Gravity based studies within the “north Porcupine Basin” image deep-crustal structures

Abstract:

Free-air gravity data helps constrain the re-processing of long-offset streamer seismic reflection data gathered in the Porcupine Basin in 2013/2014. The re-processing of the data involved advanced broadband, de-multiple and de-noise processing with pre-stack-depth migration using a velocity model constructed with full waveform inversion and tomography methods. Satellite gravity data compares very favorably with the ship borne data gathered during the seismic acquisition and is used to constrain the velocity and mass density of the basement and lower crust, where the seismic constraints are poor or absent. A forward modelling approach to the gravity modelling was taken, using a proven interactive software package. Prior knowledge from previous geophysical and geological work was included to guide the exercise and to reconcile the gravity and seismic information, within the frameworks of pre-existing knowledge. It also served to minimise the non-uniqueness inherent in the work. The results are very consistent with the available deep-crustal wide-angle-seismic crustal models, recently developed for the broad transition region for crustal stretching to hyper-extension, within the basin. They demonstrate the usefulness of the approach and the concepts behind it in understanding the tectonic extension of continental lithosphere. This project is funded by the Irish Petroleum Infrastructure Programme (PIP) and by the Irish Centre for Research in Applied Geosciences (iCRAG).