Changes in shear-wave splitting at the 2014 Bárðarbunga seismic crisis and dyke intrusion in Iceland compared with earthquakes and other eruptions

Abstract

We use shear-wave splitting (SWS) above small earthquakes to monitor stress-variations before the 2014 Bárðarbunga seismic crisis and dyke intrusion in central Iceland. SWS is sensitive to stress-induced variations in the internal geometry of the distributions of stress-aligned fluid-saturated microcracks pervading almost all crustal rocks. This allows stress-accumulation before both impending earthquakes and impending volcanic eruptions to be monitored and potentially the events stress-forecast. We compare the behaviour of SWS before Bárðarbunga with the behaviour before large earthquakes and other volcanic episodes where SWS has been monitored. On the basis of the duration of stress-changes, we classify volcanic episodes into three broad classes. During analysis of SWS before Bárðarbunga, temporal variation in polarizations and another retrospective stress-forecast earthquake were recognized.