Reviewed by USGSAlaska5y ago
M2.7 earthquake 168 km ESE of Chignik, Alaska
Monday, September 27, 2021, 04:08:54 UTC · 55.592°N, 156.020°W
A magnitude 2.7 earthquake struck 168 km ESE of Chignik, Alaska on Monday, September 27, 2021, 04:08:54 UTC, at a depth of 12.0 km (shallow).
- Magnitude
- 2.7
- Minor · ml
- Depth
- 12 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
169 kg of TNT
That is about 1/88,990 of the Hiroshima bomb. A magnitude 5.0 releases about 2,818 times more energy.
Tectonic setting
101 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
Depth: shallow
12 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 6 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.8 on October 1, 2021. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 2.5174 km SE of Chignik, Alaska4y ago · 29 km S of this epicenter
- 3.4150 km SSW of Akhiok, Alaska5y ago · 40 km NE of this epicenter
- 2.5151 km SW of Akhiok, Alaska5y ago · 40 km N of this epicenter
- 2.9137 km ESE of Chignik, Alaska5y ago · 40 km NW of this epicenter
- 4.8137 km ESE of Chignik, Alaska5y ago · 39 km NW of this epicenter
- 3.1south of Alaska5y ago · 29 km S of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 358 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.21938 Semidi Islands, Alaska EarthquakeNovember 10, 1938 · 144 km W of this epicenter
- 8.22021 Chignik, Alaska EarthquakeJuly 29, 2021 · 120 km W of this epicenter
- 7.82020 Perryville, Alaska EarthquakeJuly 22, 2020 · 173 km W of this epicenter
- 7.62020 Sand Point, Alaska EarthquakeOctober 19, 2020 · 254 km SW of this epicenter
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 253 km W of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 244 km NE of this epicenter
- 7.0113 km ESE of Chignik, AlaskaMay 4, 1923 · 54 km NW of this epicenter
- 7.026 km SSE of Karluk, AlaskaDecember 6, 1999 · 220 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1900M8.3
Kodiak Island
9 Oct 1900 · 229 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 243 km away · intensity VII
Limited damage (under $1M)tsunami
- 2020M7.8
Alaska
22 Jul 2020 · 173 km away · intensity VII
Limited damage (under $1M)tsunami
- 1970M6.0
Andreanof Islands
11 Mar 1970 · 249 km away · intensity V
Limited damage (under $1M)tsunami
- 1792
Kodiak Island
1792 · 293 km away · intensity VII
Limited damage (under $1M)tsunami
- 1938M8.2
Alaska
10 Nov 1938 · 148 km away · intensity VI
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.