Reviewed by USGSAlaska10y ago
M3.8 earthquake 102 km SSE of Atka, Alaska
Friday, December 18, 2015, 06:52:32 UTC · 51.314°N, 173.771°W
A magnitude 3.8 earthquake struck 102 km SSE of Atka, Alaska on Friday, December 18, 2015, 06:52:32 UTC, at a depth of 12.4 km (shallow).
- Magnitude
- 3.8
- Minor · mb
- Depth
- 12 km
- Shallow
- Felt reports
- 0
- Max intensity I
- 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
8 tons of TNT
That is about 1/1,992 of the Hiroshima bomb. A magnitude 5.0 releases about 63 times more energy.
Tectonic setting
43 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
12 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 4 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M5.0 on December 31, 2015. 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 883 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 · 130 km W of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 73 km W of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 269 km W of this epicenter
- 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 282 km E of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 212 km W of this epicenter
- 7.388 km WSW of Adak, AlaskaJuly 7, 1929 · 276 km W of this epicenter
- 7.346 km SSW of Adak, AlaskaJune 10, 1996 · 214 km W of this epicenter
- 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 157 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 11 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 · 130 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 73 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1901M7.8
Aleutian Islands: Fox Islands
31 Dec 1901 · 192 km away
Limited damage (under $1M)tsunami
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 269 km away · intensity VI
tsunami
- 1929M7.8
Aleutian Islands: Fox Islands
7 Mar 1929 · 265 km away · intensity V
tsunami
- 1996M7.3
Andreanof Islands
10 Jun 1996 · 214 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.