Great Sitkin volcano, looking north, as seen from Alaska Airlines Flight 161 from Adak to Anchorage. Photo by Pilot Dave Clum.

Great Sitkin volcano, looking north, as seen from Alaska Airlines Flight 161 from Adak to Anchorage. Photo by Pilot Dave Clum.

Date: Jun 8th, 2019
Volcano(es): Great Sitkin
Photographer: Clum, Dave
URL: avo.alaska.edu/image/view/138971

Great Sitkin 2019 activity

From Orr and others, 2023: "AVO identified a single small explosion associated with Great Sitkin Volcano’s seismic unrest [in 2019]. It took place at 05:40 UTC on June 2 (June 1 at 20:40 HADT) and produced an emergent waveform with most of its energy between 1 and 5 hertz, similar to other small explosions recorded at Great Sitkin Volcano since January 2017. The event had a duration of 2 minutes and 17 seconds, determined using the methodology described in Searcy and Power (2020) for calculating the duration of explosions. No associated infrasound signal was observed on the instruments AVO operates in the City of Adak, indicating that the explosion was small...
"The Aviation Color Code and Volcano Alert Level were elevated...to YELLOW and ADVISORY on June 2, after the identification of the explosion signal recorded June 1. The Aviation Color Code and Volcano Alert Level were lowered again to GREEN and NORMAL on July 15, on the basis of declining seismicity. The Aviation Color Code and Volcano Alert Level remained there through the end of the year...
"During 2019, AVO located 629 earthquakes at Great Sitkin Volcano, principally clustered within the shallow crust extending from the summit to roughly 10 km [6 mi] deep. Additional shocks were also located between 10 and 35 km [6-22 mi] deep, with waveforms and frequency contents indicating both VT and deep LP events. Local magnitudes of located events ranged from −1.37 to 2.22. The largest event was located roughly 20 km [12 mi] southwest of the summit of Great Sitkin Volcano at a depth of 8.6 km [5.3 mi]. This hypocenter was deeper than those for earthquakes typically associated with volcanic processes beneath the volcano.
"The Great Sitkin Volcano seismic network experienced several station failures in 2019, impairing AVO’s ability to locate earthquakes. The most notable failure period spanned January to mid-June. These failures are likely the cause of a reduction in the number of located earthquakes in early 2019 relative to 2018, and the cause of an absence of shallow hypocenters detected in the first half of 2019. In response to the failures, AVO carried out a major upgrade to the seismic network in June 2019. The upgrades involved changing most of the older analog stations (installed in 1999) to broadband digital stations, although the analog stations GSSP and GSCK were left in operation for continuity. These network upgrades resulted in significantly improved station performance for the remainder of 2019."

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