ST. LOUIS -- Missouri has been hit by storms, tornadoes and flooding just in the past week. If an earthquake is next, officials want people to be ready.

Homeland Security Secretary Janet Napolitano, Education Secretary Arne Duncan and Gov. Jay Nixon were at Carnahan High School of the Future in St. Louis Thursday for the 11-state "Great Central U.S. ShakeOut." The goal of the drill was to educate students and others about how to protect themselves if an earthquake happens.

Earthquakes are of particular concern in Missouri. The epicenter of the New Madrid seismic zone is in Southeast Missouri. Powerful earthquakes were centered there in 1811 and 1812, reportedly causing the Mississippi River to flow backward for a time and destroying structures hundreds of miles away.

"Planning in advance is the best way to be prepared for any type of disaster that may affect us in Missouri -- whether it's a tornado, flooding or an earthquake," Nixon said.

The Democratic governor has seen plenty of that firsthand. He was in St. Louis County following the tornado that struck Lambert Airport and nine municipalities Friday. And earlier this week, Nixon toured flood-stricken Poplar Bluff and other areas of southern Missouri, some facing record flooding.

"I have seen how preparedness education about tornadoes can save lives," Nixon said. We should take a similar approach with earthquakes."

No one was killed in the St. Louis-area tornado even though at least 750 homes were damaged, and around 100 of them destroyed. Officials lauded early warning from the National Weather Service, warning sirens, media reports and residents who knew what to do, chiefly take cover in the basement.

More than 3 million people were expected to participate in the earthquake drill, including nearly 500,000 in Missouri, according to Nixon's office. At the St. Louis high school, students were told to "drop, cover and hold on" in the event of an earthquake, meaning they should go to the ground, get under a sturdy desk or table, and hold on until the shaking stops.

The primary threat for injury or loss of life in an earthquake in the U.S. is falling debris and toppling objects, officials said.

Earthquake experts believe the New Madrid fault will produce another significant earthquake at some point, but they don't know when.

In April 2008, a magnitude-5.2 earthquake occurred in Southern Illinois along an extension of the New Madrid fault. Though 130 miles from St. Louis, the quake that struck at 4:37 a.m. awakened many people in the metropolitan area.