VARNET-96: three-dimensional upper crustal velocity structure of SW Ireland

Abstract

SUMMARY During the VARNET‐96 seismic experiment three seismic refraction/wide‐angle reflection profiles were acquired in order to examine the crustal structure in the southwest of Ireland. A total of 170 seismic stations were used on 300 recording sites. The shotpoint geometry was designed to allow for inline and offline fan shot recordings on the three profiles, using a total of 34 shots. Results from 3‐D ray‐trace and inversion modelling illustrate the pervasive lateral heterogeneity of the crust south of the Shannon Estuary. About 5 km of interpreted Palaeozoic sediment at the south coast was associated with the sedimentary infill of the Munster and South Munster Basins. This sedimentary layer, which thins to approximately 2 km in the northern Munster Basin, is significantly thinner than previously estimated from geological field studies. High‐velocity zones beneath Dingle Bay and the Kenmare River region may be associated with the deep traces of the Killarney–Mallow Fault Zone and the Cork–Kenmare line. A zone of high‐velocity upper crust (6.4–6.6 km s−1) beneath the South Munster Basin is found in the area between the Kenmare–Killarney and the Leinster Granite gravity lows. The depth to the Moho varies from approximately 28–29 km at the south coast to approximately 32–33 km in the Dingle–Shannon Basin. The interpretation of the 2‐D and 3‐D velocity models suggests that Variscan deformation is confined to sedimentary and upper crustal structures in the southwest of Ireland.

Crustal thinning, mantle exhumation and serpentinization in the Porcupine Basin, offshore Ireland: evidence from wide-angle seismic data

“…The construction of the initial model used a priori geophysical and geological knowledge about the regional P-wave velocity structure built up from both past marine seismic experiments in the Porcupine Basin region (Whitmarsh et al 1974;Makris et al 1988;O'Reilly et al 1996;Morewood et al 2005) and recent onshore wideangle seismic experiments in SW Ireland along the Irish Atlantic seaboard (Landes et al 2003). These earlier results were used to define the deeper crustal structure at the eastern and western extremities of the model, towards the Celtic Sea Platform and the Porcupine High, respectively.…”

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

“…The Irish continental shelf and many of the basins therein have been the focus of seismic reflection, seismic refraction and potential field investigations for several decades (Holder & Bott 1971;Whitmarsh et al 1974;Bunch 1979;Jacob et al 1985;Makris et al 1988;Roberts et al 1988;Lowe & Jacob 1989;O'Reilly et al 1991O'Reilly et al , 1995O'Reilly et al , 2010Vogt et al 1998;Landes et al 2000Landes et al , 2003Morewood et al 2005;Hauser et al 2008). Coupled with sparse well control, the resulting studies have allowed for the piecing together of the detailed tectonostratigraphic basin evolution of the margin (Shannon 1991;Naylor & Shannon 2009.…”

Inversion of travel times obtained during active seismic refraction experiments CELEBRATION 2000, ALP 2002 and SUDETES 2003

“…This method is a well known procedure for statisticians (Press et al, 1992), and it is also frequently used in inverse problems similar to our problem (e.g. Landes et al, 2003). Let the optimum model obtained by solving Eq.…”