earthquakes at Sakurajima volcano, Bull. Volcanol. Soc. Jpn., 32, 289–300, 1987 (in Japanese with English abstract).
About this article
Cite this article
Tameguri, T., Iguchi, M. & Ishihara, K. Reexamination of moment tensors for initial motion of explosion earthquakes using borehole seismograms at Sakurajima volcano, Japan. Earth Planet Sp 53, 63–68 (2001). https://doi.org/10.1186/BF03352363
- Seismic Moment
- Moment Tensor
- Waveform Inversion
- Diagonal Component
- Summit Crater