Reviewed by USGSAlaska40y ago
M4.7 earthquake 174 km SSE of Adak, Alaska
Thursday, November 6, 1986, 06:43:08 UTC · 50.565°N, 175.256°W
A magnitude 4.7 earthquake struck 174 km SSE of Adak, Alaska on Thursday, November 6, 1986, 06:43:08 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M4.8 on October 31, 1986.
- Magnitude
- 4.7
- Light · mb
- Depth
- 33 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
169 tons of TNT
That is about 1/89 of the Hiroshima bomb. A magnitude 5.0 releases about 3 times more energy.
Tectonic setting
24 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
33 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 492 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 · 107 km N of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 111 km N of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 178 km NW of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 202 km NW of this epicenter
- 7.2162 km WSW of Adak, AlaskaMarch 16, 1957 · 270 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 125 km NW of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 172 km NW of this epicenter
- 7.158 km WNW of Atka, AlaskaFebruary 28, 1970 · 215 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 6 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 · 107 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 111 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 233 km away
- 1971M7.1
Andreanof Islands
2 May 1971 · 165 km away · intensity VI
tsunami
- 1986M6.4
Andreanof Islands
17 May 1986 · 203 km away
tsunami
- 1946
East Aleutian Islands
1 Nov 1946 · 117 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.