Earthquake swarm detected in the vicinity of Edgecumbe volcano, U.S.

Mount Edgecumbe volcano on April 13 2022

A swarm of earthquakes has been detected in the vicinity of Edgecumbe volcano, beginning at about 10:00 UTC on April 11, 2022. The cause of the swarm is currently unknown. A small number of earthquakes were also recorded in 2020 but this swarm is unusual in the number of events. The last eruption of this volcano was in 2220 BCE (± 100 years).

The Alaska Volcano Observatory (AVO) recorded hundreds of small quakes in the swarm over the course of 48 hours, though the large majority are too small to locate.1

The National Earthquake Information Center (NEIC) reported that one of the largest earthquakes in the swarm occurred at 19:04 UTC on April 11, with a magnitude of 2.8 at a depth of 10 km (6.2 miles).

The Alaska Earthquake Center reported another earthquake occurred at 23:44 UTC on April 11, with a magnitude of 2.1 and a depth of 4 km (2.5 miles).

The swarm was still in progress on April 13, though the rate of earthquakes had declined overnight.

The cause of this earthquake swarm is currently unknown, AVO said.

“This swarm may be associated with volcanic processes, regional tectonic activity, or a combination of sources,” AVO volcanologists said, adding that the observatory does not have local seismic instruments in the area. The closest station is in Sitka, 24 km (15 miles) to the east of the volcano.

Retrospective analysis of earthquake data in the area shows that a small number of earthquakes started occurring under Edgecumbe in 2020, but this week’s activity is unusual in the number of events.

Because there is no local monitoring network, no Aviation Color Code and Volcano Alert Level are typically assigned to the volcano; Edgecumbe’s status, therefore, remains Unassigned.

Should activity increase, AVO will issue further notices and possibly increase the Aviation Color Code and Volcano Alert Level.

Mount Edgecumbe volcano on April 13 2022 map
Mount Edgecumbe volcano on April 13, 2022. Credit: Copernicus EU/Sentinel-2, TW

Geological summary

The Pleistocene-to-Holocene Edgecumbe volcanic field covers about 260 km2 (100 miles2) of Kruzov Island west of Sitka in the SE panhandle of Alaska.

The basaltic-to-dacitic field is dominated by the large composite cones of Mount Edgecumbe, Crater Ridge, and Shell Mountain, and has an unusual tectonic setting only 16 km (10 miles) E of the Queen Charlotte-Fairweather transform fault separating the North American and Pacific plates.

Mount Edgecumbe is a stratovolcano with a well-defined crater and is the largest volcano in the field.

Crater Ridge is truncated by a 1.6 km (1 mile) wide, 240 m (787 feet) deep caldera. These and other vents are oriented along a SW-NE line.

Volcanic activity originated about 600 000 years ago along fissures cutting Kruzof Island.

A series of major silicic explosive eruptions took place about 9 000 – 13 000 radiocarbon years ago.

The latest dated eruptions were phreatomagmatic explosions during the mid-Holocene, and all postglacial activity has been pyroclastic. Reports of historical eruptions of Mount Edgecumbe are unsubstantiated.2

References:

1 EDGECUMBE VOLCANO – ALASKA VOLCANO OBSERVATORY INFORMATION STATEMENT U.S. Geological Survey – Wednesday, April 13, 2022, 20:09 UTC

2 Mount Edgecumbe – Geological summary – GVP

Featured image: Mount Edgecumbe volcano on April 13, 2022. Credit: Copernicus EU/Sentinel-2, TW

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One Comment

  1. ## Comment SPAM Protection: ShieldPRO marked this comment as “Pending Moderation”. Reason: Human SPAM filter found “found this site” in “comment_content” ##
    I just now found this site and it’s really a very informative . I’ve been monitoring the Alaska volcanoes and earthquakes for a couple of years tons of research and I’m always looking for new sources that have a bit more detail than what I can find. I just recently read somewhere that the way they found the swarm under edge crumb volcano was somebody that I guess that works any of your brother saw data or something and sent it to her and said what is this? Anyways right now I don’t know if I can subscribe to your site by monetary things are kind of tightening up but I do like to help support independent people like yourself so I will definitely see what I can do. For the great information especially the feed down at the bottom here with all the info going across I never see that anywhere.

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