Thread by @FreedomFriesInc

(1) Another large #earthquake off the Alaskan coast tonight. IMO sufficiently deep & distant not to cause a major threat to life & property.

What's interesting though, is that two other EQs there in the past yr are considered #foreshocks to this one.

earthquake.usgs.gov/earthquakes/ev…

(2) I wrote a bit about them at the time. They were:

M7.8 on July 22, 2020
M7.6 on October 19, 2020

Tonight's:

M8.2 on July 29, 2021

(3) The Canterbury, New Zealand earthquakes of 2010-2011 that I lived through also involved a #foreshock event. Of course, we only find out after the main quake that an earlier one was a foreshock.

The geology of the area is what determines the likelihood of foreshocks.

(4) That's above my paygrade. Here's what the USGS said about tonight's Alaska EQ:

"Large earthquakes are common in the Alaska-Aleutian subduction zone. Since 1900, 8 other earthquakes M7 and larger have occurred within 250 km of the July 29, 2021 event, ...

(5) "... including earthquakes of M7.8 on July 22, 2020 (located 62 km west of the July 29, 2021 event) and M7.6 on October 19, 2020 (located 145 west of the July 29, 2021 event).

continued...

(6) "Given the temporal and spatial proximity of the July 29, 2021 earthquake to the two previous large earthquakes in July and October 2020, those previous events were foreshocks of the July 2021 earthquake."

Hopefully further shakes in this series are aftershocks, & smaller.