AVO Semisopochnoi ORANGE/WATCH – Elevated seismicity; no ash or other eruptive activity observed

Jul 23, 2019 18:46 – Seismic activity has increased slightly in the last 24 hours with periods of continuous tremor. No ash, steam, or gas emissions were observed in cloudy satellite images. It remains possible that activity could increase rapidly and with little warning.

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.