AVO reported that three possible small explosions at Semisopochnoi were detected in infrasound data between 1951 and 2004 on 9 November.
No associated ash clouds were observed in partly cloudy satellite images, and no other activity was noted during 7-11 November also in partly cloudy images.
Images were cloudy during 12-13 November.
The Aviation Color Code remained at Orange and Volcano Alert Level remained at Watch (both are the second highest levels on four-level scales).
Source: US Geological Survey Alaska Volcano Observatory (AVO)