59 
7.4.3 Travel Times 
With a group velocity of c i0 = ^gh 0 and a constant depth of 70 m (average depth of the 
North Sea), travel times of 10.6 hours, 5.3 hours, and 1.1 hours are computed for distances 
of 1,000 km, 500 km, and 100 km, respectively. 
The travel time from the northern boundary of the North Sea to Borkum, about 8 hours for the 
primary signal, fits well with this simple estimation. In this simulation, Cuxhaven is reached 
after about 9 hours by the wave train starting at the latitude of the Shetland Islands (Fig. 
7.4.9). From Aberdeen, the signal travels about 6 hours (Fig. 7.4.8). The good fit between the 
simple estimation at the beginning of this section and the model simulation is attributable to 
the hydrostatic assumption made in the model. It is not possible, however, to predict the 
entry time of the secondary signal by such simple estimation. It reaches its maximum at 
Cuxhaven about 7 hours after the lower primary maximum (Fig. 7.4.9). 
Aberdeen 
H 5 m 
H 6 m 
H 7 m 
H 8 m 
— 
03:00 04:00 05:00 06:00 
Fig. 7.4.8: Water levels at Aberdeen (input signal: 3 positive single signals, T 1800 s, H 5 m, 
from the north, North Sea 2 km) 
Fig. 7.4.9: Water levels at Cuxhaven (input signal: 3 positive single signals, T 1800 s, H 5 m, 
from the north, North Sea 2 km)