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M3.0 Earthquake near Old Harbor, United States — 02 September 2025, 12:47 UTC

A minor earthquake of magnitude 3.0 was recorded near Old Harbor, United States on , with an epicentre 146 km southeast of Old Harbor, at a focal depth of 81.4 km. It ranked as the 171st strongest of 7107 earthquakes recorded in the United States in the preceding 30 days.

3.0 Minor

Time (UTC): 2025-09-02 12:47:43

Time (your timezone): —

Magnitude: 3.0 (minor)

Focal depth: 81.4 km (intermediate)

Epicentre: 56.1296, -151.9360

Location: 146 km SE of Old Harbor, Alaska

Country: United States

USGS link to NOAA tsunami information: Not linked

Review status: Automatic

Source: USGS event page

How strong was this earthquake?

Minor earthquakes in this range are felt by people close to the epicentre as a brief jolt or rattle, but they very rarely cause any damage.

A magnitude 3.0 earthquake radiates roughly 477 kg of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 138, 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 02:39 local solar time at the epicentre, in the early hours of the morning.

This event was deeper than 96% of the 155,009 earthquakes recorded in the United States in our catalogue and stronger than 96% of them.

Where was the epicentre?

The epicentre was located at 56.1296, -151.9360 — 146 km southeast of Old Harbor. The closest other recorded event was a magnitude 2.4 earthquake 18 km south-southwest of here on 07 August 2026.

The nearest other settlements in our records are Chiniak (118 km east), Akhiok (128 km south), Womens Bay (157 km north-northwest) and Larsen Bay (174 km northwest).

Why the 81 km depth matters

At 81 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 may be noticed locally, especially close to the epicentre. 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 M3.0 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

11 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 3.7.

17 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.0 event near Old Harbor on 01 September 2025. This M3.0 event released about 1,000 times less energy than that event.

18 earthquakes have been recorded within 100 km of this epicentre in the past year, 13 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 September 2025 worldwide record, and of earthquakes in the United States during September 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 3 earthquakes worldwide

All magnitude 3 earthquakes →

Questions about this earthquake

How strong was the earthquake near Old Harbor?

It measured magnitude 3.0 — a minor earthquake. A magnitude 3.0 earthquake radiates roughly 477 kg of TNT equivalent in seismic energy.

How deep was the earthquake near Old Harbor?

The focus was 81 km below the surface, which counts as intermediate.

Was the Old Harbor earthquake felt at the surface?

At magnitude 3.0 and a focal depth of 81 km, the depth spreads the energy out, so shaking is weaker overhead but reaches further.

When did the earthquake near Old Harbor happen?

02 September 2025 at 12:47 UTC.

Was there a tsunami?

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

Have there been aftershocks?

11 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 3.7.

How often do earthquakes happen near Old Harbor?

17 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.0 event near Old Harbor on 01 September 2025. This M3.0 event released about 1,000 times less energy than that event.