Seismological studies of the evolution of young plate margins and associated basins

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The top 100-200 km of the solid Earth consists of a small number of (more or less) rigid 'plates', which move around Earth's surface driven by convection in the deep mantle below. Deformation and volcanism occur at plate boundaries, where adjacent plates converge, diverge or slide past one another. My research is focussed on processes at modern divergent and convergent plate boundaries. Plates diverge by continental rifting and then seafloor spreading. The rifting affects a region which may be quite wide and, in some cases, 'failed' rift basins, which do not progress to ocean opening, are left stranded on the continental shelves. In the North Atlantic there are several failed rift basins (Jeanne d'Arc, North Sea, Rockall, Porcupine) some of which are petroliferous. So, the plates are NOT rigid, especially close to their margins, and we need to account for the within-plate extensional deformation. We will estimate the variation of extension with time from faults and crustal thinning, determined from seismic images and other data, in a North Atlantic Plate Reconstruction Project using a novel deformable plate model. The results bear on fundamental Earth processes and on the prospects for finding oil and gas in the basins. Plates converge along volcanic arcs. Where arcs join, a tear in the lower, descending ('subducting') plate may produce an offset of the two arcs along a 'Subduction Transform Edge Propagator' (STEP) fault. In the eastern Mediterranean, the Hellenic arc is increasingly offset to the south of the Cyprus arc, because of the southerly 'rollback' of subduction of the lower African plate below the Hellenic arc. The causative tear in the subducting plate is responsible for a wide STEP fault zone at the junction with the Cyprus arc. The fault zone has very deep basins (Rhodes and Finike basins) and high seamounts (Anaximander) all actively deforming. My research is to make, and interpret, images of the deformation from seismic profiling. The results will aid understanding of (i) the tectonic processes associated with tearing plates, and (ii) earthquake hazards in the region.