M4.1 Earthquake 36 km NE of Larsen Bay, Alaska — September 21, 2020
2020-09-21 18:55:31 UTC (2020-09-21) · approx. 8:55 AM UTC-10 local
On September 21, 2020 at 18:55 UTC, a magnitude 4.1 shallow crustal earthquake struck 36 km NE of Larsen Bay, Alaska, at a depth of 51.9 km and coordinates 57.8043°, -153.6253°.0 The nearest populated place is Kodiak Station (population 1,301).
Physical scale: An earthquake of magnitude 4.1 releases seismic energy equivalent to roughly 21 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 406 m — a useful intuition for the size of the slip patch on the fault.
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 submitted 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 | 949 |
Earthquake Details
-153.6253°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.1 earthquake near Larsen Bay, Alaska?
The magnitude 4.1 earthquake that struck 36 km NE of Larsen Bay, Alaska on September 21, 2020 at 18:55 UTC had a depth of 51.9 km. For context, this was a light earthquake commonly felt near the epicenter.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.1 earthquakes can continue for several days and gradually diminish over time.
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Understanding This Data
Magnitude 4.1 earthquakes are often felt but rarely cause damage.
Authoritative source: USGS event page (event ID: ak020c6kgmit). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2020, September 21, 2020). M4.1 Earthquake 36 km NE of Larsen Bay, Alaska — September 21, 2020. Retrieved November 28, 2020 from https://www.earthquaketracker.org/earthquakes/event/ak020c6kgmit/