Indication of high pore-fluid pressures in a seismically-active fault zone
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 sei...
| Published in: | Geophysical Journal International |
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| Main Authors: | , , , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
2002
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| Subjects: | |
| Online Access: | http://gji.oxfordjournals.org/cgi/content/short/151/2/F1 https://doi.org/10.1046/j.1365-246X.2002.01830.x |
| Summary: | 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. |
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