Advertisement

Bulletin of Volcanology

, Volume 65, Issue 8, pp 562–577 | Cite as

Volcanic tremor related to the 1991 eruption of the Hekla volcano, Iceland

  • Heidi Soosalu
  • Páll Einarsson
  • Steinunn Jakobsdóttir
Research Article

Abstract

Volcanic tremor at the Hekla volcano is directly related to eruptive activity. It starts simultaneously with the eruptions and dies down at the end of them. No tremor at Hekla has been observed during non-eruptive times. The 1991 Hekla eruption began on 17 January, after a short warning time. Local seismograph stations recorded small premonitory earthquakes from 16:30 GMT on. At 17:02 GMT, low-frequency volcanic tremor became visible on the seismograph records, marking the onset of the eruption. The initial plinian phase of the eruption was short-lived. During the first day several fissures were active but, by the second day, the activity was already limited to a segment of one principal fissure. The eruption lasted almost 53 days. At the end of it, during the early hours of 11 March, volcanic tremor disappeared under the detection threshold and was followed by a swarm of small earthquakes. At the start of the eruption, the tremor amplitude rose rapidly and reached a maximum in only 10 min. The tremor was most vigorous during the first hour and started to decline sharply during the next hour, and later on more gently. During the eruption as a whole, the tremor had a continuous declining trend, with occasional increases lasting up to about 2 days. Spectral analysis of the tremor during the first 7 h of the eruption shows that it settled quickly, within a couple of minutes, to its characteristic frequency band, 0.5–1.5 Hz. The spectrum had typically one dominant peak at 0.7–0.9 Hz, and a few subdominant peaks. Hekla tremor likely has a shallow source. Particle motion plots suggest that it contains a significant component of surface waves. The tremor started first when the connection of the magma conduit with the atmosphere was reached, suggesting that degassing may contribute to its generation.

Keywords

Hekla eruption 1991 Volcanic tremor Earthquakes Eruption monitoring 

Notes

Acknowledgements

H. Soosalu was supported by Finnish Cultural Foundation and the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. The Icelandic Meteorological Office provided the digital SIL data. The National Power Company of Iceland funds the analog seismograph network. Comments of two anonymous reviewers improved the manuscript.

