2020 M7.8 Simeonof Earthquake and M7.6 aftershock

The location and magnitude of the M7.8 Simeonof Earthquake on July 21, 2020 at 10:12 p.m. AKDT (July 22, 06:12 UTC) triggered a tsunami warning from the National Tsunami Warning Center.

The first tsunami bulletin from the NTWC at 10:21 p.m. issued a warning for south Alaska and the Alaska Peninsula, Pacific coasts from Kennedy Entrance, Alaska (40 miles SW of Homer) to Unimak Pass, Alaska (80 miles NE of Unalaska). Subsequent bulletins widened, then refined, the warning area based on updated earthquake parameters. The warning was ultimately cancelled at 12:25 a.m. on July 22.

NTWC reported that a tsunami was observed in Sand Point with a maximum wave height of 0.8 ft.

Various social media reports stated that communities in Kodiak, Homer, and the Kenai Peninsula areas evacuated as a result of the warnings.

The M7.6 aftershock on October 19, 2020 also triggered tsunami warnings and evacuations.

The Alaska Earthquake Center and the Alaska Division of Geological and Geophysical Surveys have worked for years assessing tsunami hazards in Alaska’s coastal communities and preparing their residents for a future disaster. Historical tsunami events in the area are described in detail in the “Seismic and Tsunami History” section of the Sand Point report, page 4.

The reports for King Cove, Sand Point and Chignik contain information for communities within the warning area. Links to these and other reports are available on our website as well as the interactive tsunami web map tool.

We will continue to update this page as we learn more.