References

NHESS

Natural Hazards and Earth System Sciences

NHESS

Nat. Hazards Earth Syst. Sci.

1684-9981

Copernicus Publications

Göttingen, Germany

10.5194/nhess-7-467-2007

Seismic characterization of pyroclastic flow activity at Soufrière Hills Volcano, Montserrat, 8 January 2007

De Angelis

¹ Bass

¹ Hards

¹ Ryan

Montserrat Volcano Observatory Flemmings, Montserrat, West Indies

23 07 2007

7 4 467 472

2007

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/

This article is available from https://nhess.copernicus.org/articles/7/467/2007/nhess-7-467-2007.html

The full text article is available as a PDF file from https://nhess.copernicus.org/articles/7/467/2007/nhess-7-467-2007.pdf

A partial dome collapse with concurrent pyroclastic flow (PF) activity occurred at Soufrière Hills Volcano (SHV), Montserrat on 8 January 2007. Pyroclastic density currents were observed to propagate from the Northwest and West sectors of the summit dome into the heads of Tyres Ghaut and Gages Valley, respectively. Between 10:00 and 10:15 UTC pyroclastic flows entered Tyres Ghaut and from there descended into the Belham Valley reaching a distance of about 5 km from the source. Pyroclastic flow activity on the Northwest and West side of the edifice continued at high levels over the following 1.5 h, although run-out distances of individual flows did not exceed 1.5 km. Subsequent observations showed that material had been removed from the lower Northwest side of the dome leaving an amphitheatre-like structure cutting through the old crater rim. The seismic waves excited by the propagation of pyroclastic flows were recorded by the Montserrat Volcano Observatory's network of broadband seismometers. The seismic records show the onset of a continuous signal before 09:30 UTC with gradually increasing amplitudes and spectral energy in the 1–8 Hz band. The signal rapidly increased in amplitude and a characteristic spindle-shaped waveform with broadband energy (1–25 Hz) was observed accompanying large PF that descended along the slopes of the volcano. The main phase was followed by a sequence of individual seismic pulses which correlated well with visual observations of PF. PF are a major hazard at SHV and pose significant risk for the population living in the proximity of the volcano. They can occur with little or no warning and have the potential to reach inhabited areas to the Northwest. The study of the seismic activity associated with the generation and propagation of pyroclastic flows can help to identify characteristic precursory seismic sequences providing valuable information to improve the understanding of the hazards posed by the SHV and to allow better warning to be given to the authorities.

References 1

Aspinall, W. P., Miller A. D., Lynch L. L., Latchman J. L., Stewart R. C., White R. A., and Power J. A.: Soufriere Hills eruptions, volcanic earthquake locations and fault plane solutions, Geophys. Res. Lett., 25, 2297–3400, 1998.

Calder, E. S.: Mechanisms of lava dome instability and generation of rockfalls and pyroclastic flows at Soufrieres Hills Volcano, Montserrat, edited by: Druitt, T. H. and Kokelaar, B. P., The eruption of the Soufrière Hills Volcano, Montserrat from 1995 to 1999, Geological Society London, 21, 483–516, 2002.

Cole, P. D., Calder, E. S., Druitt, T. H., Hoblitt, R., Robertson, R., Sparks, R. S. J., and Young, S. R.: Pyroclastic flows generated by gravitational instability of the 1996-97 lava dome of Soufrière Hills Volcano, Montserra, Geophys. Res. Lett., 25, 3425–3428, 1998.

Herd, R. A., Edmonds, M., and Bass, V. A.: Castastrophic lava dome failure at Soufriere Hills volcano, Montserrat, 12–13 July 2003, TJ. Volc. Geotherm. Res. T, 148, 234–252, 2005.

Kanasewich, E. R.: Time Sequence Analysis in Geophysics, 480 pp., University of Alberta Press, Edmonton, Alberta, Canada, 1981.

Jolly, A. D., Thompson, G., and Norton, G. E.: Locating pyroclastic flows on Soufrieres Hills Volcano, Montserrat, West Indies, using amplitude signals from high dynamic range instruments, J. Volcanol. Geotherm. Res., 118, 299–317, 2002.

Loughlin, S. C., Calder, E. S., Clarke, A. B., Cole, R. D., Luckett, R., Mangan, M., Pyle, D., Sparks, R. S. J., Voight, B., and Watts, R.: Pyroclastic flows generated by the 25 June 1997 dome collapse, Soufrière Hills Volcano, Montserrat, T.H. Druitt and B.P. Kokelaar (eds), The eruption of the Soufrière Hills Volcano, Montserrat from 1995 to 1999, Geological Society London, 21, 191–209, 2002.

