Evidence for a Medieval-Earthquake with Damaging Effects on Buildings from Late Antiquity in Cologne, Germany
by
Klaus-G. Hinzen
Dep. Earthquake Geology, Cologne University, Germany
Coauthors: Schütte, Sven (Kölnisches Stadtmuseum, Cologne, Germany)

The city of Cologne, Germany has ca. 2000 years of building history. Some well-preserved remains of structures from the late Roman period (4th century AD) show severe building damage. The Praetorium, seat of the Roman administration and palace, was located on the banks of a former side arm of the Rhine River. The massive foundation walls of this ca. 95 x 30 m building show partial subsidence of more than 20 cm. Foundation walls of the central octagonal part of the building show severe cracks and are tilted towards the east by up to 7°. Until now this damage has been attributed to settlement of the foundation soil. Lack of any traces of attempted repairs and written sources which document use of the building for a long time after the end of the Roman Empire favor a sudden onset of damage over a gradual process.

Engineering seismological data from the area surrounding the Praetorium supports the possibility of dynamic settlement and/or liquefaction in the event of a proper earthquake loading. The earthquake catalogs for central Europe do not list any events with large enough destruction potential to explain the observations. However the 1992 Roermond earthquake (magnitude 5.4) showed that secondary earthquake effects on the riverbanks within the Lower Rhine Embayment are possible. It is estimated that a magnitude 5.8 earthquake on the active fault system closest to the Praetorium site could have produced the observed damage. After more than 300 years of use the late antique building was completely dismantled.

Date received: February 27, 2002