Semisopochnoi is monitored with an on-island seismic network and remotely by satellite and lightning sensors. Furthermore, an infrasound array on Adak Island may detect explosive emissions from Semisopochnoi with a 13 minute delay if atmospheric conditions permit.
Aug 6, 2019 21:08 – Seismicity has increased slightly over the past 24 hours with occasional discrete low-frequency earthquakes. A possible steam plume was observed in satellite views over the past day. It remains possible that activity could increase rapidly and with little warning.