Journal Article

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

Denis Lombardi, Lionel Benoit, Thierry Camelbeeck, Olivier Martin, Christophe Meynard and Christian Thom

in Geophysical Journal International

Volume 206, issue 2, pages 1375-1381
ISSN: 0956-540X
Published online June 2016 | e-ISSN: 1365-246X | DOI:
Bimodal pattern of seismicity detected at the ocean margin of an Antarctic ice shelf

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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.

Keywords: Seismic cycle; Transient deformation; Tides and planetary waves; Glaciology; Fracture and flow; Antarctica

Journal Article.  5032 words.  Illustrated.

Subjects: Volcanology and Seismology

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