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

Author(s)
Eibl, Eva P. S.  
Bean, Christopher J.  
Vogfjörð, Kristín  
Ying, Yingzi  
Lokmer, Ivan  
Möllhoff, Martin  
O'Brien, G. S.  
Pálsson, Finur  
Uri
http://hdl.handle.net/10197/8740
Date Issued
2017-04
Date Available
2017-09-06T01:00:12Z
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 Q.1 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 therelationships 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. 
Sponsorship
European Commission - Seventh Framework Programme (FP7)
Other Sponsorship
Geological Survey of Ireland
Type of Material
Journal Article
Publisher
Nature
Journal
Nature Geoscience
Volume
10
Start Page
299
End Page
304
Subjects

Earthquakes

Dyke propagation

Tremor models

Magma flow

DOI
10.1038/NGEO2906
Language
English
Status of Item
Peer reviewed
This item is made available under a Creative Commons License
https://creativecommons.org/licenses/by-nc-nd/3.0/ie/
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Owning collection
Earth Sciences Research Collection

Item descriptive metadata is released under a CC-0 (public domain) license: https://creativecommons.org/public-domain/cc0/.
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