Palaeoseismic investigations in Belgian caves

Abstract

In some karstic caves, the observation of numerous broken stalagmites may provide potential secondary evidence for intense palaeoearthquakes during recent past times. We have named these morpho-sedimentologic features seismothems. A methodology has been developed to discriminate broken speleothems due to earthquake-induced effects or caused by other mechanisms. A study has been carried out in the Belgian karst areas. In the Vesdre Valley, it seems difficult to find evidence of the well-known Verviers earthquake, probably the most destructive historical earthquake known in Belgium which occurred in 1692 AD. The most important concentration of broken stalagmites was discovered in the caves between Hotton and Han-sur-Lesse. The observations in the cave of Hotton suggest a seismic origin, the other origins can not be the cause of the speleothem break. This result implies a strong earthquake situated close to the cave. A preliminary AMS 14C age suggests a minimum age of 10100 ± 1200 cal 14C yr BP. for one stalagmite rupture in the Hotton cave.