Bimodal pattern of seismicity detected at the ocean margin of an Antarctic ice shelf

• Published in: Geophysical Journal International
• Main Authors: Lombardi, Denis, Benoit, Lionel, Camelbeeck, Thierry, Martin, Olivier, Meynard, Christophe, Thom, Christian
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université Paris Cité (UPCité)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: Seismic cycle; Transient deformation; Tides and planetary waves; Glaciology; Fracture and flow; Antarctica; [SDU]Sciences of the Universe [physics]; Antarctic; East Antarctica; Dronning Maud Land; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03581312; https://hal-insu.archives-ouvertes.fr/insu-03581312/document; https://hal-insu.archives-ouvertes.fr/insu-03581312/file/ggw214.pdf; https://doi.org/10.1093/gji/ggw214

International audience In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the ocean, the ice rise buttressing effect may be altered in response of changing ocean forcing. To investigate this vulnerable zone, four sites near the boundary of an ice shelf with an ice rise promontory in Dronning Maud Land, East-Antarctica were monitored for a month in early 2014 with new instruments that include both seismic and GPS sensors. Our study indicated that this transition zone experiences periodic seismic activity resulting from surface crevassing during oceanic tide-induced flexure of the ice shelf. The most significant finding is the observation of apparent fortnightly tide-modulated low-frequency, long-duration seismic events at the seaward front of the ice rise promontory. A basal origin of these events is postulated with the ocean water surge at each new spring tide triggering basal crevassing or basal slip on a local bedrock asperity. Detection and monitoring of such seismicity may help identifying ice rise zones vulnerable to intensified ocean forcing.