Free oscillations or standing waves that form
in enclosed or semi-enclosed bodies of water such as lakes,
bays, lagoons, or harbors. The waves may vary in period
from a few minutes to hours and may have amplitudes ranging
from a few centimeters to several meters. Most seiche
waves rock back and forth in the enclosed body of water parallel
to the long dimension of the basin, although some propagate
in transverse directions. Seiche waves are similar to
tsunami, except that they are confined to enclosed bodies of
water such as lakes. They are generally generated by similar
phenomena as true tsunami and may also be initiated by the
rocking motion of the ground associated with large earthquakes.
Some seiches are generated by local changes in atmospheric
pressure, winds, and tidal currents. Many seiche
waves were generated on lakes in southern Alaska during the
1964 m 9.2 earthquake, including some on Kenai Lake that
washed away piers and other structures near the shore.
Seiche-like waves sometimes resonate in bays and fiords during
large earthquakes, but these are not truly seiche waves as
they form in bodies of water connected to the sea. Seiche
waves were first described from Lake Geneva in Switzerland.
See also EARTHQUAKES; TSUNAMI.
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