Fluidization and Liquefaction Structures in North-West Germany Caused by Weichselian Late Glacial Seismicity

Abstract

A wide range of soft sediment deformation structures occurs in Weichselian Late Pleniglacial to Late Glacial alluvial fan and aeolian sand sheet sediments of the Upper Senne, located south of the North German Lowlands on the southern slope of the Teutoburger Wald Mountains. The soft sediment deformation includes sand blows, fluid escape pipes, dish structures, flame structures and ball- and pillow-structures. The main driving mechanisms for the soft sediment deformation structures were seismic shock waves that led to changes in the pore-pressure causing vertical water escape. This interpretation is supported by the presence of, characteristic sand blows, and the nearby Osning Thrust. The earthquakes were generated along the Osning Thrust, which is one of the major faults in Central Europe. It is the first time in northern Germany, that fluidization and liquefaction features can be directly related to a fault. The occurrence of repeated seismicity in the Late Pleniglacial /Late Glacial and in the 17th century indicates ongoing crustal movements along the Osning Thrust and sheds new light on the seismic activity of northern Germany.