M5.5 Earthquake near Adak, Alaska — 29 August 2025, 09:14 UTC
A moderate earthquake of magnitude 5.5 was recorded near Adak, Alaska on , with an epicentre 264 km west of Adak, at a focal depth of 83.0 km.
Time (UTC): 2025-08-29 09:14:25
Time (your timezone): —
Magnitude: 5.5 (moderate)
Focal depth: 83.0 km (intermediate)
Epicentre: 51.6321, 179.5580
Location: 264 km W of Adak, Alaska
USGS link to NOAA tsunami information: Available
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 5.5 earthquake radiates roughly 2,682 tons of TNT equivalent in seismic energy.
The USGS assigns this earthquake a significance score of 465, 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.
Where was the epicentre?
The epicentre was located at 51.6321, 179.5580 — 264 km west of Adak. The closest other recorded event was a magnitude 3.4 earthquake 16 km southeast of here on 11 June 2026.
Why the 83 km depth matters
At 83 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.
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
1 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 5.0.
44 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.9 event near Adak on 28 August 2025. This M5.5 event released about 4.0 times less energy than that event.
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. Browse the full monthly archive to compare periods.
Nearest recorded earthquakes to this epicentre
- M3.4 earthquake near Adak, Alaska — (16 km SE)
- M2.8 earthquake near Adak, Alaska — (19 km SE)
- M2.0 earthquake near Adak, Alaska — (20 km ENE)
- M1.4 earthquake near Adak, Alaska — (27 km N)
- M2.3 earthquake near Adak, Alaska — (30 km SSW)
- M2.8 earthquake near Adak, Alaska — (30 km N)
- M0.7 earthquake near Adak, Alaska — (31 km N)
- M1.8 earthquake near Adak, Alaska — (31 km N)
- M2.9 earthquake near Adak, Alaska — (33 km N)
- M2.9 earthquake near Adak, Alaska — (33 km N)
Other magnitude 5 earthquakes worldwide
- M5.6 earthquake near Port McNeill, Canada —
- M5.5 earthquake near Mutsu, Japan —
- M5.6 earthquake near San Fernando, Peru —
- M5.4 earthquake near Abepura, Indonesia —
- M5.3 earthquake near Kokopo, Papua New Guinea —
- M5.6 earthquake near Pacific-Antarctic Ridge —
- M5.4 earthquake near Rapu-Rapu, Philippines —
- M5.4 earthquake near Tsunagi, Japan —
Questions about this earthquake
How strong is a magnitude 5.5 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 5.5 earthquake radiates roughly 2,682 tons of TNT equivalent in seismic energy.
How deep was the earthquake near Adak?
At 83 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.
Was the M5.5 earthquake near Adak felt?
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.
What does the USGS tsunami field mean for this event?
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.
Have there been aftershocks?
1 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 5.0.
How often do earthquakes happen near Adak?
44 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.9 event near Adak on 28 August 2025. This M5.5 event released about 4.0 times less energy than that event.