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Seismicity and deformation associated with ice-shelf rift propagation

Citation

Bassis, JN and Fricker, HA and Coleman, R and Bock, Y and Behrens, J and Darnell, D and Okal, M and Minster, JB, Seismicity and deformation associated with ice-shelf rift propagation, Journal of Glaciology, 53, (183) pp. 523-536. ISSN 0022-1430 (2007) [Refereed Article]

DOI: doi:10.3189/002214307784409207

Abstract

Previous observations have shown that rift propagation on the Amery Ice Shelf (AIS), East Antarctica, is episodic, occurring in bursts of several hours with typical recurrence times of several weeks. Propagation events were deduced from seismic swarms (detected with seismometers) concurrent with rapid rift widening (detected with GPS receivers). In this study, we extend these results by deploying seismometers and GPS receivers in a dense network around the tip of a propagating rift on the AIS over three field seasons (2002/03, 2004/05 and 2005/06). The pattern of seismic event locations shows that icequakes cluster along the rift axis, extending several kilometers back from where the rift tip was visible in the field. Patterns of icequake event locations also appear aligned with the ice-shelf flow direction, along transverse-to-rift crevasses. However, we found some key differences in the seismicity between field seasons. Both the number of swarms and the number of events within each swarm decreased during the final field season. The timing of the slowdown closely corresponds to the rift tip entering a suture zone, formed where two ice streams merge upstream. Beneath the suture zone lies a thick band of marine ice. We propose two hypotheses for the observed slowdown: (T) defects within the ice in the suture zone cause a reduction in stress concentration ahead of the rift tip; (2) increased marine ice thickness in the rift path slows propagation. We show that the size-frequency distribution of icequakes approximately follows a power law, similar to the well-known Gutenberg-Richter law for earthquakes. However, large icequakes are not preceded by foreshocks nor are they followed by aftershocks. Thus rift-related seismicity differs from the classic foreshock and aftershock distribution that is characteristic of large earth quakes.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Physical Geography and Environmental Geoscience
Research Field:Glaciology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Coleman, R (Professor Richard Coleman)
ID Code:48588
Year Published:2007
Web of Science® Times Cited:28
Deposited By:Geography and Environmental Studies
Deposited On:2007-08-01
Last Modified:2009-06-23
Downloads:0

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