LAUSR

Abstract This study reports on neotectonic deformation represented as faults, graben, and horst structures, which have been found in the uppermost 10 m of Quaternary sediments, consisting mainly of Saalian glaciofluvial and Weichselian periglacial material in northern Germany that is generally considered as a low-seismicity area. An area with up to 35 faults in a 60 m wide zone exhibits mainly extensional structures. Most of those are SE-NW-oriented and in some cases NE-SW. Soft sediment deformation structures include sand blows, blowout-related infill structures, and growth faults. Small-scaled, soft-sediment deformation structures are also found. Based on the large size of the sand blows and the widespread occurrence of small-scaled, soft-sediment deformation structures, the magnitude of the earthquakes is estimated in the order of M ≥ 5.5. Single faults exhibit a displacement of a few metres. Because some faults are overlain by unfaulted sandur sediments the system has been active over at least ~200 ka (Saalian). Several faults extend through the Weichselian periglacial layer to the present ground surface, proving ongoing deformation during the Weichselian Lateglacial and/or the Holocene. This major activity during the Saalian and the Weichselian points to the activation of old tectonic structures. A possible process can be the glacial loading and unloading associated with the isostatic rebound. Holocene and late Holocene seismic events are shown by the penetration of the Weichselian-Lateglacial periglacial layer by faults and sand blows as well as a possible blowout-related bowl with organic material and corresponding young 14C dates of