Late Quaternary tectonic evolution and postseismic near surface fault displacements along the Geleen Fault (Feldbiss Fault Zone–Roer Valley Rift System, the Netherlands), based on trenching

Abstract

AbstractIn northwest Europe the pattern of earthquake distribution is correlated with known Quaternary faults. Excavation of fault scarps revealed that these fault zones have been active during the Late Pleistocene. In this paper we present the results of an exploratory trenching study across the Geleen Fault, part of the Feldbiss Fault Zone, the Netherlands. Middle Saalian fluvial deposits of the Meuse, overlain by local slope deposits, were excavated. The Geleen Fault has displaced the fluvial deposits by at least 5 meters. The upper layers of local slope deposits could be correlated across the fault and were all dated at approximately 15 ka B.P. This gives the opportunity to reconstruct the sequence of events that occurred about 15 ka ago. Liquefactions provide evidence for an earthquake event. However, the main offset along the Geleen Fault is not stratigraphically related to the liquefactions. The liquefactions and the fault offset are stratigraphically separated by a period of erosion. We therefore propose a sequence of events starting with an earthquake accompanied by liquefaction, followed by a period of postseismic displacement with high rates compared to the long-term average. After this period normal displacement rates occurred, comparable to the long-term average. The duration of the period of high displacement rates could not be determined.