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An 'experimental explosion' has been detected off the coast of Florida, nearly two weeks after a similar event occurred.
The US Geological Survey detected a 3.9 magnitude earthquake east of Flagler Beach on Tuesday.
The event was listed with a depth of zero feet, indicating the seismic source was at or very near the surface, a characteristic more consistent with an explosion than a typical tectonic earthquake.
The location is about 20 miles from where another event was recorded on July 16 east of Ponce Inlet, an area where the US Navy is known to conduct Full Ship Shock Trials (FSST).
The Navy periodically conducts these controlled underwater detonations to test how new or upgraded warships, like aircraft carriers or combat ships, withstand battle-like explosions near mines or torpedoes.
A Navy spokesperson said after the July 16 event that the future USS Ted Stevens (DDG 128) had successfully completed the first of two planned Full Ship Shock Trials, part of the certification process for the Navy's DDG 51 Flight III destroyer program.
The spokesperson added that the testing was the first two scheduled test events for FSST as part of the certification process for the Future USS Ted Stevens (DDG-128) under the DDG 51 Flight III Program.
In 2021, the Navy set off a test explosion near its new aircraft carrier, the USS Gerald R Ford, also off the coast of Ponce Inlet.
The US Geological Survey detected a 3.9 magnitude earthquake east of Flagler Beach on Tuesday
The Daily Mail has contacted the Navy and USGS for comment.
While Tuesday's event may have been planned, the public is still in shock after seeing it register on the USGS site.
One X user posted: 'What the hell is going on? This is the second 3.9 magnitude "experimental explosion" earthquake off northeast Florida in the last two weeks. Same spot, same magnitude.'
Another user highlighted that no explanation has been attached to the USGS listing.
The USGS records experimental explosions because its network of highly sensitive seismographs detects the ground vibrations they produce.
Seismologists then analyze the signals to distinguish human-made blasts from natural earthquakes.
Such events are typically linked to controlled military exercises, including underwater ship shock trials, as well as scientific seismic research and industrial mining operations.
These Navy tests use large explosive charges, such as tens of thousands of pounds in past cases, to simulate battle conditions like nearby mines or torpedoes and test warship resilience.
The Navy has conducted Full Ship Shock Trials (FSST) in this region in the past.' Pictured is testing in 2021
No damage or injuries are expected or reported, these are planned, permitted tests with environmental considerations for marine life.
The event in 2021 is known as a 'shock trial,' an explosion meant to test the USS Gerald R Ford's ability to withstand nearby detonations.
The Navy has been conducting these tests for decades after discovering that nearby explosions can knock out critical ship systems without inflicting significant physical damage.
The aircraft carrier was designed using advanced computer modeling, extensive testing and engineering analysis to withstand the shock of combat.
The FSST helps confirm those designs by measuring how the vessel performs when subjected to a powerful nearby underwater explosion.
The Navy has carried out Full Ship Shock Trials for decades on newly built warships.
Recent tests have included the littoral combat ships USS Jackson and USS Milwaukee in 2016, the amphibious transport dock USS Mesa Verde in 2008, the amphibious assault ship USS Wasp in 1990, and the guided missile cruiser USS Mobile Bay in 1987.
The last aircraft carrier to undergo the trial was the USS Theodore Roosevelt in 1987