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

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 unde...

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Bibliographic Details
Published in:Journal of Geophysical Research: Earth Surface
Main Authors: Heeszel, David S., Fricker, Helen A., Bassis, Jeremy N., O'Neel, Shad, Walter, Fabian
Format: Article in Journal/Newspaper
Language:unknown
Published: Academic Press 2014
Subjects:
Glacial Seismology
Back Projection
East Antarctica
Ice Shelf Rifting
Amery Ice Shelf
Geological Sciences
Science
Amery
Antarctic
Austral
Antarc*
Antarctica
Ice Shelf
Ice Shelves
Iceberg*
Online Access:https://hdl.handle.net/2027.42/106935
https://doi.org/10.1002/2013JF002849
id ftumdeepblue:oai:deepblue.lib.umich.edu:2027.42/106935
record_format openpolar
institution Open Polar
collection University of Michigan: Deep Blue
op_collection_id ftumdeepblue
language unknown
topic Glacial Seismology
Back Projection
East Antarctica
Ice Shelf Rifting
Amery Ice Shelf
Geological Sciences
Science
spellingShingle Glacial Seismology
Back Projection
East Antarctica
Ice Shelf Rifting
Amery Ice Shelf
Geological Sciences
Science
Heeszel, David S.
Fricker, Helen A.
Bassis, Jeremy N.
O'Neel, Shad
Walter, Fabian
Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
topic_facet Glacial Seismology
Back Projection
East Antarctica
Ice Shelf Rifting
Amery Ice Shelf
Geological Sciences
Science
description 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. Key Points Rift‐related seismicity controlled by mechanical heterogeneity Back projection reveals that seismic deformation is continuous in region Spacing of rift‐transverse crevasses controls the timing of seismic swarms Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/106935/1/jgrf20203.pdf
format Article in Journal/Newspaper
author Heeszel, David S.
Fricker, Helen A.
Bassis, Jeremy N.
O'Neel, Shad
Walter, Fabian
author_facet Heeszel, David S.
Fricker, Helen A.
Bassis, Jeremy N.
O'Neel, Shad
Walter, Fabian
author_sort Heeszel, David S.
title Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
title_short Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
title_full Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
title_fullStr Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
title_full_unstemmed Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure
title_sort seismicity within a propagating ice shelf rift: the relationship between icequake locations and ice shelf structure
publisher Academic Press
publishDate 2014
url https://hdl.handle.net/2027.42/106935
https://doi.org/10.1002/2013JF002849
long_lat ENVELOPE(-94.063,-94.063,56.565,56.565)
ENVELOPE(71.000,71.000,-69.750,-69.750)
geographic Amery
Amery Ice Shelf
Antarctic
Austral
East Antarctica
geographic_facet Amery
Amery Ice Shelf
Antarctic
Austral
East Antarctica
genre Amery Ice Shelf
Antarc*
Antarctic
Antarctica
East Antarctica
Ice Shelf
Ice Shelves
Iceberg*
genre_facet Amery Ice Shelf
Antarc*
Antarctic
Antarctica
East Antarctica
Ice Shelf
Ice Shelves
Iceberg*
op_relation Heeszel, David S.; Fricker, Helen A.; Bassis, Jeremy N.; O'Neel, Shad; Walter, Fabian (2014). "Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure." Journal of Geophysical Research: Earth Surface 119(4): 731-744.
2169-9003
2169-9011
https://hdl.handle.net/2027.42/106935
doi:10.1002/2013JF002849
Journal of Geophysical Research: Earth Surface
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Müller, G. ( 2001 ), Volume change of seismic sources from moment tensors, Bull. Seismol. Soc. Am., 91 ( 4 ), 880 – 884, doi:10.1785/0120000261.
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Walter, F., J. F. Clinton, N. Deichmann, D. S. Dreger, S. E. Minson, and M. Funk ( 2009 ), Moment tensor inversions of icequakes on Gornergletscher, Switzerland, Bull. Seismol. Soc. Am., 99 ( 2A ), 852 – 870, doi:10.1785/0120080110.
Walter, F., D. S. Dreger, J. F. Clinton, N. Deichmann, and M. Funk ( 2010 ), Evidence for near‐horizontal tensile faulting at the base of Gornergletscher, a Swiss Alpine Glacier, Bull. Seismol. Soc. Am., 100 ( 2 ), 458 – 472, doi:10.1785/5012090083.
