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.