Location:

Magnitude:

7.9

Time:

23 Jan 2018 09:31:40

Depth:

14.0

There are 11 swarms found nearby.

2018

PS20180123.1(29.8km)

23 Jan

1 day 12 hours

9 earthquakes

S20180123.2(47.8km)

23 Jan

10 days 6 hours

191 earthquakes

S20180123.1(29.5km)

23 Jan

9 days 3 hours

140 earthquakes

S20180124.5(65.9km)

23 Jan

10 days 3 hours

109 earthquakes

S20180124.4(22.8km)

23 Jan

2 days 6 hours

50 earthquakes

S20180124.1(51.2km)

23 Jan

1 day 13 hours

59 earthquakes

S20180124.6(36.5km)

23 Jan

2 days 8 hours

55 earthquakes

S20180123.3(36.5km)

23 Jan

5 days 2 hours

78 earthquakes

S20180124.3(72.6km)

23 Jan

3 days 20 hours

85 earthquakes

S20180124.2(44.3km)

23 Jan

2 days 1 hours

36 earthquakes

S20180208.1(62.9km)

7 Feb

1 day 15 hours

32 earthquakes

AI-generated article — for informational and entertainment purposes only. May contain inaccuracies. Full disclaimerFound an error?

The 2018 Magnitude 7.9 Earthquake Southeast of Chiniak, Alaska

On January 23, 2018, at 09:31 UTC, a magnitude 7.9 earthquake struck 261 km southeast of Chiniak, Alaska, at a depth of 14.0 km. This event ranks among the strongest recorded in the region since 2000 and originated within the tectonically active Aleutian subduction zone.

The Chiniak area lies on Kodiak Island, where the Pacific Plate converges with and subducts beneath the North American Plate at rates of approximately 6–7 cm per year. This subduction drives intense seismic activity along the Aleutian megathrust. The 2018 earthquake occurred in the intraslab portion of the subducting Pacific Plate, producing strong ground shaking felt across Kodiak Island and parts of the Alaska Peninsula. No significant tsunami was generated, consistent with its moderate depth and focal mechanism.

Alaska’s geological history reflects repeated large-magnitude earthquakes. The 1964 Great Alaska Earthquake, magnitude 9.2, remains the largest recorded in North American history and caused extensive uplift and subsidence across the Kodiak region. Paleoseismic studies indicate recurrence intervals for great subduction-zone events on the order of several centuries. Since 2000, the M7.9 event of 2018 stands as the sole magnitude 7.9 or greater earthquake within the immediate vicinity of Chiniak, underscoring the episodic nature of great earthquakes in this segment of the arc.

Post-event analyses by seismic networks confirmed aftershock activity distributed both up-dip and down-dip of the mainshock rupture. Regional monitoring continues to track strain accumulation along the megathrust, informing updated seismic hazard assessments for coastal Alaska communities.

References

U.S. Geological Survey Earthquake Catalog (event parameters for 23 Jan 2018)
Alaska Earthquake Center annual reports (regional seismicity summaries since 2000)