Luckett R., Baptie, B., Ottemoller, L., and Thompson G.: Seismic Monitoring of the Soufrière Hills Volcano Montserrat, Seism. Res. Lett., 78(2), 192–200, 2007.

Neuberg, J.: Characteristics and causes of shallow seismicity in andesite volcanoes, Royal Society of London, Philosophical Transactions, Series A., Mathematical, Phys. Eng. Sci., 358, 1533–1546, 2000.

Neuberg, J. W., Tuffen, H., Collier, L., Green, D., Powell T., and Dingwell D.: The trigger mechanism of low-frequency earthquakes on Montserrat, J. Volcanol. Geotherm. Res., 153, 37–50, 2006.

Norris, R. D.: Seismicity of rockfalls and avalanches at three cascade range volcanoes: implications for seismic detection of hazardous mass movements, Bull. Seismol. Soc. Soc. Am., 84, 1925–1939, 1994.

Robertson, R. E. A., Aspinall, W. P., Herd, R. A., Norton, G. E. Sparks, R. S. J., Young, S. R.: The 1995–1998 Eruption of the Soufriere Hills Volcano, Royal Society of London, TPhilosophical Transactions, Series A, Mathematical, Phys. Eng. Sci., 358, 1619–1637, 2000.

Scandone, R., Kashman, K. V., and Malone, S. D.: Magma supply, magma ascent and the style of volcanic eruptions, Earth Planet. Sci. Lett., 253, 513–529, 2007.

Surinach, E., Vilajosana, I., Khazaradze, B. Biescas, B., Furdada, G., and Vilaplana, J. M.: Seismic detection and characterization of landslides and other mass movements, Nat. Hazards Earth Syst. Sci., 5, 791–798, 2005.

Sparks R. S. J., Barclay, J., Calder, E. S., Herd, A., Komorowski, J. C., Luckett, R., Norton, G. E., Ritchie, L. J., Voight, B., and Woods, A. W.: Generation of a debris avalanche and violent pyroclastic density current on 26 December (Boxing Day) 1997 at Soufriere Hills volcano, Montserrat, T.H. Druitt and B.P. Kokelaar (eds), The eruption of the Soufrière Hills Volcano, Montserrat from 1995 to 1999, Geological Society London, 21, 409–434, 2002.

Uhira, K., Yamasato, H., and Takeo, M.: Source mechanism of seismic waves excited by pyroclastic flows observed at Unzen volcano, Japan, J. Geophys. Res., 99, 17 757–17 773, 1994.

Voight, B., Sparks, R. S. J. , Miller, A. D., Stewart, R. C., Hoblitt, R. P., Clarke, A., Ewert, J., Aspinall, W. P., Baptie, B., Calder, E. S., Cole, P., Druitt, T. H., Harford, C., Herd, R. A., Jackson, P., Lejeune, A. M., Lockhart, A. B., Loughlin, S. C., Luckett, R., Lynch, L., Norton, G. E., Robertson, R., Watson, I. M., Watts, R., Young, S. R.: Magma Flow Instability and Cyclic Activity at Soufrière Hills Volcano, Montserrat, British West Indies. Science, 283, 1138–1142, 1999.

Voight, B. and Elsworth, D.: Instability and collapse of hazardous gas-pressurized lava domes, Geophys. Res. Lett., 27, 1–4, 2000.

Voight, B., Komorowski, J. C., Norton, G. E., Belousov, A. B., Belousova, M., Boudon, G., Francis, P. W., Franz, W., Heinrich, P., Sparks, R. S. J., and Young, S. R.: The 26 December (Boxing Day) 1997 sector collapse and debris avalanche at Soufriere Hills volcano, Montserrat, edited by: Druitt, T. H. and Kokelaar, B. P., The eruption of the Soufrière Hills Volcano, Montserrat from 1995 to 1999, Geological Society London, 21, 363–407, 2002.

Young, S. R., Sparks, R. S. J., Aspinall, W. P., Lynch, L. L., Miller, A. D., Robertson, R. E. A., and Shepherd, J. B.: Overview of the eruption of Soufriere Hills Volcano, Montserrat, July 18 1995 to December 1997, Geophys. Res. Lett., 25, 3389–3392, 1998.