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Academics

Academic Report on Oct.24,2019(2)

Reporter Topic:Physical modeling of tsunamis generated by granular landslides in 2D and 3D scenarios from reservoirs to conical islands

Reporter: Professor Hermann M. Fritz, Georgia Institute of Technology, US

Time: 16:00, Oct.24, 2019

Location:Academic Hall of State Key Laboratory


Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events. Major tsunamis caused by landslides or volcanic island collapse were recorded at Unzen in 1792, Krakatoa in 1883 and 2018, Lituya Bay, Alaska in 1958 (Fritz et al., 2009), Vajont reservoir and dam Italy in 1963, Haiti in 2010 (Fritz et al., 2013) and Greenland in 2017 (Gauthier et al., 2018). Granular landslide impacts into 2D flumes were studied using laser-based PIV (Fritz et al., 2003, 2004). Source and runup scenarios based on real world events are physically modeled in the three dimensional NEES tsunami wave basin (TWB) at Oregon State University (OSU). A pneumatic landslide tsunami generator (LTG) was deployed to simulate landslides with varying geometry and kinematics (Mohammed and Fritz, 2012). The bathymetric and topographic scenarios tested with the LTG are the basin-wide propagation and runup, fjord, curved headland fjord and a conical island setting representing a landslide off an island or a volcano flank collapse (McFall and Fritz, 2016). The LTG consists of a sliding box filled with 1,350 kg of landslide material, which is accelerated by pneumatic pistons down slope. Two different landslide materials are used to study the granulometry effects: naturally rounded river gravel and cobble mixtures. Water surface elevations are recorded by an array of resistance wave gauges. The landslide deformation is measured from above and underwater camera recordings. The landslide deposit is measured on the basin floor with a multiple transducer acoustic array (MTA). Landslide surface reconstruction and kinematics are determined with a stereo particle image velocimetry (PIV) system. Wave runup is recorded with resistance wave gauges along the slope and verified with video image processing. The measured landslide and wave parameters are compared between the planar hill slope used in various scenarios and the convex hill slope of the conical island. The energy conversion rates from the landslide motion to the wave train is quantified for the planar and convex hill slopes. The wave runup data on the opposing headland is analyzed and evaluated with wave theories (McFall and Fritz, 2017). The measured landslide and tsunami data serve to validate and advance numerical landslide tsunami prediction models.