A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps
Bruno Wilhelm1, Hendrik Vogel2, and Flavio S. Anselmetti21University Grenoble Alpes, CNRS, IRD, Institut des Géosciences et de l'Environnement, F-38000 Grenoble, France 2Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern, Switzerland
Received: 08 Nov 2016 – Accepted for review: 21 Nov 2016 – Discussion started: 21 Nov 2016
Abstract. Mediterranean Alpine populations are particularly exposed to natural hazards like floods and earthquakes because of both the close Mediterranean humidity source and the seismically active Alpine region. Knowledge of long-term variability in flood and earthquake occurrences is of high value since it can be useful to improve risk assessment and mitigation. In this context, we explore the potential of a lake-sediment sequence from Lago Inferiore de Laures in Valle d'Aosta (Northern Italy) as a long-term record of past floods and earthquakes. The high-resolution sedimentological study revealed 77 event layers over the last ca. 270 years; 8 are interpreted as most probably induced by earthquakes and 68 by flood events. Comparison to historical seismic data suggests that the recorded earthquakes are strong (epicentral MSK intensity of VI–IX) and/or close to the lake (distance of 25–120 km). Compared to other lake-sediment sequences, Lago Inferiore de Laures sediments appear to be regionally the most sensitive to earthquake shaking, offering a great potential to reconstruct the past regional seismicity further back in time. Comparison to historical and palaeoflood records suggests that the flood signal reconstructed from Lago Inferiore de Laures sediments well represents the regional and (multi-)decennial variability of summer–autumn floods, in connection to Mediterranean mesoscale precipitation events. Overall, our results reveal the high potential of Lago Inferiore de Laures sediments to extend the regional earthquake and flood catalogues far back in time.
Wilhelm, B., Vogel, H., and Anselmetti, F. S.: A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps, Nat. Hazards Earth Syst. Sci. Discuss., doi:10.5194/nhess-2016-364, in review, 2016.