There are still three months until the Atlantic hurricane season begins, and residents of Florida aren’t yet ready to contemplate the threat of the next natural disaster. But a rare late-night rumble and shake that startled thousands along the state’s east coast barely two weeks ago has raised the specter of a different and unexpected new menace: earthquakes.
At a magnitude of 4.0, the earthquake that struck 101 miles (163km) east of Cape Canaveral in the late evening of 7 February was the strongest in the US for two years, and significantly more powerful than those experienced on an almost daily basis in more vulnerable western states such as Nevada, New Mexico and California.
It was also highly unusual. The last time Florida felt anything similar was a 3.9-magnitude jolt in June 2021, and that wasn’t an earthquake at all, rather the US navy detonating 40,000lb of explosives to test the resilience of its newest aircraft carrier, the USS Gerald Ford.
Records from the US Geological Survey (USGS) show the most recent “real” earthquake in, or close to Florida, was a relatively insignificant 1.8 shake in September 2020; and the only others of any great power were quakes of 3.5 and 4.4 magnitude in 1900 and 1879 respectively.
In fact, until now, the closest most Florida residents will ever have gotten to experiencing a real shaker was the now defunct but highly popular Earthquake ride at Orlando’s Universal Studios theme park.
“Most earthquakes occur along or very near to tectonic plate boundaries, and Florida is in the North American plate, fairly far from a boundary. But they do still happen here, rare as they are,” said Oliver Boyd, a USGS research geophysicist.
“Most of the stresses, most of the fractures, are along the plate boundaries, so that’s why most earthquakes happen there, but plates all across the planet are under some amount of stress. There are old fractures pretty much everywhere, they’re just kind of more healed, less dense.”
That means, Boyd says, earthquakes of varying magnitudes can and will occur anywhere, not just in those areas considered more at risk because of their position along fault lines or plate boundaries, albeit less frequently.
Because the epicenter of the latest earthquake was so far out to sea, and six miles beneath the surface of the Atlantic, the effects in Florida were limited to mild rumbling in a number of coastal communities, no property damage and no reports of injuries.
Still, almost 250 people were concerned enough to call in to the USGS “I Felt It!” reporting line, and several police departments received calls from worried residents.
Inhabitants of cities close to Cape Canaveral are used to feeling the ground trembling and hearing booming noises from the increasing number of space launches from the Kennedy Space Center. But, that night, there were none – adding to the initial confusion of those unaware of what they were witnessing.
Shimon Wdowinski, a professor of geodesy at Florida International University’s department of earth and environment, said the Florida earthquake was an example of intraplate seismicity, an enigmatic phenomenon in which sometimes major quakes take place deep in a tectonic plate’s interior.
Among the most extreme examples were the New Madrid, Missouri, earthquakes and aftershocks of 1811 and 1812, which caused widespread destruction and were felt from Canada to Mexico.
“The North American plate is relatively stable [but] there are stresses within the interior of the plate, which are the result of forces on the plate boundaries,” he said.
“If you push on both sides, you generate stress – it will be released in some area of weakness. Where there are fault lines like New Madrid or other places, there’s more likelihood that it happens, but it can be in other places where the frequency is very low.”
Wdowinski said activity in such areas might also be more prevalent than recorded because smaller earthquakes, particularly at sea, are less likely to be detected by a global monitoring network of seismometers.
“With this network, we can detect magnitude 3 or 4 everywhere,” he said. “Over here, there are fewer monitoring stations and it’s harder to detect lower-magnitude earthquakes with lower energy.”
Boyd, the USGS geophysicist, said events such as the Florida earthquake can provide valuable educational opportunities.
“People forget about being prepared,” he said. “Around the New Madrid seismic zone, they haven’t had these really damaging earthquakes since 1812, but we know they occur on average every 500 years. It’s important that people are aware they can happen, and there are building codes and people build correctly.”
Wdowinski echoed the message of preparation, but said for residents of Florida, because of the rarity of earthquakes, there were more pressing priorities.
“The probability is very low. We need to be more prepared for hurricanes,” he said.
