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M5.1 Earthquake near Adak, United States — 05 August 2025, 11:04 UTC

A moderate earthquake of magnitude 5.1 was recorded near Adak, United States on , with an epicentre 54 km west of Adak, at a focal depth of 85.5 km. It ranked as the 20th strongest of 8278 earthquakes recorded in the United States in the preceding 30 days.

5.1 Moderate

Time (UTC): 2025-08-05 11:04:08

Time (your timezone): —

Magnitude: 5.1 (moderate)

Focal depth: 85.5 km (intermediate)

Epicentre: 51.8182, -177.4240

Location: 54 km W of Adak, Alaska

Country: United States

USGS link to NOAA tsunami information: Not linked

Review status: Reviewed

Source: USGS event page

How strong was this earthquake?

Moderate earthquakes can damage poorly built or unreinforced structures near the epicentre, while well-engineered buildings typically escape serious harm. Shaking is often strong enough to wake sleeping residents over a wide area.

A magnitude 5.1 earthquake radiates roughly 674 tons of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 400, which is below the USGS threshold of more than 600 for its significant-earthquake list. The ranking combines magnitude with available Did You Feel It responses and PAGER alert level; it is not a direct measurement of damage.

What the magnitude scale actually measures →

When it happened locally

That is about 23:14 local solar time at the epicentre, late at night.

This event was deeper than 97% of the 156,141 earthquakes recorded in the United States in our catalogue and stronger than 100% of them.

Where was the epicentre?

The epicentre was located at 51.8182, -177.4240 — 54 km west of Adak. The closest other recorded event was a magnitude 1.1 earthquake 28 km west of here on 31 August 2026.

Why the 86 km depth matters

At 86 km this was an intermediate-depth earthquake. Energy from events at this depth spreads out before it reaches the surface, which usually means weaker shaking near the epicentre than a shallow quake of the same magnitude, but shaking felt across a wider area.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size can be felt widely and may cause minor local damage. Its intermediate depth normally reduces peak shaking near the epicentre compared with a shallow event of the same magnitude.

Read more on how focal depth changes what you feel →

What does the tsunami information flag mean?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M5.1 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

How earthquakes generate tsunamis, and what the alert levels mean →

Aftershocks and local seismic history

19 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 1.8.

108 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.2 event near Adak on 21 March 2025. This M5.1 event released about 45 times less energy than that event.

530 earthquakes have been recorded within 100 km of this epicentre in the past year, 63 of them in the past 30 days.

How long aftershock sequences last, and how large they get →

Where this event sits in the record

This earthquake is part of the August 2025 worldwide record, and of earthquakes in the United States during August 2025. Browse the full monthly archive to compare periods.

Nearest recorded earthquakes to this epicentre

Other recent earthquakes in the United States

All recorded earthquakes in the United States →

Other magnitude 5 earthquakes worldwide

All magnitude 5 earthquakes →

Questions about this earthquake

How strong was the earthquake near Adak?

It measured magnitude 5.1 — a moderate earthquake. A magnitude 5.1 earthquake radiates roughly 674 tons of TNT equivalent in seismic energy.

How deep was the earthquake near Adak?

The focus was 86 km below the surface, which counts as intermediate.

Was the Adak earthquake felt at the surface?

At magnitude 5.1 and a focal depth of 86 km, the depth spreads the energy out, so shaking is weaker overhead but reaches further.

When did the earthquake near Adak happen?

05 August 2025 at 11:04 UTC.

Was there a tsunami?

No. The USGS record carries no tsunami-information link for this event.

Have there been aftershocks?

19 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 1.8.

How often do earthquakes happen near Adak?

108 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 6.2 event near Adak on 21 March 2025. This M5.1 event released about 45 times less energy than that event.