An Investigation of Seismic Tremor on Glacier Covered Volcanoes in Iceland

 

PhD Candidate: Eva P. S. Eibl

Supervisor: Christopher J. Bean

Funded by: European Union 7th Framework Programme (FutureVolc)

 

Abstract:

Volcanoes in Iceland pose threats to environment and society through eruptions but also persistent hydrothermal activity. Additionally, some – such as Bardarbunga volcano – are covered by ice which makes ash rich eruptions and floods caused by persistent or sudden melting of the ice more likely. Eruptions or floods affect different regions and populations, which makes it important to distinguish them as early as possible to e.g. evacuate appropriately.

In monitoring a variety of instruments are employed and analysed in real-time in order to detect and interpret changes of a volcano accordingly. But also detailed studies of e.g. seismic data can help to understand the source of a signal. The challenge is with seismic data that both magma and floods create long-lasting, emergent signals – so called tremor – that look similar in terms of easily accessible properties such as amplitude, duration or frequency. Additionally, source locations with traditional location methods are difficult due to the signal properties.

In this study clusters of seismometers (so called arrays) are used in order to get information about the direction and the horizontal slowness of the signal. The latter can be used – if the velocity model and the wave types are known – to deduce the depth of the source. Tremor recordings that are clearly associated with magma movements during the 2014/15 Bardarbunga eruption (Sigmundsson et al. 2015) and tremor recordings during floods are compared in order to find characteristics for different tremor sources and use this to interpret tremor pulses where the source is unknown.

Results of this study include that microseismicity (Eibl et al. 2014) as well as pre-eruptive tremor (Eibl et al. 2016 (in review)) might be a useful tool in eruption early-warning. Two studies on helicopter tremor highlight the differences to volcanic tremor (Eibl et al. 2015) and the possibility to locate a helicopter based on seismic recordings (Eibl et al. 2016 (submitted)). The appearance of pre-eruptive tremor (Eibl et al. 2016 (in review)), eruptive tremor (Eibl et al. in prep.) and flood related tremor (Eibl et al. 2016 (in prep.)) is also detailed.

 

References:

Eibl, E. P. S., Bean, C. J., Vogfjörð, K. S., Braiden, A. (2014) 'Persistent Shallow Background Microseismicity on Hekla Volcano, Iceland: A Potential Monitoring Tool'. Journal of Volcanology and Geothermal Research, 289: 224-237, DOI: 10.1016/j.jvolgeores.2014.11.004

Eibl, E. P. S., Bean, C. J., Vogfjörð, K. S., Ying, Y., Lokmer, I., Möllhoff, M., Palsson, F., (in review), (about pre-eruptive tremor during the Bárðarbunga eruption, Iceland), Nature Geoscience

Eibl, E. P. S., et al. in prep. (about tremor during the Skaftá jokulhlaup in October 2015)

Eibl, E. P. S., et al. in prep. for Earth and Planetary Science Letters (about eruptive tremor during the Bárðarbunga eruption, Iceland)

Eibl, E. P. S., Lokmer, I., Bean, C. J., Akerlie, E., (submitted), 'Helicopter Location and Tracking Using Seismometer Recordings', Geophysical Journal International

Eibl, E. P. S., Lokmer, I., Bean, C. J., Akerlie, E., Vogfjörð, K. S. (2015) ‘Helicopter vs. volcanic tremor: Characteristic features of seismic harmonic tremor on volcanoes’. Journal of Volcanology and Geothermal Research, 304:108-117, DOI: 10.1016/j.jvolgeores.2015.08.002

Sigmundsson, F., A. Hooper, S. Hreinsdóttir, K. Vogfjord, B. Ófeigsson, E. R. Heimisson, S. Dumont, M. Parks, K. Spaans, G. B. Guðmundsson, V. Drouin, Th. Árnadóttir, K. Jónsdóttir, M.T. Gudmundsson, Th. Högnadóttir, H. M. Friðriksdóttir, M. Hensch, P. Einarsson, E. Magnússon, S. Samsonov, B. Brandsdóttir, R. S. White, Th. Agustsdottir, T. Greenfield, R. G. Green, Á. R. Hjartardóttir, R. Pedersen, R. Bennett, Halldór Geirsson7, P. LaFemina, H. Björnsson, F. Pálsson, E. Sturkell, C. J. Bean, M. Möllhoff, A. Braiden, and E. P.S. Eibl, 2015. Segmented lateral dyke growth in a rifting event at Bárðarbunga volcanic system, Iceland, Nature 517, 191-195. doi: 10.1038/nature14111 (online December 15, 2014).