Icequake-magnitude scaling relationship along a rift within the Ross Ice Shelf, Antarctica

Abstract

Fractures within ice shelves are zones of weakness, which can deform on timescales from seconds to decades. Icequakes produced during the fracturing process show a higher b-value in the Gutenberg-Richter scaling relationship than continental earthquakes. We investigate icequakes on the east side of rift WR4 in the Ross Ice Shelf, Antarctica. Our model suggests a maximum icequake slip depth that is ˜7.8 m below rift surface, where the slip area can only grow laterally along the fracture planes. We propose ductile deformation below this depth, potentially due to saturation of unfrozen water. We use remote sensing and geodetic tools to quantify surface movement on different time scales and find that the majority of icequakes occurred during falling tides. The total seismic moment is < 1% of the estimated geodetic moment during a tidal cycle. This study demonstrates the feasibility of using seismology and geodesy to investigate ice rift zone rheology.