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Abstract

This paper reviews the complex crustal and upper-mantle seismic velocity structure of Ireland and surrounding seas. Data from 11 seismic refraction profiles reveal that onshore Ireland mean crustal velocities range between 6.25 and 6.5 km s(-1) with crustal thickness of 28.5-32 km. Superimposed on a three-layer crust, the sedimentary layer has a thickness of approximately 6-8 km at the southern coastline, but only 3-4 km in the vicinity of the Shannon Estuary in western Ireland. The lateral heterogeneity of the upper-crustal layer is pervasive throughout Ireland, with velocities of 5.7-6.2 km s(-1) and a layer thickness of 3-10 km. A low-velocity zone is found in the south-east which is interpreted as the buried south-western extension of the Leinster Granite. The mid-crustal layer (6.3-6.7 km s(-1)) is between 8 and 16 km thick. Significant changes occur in the vicinity of the Shannon Estuary, around the location of the Iapetus Suture Zone. The lower crust is fairly uniform with velocities of 6.8-7.2 km s(-1) and a thickness of approximately 8-10 km except towards the south of Ireland where the Moho appears as a transition zone. Offshore Ireland, a two-layer crust with a thickness of 24-26 km beneath the North Celtic Sea Basin and only 14-15 km beneath the Rockall Trough prevails.