Cryosphere
Overview
Our lab studies the long term and short term deformation of ice through both brittle fracture (observed as "icequakes") and ductile flow (observed through remote sensing and long term GPS measurements).
Projects
ARROW (Antarctic Rift Research for Ocean Worlds)
During the austral summer of 2022 - 2023 Mong-Han and Kathrine performed field work for the ARROW project led by Dr. Terry Hurford and Dr. Nicholas Schmerr. This deployment consisted of 16 seismometers and 12 GPS stations surrounding the WR4 rift on the Ross Ice Shelf.
Field Photos
Icequake-magnitude scaling relationship along a rift within the Ross Ice Shelf, Antarctica
Fractures located on ice shelves are weak compared to the rest of the ice shelf. They deform over seconds to decades, and icequakes can be accompanied by their deformation. We find that tides, particularly falling tides, influence the frequency of icequake occurrence the most. We also find that small magnitude icequakes are a larger proportion of total icequakes when compared to the proportion of small magnitude continental earthquakes in relation to total global earthquakes. We test whether this proportion is due to the maximum depth estimated at 7.8 m below the surface of the rift zone by using satellite imagery, Global Navigation Satellite Systems (GNSS) measurements, and a seismometer located near a fracture on the Ross Ice Shelf. We propose that the rift zone below 7.8 m depth behaves as ductile deformation possibly due to saturation with unfrozen water, whereas the region above this depth is more prone to brittle fracture that can generate icequakes.
Study area. (a) View of Antarctica. The Ross Ice Shelf is at the bottom of the plot (dashed polygon). Image source: Google Earth. (b) An overview of the north part of the Ross Ice Shelf. The light blue regions are the 3 major rift zones: WR2, WR4, and WR6. The yellow triangles in b and c are the GNSS stations, with the broadband seismic station collocated at DR14. The red rectangle marks the location of WR4 shown in c. (c) The outline of WR4. The background image in b and c is from MODIS satellite imagery.
Strain rate of rift WR4. The rift zone is opening 10-50 m per year. Blue bars show the direction of opening.
Seismicity on the east side of WR4. Bright color means higher icequake density.
Publications
Huang, M.-H., Udell Lopez, K., & Olsen, K. G. (2022). Icequake-magnitude scaling relationship along a rift within the Ross Ice Shelf, Antarctica. Geophysical Research Letters, 49, e2022GL097961. https://doi.org/10.1029/2022GL097961
Olsen, K. G., Hurford, T. A., Schmerr, N. C., Huang, M.-H., Brunt, K. M., Zipparo, S., et al. (2021). Projected Seismic Activity at the Tiger Stripe Fractures on Enceladus, Saturn, from an Analog Study of Tidally Modulated Icequakes within the Ross Ice Shelf, Antarctica. Journal of Geophysical Research: Planets, 126, e2021JE006862. https://doi.org/10.1029/2021JE006862