Indication of high pore-fluid pressures in a seismically-active fault zone

Crampin Stuart, Theodora Volti, Sebastien Chastin, Agust Gudmundsson, Ragnar Stefánsson

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119 Citations (Scopus)


Polarisations of seismic shear-wave splitting observed above small earthquakes in Iceland are typically approximately NE to SW, parallel to the direction of maximum horizontal stress. In contrast, the polarisations of shear-waves at three new stations sited over the Húsavík–Flatey Fault, a major seismically-active transform fault in northern Iceland, are approximately NW to SE, orthogonal to the stress-aligned polarisations elsewhere. Modelling suggests that these 90°-flips in polarisations are caused by propagation through cracks containing fluids at high pore-fluid pressures within one or two MPa of the critical stress. These observations suggest that high pore-fluid pressures, which play a key role in earthquake source mechanisms, can be monitored by analysing shear-wave splitting above seismically-active fault planes.
Original languageEnglish
Pages (from-to)F1 - F5
Number of pages5
JournalGeophysical Journal International
Issue number2
Publication statusPublished - 1 Nov 2002


  • 90°-flips
  • earthquakes
  • fault planes
  • high pressures
  • shear-wave splitting


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