Earthquake Anniversary A Reminder That Florida Not Quake-proof

January 11, 2000

GAINESVILLE — As a professor of geology and longtime director of the University of Florida’s seismic network, Doug Smith takes his share of calls about mysterious tremors that rattle someone’s windowpanes or set the neighborhood dogs barking.

In just about all the cases, Smith tracks the cause to something other than what callers usually swear was an earthquake. But earthquakes are not unheard of in Florida. And if Smith had been here on tomorrow’s date 121 years ago, his prognosis would have been different.

Smith and other geologists agree that the largest earthquake ever recorded in Florida shook the state on Jan. 12, 1879. About 11:45 p.m., a pair of 30-second tremors, possibly centered in the Palatka area, sent crockery tumbling off shelves and jolted startled residents awake in a large part of north Florida. According to news accounts, the quake was felt in Cedar Key, Gainesville, Jacksonville, St. Augustine and Tallahassee, among other cities. “…Beds in some instance shook and trembled so that their inmates were almost thrown out upon the floor,” says a Cedar Key newspaper. “…One young man is said to have run into his yard and commenced firing off his pistol, while some other gentlemen left their premises and hastened to the square to ascertain the cause of the commotion.”

When it comes to natural disasters, Florida is better known for hurricanes. But the state, though among the most geologically stable regions in the nation, also has been home to at least five confirmed quakes in the past 200 years, Smith says.

“We have had earthquakes in Florida — and we could have one today — but it’s not as likely as other places,” Smith said. Earthquakes tend to occur in regions near the boundaries of underground plates or at weaknesses in the plates themselves, Smith said. Florida does not include any plate boundaries, and the plate the state occupies is very stable, he said. “There are no recent volcanoes and there are no known active faults in Florida,” he said.

That said, a region of north Florida bounded roughly by Jackson County in the west, Nassau County in the east and Volusia and Levy counties in the south appears slightly more likely to experience earthquakes than other parts of the state, Smith said. That’s because the basement of rock well underneath the northern part of the state is a variety of granite, contrasting the basalt beneath South Florida.

Smith’s expertise is coupled with experience. Beneath UF’s Turlington Hall, a 10-inch thick, 125-foot cement column rests on hard crust known as the “Ocala limestone” layer. Installed when Turlington was built in 1979, the pillar is attached to a seismograph.

Until recently, the seismograph was one of several that monitored earthquake activity continuously as part of a UF statewide seismic network. Due to a lack of funding — money Smith hopes to regain through grant applications — it is the only one now functioning.

In the past two decades, the network has recorded numerous earthquakes nationally and worldwide, including many of the most devastating earthquakes. But though it has registered tremors from quakes in nearby states, the seismograph hasn’t ever registered anything that Smith, who dates Florida’s most recent confirmed earthquake to one in Daytona in 1975, pegs as an earthquake centered in the state. The other confirmed quakes here are a 1973 quake in Merritt Island, a 1935 one in Palatka and a 1945 quake off Miami.

The lack of activity hasn’t stopped Smith from getting plenty of calls from Floridians reporting disturbances they think are earthquakes.

Causes of false reports range from quarry blasting to law enforcement demolition of confiscated explosives. Others are less obvious. One that Smith has ferreted out is military jet training off the Gulf Coast. When atmospheric conditions are right, the vibrations of jets breaking the sound barrier can be transmitted far inland, he said. So strong is the correlation that Smith has tied reported earthquakes to Air Force reservists’ training schedules.

“They go out there and this is their only time of year to fly, so even if they’re told to restrict their speed, they don’t,” he said. “We’ve gotten earthquake reports at the exact time that a handful of reservists are out flying.”