A seismic event that rattled Utah on Wednesday evening turned out to be a mining explosion rather than a natural earthquake, according to data from the US Geological Survey.
The USGS detected the event at 4:59pm ET, registering it as the equivalent of a 3.1-magnitude earthquake. Data showed it occurred at a depth of zero feet, indicating a surface blast. The explosion was equivalent to 1,500 pounds of TNT and was recorded outside Maeser, an area surrounded by more than 3,200 mines and mining claims.
Despite the seismic reading, residents nearby reported no shaking. One person within Vernal city limits, about nine miles from the epicenter, said they did not feel the event, and another local resident said the same.
Only one person reported shaking to the USGS. It remains unclear which mining operation caused the blast or whether it was planned. No injuries or damage were reported.
How blasts mimic earthquakes
Mining explosions can produce seismic waves that resemble those from natural earthquakes, causing monitoring equipment to register them as magnitude events. The key difference is depth: explosions occur at or near the surface, while natural earthquakes originate deeper underground when stress causes rocks to rupture along a fault.
Utah experiences frequent seismic activity and has more than 200 active faults, including the Wasatch Fault Zone, which runs beneath Salt Lake City. Wednesday's explosion occurred about 171 miles east of Salt Lake City.
Florida event linked to Navy trials
The Utah blast came days after a separate manmade seismic event was recorded off Florida's coast. On Tuesday, the USGS detected a 3.9-magnitude event east of Flagler Beach, also logged at a depth of zero feet and labeled an experimental explosion.
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. These controlled underwater detonations test how warships withstand battle-like explosions.
A Navy spokesman said the future USS Ted Stevens had successfully completed the first of two planned trials, part of the certification process for its DDG 51 Flight III destroyer program. No injuries or damage were reported from either event.
