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Abstract 
North Sea storm surges with water levels of 4 to 5 m NN (German ordnance datum) are 
annually recurring events that are dealt with by the official prediction services. The subject of 
this study is the behaviour of a hypothetical tsunami of comparable height traversing a wide, 
shallow shelf. The period of a tsunami ranges between that of wind waves and that of the 
semidiurnal tide dominating in the North Sea. Analytical wave theories, which have been 
developed for sea and swell, do not describe tsunami completely. Numerical models used to 
forecast storm surges are suitable in principle to simulate the propagation of medium-length 
waves in the North Sea. This mainly requires an adaptation of grid spacing to the shorter 
wave lengths. As an example, the propagation of three positive signals with a period of 
1800 s, which is typical of tsunami caused by slope failure, and wave heights of 5 to 8 m, has 
been simulated. Models of this type have limited applicability on the continental slope and 
are not suitable for near-shore areas. Despite all restrictions regarding the analytical 
estimations and numerical simulations used, the conclusion appears justified that 
significantly less wave energy would be present in the German Bight after a hypothetical 
tsunami has crossed the wide and shallow shelf of the North Sea than be the case on a 
coast with a steep, narrow shelf that was hit by a comparable tsunami.