Reviewed by USGSAlaska11y ago
M2.5 earthquake 245 km WSW of Adak, Alaska
Thursday, July 23, 2015, 11:46:14 UTC · 51.011°N, 179.883°W
A magnitude 2.5 earthquake struck 245 km WSW of Adak, Alaska on Thursday, July 23, 2015, 11:46:14 UTC, at a depth of 6.8 km (shallow).
- Magnitude
- 2.5
- Minor · ml
- Depth
- 7 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
85 kg of TNT
That is about 1/177,558 of the Hiroshima bomb. A magnitude 5.0 releases about 5,623 times more energy.
Tectonic setting
57 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
7 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 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M2.7 on July 25, 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 1,039 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 · 101 km W of this epicenter
- 8.31906 Western Aleutian Islands (Hawadax/Rat Islands) EarthquakeAugust 17, 1906 · 164 km NW of this epicenter
- 7.977 km WSW of Adak, AlaskaJune 10, 1996 · 168 km E of this epicenter
- 7.9Rat Islands, Aleutian Islands, AlaskaJune 23, 2014 · 134 km NW of this epicenter
- 7.8Rat Islands, Aleutian Islands, AlaskaNovember 17, 2003 · 104 km W of this epicenter
- 7.6Rat Islands, Aleutian Islands, AlaskaMarch 30, 1965 · 177 km SW of this epicenter
- 7.65 km WNW of Adak, AlaskaFebruary 14, 1905 · 241 km NE of this epicenter
- 7.4265 km WSW of Adak, AlaskaFebruary 4, 1965 · 60 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 12 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1965M8.7
Aleutian Islands: Rat Islands
4 Feb 1965 · 101 km away · intensity VI
Under $1 million damagetsunami
- 1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 164 km away
- 1905M7.9
Andreanof Islands
14 Feb 1905 · 99 km away
- 1996M7.9
Andreanof Islands
10 Jun 1996 · 168 km away · intensity VI
tsunami
- 2014M7.9
Aleutian Islands
23 Jun 2014 · 134 km away · intensity VI
tsunami
- 2003M7.8
Aleutian Islands: Rat Islands
17 Nov 2003 · 104 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.