False explosion warning prompts panic in Washington as USGS reclassifies event near Concrete

A false explosion warning issued by the U.S. Geological Survey triggered confusion across Washington state on Monday, as officials later confirmed the event was a pair of minor earthquakes near the town of Concrete. The alert briefly described a blast with the force of a magnitude 3.0 earthquake, prompting residents to seek information and reassurances from authorities before the warning was withdrawn.

USGS issued the alert just before 11:30 a.m. ET, stating that a blast similar in strength to a magnitude 3.0 quake had just occurred near Concrete. The agency quickly retracted the message and reclassified the seismic event as a magnitude 2.9 earthquake located roughly 70 miles north of Seattle. A separate, smaller tremor was detected in the same area: magnitude 2.6, recorded at 10:06 a.m. in the Concrete vicinity. Both events were shallow by seismic standards, occurring at depths of under 2,000 feet, which can make even modest quakes more noticeable to people near the epicenters.

Shaking from the events was described by residents as limited in scope, with reports indicating motion was felt only within a few miles of the quakes’ epicenters and did not reach Seattle. There were no immediate reports of damage or injuries resulting from either tremor. In the aftermath of the initial alert, USGS officials stressed that there had been no explosion in the Concrete area and that the earlier message was an erroneous classification tied to the seismic data.

The episode adds to a recent pattern of false or mistaken alerts from seismic warning systems. Less than two weeks earlier, Nevada residents were alerted to a supposed 5.9 magnitude quake that never occurred, triggering warnings across multiple states before a correction was issued. In March, USGS briefly posted—then removed—a notice that a magnitude 4.6 earthquake had been detected near Bombay Beach in San Diego. In each case, officials clarified that the alerts were incorrect and that no damaging event had occurred.

Washington state sits near the Cascadia Subduction Zone, a about 700-mile fault that runs from northern Vancouver Island to the northern California coast. While the area regularly experiences small quakes, federal officials have long warned that a major CSZ earthquake is possible and could cause widespread damage. A 2025 study found a 37 percent chance of a major CSZ quake between now and 50 years from now, with scientists warning that an 8.0–9.0 event could trigger a 100-foot tsunami that would devastate parts of the Pacific Northwest. FEMA has estimated that a mega CSZ quake could result in thousands of deaths and significant tsunami-related casualties.

Experts emphasize that the West Coast already plans for such scenarios and that residents should rely on official updates from emergency management agencies. While the specific Monday events were minor, they come as authorities continue to monitor the CSZ and work to refine early-warning systems to minimize the risk of confusion during genuine emergencies.