M 5.5 - 123 km NNE of Atka, Alaska
October 28, 2020 at 04:13:42 UTC
Depth: 239.67 km (Intermediate)
Key Takeaway
This moderate earthquake (M5.5) occurred 5 years ago near 123 km NNE of Atka, Alaska, at a depth of 239.67 km (intermediate). A tsunami warning was issued for this event.
Moderate
PAGER Alert
Tsunami
Felt Reports
Event Details
| Magnitude | 5.5 mww |
| Depth | 239.67 km (Intermediate) |
| Location | 53.2019N, 173.4156W |
| Mercalli Intensity | II (Weak) |
| Alert Level (PAGER) | Green — No fatalities or damage expected |
| Tsunami Warning | Yes |
| Significance | 465 / 3000 |
| Status | Reviewed |
| Network | us |
| USGS Event Page | View on USGS → |
Frequently Asked Questions
What was the magnitude of this earthquake?
This earthquake had a magnitude of 5.5, classified as "Moderate". Moderate earthquakes can cause damage to poorly constructed buildings.
How deep was this earthquake?
This earthquake occurred at a depth of 239.67 km, classified as "Intermediate". Intermediate-depth earthquakes are felt over a wider area but typically cause less surface damage than shallow events of the same magnitude.
Where exactly did this earthquake occur?
This earthquake occurred near 123 km NNE of Atka, Alaska, at coordinates 53.2019N, 173.4156W. The location is determined by analyzing seismic wave arrival times at multiple monitoring stations.
Were there aftershocks associated with this event?
Aftershock data for this specific event can be explored by viewing nearby recent earthquakes listed below on this page. Aftershocks are smaller earthquakes that occur in the same area following a larger event, and they can continue for days, weeks, or even months depending on the original earthquake's magnitude.
What does the magnitude of this earthquake mean in practical terms?
A magnitude 5.5 earthquake is classified as "Moderate" — these are widely felt and can cause damage to vulnerable structures, though well-built buildings typically withstand them.
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Data from the USGS Earthquake Hazards Program (ComCat). QuakeScan is not affiliated with the USGS. Event details may be updated as new data becomes available.