Reviewed by USGSAlaska2y ago
M4.4 earthquake 73 km SW of Unalaska, Alaska
Thursday, April 4, 2024, 19:57:02 UTC · 53.503°N, 167.445°W
A magnitude 4.4 earthquake struck 73 km SW of Unalaska, Alaska on Thursday, April 4, 2024, 19:57:02 UTC, at a depth of 92.9 km (intermediate). USGS received 5 “Did You Feel It?” reports, with a maximum reported intensity of III (weak).
- Magnitude
- 4.4
- Light · mb
- Depth
- 93 km
- Intermediate
- Felt reports
- 5
- Max intensity III
- Est. shaking
- III
- Weak (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
60 tons of TNT
That is about 1/251 of the Hiroshima bomb. A magnitude 5.0 releases about 8 times more energy.
Tectonic setting
142 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: intermediate
93 km
Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.
Did You Feel It?
Where it was felt
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| 99685<br>0.293 | III · Weak | 5 | 111 km |
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 M3.7 on April 4, 2024. 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 688 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 57 km S of this epicenter
- 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 213 km W of this epicenter
- 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 115 km E of this epicenter
- 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 147 km SW of this epicenter
- 7.0203 km SSE of Unalaska, AlaskaAugust 22, 1940 · 199 km SE of this epicenter
- 6.980 km SW of Nikolski, AlaskaMarch 9, 1957 · 190 km SW of this epicenter
- 6.977 km SSW of Nikolski, AlaskaJanuary 23, 1935 · 186 km SW 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. The most severe:
- 1965M6.5
Aleutian Islands: Fox Islands
2 Jul 1965 · 53 km away
Limited damage (under $1M)tsunami
- 1917M7.9
Alaska Peninsula
31 May 1917 · 180 km away · intensity V
- 1902M7.8
Aleutian Islands: Fox Islands
1 Jan 1902 · 123 km away
- 1907M7.8
Aleutian Islands
2 Sep 1907 · 183 km away
- 1916M7.5
Aleutian Islands: Fox Islands
18 Apr 1916 · 171 km away
- 1957M7.5
Aleutian Islands: Fox Islands
22 Mar 1957 · 221 km away · intensity V
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.