In communities along the New Madrid Fault, residents are preparing to leave home.
Missouri safety officials have decided to close schools Monday. Emergency provisions such as bottled water are in short supply.On both sides of the Mississippi, even in North Carolina, homeowners' insurance is in demand.
And in Dare County, officials are on alert for beach erosion.
All this because of tides.
Sunday will see the first of a tongue-twisting combination of astronomical phenomena - syzygy, perigee and perihelion - that will cause unusually high tides this month.
The tides alone aren't expected to be a problem, unless they occur during a winter storm.
But many Midwesterners are nervous: A New Mexico climatologist has said that the tidal pulls could trigger major earthquakes Monday or Tuesday along the Midwest's New Madrid Fault, California's Hayward Fault or in Tokyo.
Across the country, scientists say Iben Browning's 50-percent-chance-of-an-earthquake prediction is hooey. But high tides will be very real, they say.
``There's no convincing scientific evidence that the alignment of the planets has any effect on earthquakes,' said Michael Bevis, associate professor of geophysics with the department of marine, earth and atmospheric sciences at N.C. State University. ``Even if they did, that wouldn't point to any particular place.
``I've been getting a lot of calls from concerned citizens and also from insurance companies. People are trying to take earthquake policies on their houses.'
In making his predictions, Browning cited the gravitational pull of both the moon and the sun. Those forces nearly will align this month, making the pull on Earth's water almost as strong as possible.
The tides will be influenced three ways, said Lee Shapiro, director of the Morehead Planetarium at the University of North Carolina at Chapel Hill.
Syzygy, pronounced siz-uh-gee, is the lineup of three celestial bodies - in this case the sun, Earth and moon. At every new and full moon, the combined gravitational pull from this lineup causes higher-than-average tides, known as spring tides.
The moon exerts its strongest pull on tides at its closest approach to Earth, called perigee, Shapiro said. In December, perigee occurs twice: at 6 a.m. Dec. 2 and 7 p.m. Dec. 30 - extremely close to the month's two full moons, 2:51 a.m. Dec. 2 and 1:36 p.m. Dec. 31, Shapiro said.
Then there are the added effects of annual perihelion, Earth's closest approach to the sun. Perihelion occurs at 10 p.m. Jan. 2 - close enough possibly to influence December tides.
Alone, the combination isn't much to worry about, Shapiro said. But if it were to occur in conjunction with a winter storm, storm surge could become a concern, he said.
National Weather Service forecasts Friday didn't show much reason for worry: partly cloudy Sunday with a high in the 60s.
``We sort of watch the weather conditions, particularly this time of year,' said W.A. Hoggard, Kill Devil Hills town manager. ``We'll be watching for any type of beach erosion that may occur, or any overwash.
``We're not taking any unusual precautions at this point. It's going to be a beautiful weekend.'
Carolina Beach residents had a similar outlook.
``They had talked about it this summer,' said Laura Phelps, who works at the Carolina Beach Pier. ``We had it marked down on our calendars, but nobody's really concerned about it right now.'