M4.1 Earthquake 114 km E of Chignik, Alaska — October 11, 2021
2021-10-11 19:40:25 UTC (2021-10-11) · approx. 9:40 AM UTC-10 local
On October 11, 2021 at 19:40 UTC, a magnitude 4.1 shallow crustal earthquake struck 114 km E of Chignik, Alaska, at a depth of 53.4 km and coordinates 56.2849°, -156.5569°. The earthquake was reported felt by 1 personacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 3.1 (light).
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 1 citizen response 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 |
|---|
Earthquake Details
-156.5569°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.1 earthquake near Chignik, Alaska?
The magnitude 4.1 earthquake that struck 114 km E of Chignik, Alaska on October 11, 2021 at 19:40 UTC had a depth of 53.4 km. It was felt by 1 person with maximum shaking intensity of MMI 3.1 (light). 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: ak021d206f9o). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, October 11, 2021). M4.1 Earthquake 114 km E of Chignik, Alaska — October 11, 2021. Retrieved August 8, 2022 from https://www.earthquaketracker.org/earthquakes/event/ak021d206f9o/