The story of the last big one is the stuff of legend in Tennessee: In the winter of 1812, when a series of massive earthquakes struck the Mississippi River valley, the shaking was so violent, folks say, that the mighty river ran backward for a time, and church bells and curtain tassels on the East Coast were set ringing and swaying.

Those who survived were left to wonder if the end of the world was upon them.

The cataclysm along the New Madrid fault dissolved into local lore and the perennial threat in this seismic zone in the central United States was largely forgotten — until Katrina.

These days, in Memphis and in many other places across the country that have predictable threats of disasters — from hurricane- and quake-prone stretches of the coasts to tornado alleys in the Plains, from Northwest towns where volcanoes loom to busy cities where terrorists could strike — talk has moved from the last big one to the next big one.

Katrina has revived scenarios of tornadoes landing on downtown Kansas City, of mud burying Tacoma, of a Category 5 hurricane wrecking Houston, of chemical agents released on the Las Vegas Strip, of wildfires sweeping Los Angeles.

The images of destruction and suffering in New Orleans have chastened officials and average citizens, stretching their imaginations. Suddenly, those dusty worst-case scenarios, long unthinkable and almost theoretical, are plausible, frightening, and no longer ignored.

"I think people are going, 'Will Memphis be next?' " said Ray Pohlman, who works at the corporate headquarters of Memphis-based AutoZone, the auto parts giant that occupies an eight-story building on a bluff overlooking the Mississippi River. The threat seems more real today, he said, than it did last month.

Time to re-evaluate

Katrina showed the largest-scale natural disasters can and do happen, and that even with considerable warning and precaution, so much can still go wrong. And the hurricane has given tangible form to fears of a terrorist attack bigger than that of Sept. 11.

President Bush, in his Thursday night speech from New Orleans, announced that the Department of Homeland Security will undertake an immediate review of emergency plans in every major city in America. "This government will learn the lessons of Hurricane Katrina," he said.