Lake tsunamis

Tsunamis are a major threat to on-shore communities not only in marine environments but also in lacustrine settings. Similar to marine tsunamis, waves in lakes can be generated by mass-movements, atmospheric changes, earthquakes and volcanic processes. Considering the high vulnerability of lake shores due to the high density of populations and their relative infrastructures, meticulous studies are needed to assess the hazard that such occurrence might locally pose. Delta failures are a common phenomenon, and their traces are mainly recognized in the lake basins "sink" adjacent to deltas as thick turbidites. Moreover, several historic reports document the effects of delta failures. Due to high sedimentation rates from rivers’ load, the "source" traces of delta failures heal within a short period, thus no failure scars are yet described on the bathymetric maps. The Aare delta failure in 1996 in Lake Brienz (Switzerland) provides a recent example of such an event, where ~3 x 10⁶ m³ of delta sediments moved from the sublacustrine Aare delta towards the deep basin and resulted in a megaturbidite; however, no traces of potential failures are visible today in the deltaic areas. Absence of the traces of failure areas cause also missing information on the potential failure plane and on the mass-movement process initiation. Further challenges of understanding delta failures root in the missing seismic stratigraphic subsurface information, as proximal delta deposits do not allow acoustic penetration due to free gas in the pore space that derives from the degradation of degrading organic matter. Within this research framework, two projects are currently active in our group: