Geoscience Reference
In-Depth Information
Fig. 1.1 The 1775 Lisbon earthquake and tsunami. Old engraving by unknown author
which the city of Lisbon was destroyed. This event was reflected in an old engrav-
ing (Fig. 1.1). At present, researchers are paying particular attention to the Indian
Ocean, although in the past, also, its coasts were repeatedly attacked by catastrophic
tsunami waves.
The seaquake phenomenon caused by seismic oscillations of the sea-floor is only
known to specialists and to experienced seafarers. Even the edition of the Grand
Soviet Encyclopedia had no place for this term, although the amount of registered
natural events of this type already exceeded 250. Other transitory, but violent, phe-
nomena in the ocean (killer waves, temperature anomalies and acoustic effects) have
only recently attracted the interest of scientists owing to the rapid development of
methods for remote observation, the improvement of methods of data handling and
the accessibility of electronic databases and catalogues. Investigation of the entire
complex of mentioned phenomena in the Ocean sheds light on the interaction mech-
anisms of various media in the communicating and interpenetrative lithosphere-
hydrosphere-atmosphere system.
1.1 Tsunami: Definition of Concepts
The word tsunami originates from a combination of two Japanese hierogliphs
(Fig. 1.2), translated together as a 'wave in the harbour'. This term has already been
conventionally adopted in scientific literature, although in mass media one may still
encounter terms that prevailed some time ago, such as 'high-tide wave', and 'seis-
mic sea wave' and 'seaquake'. Sometimes the antique European terms 'zeebeben'
and 'maremoto' are also used.
Usually, tsunami waves are understood to be surface gravitational waves exhibit-
ing periods within the range of
T
10
2
-10
4
s. Tsunamis pertain to long waves;
∼
