Sunday's earthquake and following tsunamis were great tragedies. Here are three archived Ask Tom Why questions dealing with tsunamis and seiches.
July 28, 1998
Dear Tom,
Could an earthquake in Lake Michigan cause a catastrophic tidal wave to hit Chicago like the one that happened at Papau, New Guinea?
MTM, Bartlett
Dear MTM,
There is no known historical precedent for a tsunami even remotely close to the magnitude of the Papau, New Guinea, event on the Great Lakes. The probability of such an event here has to be considered exceedingly low. says Guy Urban, geophysicist at the Palmer, Alaska, based West Coast and Alaska Tsunami Warning Center.
Urban does add that several catastrophic, rare and rather improbable occurrences would be required to set up a tsunami here. He’s quick to point out the near impossibility, absent careful modeling of such an event, of even beginning to speculate on the dimensions of such a wave. Only a direct asteroid strike, a huge thermonuclear explosion beneath the lake or a massive earthquake might initiate one, and while not impossible, the odds are not high.
Copyright © 2004, WGN-TV
March 18, 2003
Dear Tom, When and where was the most recent destructive tsunami? Shaqueda Green
Dear Shaqueda,
Tsunamis are ocean waves generated by undersea earthquakes, landslides or volcanic eruptions. They can be only a few inches high in the open ocean, but steepen and rise as they approach shallow water, reaching heights of 200 feet in extreme cases. Last year on Sept. 8, an earthquake with a Richter scale magnitude of 7.6, centered off the coast of Papua New Guinea, generated two tsunamis with heights up to 7 feet that caused two fatalities. The most recent devastating tsunami also struck Papua New Guinea, occurring on July 17, 1998, following a 7.1 magnitude earthquake. The resulting 30- to 50-foot-high wall of water struck a 25-mile stretch on the island's north coast, killing nearly 3,000 people.
Copyright © 2004, WGN-TV
May 17, 2004
Dear Tom, I once read that a tsunami wave hit Chicago in the 1950s. Did this actually happen? Anne Violante
Dear Anne,
On June 26, 1954, the Chicago lakefront was hit a 10 foot wall of water called a seiche (pronounced saysh) that swept eight unsuspecting fishermen off the Montrose Harbor pier to their deaths. While a tsunami or seismic sea wave is generated by underwater earthquake or volcanic activity, Chicago's 1954 seiche was caused by line of thunderstorms racing southeast across Lake Michigan at speeds in excess of 50 m.p.h. The cold downdrafts of air flowing out of the thunderstorms caused a rapid rise in air pressure that pushed a building bulge of lake surface water toward the southeastern shore. This surge of water then reflected back to the Chicago shore as a large wave, taking nearly 90 minutes to make the return trip.
Copyright © 2004, WGN-TV
Steve Kahn
