Shear-wave splitting observations across southwest Ireland

Shear-wave splitting analyses have been carried out on teleseismic data from the southwest of Ireland acquired during the Irish Seismological Lithospheric Experiment (ISLE). The data were gathered over a ten-month period by a temporary network of 23 broadband and short-period stations. The results are compared with data from two permanent broadband seismic stations, which have recorded SKS and SKKS phases for up to 10 years. The purpose of the experiment was to investigate possible anisotropy within the crust and mantle related to Caledonian deformation. Here we report splitting results which show an average delay time of 1.2 s and a variation of fast-polarisation direction with back azimuth that surprisingly suggests a much deeper origin for anisotropy than was anticipated.