S U M M A R YTeleseismic receiver functions have been calculated from data of a temporary seismological network of broad-band three-component stations to investigate the lithospheric and asthenospheric structure across the Late Caledonian Iapetus Suture Zone (ISZ) in southern Ireland. The stations were deployed during the Irish Seismological Lithospheric Experiment (ISLE 2002/3) and straddle the Killarney-Mallow Fault Zone, a remnant of the Variscan orogeny, and the ISZ, the inferred boundary between the Laurentia and Eastern Avalonia plates fused together during the Caledonian orogeny.Receiver functions from the western part of the network were projected onto the N-S VAR-NET 1996 seismic refraction profile, extending from the Old Head of Kinsale to Galway Bay in SW Ireland. Laterally continuous P to S conversions from the Moho at delay times of about 3.8-4.1 s are clearly observed, and correspond to Moho depths of about 29-32 km. The Moho has a transitional character to the south of the ISZ. Synthetic receiver functions, calculated from a 2-D velocity model of the previous VARNET experiment, show Moho conversions and multiple crustal phases compatible to those observed in the ISLE data. Furthermore, P to S conversions from the 660 km discontinuity (66-68 s delay time) are well determined at the stations. In comparison, the conversion from the 410 km discontinuity at about 43-45 s delay time is considerably weaker. Delay times of stacked receiver functions from the mantle transition zone are in agreement with the standard iasp91 earth model and thus no structural changes are observed across the ISZ at this depth interval.
The Irish Seismological Lithospheric Experiment (ISLE 2002) has been designed to investigate the deep lithospheric and asthenospheric structure across the late‐Caledonian Iapetus Suture Zone in southern Ireland. The project is a collaboration between the Dublin Institute for Advanced Studies (DIAS), Ireland, and the Geophysical Institute (GPI) of the University of Karlsruhe, Germany. This is the first passive teleseismic experiment conducted in Ireland, building upon a large body of earlier work on the crustal structure offshore and onshore Ireland, based on controlled source seismics and potential field studies.
[1] 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.
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