Speaker
Dr
Hervé Jomard
(IRSN)
Description
The north-western Alps foreland (Jura Mountains) is considered as still experiencing distal effects of the Alpine collision, resulting in a moderate but significant seismicity. This study focuses on the Culoz strike slip fault, developing from the Jura Mountains to the West, to the Chautagne swamp and through Lake Le Bourget to the East. Because erosion and anthropogenic activities erased most of the potential geological markers of quaternary deformations on land, we used high resolution seismic imaging to detect and characterize active faulting in the Quaternary sediments of the Bourget post-glacial Lake. The well-stratified character of the lake infill is locally disturbed by tectonic deformations associated with the activity of the left lateral Culoz fault as well as gravity reworking. Taking into account the age of the sediments (based on core samples), a quantification of the observed deformations together with the analysis of a well preserved outcrop on land, attest for fault slip-rates ranging from 0.055 to 3.11 mm/yr, the latter being surprisingly high in comparison with what we know elsewhere in France. A comparison with core-drills obtained in the neighboring lakes (Beck, 2009) allows us to envisage a non-stable seismic activity along the fault through time, and to propose a dominant control of the deglaciation on the observed fault slip-rates.
Primary author
Dr
Hervé Jomard
(IRSN)
Co-authors
Dr
Camille De La Taille
(IRSN)
Dr
Christian Beck
(USMB - Isterre)
Dr
Christian Crouzet
(USMB - Isterre)
Dr
François Jouanne
(USMB - Isterre)
