1822 earthquake-triggered homogenite in Lake Le Bourget (NW Alps)


E. Chapron Laboratoire de Géodynamique des Chaînes Alpines, Université de Savoie, Campus scientifique Savoie-Technolac, F-73376 Le Bourget du Lac Cedex, France. Tel.: + 33/4 79758102; Fax: + 33/4 79758777; E-mail: emmanuel.chapron@univ-savoie.fr


High-resolution textural signatures of an earthquake-induced historical ‘homogenite’ layer are presented, as well as its 3D distribution. This homogeneous deposit is correlated with the AD 1822 event (VII–VIII MSK intensity), the main historical earthquake of the French outer Alps, using 210Pb dating and historical chronicles. During this earthquake a violent lake water oscillation was reported (seiche effect). In the present study we discuss the influence of lake water oscillations during earthquake-induced subaqueous slide, through a pluridisciplinary analysis of subbottom sediments including high-resolution seismic, sidescan sonar and short gravity coring.