Rockfalls triggered by the AD 1356 Basle earthquake
by
Arnfried Becker
Institut für Geophysik, ETH Zürich, CH-8092 Zürich
Coauthors: C.A. Davenport (School of Environmental Sciences, University of East Anglia, Norwich NR4 7TG, U.K), D. Giardini (Institut für Geophysik, ETH Zürich, CH-8092 Zürich)

The AD 1356 Basle earthquake is the strongest earthquake known from historical and archaeological records for the region north of the Alps. With its epicentral intensity MSK IX (possibly X) it is responsible for the damage of the cities of Basle and Liestal and many castles in the region. The epicentre lies south of Basle, as indicated by the levels of damage to castles in the area around Aesch where the Folded Jura Mountains and the Upper Rhine Graben meet. Recent investigations of geologically young displacements on a north-south trending fault forming a scarp near Reinach, between Basle and Aesch, has been envisaged as the source of the AD 1356 Basle earthquake and three older events. The amount of displacement seen in trench excavations across the fault indicates a minimum magnitude of M=6.2 for the Basle earthquake. This earthquake should have triggered local mass movements, particularly rockfalls on the steep craggy limestone slopes of the Jura valleys. However, the expected rock falls are not reported in the historical records. Systematic mapping of the distribution of blocks, both in the cliff faces and in the debris fields, indicates that some rock falls may have been triggered simultaneously during an earthquake. The radiocarbon ages for samples of organic material from beneath a number of such blocks provide dates of fall close to the 1356 earthquake. Continuing research is expected to provide evidence of earlier rockfalls which may have been caused by unrecorded ancient earthquakes.

Date received: March 5, 2002

Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caiq-50.