Strike-slip faulting during the 2014 Bároarbunga-Holuhraun dike intrusion, central Iceland

Abstract

Over a 13 day period magma propagated laterally from the subglacial Bároarbunga volcano in the northern rift zone, Iceland. It created > 30,000 earthquakes at 5-7 km depth along a 48 km path before erupting on 29 August 2014. The seismicity, which tracked the dike propagation, advanced in short bursts at 0.3-4.7 km/h separated by pauses of up to 81 h. During each surge forward, seismicity behind the dike tip dropped. Moment tensor solutions from the leading edge show exclusively left-lateral strike-slip faulting subparallel to the advancing dike tip, releasing accumulated strain deficit in the brittle layer of the rift zone. Behind the leading edge, both left- and right-lateral strike-slip earthquakes are observed. The lack of non-double-couple earthquakes implies that the dike opening was aseismic.