Magnitude 4.8 Moderate Earthquake Recorded Near 188 km SE of Perryville, Alaska

A magnitude 4.8 earthquake struck the United States at 15:16 UTC on Saturday, August 29, 2026, according to data from the United States Geological Survey (USGS). The earthquake's epicentre was located 188 km SE of Perryville, Alaska, at a focal depth of 5.7 km.

Event Details

At a focal depth of 5.7 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 4.8 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 4.8 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 4.8 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

During and after an earthquake, follow instructions from official civil protection, emergency services, and government authorities. Avoid spreading unverified information on social media. Official channels provide the most reliable information about aftershock risk, evacuation orders, and available assistance.

After an earthquake, expect aftershocks. Check yourself and others for injuries. Inspect your surroundings for hazards before moving — broken glass, gas leaks (smell), downed power lines, and structural damage. If you suspect a gas leak, open windows and evacuate without using electrical switches or open flames.

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.

Community Felt Reports

If you felt this earthquake, your experience contributes to an important scientific dataset. The USGS "Did You Feel It?" (DYFI) system and QuakeWatch's own community reports platform collect first-hand accounts of shaking intensity from people across the affected region. These reports — describing where people were, what they felt, and what moved or was damaged — help seismologists map shaking intensity across an area much larger than any single seismograph can cover. Visit the earthquake's detail page on our live map to submit your own report.