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Tremor-rich shallow dyke formation followed by silent magma flow at Bárðarbunga in Iceland

Nature Geoscience volume 10, pages 299304 (2017) | Download Citation

Abstract

The Bárðarbunga eruption in Iceland in 2014 and 2015 produced about 1.6 km3 of lava. Magma propagated away from Bárðarbunga to a distance of 48 km in the subsurface beneath Vatnajökull glacier, emerging a few kilometres beyond the glacier’s northern rim. A puzzling observation is the lack of shallow (<3 km deep), high-frequency earthquakes associated with shallow dyke formation near the subaerial and subglacial eruptive sites, suggesting that near-surface dyke formation is seismically quiet. However, seismic array observations and seismic full wavefield simulations reveal the presence and nature of shallow, pre-eruptive, long-duration seismic tremor activity. Here we use analyses of seismic data to constrain the relationships between seismicity, tremor, dyke propagation and magma flow during the Bárðarbunga eruption. We show that although tremor is usually associated with magma flow in volcanic settings, pre-eruptive tremor at Bárðarbunga was probably caused by swarms of microseismic events during dyke formation, and hence is directly associated with fracturing of the upper 2–3 km of the crust. Subsequent magma flow in the newly formed shallow dyke was seismically silent, with almost a complete absence of seismicity or tremor. Hence, we suggest that the transition from temporarily isolated, large, deep earthquakes to many smaller, shallower, temporally overlapping earthquakes (<magnitude 2) that appear as continuous tremor announces the arrival of a dyke opening in the shallow crust, forming a pathway for silent magma flow to the Earth’s surface.

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References

  1. 1.

    Volcanic tremor wags on. Nature 470, 471–472 (2011).

  2. 2.

    Dynamics of a fluid-driven crack in three dimensions by the finite difference method. J. Geophys. Res. 91, 13967 (1986).

  3. 3.

    Excitation of a buried magmatic pipe: a seismic source model for volcanic tremor. J. Geophys. Res. 90, 1881–1893 (1985).

  4. 4.

    Volcanic tremor: nonlinear excitation by fluid flow. J. Geophys. Res. 99, 11859–11877 (1994).

  5. 5.

    Physical models for the source of Lascar’s harmonic tremor. J. Volcanol. Geotherm. Res. 101, 183–198 (2000).

  6. 6.

    , & The feasibility of generating low-frequency volcano seismicity by flow through a deformable channel. Geol. Soc. Lond. 307, 45–56 (2008).

  7. 7.

    & Time dependent features in tremor spectra. J. Volcanol. Geotherm. Res. 128, 177–185 (2003).

  8. 8.

    , , & Strongly gliding harmonic tremor during the 2009 eruption of Redoubt Volcano. J. Volcanol. Geotherm. Res. 259, 89–99 (2013).

  9. 9.

    Long-period volcano seismicity: its source and use in eruption forecasting. Nature 380, 309–316 (1996).

  10. 10.

    et al. Segmented lateral dyke growth in a rifting event at Barðarbunga volcanic system, Iceland. Nature 517, 191–195 (2015).

  11. 11.

    , , & Fracture movements and graben subsidence during the 2014 Bárðarbunga dike intrusion in Iceland. J. Volcanol. Geotherm. Res. 310, 242–252 (2015).

  12. 12.

    et al. Environmental pressure from the 2014–15 eruption of Bárðarbunga volcano, Iceland. Geochem. Perspect. Lett. 1, 84–93 (2015).

  13. 13.

    Scientific Advisory Board of the Icelandic Civil Protection. Factsheet-Bárðarbunga-20140906 (Icelandic Met Office, 2014);

  14. 14.

    et al. Factsheet-Bárðarbunga-20140823 (Icelandic Met Office, 2014);

  15. 15.

    et al. Strike-slip faulting during the 2014 Bárðarbunga-Holuhraun dike intrusion, central Iceland. Geophys. Res. Lett. 43, 1495–1503 (2016).

  16. 16.

    et al. Micrometre-scale deformation observations reveal fundamental controls on geological rifting. Sci. Rep. 6, 36676 (2016).

  17. 17.

    , , & Array analysis of the seismic wavefield of long-period events and volcanic tremor at Arenal volcano, Costa Rica. J. Geophys. Res. 119, 5536–5559 (2014).

