A magnitude 5.3 earthquake struck about 151 kilometers (94 miles) west southwest of Adak, Alaska, on September 11, 2026, at 10:47 UTC, according to the U.S. Geological Survey. The agency placed the epicenter at 51.213 degrees north, 178.543 degrees west, at a depth of roughly 40.9 kilometers (25.4 miles). The USGS reported a ShakeMap intensity of V, indicating moderate shaking near the epicenter.
KEY FACTS
- The U.S. Geological Survey reported the quake at magnitude 5.3, with an epicenter 151 kilometers west southwest of Adak, Alaska.
- The agency recorded the event at 10:47 UTC on September 11, 2026, at a depth of about 40.9 kilometers.
- The USGS assigned a ShakeMap intensity of V, meaning moderate shaking was possible near the epicenter.
- Adak is a small community on a remote Aleutian island, and the epicenter lies well offshore in a sparsely populated stretch of the North Pacific.
CONTEXT
The Aleutian Islands arc curves roughly 1,900 kilometers from the Alaska Peninsula toward Russia's Kamchatka Peninsula and marks where the Pacific plate dives beneath the North American plate. That subduction zone produces frequent earthquakes, and the USGS event page is the standard public record for each one. The agency's ShakeMap system estimates shaking intensity from instrument readings and ground motion models; intensity V on the Modified Mercalli scale corresponds to shaking felt widely but causing at most light damage. The USGS summary did not list casualties, damage or a tsunami warning. The National Tsunami Warning Center, which issues alerts for this region, was not cited in the supplied information, so its status is not established here.
WHY IT MATTERS
The Aleutian arc is one of the most seismically active places on Earth, and offshore quakes there can generate tsunamis that cross the Pacific within hours. Even a moderate event is a reminder that monitoring and warning systems for this sparsely populated region carry consequences far beyond Alaska's shores.
WHAT TO WATCH
- Whether the U.S. Geological Survey revises the magnitude or depth as more seismic data are analyzed.
- Whether the National Tsunami Warning Center issues, or explicitly rules out, any advisory for the Aleutians or the wider Pacific.
- Whether local authorities in Adak or nearby communities report any shaking effects or damage.
- Whether the event is followed by aftershocks large enough to appear in the USGS catalog.