The Roman Eifel Aqueduct: archaeoseismological evidence for neotectonic movement at the transition of the Eifel to the Lower Rhine Embayment

Abstract

The Lower Rhine Embayment and adjacent areas are characterised by neotectonic deformation resulting in differential crustal movement. Slip rates along the fault systems are very low (< 0.1 mm/a). Significant earthquakes are known to have occurred in the past but the faulting behaviour is not adequately known which hampers the risks assessment. We analysed the archaeological record of the largest Roman aqueduct north of the Alps. This so called Eifel Aqueduct is 95.4 km long, has its source in the Eifel mountains and supplied the ancient city of Cologne with calcareous fresh water. The aqueduct crosses major faults of the Lower Rhine Embayment perpendicular. Analyses of the aqueduct´s gradient gives weak evidence for creep along the Kirspenich Fault resulting in differential movement of hanging and foot wall in the order of a few centimetres. Vertical offsets of 15 and 35 cm are documented exactly where the aqueduct crosses the Holzheim Fault system close to the city of Mechernich. Here, also structural damage of the aqueduct is recorded and archaeological evidence exists for repair works on the aqueduct. We interpret these observations as well as the construction of a 4 km long deviation as necessary measures to keep the aqueduct operational after earthquake damage. The timing of the event falls within the period of aqueduct operation which is reconstructed to be between 80 ± 10 and 270 ± 10 CE. Supporting evidence for earthquake activity within this period is seen in the roof collapse of the nearby Kakus cave.