TSUNAMI HAZARD AND DESIGN OF COASTAL STRUCTURES

George Pararas-Carayannis

Abstract


Damage of coastal structures by tsunamis results by the direct and indirect action of hydrostatic and dynamic pressures, foundation failures, overtopping and flooding. Reliable assessment of the potential tsunami hazard at a coastal site and adequate engineering design of critical structures require analysis and understanding of all aspects of a tsunami system leading to its terminal behavior. Description of the space-time history of tsunami waves generated by impulsive disturbances require consideration of events and processes in the following regimes: (a) generation; (b) propagation and dispersion; and (c) termination. Processes and events in each regime during the development of a tsunami are under their own unique hydrodynamic constraints but are dependent on what has preceeded. In predicting tsunami wave characteristics at some distance from the generating source, the error structure may be pyramidal. Essential to any method of tsunami prediction at a distant or a nearby coast will be the full consideration and study of tsunami generative mechanisms. If the tsunami generation mechanics cannot be deduced with a reasonable degree of accuracy, it is not likely that the tsunami terminal aspects will be reliably predicted. Prediction of tsunami height at a distant or at a nearby coast requires knowledge of the magnitude and type of ground displacements in the tsunami generating area and of the characteristics of the surface waves resulting from such action. Although all mechanisms involved during tsunami generation are not fully understood, it is possible to obtain a suitable tsunami initiating function through the use of experimental data, historical data, and established empirical relationships, for each type of generating mechanism. Reliable computation of the tsunami propagation effects over and across the ocean can be obtained with proper modeling to provide an adequate description of the tsunami energy flow through the use of physical and numerical studies. Similarly, the terminal aspects and nearshore modification of the tsunami wave system can be approximated to provide the engineering criteria necessary for the assessment of the potential tsunami hazard at a coastal site.

Keywords


tsunami; tsunami hazard; coastal structures

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