Seismic Investigations in the North Sea, 1 and 2

Gravity measurements indicate that the post-Hercynian basins in the North Sea area are in isostatic equilibrium. This means that most probably the crust underwent a considerable thinning since the Permian. Part 1 describes the seismic programme that is carried out to investigate some aspects of this problem. Part 2 gives the results of a series of five reverse refraction lines to cover the surface structure of a crustal refraction line shot east of Flamborough Head. In a following part the results of this latter line will be discussed and of other seismic investigations in this programme.