  18. 18.

    High-resolution frequency-wavenumber spectrum analysis. Proc. IEEE 57, 1408–1418 (1969).

  19. 19.

    , , & Imaging the dynamics of magma propagation using radiated seismic intensity. Geophys. Res. Lett. 38, L04304 (2011).

  20. 20.

    , , & Persistent shallow background microseismicity on Hekla volcano, Iceland: A potential monitoring tool. J. Volcanol. Geotherm. Res. 289, 224–237 (2014).

  21. 21.

    , & Grundlagen der Technischen Thermodynamik (Springer, 2008).

  22. 22.

    et al. Gradual caldera collapse at Bárðarbunga volcano, Iceland, regulated by lateral magma outflow. Science 353, aaf8988 (2016).

  23. 23.

    , & Instability in flow through elastic conduits and volcanic tremor. J. Fluid Mech. 527, 353–377 (2005).

  24. 24.

    & Volcanoes beneath Vatnajökull, Iceland: evidence from radio echo-sounding, earthquakes and jökulhlaups. Jökull 40, 147–168 (1990).

  25. 25.

    & Seismic crustal structure in Iceland and surrounding area. Tectonophysics 189, 1–17 (1991).

  26. 26.

    , & Characteristics of seismic waves composing Hawaiian volcanic tremor and gas-piston events observed by a near-source array. J. Geophys. Res. 96, 6199 (1991).

  27. 27.

    , , & Shallow structure of Mt Vesuvius volcano, Italy, from seismic array analysis. Geophys. Res. Lett. 24, 481–484 (1997).

  28. 28.

    & Seismological evidence for lateral magma intrusion during the July 1978 deflation of the Krafla Volcano in NE-Iceland. J. Geophys. 47, 160–165 (1980).

  29. 29.

    et al. Comparison of dike intrusions in an incipient seafloor-spreading segment in Afar, Ethiopia: seismicity perspectives. J. Geophys. Res. 116, 2156–2202 (2011).

  30. 30.

    , & Tectonic stress and magma chamber size as controls on dike propagation: constraints from the 1975-1984 Krafla rifting episode. J. Geophys. Res. 111, B12404 (2006).

  31. 31.

    & Deep volcanic tremor and magma ascent mechanism under Kilauea, Hawaii. J. Geophys. Res. 86, 7095–7109 (1981).

  32. 32.

    , & Source mechanicm of volcanic tremor. J. Geophys. Res. 87, 8675–8683 (1982).

  33. 33.

    Multiple emitter location and signal parameter estimation. IEEE Trans. Antennas Propag. AP-34, 276–280 (1986).

  34. 34.

    & Array analysis of seismic signals. Geophys. Res. Lett. 14, 13–16 (1987).

  35. 35.

    , , & Observations of Loma Prieta aftershocks from a dense array in Sunnyvale, California. Bull. Seismol. Soc. Am. 81, 1900–1922 (1991).

  36. 36.

    , & Observations of high-frequency scattered waves using dense arrays at Teide volcano. Bull. Seismol. Soc. Am. 87, 1637–1647 (1997).

  37. 37.

    & A probabilistic approach to the inversion of data from a seismic array and its application to volcanic signals. Geophys. J. Int. 143, 249–261 (2000).

  38. 38.

    & Array seismology: methods and applications. Rev. Geophys. 40, RG000100 (2002).

  39. 39.

    et al. ObsPy: a python toolbox for seismology. Seismol. Res. Lett. 81, 530–533 (2010).

  40. 40.

    , , , & ObsPy—what can it do for data centers and observatories? Ann. Geophys. 54, 47–58 (2011).

  41. 41.

    et al. Testing small-aperture array analysis on well-located earthquakes, and application to the location of deep tremor. Bull. Seismol. Soc. Am. 98, 620–635 (2008).

  42. 42.

    et al. A double seismic antenna experiment at Teide volcano: existence of local seismicity and lack of evidences of volcanic tremor. J. Volcanol. Geotherm. Res. 103, 439–462 (2000).

  43. 43.

    et al. Broadband seismic monitoring of active volcanoes using deterministic and stochastic approaches. J. Geophys. Res. 115, 2156–2202 (2010).

  44. 44.

