Lake water can slosh like bathtub water
 Q: What is a seiche? Do it have something to do with tsunamis? -Jack W., Washington D.C.
A: Yes, a tsunami can cause a seiche (pronounced SAYSH), which is a sloshing of water back and forth
in a lake, much like what you cause in a bathtub by sliding forward and pushing back until you get the
water moving. Also earthquakes can cause seiches.
[USGS] The 1964 quake tore rails from their ties
A seiche can occur in a lake far from the earthquake source if the earthquake is large. In March 1964, the
largest earthquake that ever hit the United States hammered Prince William Sound, about 75 miles (120
kilometers) southeast of Anchorage. This 9.2 jolt-the second largest in recorded history-created seiches
thousands of miles away.
Seismic waves from the earthquake traveled over 3,000 miles through the Earth and caused seiches in rivers, lakes, and bayous along the
Gulf Coast of Louisiana and Texas. Thick sediments may have amplified the seismic waves enough to start the seiches. The basins
probably had a natural period close to the period of the seismic waves and that, in turn, reinforced the sloshing.
Tsunamis can also trigger seiches by entering a bay or harbor.
Another way seiches start is when land tilts. Someday a nearby fault may rupture and tilt Lake Tahoe's lakebed. That could start a huge
flow in the lake and thus create a seiche in Tahoe, says Eric Geist, US Geological Survey geophysicist in Menlo Park, California.
Strong winds cause seiches on the Great Lakes almost every day. The wind blows the water along and piles it up at one end of the lake.
When the wind dies, the bulging high water surges back and creates a wave that heads for the opposite shore.
Seiches on Lake Michigan can reach ten feet and, in 1954, one killed seven people on a Chicago dock. Great Lakes seiches take
anywhere from about 15 minutes to over eight hours to swish a round trip: back and forth. Consequently, seiches can be sneaky-hitting
folks hours after the winds have subsided.
(Answered by April Holladay, science correspondent, May 15, 2002)
Further Surfing:
How a tsunami
forms, and why the water goes out sometimes
The
highest tsunami, Alaska, 1958
Tsunamis
in a river? USGS: Largest US earthquake, Alaska 1964
Science News: Tsunami! At Lake Tahoe?
U of Wisconsin: Storm Surges, Seiches
U of Minnesota: Seiches
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