Geoscience Reference
In-Depth Information
Fig. 6.14 Map of north-eastern part of the Indian Ocean with isochrones, showing the calculated
front position of the tsunami of December 24, 2004 (with an interval of 0.5 an hour). 1—epicentre
of the main earthquake, 2—epicentres of main aftershocks. Route of JASON-1 satellite (circuit
109-129). The profile of the ocean level determined from altimetry data is shown along the route
(Adapted from [Kulikov et al. (2005)]) (see also Plate 14 in the Colour Plate Section on page 322)
model. This error is especially noticeable in calculations of the wave field at sig-
nificant distances from the source. In [Kulikov et al. (1995)] it was shown that
the effect of linear dispersion can actually totally distort the form of the tsunami
signal in the open ocean. In this case, the main energy is concentrated in the region
of periods around 30-50 min, and at a distance of about 1,000 km from the source
the distortion is not so significant.
The results described above, in principle, demonstrate the possibility of timely
registration of a dangerous tsunami wave in the open ocean with the aid of modern
systems, permitting to observe the ocean from outer space. Such methods of effec-
tive tsunami forecasting will obviously develop in the direction of creating a tech-
nology for continuous monitoring of the ocean surface both with the aid of sensors
of the open ocean level, equipped with telemetric connection to the processing cen-
ters, and making use of satellite altimetry measurements.
Note that the sensor of bottom pressure (see Sect. 6.1) used for measuring
the level of the open ocean possesses an essential advantage as compared to
the satellite altimeter. The point is that the frequency range of tsunami waves is
practically free of irrelevant signals, while the corresponding range of wavelengths
is quite noisy (e.g. owing to vortical formations). Therefore, a tsunami wave can be