    & Location of seismic events and eruptive fissures on the Piton de la Fournaise volcano using seismic amplitudes. J. Geophys. Res. 108, 2364 (2003).

  45. 45.

    Surface and bedrock topography of ice caps in Iceland, mapped by radio echo-sounding. Ann. Glaciol. 8, 11–18 (1986).

  46. 46.

    , & Spectral-element and adjoint methods in seismology. Commun. Comput. Phys. 3, 1–32 (2008).

  47. 47.

    et al. Dense seismic network provides new insight into the 2007 Upptyppingar dyke intrusion. Jökull 60, 47–66 (2010).

  48. 48.

    , , & Tomographic image of melt storage beneath Askja Volcano, Iceland using local microseismicity. Geophys. Res. Lett. 40, 5040–5046 (2013).

  49. 49.

    , , & Compressional and shear velocity structure of the lithosphere in Northern Iceland. Bull. Seismol. Soc. Am. 88, 1561–1571 (1998).

  50. 50.

    Seismic refraction investigation of the basalt lavas in northern and eastern Iceland. Jökull 13, 40–60 (1963).

  51. 51.

    , , & Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile. Geophys. J. Int. 135, 1131–1149 (1998).

  52. 52.

    , & Formation velocity and density—the diagnostic basics for statigraphic traps. Geophysics 39, 770–780 (1974).

  53. 53.

    The temperature dependence of seismic waves in ice. J. Glaciol. 13, 144–147 (1974).

  54. 54.

    Seismic-wave velocities in anisotropic ice: a comparison of measured and calculated values in and around the deep drill hole at Byrd Station, Antarctica. J. Geophys. Res. 77, 4406–4420 (1972).

  55. 55.

    Seismic Investigation of Ice Properties and Bedrock Topography at the Confluence of Two Glaciers, Kaskawulsh Glacier, Yukon Territory, Canada. Technical Report, Institute of Polar Studies Report No. 27 (Institute of Polar Studies, The Ohio State University, 1968).

  56. 56.

    , , , & Structure of the Grímsvötn central volcano under the Vatnajökull icecap, Iceland. Geophys. J. Int. 168, 863–876 (2007).

  57. 57.

    The Grímsvötn caldera, Vatnajökull: subglacial topography and structure of caldera infill. Jökull 39, 1–20 (1989).

  58. 58.

    & Ultrasonic velocity investigations of crystal anisotropy in deep ice cores from Antarctica. J. Geophys. Res. 84, 4865–4874 (1979).

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Acknowledgements

The data were collected and analysed within the framework of FutureVolc, which has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement no. 308377. The Geological Survey of Ireland (GSI) provided additional financial support for field work. We thank B. H. Bergsson and H. Buxel for technical support, and M. H. Steinarsson and A. Braiden for support in the field. We are grateful to J. Almendros for helpful discussions and comments.

Author information

Author notes

    • Eva P. S. Eibl
    • , Christopher J. Bean
    • , Yingzi Ying
    •  & Martin Möllhoff

    Present address: Geophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland.

Affiliations

  1. School of Earth Sciences, University College Dublin, Belfield, Dublin 4, Ireland

    • Eva P. S. Eibl
    • , Christopher J. Bean
    • , Yingzi Ying
    • , Ivan Lokmer
    •  & Martin Möllhoff
  2. Icelandic Meteorological Office, Bústaðavegi 7–9, 108 Reykjavík, Iceland

    • Kristín S. Vogfjörd
  3. Tullow Oil, Leopardstown, Dublin 18, Ireland

    • Gareth S. O’Brien
  4. Institute of Earth Sciences, University of Iceland, Askja, Building of Natural Sciences, Sturlugata 7, 101 Reykjavík, Iceland

    • Finnur Pálsson

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Contributions

E.P.S.E., C.J.B. and M.M. participated in instrument installation and data collection from seismometers in Iceland and analysing the data. E.P.S.E carried out processing including amplitude locations, array locations and tremor simulations. K.S.V. relocated earthquakes in the dyke and participated with E.P.S.E., C.J.B. and I.L. in the interpretation of the results. Numerical wavefield simulations were performed by Y.Y. on the basis of the topography provided by F.P. G.S.O’B. performed tremor simulations due to magma flow. All authors contributed to the preparation of the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Eva P. S. Eibl.

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