2021 Chignik earthquake
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude (Mw) of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
Anchorage Kodiak Perryville | |
| UTC time | 2021-07-29 06:15:49 |
|---|---|
| ISC event | 620857937 |
| USGS-ANSS | ComCat |
| Local date | July 28, 2021 |
| Local time | 22:15:49 AKDT |
| Magnitude | 8.2 Mw |
| Depth | 32.2 km (20.0 mi) |
| Epicenter | 55.474°N 157.917°W |
| Fault | Aleutian subduction zone |
| Type | Megathrust |
| Areas affected | Alaska |
| Max. intensity | MMI VII (Very strong) |
| Peak acceleration | 0.26 g |
| Tsunami | 2.62 m (8.6 ft) |
| Foreshocks | 7.8 Mw and 7.6 Mw in 2020 |
| Aftershocks | 1,629 (As of 12 July 2022) Largest 6.9 Mw |
| Casualties | None |
This was the largest earthquake in the United States since the 1965 Rat Islands earthquake, and the 7th largest earthquake in US history. It was also the strongest earthquake globally since the 2015 Illapel earthquake, tying the 2017 Chiapas earthquake and 2018 Fiji earthquake.
No casualties or serious damage were reported in the aftermath of the mainshock, as well as some of the strong aftershocks. In Perryville, the closest populated area to the quake, cracks appeared in drywalls and on the ground. Some homes were also shifted. The limited impact from this earthquake was attributed to it occurring offshore from the sparsely-populated Alaska Peninsula. A tsunami warning was rescinded and no large waves were observed because the earthquake took place 32 km beneath the seafloor; deep enough that vertical uplift of the seafloor was limited therefore displacing smaller amounts of water.