M6.1 Earthquake 73 km N of Chickaloon, Alaska — May 31, 2021
2021-05-31 06:59:55 UTC (2021-05-31) · approx. 8:59 PM UTC-10 local
Felt by 4,618 people across a wide area. Maximum shaking intensity MMI 5.9 (strong).
On May 31, 2021 at 06:59 UTC, a magnitude 6.1 shallow crustal earthquake struck 73 km N of Chickaloon, Alaska, at a depth of 44.0 km and coordinates 62.4492°, -148.2512°. The earthquake was reported felt by 4,618 peopleacross a wide area, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 5.9 (strong). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. The nearest populated place is Girdwood (population 2,250).
Physical scale: An earthquake of magnitude 6.1 releases seismic energy equivalent to roughly 21 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 9.7 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Alaska, a region characterized by Pacific Plate subduction beneath the North American Plate, producing frequent megathrust and crustal earthquakes along the Aleutian arc. The nearest mapped fault system is the Aleutian megathrust. View all earthquakes in Alaska.
Learn more: Magnitude scale · Aftershock sequences
Nearest Populated Places
What the Shaking Felt Like
At MMI 5.9 (strong), people in the most strongly affected areas would have experienced: Moderate shaking that everyone in the area would feel. Sleeping people are awakened. Dishes and windows may break. Unstable objects may be knocked over.
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 4,618 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 13,693 |
| MMI 4 | light | 383,241 |
| MMI 5 | moderate | 27,224 |
Earthquake Details
-148.2512°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 6.1 earthquake near Chickaloon, Alaska?
The magnitude 6.1 earthquake that struck 73 km N of Chickaloon, Alaska on May 31, 2021 at 06:59 UTC had a depth of 44.0 km. It was felt by 4,618 people with maximum shaking intensity of MMI 5.9 (strong). For context, this was a strong earthquake capable of causing significant damage.
Where did the earthquake occur?
The earthquake epicenter was located at 62.4492°, -148.2512°, which is 73 km N of Chickaloon, Alaska. The nearest populated place is Girdwood (population 2,250). View all earthquakes in Alaska.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 6.1 earthquakes can continue for weeks to months and gradually diminish over time.
Has Alaska had earthquakes this big before?
The largest recorded earthquake in Alaska was the M9.2 Great Alaska earthquake of March 27, 1964. Today's magnitude 6.1 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: ak0216xu2rod). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, May 31, 2021). M6.1 Earthquake 73 km N of Chickaloon, Alaska — May 31, 2021. Retrieved December 29, 2025 from https://www.earthquaketracker.org/earthquakes/event/ak0216xu2rod/