Holocene movements and state of stress in the rhinegraben rift system

Abstract

(Accepted for publication May 22, 1978) ABSTRACT: Illies, J.H. and Greiner, G., 1979. Holocene movements and state of stress in the Rhinegraben rift system. In: C.A. Whitten, R. Green and B.K. Meade (Editors), Recent Crustal Movements, 1977. Tectonophysics, 52: 349-359. A belt of seismotectonic activity and Holocene crustal deformations traverses Western Europe and forms a 800-km-long subplate boundary. The main segments are the Rhinegraben, the seismic zone straight through the Rhenish massif, the Lower Rhine embayment, and the Zuider Zee depression (The Netherlands). Seismicity and Holocene fault action of the Rhinegraben are controlled by a sinistral shear motion parallel to the graben axis. Accompanying this simple shear motion there are also extension shear, compression shear, and Riedel shear. Extensional tectonics characterize the faulting in the Rhenish massif and the rifting in the Lower Rhine embayment. In-situ stress data, obtained by using the strain relief technique, confirm principal stress directions, approximately equal to those obtained by fault plane solutions of earthquakes. The calculation of excess stress revealed very high stresses in the Central Alps, whereas minimal to negative values were found in the Rhinegraben and other zones of seismic activity. Stress generation in the area of the Central Alps corresponds with strain release along the rift system which traverses the foreland. The Upper Cretaceous to end-Miocene process of Alpine plate convergence and folding has been replaced since Pliocene times by epeirogenic uplift and consequent denudation of the mountain range. We assume that the observed state of stress is mainly caused by a sideways extension of the mountain body due to the effects of unloading and topography.