The Alaska Makushin Volcano 2016–2018 inflation and its potential relation to the 2020 earthquake swarm, from GNSS observations

Abstract

Makushin volcano on Unalaska Island along the Aleutian Chain in Alaska experienced a period of unrest from 2016 to 2020, including 2016–2018 surface inflation observed by 5 continuous Global Navigation Satellite System stations, and an earthquake swarm in the second half of 2020 consisting of hundreds of earthquakes, including two greater than M4. A Bayesian inversion of the geodetic data applied to a range of analytical source models suggests that the observed deformation pattern can be explained by an inflating pressure point source located 2 km east of the summit at a depth of approximately 5 km below sea level, with a chamber volume increase of approximately 0.004 km3. A stress change analysis suggests that the 2016–2018 magma intrusion may have played a role in advancing the 2020 seismicity anomaly by modulating the regional stress field. Our study highlights the importance of stress transfer between magmatic and tectonic processes and the potential for using this information to better understand and mitigate the risk of volcanic eruptions.