ST. LOUIS - When emergency responders in parts of several states wake up Tuesday, they know they're going to be responding to a fake earthquake.

What they don't specifically know is how their communities will be affected during three days of drills: scenarios where communications are cut, bridges are down, even instances where leadership doesn't survive the mock quake.

Officials say the public probably won't notice the drills, which include tabletop exercises, but also practice in the field.

The exercises relate to a mock 7.7-magnitude earthquake along the New Madrid fault, a network of deep cracks in the earth's surface from southern Illinois to northeastern Arkansas. It produces hundreds of small quakes a year, most too weak to be noticed without scientific equipment.

But in 1811 and 1812, it produced a series of big earthquakes estimated at magnitude 7.0 or greater, and officials know a similar quake today would cause extensive damage.

The U.S. Coast Guard and Environmental Protection Agency will test how they'd respond to multiple spills following an earthquake, say if toxic substances began leaking into waterways at the same time broken pipelines began to spill.

In Missouri, more than 80 cities and counties will take part in exercises, at first taking a look at how they'd respond to people in need at the start of a catastrophic quake.

Then, they'll fast forward over the next two days, examining what they would do in the days and weeks after a major earthquake - how they would do things like provide social services, coordinate with insurance companies, or reopen banks and universities, said Missouri State Emergency Management Agency spokeswoman Susie Stonner.

Jim Wilkinson, executive director of the Central United States Earthquake Consortium in Memphis, Tenn., said Missouri, Arkansas and Tennessee will be running earthquake drills and reviewing their state plans. Several other states, including Kentucky, will support the drills related to spills in an emergency.

Wilkinson said the drills this week had been planned for about two years. They will allow agencies to identify shortfalls and areas that need improvement. Responders can also build relationships with one another prior to an emergency.

“We don't want to be exchanging business cards at the event,” he said.

Some agencies will be checking in for certain parts of the drills. Cape Girardeau's emergency management director, Mark Hasheider, noted that responders in that southeast Missouri community will do tabletop exercises related to earthquake emergency response on Tuesday. Then, on Wednesday and Thursday, they'll simulate a building collapse, where crews will perform search and rescue drills to locate 18 mannequins in part of a collapsed building.

The exercises will allow them to cut through concrete floors and walls and shore up wooden walls to get to the mannequins.

Wilkinson noted more work needs to be done.

“The federal government doesn't have a New Madrid-specific plan,” he said.

Work is being done to tailor federal emergency plans to specific possible disasters following Hurricane Katrina, which devastated parts of the Gulf Coast. New Madrid earthquake drills led by FEMA are currently planned for 2011, he said.