Reviewed by USGSAlaska40y ago
M4.7 earthquake 67 km SE of Adak, Alaska
Tuesday, October 7, 1986, 14:40:11 UTC · 51.513°N, 175.851°W
A magnitude 4.7 earthquake struck 67 km SE of Adak, Alaska on Tuesday, October 7, 1986, 14:40:11 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.2 on October 6, 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 earthquakeDashed circle: 50 km aftershock search area
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
87 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 lists 3 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.6 on October 18, 1986. 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 532 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 · 16 km E of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 74 km E of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 72 km NW of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 131 km W of this epicenter
- 7.2238 km WSW of Adak, AlaskaMarch 22, 1905 · 281 km W of this epicenter
- 7.2162 km WSW of Adak, AlaskaMarch 16, 1957 · 209 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 71 km SW of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 96 km W 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 · 16 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 74 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 208 km away
- 1971M7.1
Andreanof Islands
2 May 1971 · 94 km away · intensity VI
tsunami
- 1986M6.4
Andreanof Islands
17 May 1986 · 129 km away
tsunami
- 1946
East Aleutian Islands
1 Nov 1946 · 94 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.