The Continuing Underestimated Tsunami Hazard from Submarine Landslides

Tsunamis generated by submarine landslides are, relatively, a recently identified hazard, which resulted from the Papua New Guinea event of 1998, when 2200 people died. Recognition of the tsunami hazard from submarine landslides has been possible mainly because of the recent development of advanced technology, such as multibeam echosounders, now available to image the seabed to high resolution. In addition, the architecture of submarine landslides developed from the marine mapping has been the basis for new numerical models of tsunami generation from seabed sediment movement. Tsunamis, post-dating PNG, where an earthquake mechanism was not realistic, have been considered in this recent context, and new relationships identified. These relationships have been particularly with strike-slip and large magnitude (great) earthquakes, as well as with small magnitude earthquake events where a dual mechanism (earthquake and landslide) is most likely. As a result, submarine landslide tsunamis are now recognised from all geological environments; passive, convergent and strike-slip margins as well as volcanoes. Despite these new advances in understanding, however, recognition of the hazard from submarine landslide tsunamis is still limited.