Hydroacoustic and Seismic Observations of the 2016-17 Bogoslof Eruption, Alaska

Date: 4/26/2019

Time: 06:00 PM

Room: Fifth Avenue

In December 2016, Bogoslof volcano unexpectedly began erupting from a vent just below the ocean’s surface. Over the next 8.5 months, Bogoslof produced 70 major explosions with ash plumes up to 13 km, three lava domes that broke the sea surface, around 40 earthquake swarms, and other seismicity. Bogoslof is an unmonitored seamount with a summit that forms a small island. Thus, the eruption was only monitored by seismometers on nearby islands (>45 km away), regional infrasound arrays, satellites, and lightning sensor networks. For the last 3.5 months of the eruption, a campaign hydrophone was moored about 7 km from the summit, allowing for more detailed seismo-acoustic recordings than were possible with the available telemetered networks.

We analyze and compare the seismic and hydroacoustic recordings to outline the seismic story of the eruption, which can be broken into five phases. The Precursory Phase comprised a major earthquake swarm in late September 2016, a smaller swarm a week later, and many sporadic earthquakes. The Opening Phase followed with near-continuous, alternating tremor and earthquakes between 11-15 December. This seismicity led into Explosive Phase I, which included 38 of the major explosions and most of the precursory earthquake swarms. After an explosion on 13 March, the eruption went into a 2-month-long Pause during which the only activity was a single earthquake swarm. On 17 May, an explosion opened Explosive Phase II, which lasted until the eruption ended on 30 August. Additionally, we further examine the characteristics of the eruptive tremor and the earthquake swarms that were common throughout the eruption. We then put the seismic and hydroacoustic observations into context with other observations of the eruption.

Presenting Author: Gabrielle Tepp

Authors