Wiens, D. A., J. J. McGuire, P. J. Shore, M. G. Bevis, K. Draunidalo, G. Prasad, and S. P. Helu ( 1994 ), A deep earthquake aftershock sequence and implications for the rupture mechanism of deep earthquakes, Nature, 372, 540 – 543.
Wiens, D. A., S. Anandakrishnan, J. P. Winberry, and M. A. King ( 2008 ), Simultaneous teleseismic and geodetic observations of the stick‐slip motion of an Antarctic ice stream, Nature, 453, 770 – 775, doi:10.1038/nature06990.
Xu, Y., K. D. Koper, O. Sufri, L. Zhu, and A. R. Hutko ( 2009 ), Rupture imaging of the M w 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves, Geochem. Geophys. Geosyst., 10, Q04006, doi:10.1029/2008GC002335.
Young, N. W., and G. Hyland ( 2002 ), Velocity and strain rates derived from InSAR analysis over the Amery Ice Shelf, East Antarctica, Ann. Glaciol., 34, 228 – 234.
Bartholomaus, T. C., C. F. Larsen, S. O'Neel, and M. E. West ( 2012 ), Calving seismicity from iceberg‐sea surface interactions, J. Geophys. Res., 117, F04029, doi:10.1029/2012JF002513.
Bassis, J. N., R. Coleman, H. A. Fricker, and J. B. Minster ( 2005 ), Episodic propagation of a rift on the Amery Ice Shelf, East Antarctica, Geophys. Res. Lett., 32, L06502, doi:10.1029/2004GL022048.
Bassis, J. N., H. A. Fricker, R. Coleman, Y. Bock, J. Behrens, D. Darnell, M. Okal, and J. B. Minster ( 2007 ), Seismicity and deformation associated with ice‐shelf rift propagation, J. Glaciol., 53 ( 183 ), 523 – 536.
Bassis, J. N., H. A. Fricker, R. Coleman, and J. B. Minster ( 2008 ), An investigation into the forces that drive ice‐shelf rift propagation on the Amery Ice Shelf, East Antarctica, J. Glaciol., 54 ( 184 ), 17 – 27.
Budd, W. ( 1966 ), The dynamics of the Amery Ice Shelf, J. Glaciol., 6 ( 45 ), 335 – 358.
Craven, M., I. Allison, H. A. Fricker, and R. Warner ( 2009 ), Properties of a marine ice layer under the Amery Ice Shelf, East Antarctica, J. Glaciol., 55 ( 192 ), 717 – 728.
Dierckx, M., and J.‐L. Tison ( 2013 ), Marine ice deformation experiments: An empirical validation of creep parameters, Geophys. Res. Lett., 40, 134 – 138, doi:10.1029/2012GL054197.
Dreger, D. S. ( 2003 ), TDMT_INV: Time domain seismic moment tensor Inversion, in International Handbook of Earthquake and Engineering Seismology, edited by W. H. K. Lee et al., p. 1627, Academic Press, London.
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Fricker, H. A., S. Popov, I. Allison, and N. Young ( 2001 ), Distribution of marine ice beneath the Amery Ice Shelf, Geophys. Res. Lett., 28 ( 11 ), 2241 – 2244.
Fricker, H. A., N. W. Young, I. Allison, and R. Coleman ( 2002 ), Iceberg calving from the Amery Ice Shelf, East Antarctica, Ann. Glaciol., 34, 241 – 246.
Fricker, H. A., J. N. Bassis, B. Minster, and D. R. MacAyeal ( 2005a ), ICESat's new perspective on ice shelf rifts: The vertical dimension, Geophys. Res. Lett., 32, L23S08, doi:10.1029/2005GL025070.
Fricker, H. A., N. W. Young, R. Coleman, J. N. Bassis, and J. B. Minster ( 2005b ), Multi‐year monitoring of rift propagation on the Amery Ice Shelf, East Antarctica, Geophys. Res. Lett., 32, L02502, doi:10.1029/2004GL021036.
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Heeszel, D. S., D. A. Wiens, H. Shiobara, and H. Sugioka ( 2008 ), Earthquake evidence for along‐arc extension in the Mariana Islands, Geochem. Geophys. Geosyst., 9, Q12X03, doi:10.1029/2008GC002186.
Hulbe, C. L., C. LeDoux, and K. Cruikshank ( 2010 ), Propagation of long fractures in the Ronne Ice Shelf, Antarctica, investigated using a numerical model of fracture propagation, J. Glaciol., 57 ( 97 ), 459 – 472.
