. >> kent moran at the you university studies the event. >> people screaming this panic, the ground openingt was apocalyptic. >> it was felt as far away as louisville, kentucky, and cincinnati. it range church bells in charleston, california. >> they were all puzzled by it. why is the grounds moving? why are objects swinging back and forth? why is the water sloshing back and forth in the seam or pond by my house? >> about 3.5 million acres of the mississippi and ohio river valleys were reshaped. hills and lakes appeared on previously flat, dryer the rain. two centuries later the effects are still visible. stretches of sand as the pressure of the shifting earth forced to the service. a phenomenon known as sand blows. >> it de populated and depressed that area of the population for years afterwards. >> but now the area is home to millions and at least five states including memphis, tennessee, little rock, arkansas and st. louis. in the next 50 years there's a 25% to 40% chance of an earthquake of at least magnitude 6.0 in the area and a 10% probability of a repeat of the 1811461812 earthquake