Magnitude 4.9 Light Earthquake Strikes Near Adak, Alaska

Source: USGS · Alaska

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A magnitude 4.9 earthquake occurred 120 km west-southwest of Adak, Alaska, on February 18, 2026. The shallow quake did not trigger a tsunami advisory.

What this USGS earthquake report tells you, and what most readers miss

This notice was issued by USGS on February 18, 2026 and geographically references Alaska. Its severity classification of "medium" signals how the issuing agency weighs the risk of harm if no action is taken — "critical" and "high" tier alerts typically carry direct consumer actions, while "medium" and "low" tend toward informational guidance or monitoring advisories. The category it belongs to — Earthquakes — determines the regulatory framework behind it, which shapes what remedies (refunds, replacements, recalls, evacuations) are available to affected individuals and who holds statutory responsibility for enforcement.

Most readers skim a notice like this, check whether they are personally affected, and move on. The more useful lens is to read it as a data point about the issuing system: how quickly USGS detected the hazard, how precise the geographic or product-identifier scope is, and whether similar notices have clustered in the same category or region in the last 90 days. Cluster patterns frequently precede a broader regulatory action — a single localized USGS earthquake report is isolated; three of them within a quarter often indicate a supply-chain, infrastructure, or seasonal driver that will keep producing notices until something structural changes.

For decision-making, Areazine pairs each alert with the original agency URL, the full agency name, and a timestamp so you can verify the notice against the primary source before acting on it. Tags on this item (earthquake, seismic, usgs, Alaska) map to related alerts in the same area of risk — browsing them together gives a clearer picture than any single notice alone, because the shape of an ongoing issue only becomes visible across multiple sequential alerts.

What Happened

A light earthquake with a magnitude of 4.9 ml occurred on Wednesday, February 18, 2026, at 23:12:50 UTC (approximately 1:12 PM local time in Adak). The event was centered approximately 120 km west-southwest of Adak, Alaska, at a shallow depth of 18.6 km.

Location Details

The seismic event was located at coordinates 51.288°N and 178.094°W. The recorded depth of 18.6 km is classified as shallow. Shallow earthquakes—those occurring at depths of less than 20 km—are typically felt more distinctly at the surface than deeper seismic events of the same magnitude.

Impact Assessment

According to the U.S. Geological Survey (USGS), there are currently no felt reports associated with this event. The Modified Mercalli Intensity (MMI) was calculated at 4.366, which corresponds to light shaking. Data indicates there is no tsunami advisory, watch, or warning in effect. No specific PAGER alert level (color) was issued for this event.

What You Should Know

A magnitude 4.9 earthquake is categorized as a "light" earthquake. While these events cause noticeable shaking and are frequently felt, they rarely result in significant structural damage. Residents in the Aleutian Islands region should be aware that aftershocks are a routine possibility following an event of this size. In the event of further shaking, safety officials recommend you "Drop, Cover, and Hold On."

Source

Data and attribution provided by the USGS Earthquake Hazards Program.

Original source: USGS Official Notice ↗

All Earthquakes →

Frequently Asked Questions

Common questions about this USGS earthquake report.

What is this USGS earthquake report about?
A magnitude 4.9 earthquake occurred 120 km west-southwest of Adak, Alaska, on February 18, 2026. The shallow quake did not trigger a tsunami advisory.
Which agency issued this alert?
This alert was issued by USGS. The original notice is available at the source link at the bottom of this article.
How severe is this alert?
This alert is classified as "medium" severity. Stay informed and follow agency guidance.
What area is affected?
This alert affects Alaska. Check with USGS for the most current geographic scope.
Where can I find more Earthquakes updates?
Browse the full Earthquakes feed on Areazine at areazine.com/earthquakes/ for the latest updates from USGS and other agencies.