Jacobs, S. S., D. R. MacAyeal, and J. L. Ardai Jr. ( 1986 ), The recent advance of the Ross Ice Shelf, Antarctica, J. Glaciol., 32 ( 112 ), 464 – 474.
Jansen, D., B. Kulessa, P. R. Sammonds, A. Luckman, E. C. King, and N. F. Glasser ( 2010 ), Present stability of the Larsen C ice shelf, Antarctic Peninsula, J. Glaciol., 56 ( 198 ), 593 – 600, doi:10.3189/002214310793146223.
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spelling ftumdeepblue:oai:deepblue.lib.umich.edu:2027.42/106935 2023-08-20T03:59:31+02:00 Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure Heeszel, David S. Fricker, Helen A. Bassis, Jeremy N. O'Neel, Shad Walter, Fabian 2014-04 application/pdf https://hdl.handle.net/2027.42/106935 https://doi.org/10.1002/2013JF002849 unknown Academic Press Wiley Periodicals, Inc. Heeszel, David S.; Fricker, Helen A.; Bassis, Jeremy N.; O'Neel, Shad; Walter, Fabian (2014). "Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure." Journal of Geophysical Research: Earth Surface 119(4): 731-744. 2169-9003 2169-9011 https://hdl.handle.net/2027.42/106935 doi:10.1002/2013JF002849 Journal of Geophysical Research: Earth Surface Quinlan, D. M., D. Harvey, and G. Wagner ( 1996 ), Datascope seismic application package, Seismol. Res. Lett., 67 ( 2 ), 51. Khazendar, A., E. Rignot, and E. Larour ( 2009 ), Roles of marine ice, rheology, and fracture in the flow and stability of the Brunt/Stancomb‐Wills Ice Shelf, J. Geophys. Res., 114, F04007, doi:10.1029/2008JF001124. Korger, E. I. M., and V. Schlindwein ( 2012 ), Performance of localization algorithms for teleseismic mid‐ocean ridge earthquakes: The 1999 Gakkel Ridge earthquake swarm and its geological interpretation, Geophys. J. Int., 188, 613 – 625, doi:10.1111/j.1365‐246X.2011.05282.x. Lazzara, M. A., K. C. Jezek, T. A. Scambos, D. R. MacAyeal, and C. J. Van Der Veen ( 1999 ), On the recent calving of icebergs from the Ross Ice Shelf, Polar Geogr., 23 ( 3 ), 201 – 212, doi:10.1080/10889370802175937. McMahon, K. L., and M. A. Lackie ( 2006 ), Seismic reflection studies of the Amery Ice Shelf, East Antarctica: Delineating meteoric and marine ice, Geophys. J. Int., 166 ( 2 ), 757 – 766, doi:10.1111/j.1365‐246X.2006.03043.x. Minson, S. E., and D. S. Dreger ( 2008 ), Stable inversions for complete moment tensors, Geophys. J. Int., 174, 585 – 592, doi:10.1111/j.1365‐246X.2008.03797.x. Minson, S. E., D. S. Dreger, R. Burgmann, H. Kanamori, and K. M. Larson ( 2007 ), Seismically and geodetically determined nondouble‐couple source mechanisms from the 2000 Miyakejima volcanic earthquake swarm, J. Geophys. Res., 112, B10308, doi:10.1029/2006JB004847. Müller, G. ( 2001 ), Volume change of seismic sources from moment tensors, Bull. Seismol. Soc. Am., 91 ( 4 ), 880 – 884, doi:10.1785/0120000261. Pavlis, G. L., F. Vernon, D. Harvey, and D. Quinlan ( 2004 ), The generalized earthquake‐location (GENLOC) package: An earthquake‐location library, Comput. Geosci., 30, 1079 – 1091, doi:10.1016/j.cageo.2004.06.010. Pritchard, H. D., S. R. M. Ligtenberg, H. A. Fricker, D. G. Vaughan, M. R. van den Broeke, and L. Padman ( 2012 ), Antarctic ice‐sheet loss driven by basal melting of ice shelves, Nature, 484, 502 – 505, doi:10.1038/nature10968. Richardson, J. P., G. P. Waite, K. A. FitzGerald, and W. D. Pennington ( 2010 ), Characteristics of seismic and acoustic signals produced by calving, Bering Glacier, Alaska, Geophys. Res. Lett., 37, L03503, doi:10.1029/2009GL041113. Richardson, J. P., G. P. Waite, W. D. Pennington, R. M. Turpening, and