CRUSTAL STRUCTURE BENEATH RHINEGRABEN FROM SEISMIC REFRACTION AND REFLECTION MEASUREMENTS

A model of the crustal structures beneath the Rhinegraben rift system has been derived based on results of seismic refraction and reflection measurements. Observations along two lines parallel to the strike of the graben and along two overlapping profiles traversing the rift normal to its axis provided the necessary data. They were supplemented by results of deep seismic reflection experiments carried out within the graben and in its adjacent regions. Important findings are the existence of two velocity inversions within the crust and of a characteristic rift cushion" with a compressional velocity of 7.6-7.7 km/sec and of a correspondingly high shear velocity. This body is considered to be the driving mechanism of the rifting process. Immediately below the pronounced low-velocity channel in the upper crust an intermediate layer with lamellar structure and of presumably basic composition has been found. The most conspicuous feature of the crustal cross-section is its asymmetry. It seems as if the rifting process must have started at the eastern margin of the graben. Complete bilateral symmetry of the structure has not yet been achieved. © 1969."