Imaging Torfajökull's Magmatic Plumbing System With Seismic Interferometry and Phase Velocity Surface Wave Tomography

Imaging Torfajökull's Magmatic Plumbing System With Seismic Interferometry and Phase Velocity Surface Wave Tomography

Martins, Joana E. (TU Delft Mathematical Geodesy and Positioning; TNO)
Ruigrok, Elmer (Universiteit Utrecht; Royal Netherlands Meteorological Institute (KNMI))
Draganov, D.S. (TU Delft Applied Geophysics and Petrophysics)
Hooper, A. (University of Leeds)
Hanssen, R.F. (TU Delft Mathematical Geodesy and Positioning)
White, R.S. (University of Cambridge)
Soosalu, Heidi (University of Cambridge; Geological Survey of Estonia)

2019

Torfajökull volcano, Iceland, has not erupted since 1477. However, intense geothermal activity, deformation, and seismicity suggest a long‐lasting magmatic system. In this paper, we use ambient noise tomography to image the magmatic system beneath Torfajökull volcano. One hundred days of ambient noise data from 23 broadband seismometers show the consistent presence of double‐frequency microseism noise with significant power between ∼0.1 and 0.5 Hz. Beamforming results indicate microseism noise with persistent higher energy propagating from west and SE directions and apparent velocities below 3 km/s. We use ambient noise seismic interferometry to retrieve Rayleigh waves, and we introduce a method to estimate the reliability of the retrieved surface waves. We find stable estimation of surface wave phase velocities between 0.16 and 0.38 Hz. Azimuthal velocity variations show a trend of higher velocities in the NE/SW direction, the strike of the rift zone intersecting Torfajökull, and orientation of erupted lavas on a NE‐SW fissure swarm. Tomographic results indicate low‐velocity anomalies beneath the volcano caldera (between −5% and −10%) and even lower velocity variations in the southeast and southwest study area (below −10%), outside the volcano caldera. Low anomalies may indicate the existence of hot material, more prominent outside the caldera outskirts. High‐velocity variations (between 5% and 10%) outline the volcano caldera between 4‐ and 5‐km depth and more pronounced velocities (between 10% and 15%) up to 5‐km depth in the north of the volcano caldera. We interpret the former as possible caldera collapse structure and the latest as solidified intrusive magma from the old preferred magma paths.

3-D S wave velocity
ambient noise tomography (ANT)
low-velocity anomalies
seismic interferometry
Torfajokull volcano
volcano caldera

http://resolver.tudelft.nl/uuid:4a7d5784-f0be-417b-8501-792a877fc7fa

https://doi.org/10.1029/2018JB016002

2169-9313

JGR Solid Earth, 124 (3), 2920-2940

Institutional Repository

journal article

© 2019 Joana E. Martins, Elmer Ruigrok, D.S. Draganov, A. Hooper, R.F. Hanssen, R.S. White, Heidi Soosalu