Reviewed by USGSAlaska104y ago
M7.0 earthquake 113 km ESE of Chignik, Alaska
Friday, May 4, 1923, 16:26:48 UTC · 55.840°N, 156.771°W
A magnitude 7.0 earthquake struck 113 km ESE of Chignik, Alaska on Friday, May 4, 1923, 16:26:48 UTC, at a depth of 25.0 km (shallow). It is the strongest earthquake within 300 km since an M7.4 on May 31, 1917.
- Magnitude
- 7.0
- Major · mw
- Depth
- 25 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 earthquake
In context
How big was it, and why here?
Energy released
477 kilotons of TNT
That is about 32 times the Hiroshima bomb. It released about 1,000 times the energy of a magnitude 5.0.
Tectonic setting
147 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
25 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 200 km
USGS has not published any M2.5+ earthquake within 200 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 60 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.454 km SE of Sand Point, AlaskaMay 31, 1917 · 218 km SW of this epicenter
- 7.14 km ENE of Karluk, AlaskaNovember 7, 1912 · 243 km NE of this epicenter
- 6.8Event 48 Novarupta-Mount Katmai area, Alaska PeninsulaJune 10, 1912 · 287 km N of this epicenter
- 6.688 km SSE of Old Harbor, AlaskaDecember 21, 1917 · 253 km E of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 7 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1900M8.3
Kodiak Island
9 Oct 1900 · 245 km away · intensity VIII
Limited damage (under $1M)
- 1788M8.0
Unga Island
21 Jul 1788 · 265 km away · intensity VII
Limited damage (under $1M)tsunami
- 1788M8.0
Alaska Peninsula
6 Aug 1788 · 283 km away
tsunami
- 1906M7.6
Aleutian Islands
23 Dec 1906 · 210 km away
- 1912M7.5
Alaska Peninsula
7 Nov 1912 · 214 km away · intensity V
- 1868
Alaska Peninsula
15 May 1868 · 283 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.