PAPER NO: 299 WAVES AND RUN-UP GENERATED BY A THREE-DIMENSIONAL SLIDING MASS

This investigation is directed to a better understanding of the water waves generated by partially aerial and submarine landslides. It has become apparent in recent years that there may be a serious threat due to tsunamis generated near the shoreline by massive underwater landslides. For example, in Skagway, Alaska in 1994 a large underwater landslide generated waves that caused several million dollars damage to harbor facilities and killed one person. This took place during construction of a new cruise ship wharf. If it had occurred when a ship had been moored and unloading passengers the results could have been catastrophic. A more recent event, which was indeed catastrophic, occurred in July 1998 in Papua New Guinea. More that 2000 lives were lost due to a tsunami associated with a relatively small (for tsunamis) earthquake of magnitude seven. Upon further investigation it appeared that the tsunami, which some estimate to be 7 m to 8 m high at the shoreline, may have been generated by a massive underwater slump caused by the earthquake, see Kawata et. al. (1999). Southern California is especially susceptible to such events due to the combination of offshore faults and near-shore submarine canyons with stored sediment as well as bottom material on relatively steep slopes that may fail due to earthquake shaking. The resulting waves generated by the submarine landslides may generate sizeable onshore and offshore propagating waves; the former leading to significant danger of coastal inundation with little warning time.