Reviewed by USGSAlaska57y ago
M7.1 earthquake 58 km WNW of Atka, Alaska
Saturday, February 28, 1970, 10:52:33 UTC · 52.487°N, 174.915°W
A magnitude 7.1 earthquake struck 58 km WNW of Atka, Alaska on Saturday, February 28, 1970, 10:52:33 UTC, at a depth of 164.1 km (intermediate). It is the strongest earthquake within 300 km since an M7.2 on March 16, 1957.
- Magnitude
- 7.1
- Major · mw
- Depth
- 164 km
- Intermediate
- 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
697 kilotons of TNT
That is about 46 times the Hiroshima bomb. It released about 1,462 times the energy of a magnitude 5.0.
Tectonic setting
181 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: intermediate
164 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
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 206 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 120 km SW of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 139 km SW of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 224 km SW of this epicenter
- 7.2162 km WSW of Adak, AlaskaMarch 16, 1957 · 296 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 190 km SW of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 195 km SW of this epicenter
- 7.0101 km S of Adak, AlaskaSeptember 9, 1910 · 195 km SW 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, which together caused about 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 120 km away
2 deathsSevere damage ($5–24M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 291 km away
Limited damage (under $1M)tsunami
- 1946
East Aleutian Islands
1 Nov 1946 · 113 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.