Teleseismic earthquake wavefields observed on the Ross Ice Shelf

• Published in: Journal of Glaciology
• Main Authors: Michael G. Baker, Richard C. Aster, Douglas A. Wiens, Andrew Nyblade, Peter D. Bromirski, Peter Gerstoft, Ralph A. Stephen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2021
• Subjects: Glacier geophysics; ice shelves; seismology; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Ross Ice Shelf; Ice Shelf; Ice Shelves; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2020.83; https://doaj.org/article/dc4cbbeaba5f45968e61add8f780e6b2

Observations of teleseismic earthquakes using broadband seismometers on the Ross Ice Shelf (RIS) must contend with environmental and structural processes that do not exist for land-sited seismometers. Important considerations are: (1) a broadband, multi-mode ambient wavefield excited by ocean gravity wave interactions with the ice shelf; (2) body wave reverberations produced by seismic impedance contrasts at the ice/water and water/seafloor interfaces and (3) decoupling of the solid Earth horizontal wavefield by the sub-shelf water column. We analyze seasonal and geographic variations in signal-to-noise ratios for teleseismic P-wave (0.5–2.0 s), S-wave (10–15 s) and surface wave (13–25 s) arrivals relative to the RIS noise field. We use ice and water layer reverberations generated by teleseismic P-waves to accurately estimate the sub-station thicknesses of these layers. We present observations consistent with the theoretically predicted transition of the water column from compressible to incompressible mechanics, relevant for vertically incident solid Earth waves with periods longer than 3 s. Finally, we observe symmetric-mode Lamb waves generated by teleseismic S-waves incident on the grounding zones. Despite their complexity, we conclude that teleseismic coda can be utilized for passive imaging of sub-shelf Earth structure, although longer deployments relative to conventional land-sited seismometers will be necessary to acquire adequate data.