References

  1. Aki K, Fehler M, Das S (1977) Source mechanism of volcanic tremor: fluid-driven crack models and their application to the 1963 Kilauea eruption. J Volcanol Geotherm Res 2:259–287Google Scholar
  2. Brandsdóttir B, Einarsson P (1992) Volcanic tremor and low-frequency earthquakes in Iceland. In: Gasparini P, Scarpa R, Aki K (eds) Volcanic seismology. Springer, Berlin Heidelberg New York, pp 212–222Google Scholar
  3. Chouet B (1981) Ground motion in the near field of a fluid-driven crack and its interpretation in the study of shallow volcanic tremor. J Geophys Res 86:5985–6016Google Scholar
  4. Chouet B (1985) Excitation of a buried magmatic pipe: a seismic source model for volcanic tremor. J Geophys Res 90:1881–1893Google Scholar
  5. Chouet B (1988) Resonance of a fluid-driven crack: radiation properties and implications for the source of long-period events and harmonic tremor. J Geophys Res 93:4375–4400Google Scholar
  6. Chouet B (1992) A seismic model for the source of long-period events and harmonic tremor. In: Gasparini P, Scarpa R, Aki K (eds) Volcanic seismology. Springer, Berlin Heidelberg New York, pp 133–156Google Scholar
  7. Cristofolini R, Gresta S, Imposa S, Menza S, Patanè G (1987) An approach to problems on energy sources at Mount Etna based on seismological and volcanological data. Bull Volcanol 49:729–736Google Scholar
  8. Einarsson P (1991) Earthquakes and present-day tectonism in Iceland. Tectonophysics 189:261–279Google Scholar
  9. Einarsson P (2000) The seismograph station on Litla-Hekla and the 2000 eruption (in Icelandic). In: Abstr Vol Geoscience Society of Iceland Spring Meet 2000, p 41Google Scholar
  10. Einarsson P, Björnsson S (1976) Seismic activity associated with the 1970 eruption of volcano Hekla in Iceland. Jökull 26:8–19Google Scholar
  11. Einarsson P, Saemundsson K (1987) Earthquake epicenters 1982–1985 and volcanic systems in Iceland. In: Sigfússon ÞI (ed) Í hlutarins eðli, Festschrift for Þorbjörn Sigurgeirsson. Menningarsjóður, Reykjavík (map)Google Scholar
  12. Ereditato D, Luongo G (1994) Volcanic tremor wave field during quiescent and eruptive activity at Mt. Etna (Sicily). J Volcanol Geotherm Res 61:239–251Google Scholar
  13. Ferrick MG, Qamar A, St Lawrence WF (1982) Source mechanism of volcanic tremor. J Geophys Res 87:8675–8683Google Scholar
  14. Goldstein P, Chouet B (1994) Array measurements and modeling of sources of shallow volcanic tremor at Kilauea Volcano, Hawaii. J Geophys Res 99:2637–2652Google Scholar
  15. Gordeev EI (1992) Modelling of volcanic tremor wave fields. J Volcanol Geotherm Res 51:145–160Google Scholar
  16. Gordeev EI, Saltykov VA, Sinitsyn VI, Chebrov VN (1990) Temporal and spatial characteristics of volcanic tremor wave fields. J Volcanol Geotherm Res 40:89–101Google Scholar
  17. Grönvold K, Larsen G, Einarsson P, Þórarinsson S, Saemundsson K (1983) The Hekla eruption 1980–1981. Bull Volcanol 46:349–363Google Scholar
  18. Guðmundsson Á, Saemundsson K (1992) The Hekla eruption 1991: course of the eruption and the mechanics of Hekla (in Icelandic). Náttúrufraeðingurinn 61:145–158Google Scholar
  19. Guðmundsson Á, Óskarsson N, Grönvold K, Saemundsson K, Sigurðsson O, Stefánsson R, Gíslason SR, Einarsson P, Brandsdóttir B, Larsen G, Jóhannesson H, Þórðarson Þ (1992) The 1991 eruption of Hekla, Iceland. Bull Volcanol 54:238–246Google Scholar
  20. Jóhannesson H, Jakobsson SP, Saemundsson K (1990) Geological map of Iceland, sheet 6, South Iceland, 3rd edn. Icelandic Museum of Natural History and Iceland Geodetic Survey, ReykjavíkGoogle Scholar
  21. Linde AT, Ágústsson K, Sacks IS, Stefánsson R (1993) Mechanism of the 1991 eruption of Hekla from continuous borehole strain monitoring. Nature 365:737–740Google Scholar
  22. McNutt SR (1986) Observations and analysis of B-type earthquakes, explosions, and volcanic tremor at Pavlof Volcano, Alaska. Bull Seismol Soc Am 76:153–175Google Scholar
  23. McNutt SR (1994a) Volcanic tremor amplitude correlated with the volcanic explosivity index and its potential use in determining ash hazards to aviation. Acta Vulcanologica 5:193–196Google Scholar
  24. McNutt SR (1994b) Volcanic tremor from around the world: 1992 update. Acta Vulcanologica 5:197–200Google Scholar
  25. Montalto A, Longo V, Patanè G (1995) Echo-resonance and hydraulic perturbations in magma cavities: application to the volcanic tremor of Etna (Italy) in relation to its eruptive activity. Bull Volcanol 57:219–228CrossRefGoogle Scholar
  26. Þórarinsson S (1967) The eruption of Hekla 1947–1948. I. The eruptions of Hekla in historical times, a tephrochronological study. Soc Scientiarum Islandica, Reykjavík, pp 1–170Google Scholar
  27. Þórarinsson S, Sigvaldason GE (1972) The Hekla eruption of 1970. Bull Volcanol 36:269–288Google Scholar
  28. Ripepe M, Poggi P, Braun T, Gordeev E (1996) Infrasonic waves and volcanic tremor at Stromboli. Geophys Res Lett 23:181–184Google Scholar
  29. Schick R (1988) Volcanic tremor-source mechanisms and correlation with eruptive activity. Natural Hazards 1:125–144Google Scholar
  30. Schick R (1992) Volcanic tremor: seismic signals of (almost) unknown origin. In: Gasparini P, Scarpa R, Aki K (eds) Volcanic seismology. Springer, Berlin Heidelberg New York, pp 157–167Google Scholar
  31. Schlindwein V, Wassermann J, Scherbaum F (1995) Spectral analysis of harmonic tremor signals at Mt. Semeru volcano, Indonesia. Geophys Res Lett 22:1685–1688Google Scholar
  32. Seidl D, Schick R, Riuscetti M (1981) Volcanic tremors at Etna: a model for hydraulic origin. Bull Volcanol 44:43–56Google Scholar
  33. Soosalu H, Einarsson P (2002) Earthquake activity related to the 1991 eruption of the Hekla volcano, Iceland. Bull Volcanol 63:536–544CrossRefGoogle Scholar
  34. Stefánsson R, Böðvarsson R, Slunga R, Einarsson P, Jakobsdóttir S, Bungum H, Gregersen S, Havskov J, Hjelme J, Korhonen H (1993) Earthquake prediction research in the South Iceland Seismic Zone and the SIL project. Bull Seismol Soc Am 83:696–716Google Scholar
  35. Stefánsson R, Ágústsson K, Guðmundsson GB, Þorbjarnardóttir BS, Einarsson P (2000) A successful prediction and warning of an eruption in the Hekla volcano, Iceland.In: Abstr Vol AGU 2000 Spring Meet, p 442Google Scholar
  36. Ukawa M (1993) Excitation mechanism of large-amplitude volcanic tremor associated with the 1989 Ito-oki submarine eruption, central Japan. J Volcanol Geotherm Res 55:33–50Google Scholar
  37. Wessel P, Smith WHF (1998) New, improved version of the Generic Mapping Tools released. Eos 79:579Google Scholar

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Heidi Soosalu
    • 1
    • 4
  • Páll Einarsson
    • 2
  • Steinunn Jakobsdóttir
    • 3
  1. 1.Institute of SeismologyUniversity of HelsinkiHelsinkiFinland
  2. 2.Science InstituteUniversity of IcelandReykjavíkIceland
  3. 3.Icelandic Meteorological OfficeReykjavíkIceland
  4. 4.Nordic Volcanological InstituteReykjavíkIceland

Personalised recommendations