Experimental Investigation of Submarine Landslide Induced Tsunami Waves

Abstract

This MSc thesis was initiated as part of an interdisciplinary project researching post-disaster coastal reconstruction in the Tohoku region of Japan. On March 11, 2011, a highly destructive earthquake induced tsunami hit the north-eastern part of Honshu island, causing enormous damage to numerous small towns along the coast. Since 2011 various studies have been completed to better understand this historical event and explain the nature of tsunamis. However, some researchers have noted the inability of tsunami models, using only an earthquake as a source, to reproduce the timing, frequency and wave heights recorded along the Tohoku coast in March 2011. The differences are especially striking for the Sanriku coast – a relatively small area north of Sendai plain characterised by a ria-type coastline. D. R. Tappin et al. (2014) suggested that a secondary source is required to explain the deviating model results and locally higher tsunami waves, such as a submarine landslide. In low-lying coastal areas, tsunamis are an unavoidable hazard to human lives. A common way of addressing natural disasters of this scale is with timely warning and evacuation, which in turn requires appropriate techniques for prediction of an upcoming disaster. While earthquake induced tsunamis provide a sort of a warning signal, tsunamis generated by a submarine landslide can be much more difficult to predict. Landslide tsunamis are usually concentrated in local areas and do not propagate far, as they are more dispersive than earthquake tsunamis. However, the source of landslide tsunamis is often located on a continental slope near the coastal line. As a result, waves reach the shore in a very short period of time and run-up heights can reach extremely high levels (Harbitz et al., 2006). Thus, landslide generated tsunamis pose a serious hazard to densely populated coastal areas. Within the scope of this thesis, a number of experimental simulations on submarine slope failures were conducted in a so-called static liquefaction tank – a unique testing facility for large scale experiments at the Geo-Engineering Laboratory of TU Delft. To improve the understanding of tsunami generation, this study focuses on the moment of onset of a submarine slope failure and wave generation, linking the processes within failing soil mass to initial characteristics of waves. This study illustrates the connection between these two processes that are usually only considered individually from either a geotechnical or hydraulic perspective.