UPDATE: No Tsunami Threat to Hawaii After Large 7+ Alaska Quake

By Wendy Osher

Update: 9:34 p.m. 7.21.20:

There is no tsunami threat to Hawaii following a large 7.8 magnitude earthquake reported at 8:13 p.m. HST on Tuesday, July 21, in the Alaska Peninsula. The Pacific Tsunami Warning Center issued an update saying that based on all available data, a destructive Pacific-Wide tsunami is not expected and there is no tsunami threat to Hawaii.

Authorities say there were no tsunamis observed at nearby deep ocean gages.

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The Pacific Tsunami Warning Center has issued an update saying that based on all available data, the tsunami threat from a large earthquake in the Alaska Peninsula has now passed for areas covered by their bulletin.  No tsunamis were observed at nearby deep ocean gages and there is no longer a tsunami threat from this earthquake.  The public is advised to “remain observant and exercise normal caution near the sea. Otherwise, no action is required.”

Update: 9:01 p.m. 7.21.20:

An evaluation is still underway to determine if there is a tsunami threat to Hawaii after a large earthquake in the Alaska Peninsula.  The USGS has since upgraded the quake form a preliminary magnitude 7.4 to a 7.8 and say it occurred at a depth of 8 miles.

A tsunami threat exists for parts of the Pacific located closer to the earthquake, but it is still too early to determine whether there is a possible tsunami threat to Hawaii. If there is a threat to Hawaii, the earliest estimated time the hazard might begin is 12:48 a.m. HST on Wednesday, July 22, 2020.

According to updated information provided by authorities, tsunami waves are forecast to be less than 0.3 meters above the tide level for the coasts of Hawaii.  The latest advisory notes that: actual amplitudes at the coast may vary from forecast amplitudes due to uncertainties in the forecast and local features.  In particular, maximum tsunami amplitudes on atolls and at locations with fringing or barrier reefs will likely be much smaller than the forecast indicates.

Stay with us for further updates.

Posted: 8:32 p.m. 7.21.20

The Pacific Tsunami Warning Center is evaluating a preliminary magnitude 7.4 earthquake reported at 8:13 p.m. HST on Tuesday, July 21, 2020 in the Alaska Peninsula. The PTWC says it’s till too early to determine whether there is a potential threat to Hawaii. If there is a tsunami threat to Hawaii, the earliest estimated time the hazard might begin is 12:49 a.m. on Wednesday, July 22, 2020. Stay with us for updates.

The situation is currently under investigation.  The threat evaluation will be updated as soon as further information becomes available.

Alaska Earthquake, July 22, 2020. PC: NOAA/NWS