This seismogram is from the Shishaldin Broadband A seismic station on Unimak Island in the Aleutians of Alaska, USA. The thick noise in the top third of the graph is seismicity ("volcanic tremor") at Shishaldin Volcano, a subduction zone stratovolcano on Unimak Island in the late evening of 13 July 2023. The very thick noise on the 00:30 to 02:00 lines represents explosive ash eruptions from Shishaldin. Notable explosions occurred at 1:09 AM and 1:36 AM, local time, on 14 July 2023. The Alaska Volcano Observatory reported ash clouds from this activity reaching 9 to 12 kilometers above sea level - that's 30 to 40 thousand feet high - and drifted over the Pacific Ocean. This explosive activity was preceded by minor lava eruptions in Shishaldin's summit crater on 12 and 13 July 2023.
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