9523414 Raichlen This project addresses two areas related to the damage resulting from tsunamis, namely generation and coastal effects. Tsunamis are ocean waves which are generated by impulsive events such as earthquakes, landslides, and volcanic eruptions occurring on the ocean bottom. The tsunami problem can be divided into three general areas: generation, propagation and coastal effects. This investigation is directed toward mitigation of the tsunami hazard primarily due to nearshore underwater landslides. In California, numerous submarine canyons are oriented perpendicular to the shore, with the canyon heads nearshore where the underwater sliding of sediment layers stored in the nearshore regions of these canyons could generate large waves. An important mechanism which could cause such landslides could be a distant or an offshore earthquake, such as the Northridge earthquake of January 1994 which caused considerable shaking and damage in the coastal community of Santa Monica, approximately 20 miles from the epicenter. If such shaking had triggered the failure of sediment layers in the nearshore canyons, it is possible that a damaging tsunami could have been generated in the nearshore waters. The shape and the kinematic properties of waves generated by underwater landslides and their modification as they propagate shoreward and overland are important in defining the forces on structures, such as seawalls and buildings which may be in the path of such potentially-destructive waves. The project involves experiments to understand the tsunami generation mechanism through underwater sediment slides, in conjunction with the development of an analytical model for the generation mechanism. It will provide data to assist in the evaluation of inundation distances to predict coastal flooding, and suggest reliable limits to evacuation zones. Such data are important for the engineering design, urban planning, and for improvement of the tsunami warning syste m. The results will be directly applicable also to engineering problems associated with other wave-structure interactions, such as the shoreward propagation of long-wavelength storm waves, and to waves generated in inland reservoirs and coastal inlets by landslides. ***
