Return from Dormancy: Rapid inflation and seismic unrest at Mt.
Edgecumbe (L’ux Shaa) Volcano, Alaska
Abstract
In April 2022 a seismic swarm near Mt. Edgecumbe in southeast Alaska
suggests renewed activity at this dormant volcano located in a transform
fault setting. Oral Tlingit history describes low-level basaltic
eruptions $\approx$800 years ago. Thin rhyolitic
tephras deposited 5-4 ka. We analyze synthetic aperture radar data from
2014-2022 and resolve rapid inflation up to 8.7\,cm/yr
beginning in August 2018. Bayesian modeling suggests a gently westward
dipping sill opened 0.65\,m between
7.6\,km to 5.3\,km depth, centered about
2-3\,km east of Mt. Edgecumbe. Reanalyzed seismicity,
recorded 25\,km away, shows increased activity since July
2019. We hypothesize mafic magma ascent through ductile material,
accumulating below a silicic seal or in a silicic reservoir, and
triggering seismicity in the overburden. Cloud-native open data and
workflows enabled discovery and analysis of this rapid inflation within
days after going unnoticed for $>$3 years.