Reviewed by USGSAlaska98y ago
M7.9 earthquake 93 km NW of Attu Station, Alaska
Tuesday, December 17, 1929, 10:58:41 UTC · 53.439°N, 172.202°E
A magnitude 7.9 earthquake struck 93 km NW of Attu Station, Alaska on Tuesday, December 17, 1929, 10:58:41 UTC, at a depth of 20.0 km (shallow). No earthquake of this size or larger appears within 300 km in the USGS catalog since 1900.
- Magnitude
- 7.9
- Major · mw
- Depth
- 20 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: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
9.3 megatons of TNT
That is about 618 times the Hiroshima bomb. It released about 19,498 times the energy of a magnitude 5.0.
Tectonic setting
142 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
20 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 lists 1 M2.5+ earthquake within 200 km in the following 30 days; the largest was M5.7 on December 17, 1929. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 12 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.4151 km S of Attu Station, AlaskaSeptember 2, 1907 · 219 km S of this epicenter
- 7.0167 km WSW of Attu Station, AlaskaApril 10, 1909 · 158 km SW of this epicenter
- 6.8129 km SSE of Attu Station, AlaskaNovember 13, 1911 · 216 km SE of this epicenter
- 6.78 km SE of Attu Station, AlaskaOctober 18, 1912 · 102 km SE of this epicenter
- 6.6216 km WNW of Attu Station, AlaskaJanuary 6, 1906 · 139 km W of this epicenter
- 6.566 km S of Attu Station, AlaskaJuly 22, 1923 · 146 km SE of this epicenter
- 6.4124 km SSW of Attu Station, AlaskaJuly 31, 1923 · 181 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1909M7.8
Aleutian Islands
10 Apr 1909 · 247 km away
- 1929M7.8
Aleutian Islands: Near Islands
17 Dec 1929 · 115 km away
- 1898M7.6
Aleutian Islands: Near Islands
29 Jun 1898 · 161 km away
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.