Reviewed by USGSAlaska40y ago
M5.5 earthquake 89 km SSE of Atka, Alaska
Friday, November 14, 1986, 21:42:43 UTC · 51.426°N, 173.821°W
A magnitude 5.5 earthquake struck 89 km SSE of Atka, Alaska on Friday, November 14, 1986, 21:42:43 UTC, at a depth of 33.0 km (shallow). It is the strongest earthquake within 300 km since an M5.9 on November 6, 1986.
- Magnitude
- 5.5
- Moderate · 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: 75 km aftershock search area
In context
How big was it, and why here?
Energy released
3 kilotons of TNT
That is about 1/6 of the Hiroshima bomb. It released about 6 times the energy of a magnitude 5.0.
Tectonic setting
55 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 75 km
USGS lists 1 M2.5+ earthquake within 75 km in the following 30 days; the largest was M4.9 on December 1, 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 466 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 · 125 km W of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 67 km W of this epicenter
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 287 km E of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 205 km W of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 272 km W of this epicenter
- 7.175 km S of Adak, AlaskaMarch 14, 1957 · 204 km W of this epicenter
- 7.160 km SW of Adak, AlaskaMarch 12, 1957 · 237 km W of this epicenter
- 7.158 km WNW of Atka, AlaskaFebruary 28, 1970 · 140 km NW 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, which together caused about 2 recorded deaths. The most severe:
- 1957M8.6
Alaska
9 Mar 1957 · 125 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 67 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 194 km away
Limited damage (under $1M)tsunami
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 270 km away · intensity V
tsunami
- 1971M7.1
Andreanof Islands
2 May 1971 · 234 km away · intensity VI
tsunami
- 1986M6.4
Andreanof Islands
17 May 1986 · 111 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.