Multiple earthquakes hit just miles outside of a military base in Nevada, which played a significant role in America's nuclear bomb testing.
The US Geological Survey (USGS) detected three tremors on Thursday, with a magnitude 3.3 quake hitting at 9:52am ET about 14 miles northeast of Nellis Air Force Base. This was followed by two smaller tremors just minutes later.
Nellis Air Force Base tested US nuclear weapons above ground during the 1950s and 1960s, but testing moved underground until all operations ceased in 1992.
Nellis sits within the same large federally protected area as the classified Area 51 base.
The USGS received reports of shaking as far west as North Las Vegas, but no injuries or damage have been reported.
The seismic activity occurred along the California Wash Fault, part of the broader Basin and Range Province that stretches across much of the western US.
In this region, the Earth's crust is gradually being pulled apart, causing faulting and frequent earthquakes.
Nevada is the nation's third-most seismically active state, ranking behind only California and Alaska.
Scientists estimate that the California Wash Fault is capable of producing a powerful earthquake of up to magnitude 6.5.
The most recent major tremor, a magnitude 6.3, occurred in 1943 near Caliente. Due to the remote location, no significant damage was reported.
Nellis was designated as part of the Nevada Proving Grounds in 1950 and later supported the Nevada Test Site (NTS), established in 1951 for nuclear testing.
On January 27, 1951, the first atmospheric nuclear test, code-named 'Able,' was detonated at the NTS.
A total of 100 atmospheric tests were conducted at the site until July 1962.
However, atmospheric testing was banned in the U.S. in August 1963, forcing all operations underground.
The US conducted 828 underground tests at the NTS, with the final test, 'Divider,' taking place on September 23, 1992.
The decision to cease testing came as the Cold War ended, with US officials hoping the move would encourage other nations to follow suit.
The classified Area 51 was built four years after the nuclear testing first started.
The base has become a cultural phenomenon thanks to decades of conspiracy theories connecting the base to UFOs, aliens and experimental aircraft testing.
Area 51 is not accessible by the public and is even off-limits to regular military air traffic.
In fact, a Google map of the area where Monday's earthquake took place will show you nothing at all - no base or mention of the Air Force's presence in the Nevada desert.
The base remained largely unknown until 1989 when Robert Lazar claimed on TV that he worked at a secret site near Groom Lake, 'S-4,' studying alien technology and spacecraft.
And it was not until 2013 did the CIA official confirm its existence.
The agency declassified a more than 400-page report that detailed how testing its secret spy planes 'accounted for more than one-half of all UFO reports during the late 1950s and most of the 1960s.'
The U-2 spy and A-12 reconnaissance planes were being flown in the shadows of the desert amid the Cold War, but the extreme altitudes sparked fears of an alien invasion.
'High-altitude testing of the U-2 soon led to an unexpected side effect—a tremendous increase in reports of unidentified flying objects (UFOs),' the report states.
'Once U-2s started flying at altitudes above 60,000 feet, air-traffic controllers began receiving increasing numbers of UFO reports.'
However, the CIA report does not mention Area 51's purpose after 1974.
