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Geohazards pp 65-79 | Cite as

Seismic monitoring of Lake Nyos, Cameroon, following the gas release disaster of August 1986

  • Alice B. Walker
  • D. W. Redmayne
  • C. W. A. Browitt
Part of the AGID Report Series book series (ARS)

Abstract

On 21 August 1986 a cloud of dense gas was emitted from Lake Nyos in Cameroon causing death, by asphixiation, of over 1700 people in the nearby villages. An international relief effort was initiated and scientific teams from a number of countries were sent to Lake Nyos in order to determine the cause of the gas release. It was agreed that the carbon dioxide, which was the predominant gas in the cloud, had a deep-seated magmatic origin and that the lake was charged with it to near-saturation levels prior to the gas outburst. Uncertainty remained, however, about the mechanism of its eruption from the lake; in particular, whether the lake overturned in response to a small external trigger or whether a phreatic volcanic eruption occurred.

In an attempt to resolve this problem, and following the report of a second ‘eruptive event’ on 30 December 1986, the British Geological Survey installed a network of hydrophones and geophones in and around the lake during February 1987. During the following six months, regional earthquakes and small local seismic events, interpreted as rockfalls, were detected but no significant crustal earthquakes were found beneath or close to the lake. No clear evidence of magma movement or other signs of volcanic activity were found, suggesting that direct volcanic activity was not involved. Noise outbursts detected, mainly at night, may have been due to gas emissions from rock fissures.

The lack of tectonic seismicity at the lake during the monitoring period argues against an earthquake trigger for the gas release. In the wider volcanic province, however, many earthquakes were detected and such a trigger cannot be completely ruled out.

The future safety of people who live around the lake depends either on controlled degassing or lowering of the lake level with monitoring of CO2 levels in the lake on a continuous basis. The data recording techniques used in this study could readily be applied to such a broadly-based monitoring system.

