hi Brian, I too am not informed enough about tsunamis, nor about all that
just happened. Anyway, here's what I found in Encyclopedia Britannica (1969
edition):
under "Waves of the Sea"
...
Far more destructive are the waves caused by vertical displacements along
earthquake faults on the sea bottom, by submarine landslides and by volcanic
eruptions beneath the sea. A series of so-called tidal waves (more correctly
designated by their Japanese name, tsunamis) may result. The velocity of
these waves in the open sea is large and depends upon the depth of water in
the following manner:
depth = 500 ft. / velocity = 75 knots
[up to]
depth = 1500 ft / velocity = 420 knots
The average depth of the Pacific Ocean was estimated for the first time from
the velocity of tsunamis and turned out to be only one-third of the
previously assumed value. These computations were later confirmed by
soundings. Tsunamis quickly lose height and become exceedingly long,
sometimes up to 500 miles, and in the open sea they can be observed only in
the immediate vicinity of their origin. Their period may lie between 10
minutes and 60 minutes.
The tsunami is usually led by a small rise, followed by a distinct trough.
On shore the arrival is first noticed by a fall in the sea level for a
number of minutes, as if there were an abnormally low tide, followed by a
rapid rise to levels far exceeding the high-tide level. Tsunami waves do not
usually break in the manner in which sea and swell break, but coming over
the reefs of coral islands they give rise to extremely turbulent and
dangerous conditions. At the mouths of large rivers tidal bores may be
formed, which may travel many miles upstream as solitary waves.
-----
It would be interesting to know what (and how effective) the warning system
would have been if there indeed was a tsunami detection system within the
Indian Ocean. I guess I'm asking what would be the 'architecture' or
'infrastructure' of the warning system for such a wide-spread area in these
'global' times.
just happened. Anyway, here's what I found in Encyclopedia Britannica (1969
edition):
under "Waves of the Sea"
...
Far more destructive are the waves caused by vertical displacements along
earthquake faults on the sea bottom, by submarine landslides and by volcanic
eruptions beneath the sea. A series of so-called tidal waves (more correctly
designated by their Japanese name, tsunamis) may result. The velocity of
these waves in the open sea is large and depends upon the depth of water in
the following manner:
depth = 500 ft. / velocity = 75 knots
[up to]
depth = 1500 ft / velocity = 420 knots
The average depth of the Pacific Ocean was estimated for the first time from
the velocity of tsunamis and turned out to be only one-third of the
previously assumed value. These computations were later confirmed by
soundings. Tsunamis quickly lose height and become exceedingly long,
sometimes up to 500 miles, and in the open sea they can be observed only in
the immediate vicinity of their origin. Their period may lie between 10
minutes and 60 minutes.
The tsunami is usually led by a small rise, followed by a distinct trough.
On shore the arrival is first noticed by a fall in the sea level for a
number of minutes, as if there were an abnormally low tide, followed by a
rapid rise to levels far exceeding the high-tide level. Tsunami waves do not
usually break in the manner in which sea and swell break, but coming over
the reefs of coral islands they give rise to extremely turbulent and
dangerous conditions. At the mouths of large rivers tidal bores may be
formed, which may travel many miles upstream as solitary waves.
-----
It would be interesting to know what (and how effective) the warning system
would have been if there indeed was a tsunami detection system within the
Indian Ocean. I guess I'm asking what would be the 'architecture' or
'infrastructure' of the warning system for such a wide-spread area in these
'global' times.