Daily Archives: 30 July 2021

Shaking in Chignik

The 8.2 magnitude earthquake and the 140 aftershocks

At around 10:30 on Wednesday night, the alarm bells went off, and people across Alaska’s southern coast made a bee-line for higher ground. An 8.2 magnitude earthquake struck the interface between the subducting Pacific and overriding North American plates. This interface is known as the Aleutian Megathrust,and it is a very active seismic region. In fact, a 7.6 magnitude earthquake hit the area almost a year ago exactly.

Wave action

A tsunami warning was immediately issued for coastal communities, but luckily incoming waves never reached heights over a 1/4 meter, and the warning was lifted a little over two hours later.

This was the first 8.0+ earthquake to hit the United States in 50 years. In the 12 hours after the initial quake, the area received 140 aftershocks, with the largest being a 6.1. In 1938, the same area experienced an 8.3 magnitude shaker.

NWS Priority Warnings Chart

Interestingly, Tsunami Warning is Priority #1 on the National Weather Service priority list. One would hope that Nuclear Power Plant Meltdown is higher on a different agency’s list.