Keywords

Lake Level Crater Lake Seismic Monitoring British Geological Survey Phreatic Eruption 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Ambeh, W.A., J.D. Fairhead, D.J. Francis, J.M. Nange and S. Djallo, 1989. Seismicity of the Mount Cameroon Region. Journal of African Earth Sciences, vol 9(1), p 1–7.CrossRefADSGoogle Scholar
  2. Clark, M.A., H.R. Compton, J.D. Divine, W.C. Evans, A.M. Humphrey, G.W. Kling, E.J. Koenigsberg, J.P. Lockwood, M.L. Tuttle and G.N. Wagner, 1987. The 21 August 1986 Lake Nyos Gas Disaster, Cameroon: Final Report of the United States Scientific Team to the Office of US Foreign Disaster Assistance.Google Scholar
  3. Chevrier, R.M., 1987. Phenomenologie: Lac Nyos: explosions phreatiques 30 decembre 1986. Unesco, International Scientific Conference of the Lake Nyos Disaster, Yaoundé, 16–20 March 1987.Google Scholar
  4. Fitton, J.G., 1980. The Benue trough and Cameroon line—a migrating rift system in West Africa. Earth and Planetary Science Letters, vol 51, p 132–138.CrossRefADSGoogle Scholar
  5. Fitton, J.G., and H.M. Dunlop, 1985. The Cameroon line, West Africa, and its bearing on the origin of oceanic and continental alkali basalt. Earth and Planetary Science Letters, vol 72, p 23–38.CrossRefADSGoogle Scholar
  6. Freeth, S.J., and R.L.F. Kay, 1987. The Lake Nyos gas disaster. Nature, vol 325, p 104–105.CrossRefADSGoogle Scholar
  7. Freeth, S.J., R.L.F. Kay, and P.J. Baxter, 1987. Reports by the British scientific mission sent to investigate the Lake Nyos disaster. Commissioned report by the Disaster Unit of the Overseas Development Administration, Foreign and Commonwealth Office, London, UK.Google Scholar
  8. Hassert, K., 1912. Seenstudien in Nord-Kamerun. Zeitschrift der Gesellschaft für Erdkunde zu Berlin, vol 7–41, p 135–144 and 203–216.Google Scholar
  9. Houliston, D.J., J. Laughlin and G. Waugh, 1985. Eventtriggered seismic detection systems developed by the British Geological Survey. Earthquake Engineering in Britain, Thomas Telford Ltd, London.Google Scholar
  10. Kling, G.W., M.A. Clark, H.R. Compton, J.D. Devine, W.C. Evans, A.M. Humphrey, E.J. Koenigsberg, J.P. Lockwood, M.L. Tuttle and G.N. Wagner, 1987. The 1986 Lake Nyos gas disaster in Cameroon, West Africa. Science, vol 236, p 169–174.CrossRefADSGoogle Scholar
  11. Lee, W.H.K., R.E. Bennet, and K.L. Meagher, 1972. A method of estimating magnitude of local earthquakes from signal duration. US Geological Survey Open File Report 28.Google Scholar
  12. Lienert, B.R., E. Berg and L.N. Fraser, 1986. HYPOCENTER: an earthquake location method using centered scaled and adaptively damped least squares. Bulletin of the Seismological Society of America, vol 76(3), p 771–783.Google Scholar
  13. Lockwood, J.P., 1987. Geological setting and origin of Lake Nyos, Northwest Cameroon. Unesco, International Scientific Conference of the Lake Nyos Disaster, Conclusions and Recommendations, Yaoundé, 16–20 March 1987.Google Scholar
  14. Lockwood, J.P., J.E. Costa, M.L. Tuttle, J. Nni and S.G. Tebor, 1989. The potential for catastrophic dam failure at Lake Nyos maar, Cameroon. Bulletin of Volcanology (1988), vol 50, p 340–349.CrossRefADSGoogle Scholar
  15. McNutt, S.R., 1986. Observations and analysis of B-type earthquakes, explosions and volcanic tremor at Pavlof volcano, Alaska. Bulletin of the Seismological Society of America, vol 76(1), p 153–175.Google Scholar
  16. Sigurdsson, H., 1987. Reporter general, Unesco, International Scientific Conference of the Lake Nyos Disaster, Conclusions and Recommendations, Yaoundé, 16–20 March 1987.Google Scholar
  17. Sigurdsson, H., J.D. Divine, F.M. Tchoua, T.S. Presser, M.K.W. Pringle and W.C. Evans, 1987. Origin of the lethal gas burst from Lake Monoun, Cameroon. Journal of Volcanic and Geothermal Research, vol 31, p 1–16.CrossRefADSGoogle Scholar
  18. Stuart, G.W., J.D. Fairhead, L. Dorbath and C. Dorbath, 1985. A seismic refraction study of the crustal structure associated with the Adamawa Plateau and Garoua Rift, Cameroon, West Africa. Geophysical Journal of the Royal Astronomical Society, vol 81, p 1–12.Google Scholar
  19. Tazieff, H., 1987. Nyos disaster: limnic overturn or phreatic eruption? Unesco, International Scientific Conference of the Lake Nyos Disaster, Conclusions and Recommendations, Yaounde, 16–20 March 1987.Google Scholar
  20. Tsumura, K., 1967. Determination of earthquake magnitude from total duration of oscillation. Bulletin of the Earth Resources Institute, Tokyo, vol 45, p 7–18.Google Scholar
  21. Walker, A.B., D.W. Redmayne and C.W.A. Browitt, 1988. Seismic monitoring of Lake Nyos, Cameroon, following the gas release disaster of August 1986: final report to the Overseas Development Administration by the British Geological Survey. Global Seismology Report No WL/88/14, Natural Environment Research Council open-file report, British Geological Survey, June 1988, 24 p.Google Scholar

Copyright information

© G.J.H. McCall, D.J.C. Laming and S.C. Scott 1992

Authors and Affiliations

  • Alice B. Walker
  • D. W. Redmayne
  • C. W. A. Browitt

There are no affiliations available

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