Seismic character and progression of explosive activity during the 2016–2017 eruption of Bogoslof volcano, Alaska

Bogoslof volcano, in the central Aleutian arc, experienced a major eruption between December 2016 and August 2017 that was characterized by explosive activity (Volcanic Explosivity Index 2 to 3) and the extrusion of lava domes. The Alaska Volcano Observatory tracked the activity in real time using seismicity observed on distant stations as well as infrasound, lightning, satellite data, and occasional visual observations. In this study, we measure the duration of seismic signals associated with individual explosive events to track their progression during the two explosive phases of the eruption. Seismic recordings of Bogoslof explosions show complex waveforms that suggest both individual explosive events and sequences of several explosions separated by lower amplitude tremor. The lack of local seismic monitoring (stations at distances of 1 km to 15 km distance) unfortunately limits our ability to closely observe seismicity and to interpret changing conditions at the vent such as position, the presence of a lava dome or plug, and the role of seawater associated with the eruption. We use the rate of explosive activity, seismic waveform character, and repose time between explosions to infer the conditions within the conduit.