Overview
- The U.S. Geological Survey recorded a magnitude‑3.9, surface‑level seismic event about 3:04 PM on Thursday roughly 91 miles east‑northeast of Ponce Inlet and listed the origin at 0 feet depth.
- USGS classified the reading as an “experimental explosion” because the recorded ground motions and waveforms matched an artificial blast rather than a tectonic quake.
- The agency noted the Navy has conducted Full Ship Shock Trials in the same Atlantic testing area and Thursday’s entry was the ninth similar classification there since 2016; reporters have contacted the Navy but had not received on‑the‑record confirmation.
- People along Florida’s Atlantic coast reported feeling a rumble and rattling, yet no injuries, structural damage, or service disruptions were reported and major sites including Walt Disney World operated normally.
- Seismometers register large underwater blasts because blast energy couples into the seabed and travels as seismic waves, which is why controlled Navy detonations and other large explosions can produce measurable magnitudes on monitoring networks.