Speaker
Dr
Sophie Verheyden
(Royal Belgian Institute of Natural Sciences -Geopark Famenne-Ardenne- VUB - BELSPO)
Description
The two most recent collapses in the Han-sur-Lesse Cave (Belgian Ardenne), more precisely in the Dôme room, occurred on or shortly after 3rd December 1828 and between the 13th and 14th of March 1984. These collapses were directly observed by cave guides and occurred less than a year after the
23rd February 1828 (Mw =5.1 in Central Belgium) and 8th November 1983 (Mw=4.8 in Liège) earthquakes, which are the two earthquakes that generated the strongest ground motions in Han-sur-Lesse since 1800. Our study demonstrates the low probability that these occurrences are coincidental and therefore suggest a a causal link between earthquakes and successive collapses in the Han-sur-Lesse cave.
Lamina counting of a stalagmite growing on the 1828 debris dates the collapse at 1826 ±9 CE, demonstrating the possibility of dating previous collapses with a few years of uncertainty. Radiometric dating techniques such as U/Th opens the possibility to date older collapses and gain some insights in potential seismic periodicities where other indications are totally absent. Our study opens the debate whether collapse activation is an on-going process in the evolution of karstic networks related to the weakening of cave vaults. We suggest that earthquake activity could play a stronger role than previously thought in initiating cave collapses.
Primary author
Dr
Sophie Verheyden
(Royal Belgian Institute of Natural Sciences -Geopark Famenne-Ardenne- VUB - BELSPO)
Co-authors
Ms
Elisabeth Knuts
(ROB)
Dr
Kris Vanneste
(Royal Observatory of Belgium)
Serge Delaby
(Geopark Famenne Ardenne)
Dr
Thierry Camelbeeck
(Royal Observatory of Belgium)
Prof.
Yves Quinif
(Université de Mons)
