The combined use of satellite and seismic monitoring during the 1996 eruption of Pavlof volcano, Alaska

The 1996 eruption of Pavlof volcano provided a unique opportunity for the combined use of satellite and seismic monitoring techniques. Advanced Very High Resolution Radiometer (AVHRR) satellite data provided observations of both thermal anomalies and eruption plumes. A thermal anomaly appeared in AVHRR data 3 days prior to the eruption and continued to grow until shortly before the height of eruptive activity. Eruption plumes observed in AVHRR images ranged from tens to hundreds of kilometers in length; ground observations indicate that they reached elevations between 2,750 m and 9,150 m above sea level. The largest, ash-rich plumes reached great lengths (>200 km) due to increased wind velocity at altitude; small, steam-rich plumes were less predictable. Seismic data were received from a newly installed network around the volcano. Stations at intermediate distances (from 8 to 12 km) from the volcano provided the most useful information for monitoring the eruption. As is typical for Pavlof, the eruption produced no A-type events, and monitoring was based exclusively on tremor and explosion events. Broad increases in tremor amplitude occurred before the appearance of the largest eruption plumes. The combination of satellite and seismic data revealed several interesting correlations. The sizes of thermal anomalies increased concurrently with the number of explosions for small plumes and with plume height for the largest plumes. Further, a general relationship between plume height and tremor amplitude was observed for the largest eruption plumes. Finally, the combination of monitoring methods revealed the general course of the eruption sequence; steady increases in the size of the thermal anomaly and seismicity presaged the eruption of several large plumes.