Earthquake.now

M4.6 Earthquake near Old Harbor, United States — 17 September 2025, 06:35 UTC

A light earthquake of magnitude 4.6 was recorded near Old Harbor, United States on , with an epicentre 117 km southeast of Old Harbor, at a focal depth of 11.8 km. It ranked as the 26th strongest of 7367 earthquakes recorded in the United States in the preceding 30 days.

4.6 Light

Time (UTC): 2025-09-17 06:35:40

Time (your timezone): —

Magnitude: 4.6 (light)

Focal depth: 11.8 km (shallow)

Epicentre: 56.3453, -152.1760

Location: 117 km SE of Old Harbor, Alaska

Country: United States

USGS link to NOAA tsunami information: Available

Review status: Reviewed

Source: USGS event page

How strong was this earthquake?

Light earthquakes are widely felt near the epicentre and can rattle windows, dishes and hanging objects. Damage is uncommon and usually limited to cracked plaster or fallen loose items.

A magnitude 4.6 earthquake radiates roughly 120 tons of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 326, 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 20:26 local solar time at the epicentre, in the evening.

This event was deeper than 75% of the 155,964 earthquakes recorded in the United States in our catalogue and stronger than 100% of them.

Where was the epicentre?

The epicentre was located at 56.3453, -152.1760 — 117 km southeast of Old Harbor. The closest other recorded event was a magnitude 3.1 earthquake 17 km southwest of here on 06 July 2026.

The nearest other settlements in our records are Chiniak (124 km east), Larsen Bay (146 km northwest), Kodiak (151 km northwest) and Kodiak Station (153 km north).

Why the 12 km depth matters

At 12 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size is often felt across the surrounding area. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

Read more on how focal depth changes what you feel →

What does the tsunami information flag mean?

The USGS event record links to NOAA tsunami information because this was a large event in an oceanic region. That link flag does not mean a tsunami occurred or that a warning is active. Check tsunami.gov and instructions from your local authority for the current status of your coastline.

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

Aftershocks and local seismic history

5 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 3.1.

19 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.6 event near Akhiok on 22 December 2024. This M4.6 event released about 32 times less energy than that event.

30 earthquakes have been recorded within 100 km of this epicentre in the past year, 22 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 4 earthquakes worldwide

All magnitude 4 earthquakes →

Questions about this earthquake

How strong was the earthquake near Old Harbor?

It measured magnitude 4.6 — a light earthquake. A magnitude 4.6 earthquake radiates roughly 120 tons of TNT equivalent in seismic energy.

How deep was the earthquake near Old Harbor?

The focus was 12 km below the surface, which counts as shallow.

Was the Old Harbor earthquake felt at the surface?

At magnitude 4.6 and a focal depth of 12 km, shaking would have been concentrated near the epicentre.

When did the earthquake near Old Harbor happen?

17 September 2025 at 06:35 UTC.

Was there a tsunami?

The USGS record carries a link to NOAA tsunami information for this event. That is not a warning: check your regional tsunami warning centre for any live alert.

Have there been aftershocks?

5 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 3.1.

How often do earthquakes happen near Old Harbor?

19 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.6 event near Akhiok on 22 December 2024. This M4.6 event released about 32 times less energy than that event.