Open AccessIndication of high pore‐fluid pressures in a seismically‐active fault zone
Author(s) -
Crampin Stuart,
Gudmundsson Agust,
Stefánsson Ragnar
Publication year - 2002
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.2002.01830.x
Subject(s) - geology , seismology , shear (geology) , fluid pressure , active fault , fault (geology) , shear stress , seismic zone , shear wave splitting , seismic wave , pore water pressure , induced seismicity , geotechnical engineering , petrology , mechanics , physics
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.