Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure

TitleSeismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
Publication TypeJournal Article
Year of Publication2014
AuthorsHeeszel D.S, Fricker H.A, Bassis J.N, O'Neel S., Walter F.
JournalJournal of Geophysical Research-Earth Surface
Date Published2014/04
Type of ArticleArticle
ISBN Number2169-9003
Accession NumberWOS:000336487100003
Keywordsamery ice; Amery Ice Shelf; Back projection; earthquakes; east antarctica; Glacial seismology; gornergletscher; Ice Shelf Rifting; inversions; marine ice; moment tensors; parameters; velocity; waves

Iceberg calving is a dominant mass loss mechanism for Antarctic ice shelves, second only to basal melting. An important process involved in calving is the initiation and propagation of through-penetrating fractures called rifts; however, the mechanisms controlling rift propagation remain poorly understood. To investigate the mechanics of ice shelf rifting, we analyzed seismicity associated with a propagating rift tip on the Amery Ice Shelf, using data collected during the austral summers of 2004-2007. We apply a suite of passive seismological techniques including icequake locations, back projection, and moment tensor inversion. We confirm previous results that show ice shelf rifting is characterized by periods of relative quiescence punctuated by swarms of intense seismicity of 1 to 3 h. Even during periods of quiescence, we find significant deformation around the rift tip. Moment tensors, calculated for a subset of the largest icequakes (M-w>-2.0) located near the rift tip, show steeply dipping fault planes, horizontal or shallowly plunging stress orientations, and often have a significant volumetric component. They also reveal that much of the observed seismicity is limited to the upper 50 m of the ice shelf. This suggests a complex system of deformation that involves the propagating rift, the region behind the rift tip, and a system of rift-transverse crevasses. Small-scale variations in the mechanical structure of the ice shelf, especially rift-transverse crevasses and accreted marine ice, play an important role in modulating the rate and location of seismicity associated with the propagating ice shelf rifts.

Short TitleJ. Geophys. Res.-Earth Surf.
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