J. M. Robinson ( 2012 ), Icequake locations and discrimination of source and path effects with small aperture arrays, Bering Glacier terminus, AK, J. Geophys. Res., 117, F04013, doi:10.1029/2012JF002405. Rignot, E., S. Jacobs, J. Mouginot, and B. Scheuchl ( 2013 ), Ice‐shelf melting around Antarctica, Science, 341, 266 – 270, doi:10.1126/science.1235798. Saikia, C. K. ( 1994 ), Modified frequency‐wavenumber algorithm for regional seismograms using Filon's quadrature: Modelling of L g waves in eastern North America, Geophys. J. Int., 118, 142 – 158. Stein, S., and M. Wysession ( 2003 ), An Introduction to Seismology, Earthquakes, and Earth Structure, pp. 498, Blackwell, Malden, MA. Tape, W., and C. Tape ( 2012 ), A geometric setting for moment tensors, Geophys. J. Int., 190, 476 – 498, doi:10.1111/j.1365‐246X.2012.05491.x. VanDecar, J. C., and R. S. Crosson ( 1990 ), Determination of teleseismic relative phase arrival times using multi‐channel cross‐correlation and least squares, Bull. Seismol. Soc. Am., 80 ( 1 ), 150 – 169. Walker, C. C., J. N. Bassis, H. A. Fricker, and R. J. Czerwinski ( 2013 ), Structural and environmental controls on Antarctic ice shelf rift propagation inferred from satellite monitoring, J. Geophys. Res. Earth Surface, 118, 2354 – 2364, doi:10.1002/2013JF002742. Walter, F., J. F. Clinton, N. Deichmann, D. S. Dreger, S. E. Minson, and M. Funk ( 2009 ), Moment tensor inversions of icequakes on Gornergletscher, Switzerland, Bull. Seismol. Soc. Am., 99 ( 2A ), 852 – 870, doi:10.1785/0120080110. Walter, F., D. S. Dreger, J. F. Clinton, N. Deichmann, and M. Funk ( 2010 ), Evidence for near‐horizontal tensile faulting at the base of Gornergletscher, a Swiss Alpine Glacier, Bull. Seismol. Soc. Am., 100 ( 2 ), 458 – 472, doi:10.1785/5012090083. Wiens, D. A., J. J. McGuire, P. J. Shore, M. G. Bevis, K. Draunidalo, G. Prasad, and S. P. Helu ( 1994 ), A deep earthquake aftershock sequence and implications for the rupture mechanism of deep earthquakes, Nature, 372, 540 – 543. Wiens, D. A., S. Anandakrishnan, J. P. Winberry, and M. A. King ( 2008 ), Simultaneous teleseismic and geodetic observations of the stick‐slip motion of an Antarctic ice stream, Nature, 453, 770 – 775, doi:10.1038/nature06990. Xu, Y., K. D. Koper, O. Sufri, L. Zhu, and A. R. Hutko ( 2009 ), Rupture imaging of the M w 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves, Geochem. Geophys. Geosyst., 10, Q04006, doi:10.1029/2008GC002335. Young, N. W., and G. Hyland ( 2002 ), Velocity and strain rates derived from InSAR analysis over the Amery Ice Shelf, East Antarctica, Ann. Glaciol., 34, 228 – 234. Bartholomaus, T. C., C. F. Larsen, S. O'Neel, and M. E. West ( 2012 ), Calving seismicity from iceberg‐sea surface interactions, J. Geophys. Res., 117, F04029, doi:10.1029/2012JF002513. Bassis, J. N., R. Coleman, H. A. Fricker, and J. B. Minster ( 2005 ), Episodic propagation of a rift on the Amery Ice Shelf, East Antarctica, Geophys. Res. Lett., 32, L06502, doi:10.1029/2004GL022048. Bassis, J. N., H. A. Fricker, R. Coleman, Y. Bock, J. Behrens, D. Darnell, M. Okal, and J. B. Minster ( 2007 ), Seismicity and deformation associated with ice‐shelf rift propagation, J. Glaciol., 53 ( 183 ), 523 – 536. Bassis, J. N., H. A. Fricker, R. Coleman, and J. B. Minster ( 2008 ), An investigation into the forces that drive ice‐shelf rift propagation on the Amery Ice Shelf, East Antarctica, J. Glaciol., 54 ( 184 ), 17 – 27. Budd, W. ( 1966 ), The dynamics of the Amery Ice Shelf, J. Glaciol., 6 ( 45 ), 335 – 358. Craven, M., I. Allison, H. A. Fricker, and R. Warner ( 2009 ), Properties of a marine ice layer under the Amery Ice Shelf, East Antarctica, J. Glaciol., 55 ( 192 ), 717 – 728. Dierckx, M., and J.