Geoscience Reference
In-Depth Information
Chapter 4
The Physics of Tsunami Formation by Sources
of Nonseismic Origin
Abstract The physics is described of tsunami formation by sources of nonseis-
mic origin: landslides, volcanic eruptions, meteorological causes and cosmic bodies
falling into the ocean. Short descriptions are given of certain remarkable historical
events (with the exception of cosmogenic tsunamis). Approaches to the mathemat-
ical description of tsunami generation by these sources are expounded. Basic regu-
larities, relating parameters of a source and of the tsunami wave generated by it are
presented.
Keywords Tsunami generation
·
gravitational surface wave
·
earthquake
·
landslide
·
slump
·
mud flow
·
river tsunami
·
erosion
·
sedimentary layer
·
viscous fluid
·
long
waves
·
Froude number
·
volcano
·
volcanic eruption
·
caldera collapse
·
explosive
eruption
·
underwater volcano
·
pyroclastic flow
·
equivalent source
·
stationary-
phase method
·
meteotsunami
·
anemobaric waves
·
resonance
·
Proudman reso-
nance
·
internal waves
·
storm surges
·
tension of friction
·
atmospheric pressure
·
long-wave theory
·
meteorite
·
cosmogenic tsunami
·
asteroid
·
kinetic energy
·
parametrization
·
numerical simulation
·
dispersion
Tsunami generation is mainly caused by sharp vertical displacements of separate ar-
eas of the ocean bottom, taking place during strong underwater earthquakes. Details
of this process are described in Chapters 2 and 3. But seismotectonic movements
are not the only possible mechanisms of tsunami formation. A significant number
of events are caused by landslides (slumps), processes related to volcanic eruptions
and meteorological causes. In accordance with the historical database of tsunamis in
the Pacific Ocean (Institute of Computational Mathematics and Mathematical Geo-
physics of the RAS Siberian Branch [SB], Novosibirsk), 79% of events were due to
earthquakes, 6% to landslides, 5% to volcanic eruptions and 3% to meteorological
causes. The sources of the remaining 7% of events are still unknown.
Recently, tsunami generation by meteorites falling into the ocean has been the is-
sue of active discussions. Such events are extremely rare. Such an event may even
never have occurred during the whole history of our civilization. But, bearing in
mind the scale of such a catastrophe, the authors considered it necessary to present
certain results of studies of this tsunami generation mechanism.
