Temporal Seismic Velocity Changes During the 2020 Rapid Inflation at Mt.
Thorbjorn-Svartsengi, Iceland, Using Seismic Ambient Noise
Abstract
Repeated periods of inflation‐deflation in the vicinity of Mt.
Thorbjorn‐Svartsengi, SW‐Iceland, were detected in January–July, 2020.
We used seismic ambient noise and interferometry to characterize
temporal variations of seismic velocities (dv/v, %). This is the first
time in Iceland that dv/v variations are monitored in near real‐time
during volcanic unrest. The seismic station closest to the inflation
source center (∼1 km) showed the largest velocity drop (∼ 1%).
Different frequency range measurements, from 0.1 to 2 Hz, show dv/v
variations, which we interpret in terms of varying depth sensitivity.
The dv/v correlates with deformation measurements (GPS, InSAR), over the
unrest period, indicating sensitivity to similar crustal processes. We
interpret the velocity drop to be caused by crack opening triggered by
intrusive magmatic activity. We conclude that single‐station
cross‐component analyses provide the most robust solutions for early
detection of magmatic activity.