Reviewed by USGSAlaska11y ago
M3.3 earthquake 44 km WSW of Adak, Alaska
Thursday, July 23, 2015, 13:44:58 UTC · 51.664°N, 177.179°W
A magnitude 3.3 earthquake struck 44 km WSW of Adak, Alaska on Thursday, July 23, 2015, 13:44:58 UTC, at a depth of 60.8 km (shallow).
- Magnitude
- 3.3
- Minor · ml
- Depth
- 61 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
1 tons of TNT
That is about 1/11,203 of the Hiroshima bomb. A magnitude 5.0 releases about 355 times more energy.
Tectonic setting
128 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: shallow
61 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 2 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.5 on July 27, 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 1,211 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.71965 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeFebruary 4, 1965 · 288 km W of this epicenter
- 8.61957 Atka, Alaska EarthquakeMarch 9, 1957 · 109 km E of this epicenter
- 8.01986 Atka, Alaska EarthquakeMay 7, 1986 · 167 km E of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 33 km W of this epicenter
- 7.9Rat Islands, Aleutian Islands, AlaskaJune 23, 2014 · 282 km W of this epicenter
- 7.8Rat Islands, Aleutian Islands, AlaskaNovember 17, 2003 · 295 km W of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 41 km NE of this epicenter
- 7.4265 km WSW of Adak, AlaskaFebruary 4, 1965 · 225 km W of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 13 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 · 109 km away
2 deathsSevere damage ($5–24M)tsunami
- 1986M8.0
Aleutian Islands: Adak
7 May 1986 · 167 km away · intensity VI
Moderate damage ($1–5M)tsunami
- 1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 288 km away · intensity VI
Under $1 million damagetsunami
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 141 km away
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 33 km away · intensity VI
tsunami
- 2014M7.9
Aleutian Islands
23 Jun 2014 · 282 km away · intensity VI
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.