Co-seismic ruptures and deformations recorded by speleothems in the epicentral zone of the Basel earthquake

The study of growth anomalies of speleothems in a karstic environment can p rovide potential evidence for palaeoearthquakes. These data are used to stu dy the recurrence times of major earthquakes in areas where evidence for hi storic seismicity is lacking. A study has been carried out in the epicentra l area of the 1356 Basel earthquake (epicentral intensity = VII-VIII, macro seismic magnitude = 6.2). The Battler loch and Dieboldslochli caves, situat ed in the area of greatest damage, show growth anomalies of speleothems pos sibly related to a seismic event (several breaks of speleothems and offsets of the axis of the regrowths). The first U/Th disequilibrium measurements by alpha spectrometry show recent ages (less than several tens of thousands of years and probably historic). C-14 dating by AMS of carbonate laminatio ns taken on both sides of the anomalies confirm the evidence of a seismic e vent around 1300 AD. More accurate datings by U/Th TIMS are carried our in order to compare the information provided by the two different dating metho ds. (C) Elsevier, Paris.