Moderate Earthquake (M4.9) Reported Near 88 km SW of Nikolski, Alaska

A magnitude 4.9 earthquake struck the United States at 23:05 UTC on Thursday, June 25, 2026, according to data from the United States Geological Survey (USGS). The earthquake's epicentre was located 88 km SW of Nikolski, Alaska, at a focal depth of 59.3 km.

Event Details

At a focal depth of 59.3 km, this is classified as a shallow earthquake (0–70 km). Shallow events are typically the most damaging: the seismic energy has less distance to travel before reaching the surface, resulting in stronger and more abrupt ground shaking at the epicentre.

The earthquake registered a magnitude of 4.9 on the moment magnitude scale — the standard measurement used by seismologists worldwide. At this magnitude, the shaking is felt strongly by everyone; minor to moderate damage possible in vulnerable buildings.

Where Did This Earthquake Occur?

The United States experiences significant seismic activity primarily along the West Coast (Cascadia Subduction Zone, San Andreas Fault), in Alaska (subduction of the Pacific Plate), and in the intermountain West. The New Madrid Seismic Zone in the central US represents a significant intraplate hazard.

Alaska is the most seismically active US state, regularly producing large earthquakes including the 1964 Good Friday earthquake (M9.2 — the second largest ever recorded). California's San Andreas Fault system poses long-term risk to millions of residents. The USGS ShakeAlert early-warning system now covers the entire West Coast.

What Does Magnitude 4.9 Mean?

Moderate earthquakes are felt by virtually everyone near the epicentre. Strong shaking lasting 10–30 seconds can topple unsecured items, crack plaster, and cause poorly anchored objects to fall. Aftershocks are common following moderate events.

Significant damage can occur to vulnerable structures — particularly unreinforced masonry, old adobe buildings, and poorly maintained older construction. Well-engineered modern buildings are designed to withstand this level of shaking with minimal structural impact, though contents may shift and non-structural elements (ceilings, partitions) can be damaged.

A magnitude 4.9 earthquake releases approximately approximately 30,000 tonnes of TNT — comparable to the Hiroshima atomic bomb of energy. For comparison, this exceeds the energy released by most conventional explosive events and is sufficient to shift tectonic stress in measurable ways across a wide region.

Safety Guidance

Agree on an out-of-area contact that family members can reach if local communications are disrupted. Identify two meeting points: one near your home and one further away. Practise earthquake drills, especially with children and elderly household members.

If you are on or near a coast and experience strong or prolonged earthquake shaking, treat it as a potential tsunami warning and move immediately to high ground. Do not wait for an official alert — natural warning signs (severe shaking, unusual sea withdrawal) are your first alert.

The USGS ShakeAlert system delivers earthquake warnings to smartphones via Wireless Emergency Alerts on the West Coast. California residents can also use the MyShake app. Drop, Cover, Hold On is the recommended protective action.

Monitoring and Aftershocks

Seismologists are continuing to monitor the region for aftershocks, which are common following earthquakes of this magnitude. Aftershocks can occur minutes, hours, or even days after the main event and are sometimes strong enough to cause additional damage to already-weakened structures. Residents in the area are advised to remain cautious and follow guidance from local authorities.

Real-time seismic data is being collected by the USGS and contributing regional networks. Updated information will be published as it becomes available. You can track this and all other global seismic activity in real time on our live earthquake map.

How QuakeWatch Tracks This Event

QuakeWatch sources earthquake data directly from the USGS ComCat (Comprehensive Catalog), which aggregates data contributed by seismic networks worldwide including JMA (Japan), EMSC (Europe and Mediterranean), GFZ (Germany and global), Geoscience Australia, and dozens of national and regional networks. This data is refreshed every 60 seconds, ensuring that new earthquakes appear on our live map within minutes of being processed by the USGS. You can also submit a felt report for this earthquake directly on its detail page.