‐L. Tison ( 2013 ), Marine ice deformation experiments: An empirical validation of creep parameters, Geophys. Res. Lett., 40, 134 – 138, doi:10.1029/2012GL054197. Dreger, D. S. ( 2003 ), TDMT_INV: Time domain seismic moment tensor Inversion, in International Handbook of Earthquake and Engineering Seismology, edited by W. H. K. Lee et al., p. 1627, Academic Press, London. Emry, E. L., D. A. Wiens, H. Shiobara, and H. Sugioka ( 2011 ), Seismogenic characteristics of the Northern Mariana shallow thrust zone from local array data, Geochem. Geophys. Geosyst., 12, Q12008, doi:10.1029/2011GC003853. Fricker, H. A., S. Popov, I. Allison, and N. Young ( 2001 ), Distribution of marine ice beneath the Amery Ice Shelf, Geophys. Res. Lett., 28 ( 11 ), 2241 – 2244. Fricker, H. A., N. W. Young, I. Allison, and R. Coleman ( 2002 ), Iceberg calving from the Amery Ice Shelf, East Antarctica, Ann. Glaciol., 34, 241 – 246. Fricker, H. A., J. N. Bassis, B. Minster, and D. R. MacAyeal ( 2005a ), ICESat's new perspective on ice shelf rifts: The vertical dimension, Geophys. Res. Lett., 32, L23S08, doi:10.1029/2005GL025070. Fricker, H. A., N. W. Young, R. Coleman, J. N. Bassis, and J. B. Minster ( 2005b ), Multi‐year monitoring of rift propagation on the Amery Ice Shelf, East Antarctica, Geophys. Res. Lett., 32, L02502, doi:10.1029/2004GL021036. Gammon, P. H., H. Kiefte, M. J. Clouter, and W. W. Denner ( 1983 ), Elastic constants of artificial and natural ice samples by Brillouin spectroscopy, J. Glaciol., 29 ( 103 ), 433 – 460. Haran, T., J. Bohlander, T. Scambos, and M. Fahnestock ( 2005 ), MODIS Mosaic of Antarctica (MOA) Image Map, National Snow and Ice Data Center Digital Media, Boulder, CO, U.S.A. Heeszel, D. S., D. A. Wiens, H. Shiobara, and H. Sugioka ( 2008 ), Earthquake evidence for along‐arc extension in the Mariana Islands, Geochem. Geophys. Geosyst., 9, Q12X03, doi:10.1029/2008GC002186. Hulbe, C. L., C. LeDoux, and K. Cruikshank ( 2010 ), Propagation of long fractures in the Ronne Ice Shelf, Antarctica, investigated using a numerical model of fracture propagation, J. Glaciol., 57 ( 97 ), 459 – 472. Jacobs, S. S., D. R. MacAyeal, and J. L. Ardai Jr. ( 1986 ), The recent advance of the Ross Ice Shelf, Antarctica, J. Glaciol., 32 ( 112 ), 464 – 474. Jansen, D., B. Kulessa, P. R. Sammonds, A. Luckman, E. C. King, and N. F. Glasser ( 2010 ), Present stability of the Larsen C ice shelf, Antarctic Peninsula, J. Glaciol., 56 ( 198 ), 593 – 600, doi:10.3189/002214310793146223. Jordan, T. H., and K. A. 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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. Key Points Rift‐related seismicity controlled by mechanical heterogeneity Back projection reveals that seismic deformation is continuous in region Spacing of rift‐transverse crevasses controls the timing of seismic swarms Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/106935/1/jgrf20203.pdf Article in Journal/Newspaper Amery Ice Shelf Antarc* Antarctic Antarctica East Antarctica Ice Shelf Ice Shelves Iceberg* University of Michigan: Deep Blue Amery ENVELOPE(-94.063,-94.063,56.565,56.565) Amery Ice Shelf ENVELOPE(71.000,71.000,-69.750,-69.750) Antarctic Austral East Antarctica Journal of Geophysical Research: Earth Surface 119 4 731 744

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