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Seismograms from local earthquakes recorded on Milos have been analysed for shear-wave splitting diagnostic of seismic anisotropy. Complex P and shear wavetrains indicated the presence of much heterogeneity, but shear-wave splitting was identified in most shear-wave arrivals within the shear-wave window. The polarisations of the leading shear-waves show alignments which in general are consistent at each station and at groups of stations, suggesting the presence of vertical cracks aligned approximately north-south along the propagation paths. This suggests that the local maximum compressional stress is also north-south. This crack distribution probably exists within 5km of the surface, since the earthquake mechanisms (at focal depths from 5 to 11km) do not appear to be controlled by a north-south stress.

Additional information

Authors: BOOTH D C, British Geological Survey, Edinburgh (GB);SCHLEPER S, British Geological Survey, Edinburgh (GB);CRAMPIN S, British Geological Survey, Edinburgh (GB);OCHMANN N, British Geological Survey, Edinburgh (GB);WOHLENBERG J, British Geological Survey, Edinburgh (GB)
Bibliographic Reference: EUR 12131 EN (1990) 43 pp., MF, ECU 4
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