TY - JOUR
T1 - Investigating ultra-low velocity zones in the southern hemisphere using an Antarctic dataset
AU - Hansen, Samantha E.
AU - Carson, Sarah E.
AU - Garnero, Edward J.
AU - Rost, Sebastian
AU - Yu, Shule
N1 - Funding Information:
We thank two anonymous reviewers for their thorough comments that helped to improve this manuscript. Data management handling was provided by the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC), and all TAMNNET data are openly available through the DMC ( http://www.fdsn.org/networks/detail/ZJ_2012 ). The facilities of the IRIS Consortium are supported by the National Science Foundation (NSF) under cooperative agreements EAR-1851048 and OPP-1851037 . Funding for this research was provided by NSF grant PLR-1643551 , and SR has been partially supported by NERC grants NE/K006290/1 and NE/R012199/1 . Some figures were generated with Generic Mapping Tools ( Wessel and Smith, 1995 ).
Funding Information:
We thank two anonymous reviewers for their thorough comments that helped to improve this manuscript. Data management handling was provided by the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC), and all TAMNNET data are openly available through the DMC (http://www.fdsn.org/networks/detail/ZJ_2012). The facilities of the IRIS Consortium are supported by the National Science Foundation (NSF) under cooperative agreements EAR-1851048 and OPP-1851037. Funding for this research was provided by NSF grant PLR-1643551, and SR has been partially supported by NERC grants NE/K006290/1 and NE/R012199/1. Some figures were generated with Generic Mapping Tools (Wessel and Smith, 1995).
Publisher Copyright:
© 2020 The Author(s)
PY - 2020/4/15
Y1 - 2020/4/15
N2 - Given limited seismic coverage of the lowermost mantle, less than one-fifth of the core-mantle boundary (CMB) has been surveyed for the presence of ultra-low velocity zones (ULVZs). Investigations that sample the CMB with new geometries are therefore important to further our understanding of ULVZ origins and their potential connection to other deep Earth processes. Using core-reflected ScP waves recorded by the recently deployed Transantarctic Mountains Northern Network in Antarctica, the current study aims to expand ULVZ investigations in the southern hemisphere. Our dataset samples the CMB in the vicinity of New Zealand, providing coverage between an area to the northeast, where ULVZ structure has been previously identified, and another region to the south, where prior evidence for a ULVZ was inconclusive. This area is of particular interest because the data sample across the boundary of the Pacific Large Low Shear Velocity Province (LLSVP). The Weddell Sea region near Antarctica is also well sampled, providing new information on a region that has not been previously studied. A correlative scheme between a large database of 1-D synthetic seismograms and the observed ScP data demonstrates that ULVZs are required in both study regions. Modeling uncertainties limit our ability to definitively define ULVZ characteristics but also likely indicate more complex 3-D structure. Given that ULVZs are detected within, along the edge of, and far from the Pacific LLSVP, our results support the hypothesis that ULVZs are compositionally distinct from the surrounding mantle and are not solely related to partial melt. ULVZs may be ubiquitous along the CMB; however, they may be thinner in many regions than can be resolved by current methods. Mantle convection currents may sweep the ULVZs into thicker piles in some areas, pushing these anomalies toward the boundaries of LLSVPs.
AB - Given limited seismic coverage of the lowermost mantle, less than one-fifth of the core-mantle boundary (CMB) has been surveyed for the presence of ultra-low velocity zones (ULVZs). Investigations that sample the CMB with new geometries are therefore important to further our understanding of ULVZ origins and their potential connection to other deep Earth processes. Using core-reflected ScP waves recorded by the recently deployed Transantarctic Mountains Northern Network in Antarctica, the current study aims to expand ULVZ investigations in the southern hemisphere. Our dataset samples the CMB in the vicinity of New Zealand, providing coverage between an area to the northeast, where ULVZ structure has been previously identified, and another region to the south, where prior evidence for a ULVZ was inconclusive. This area is of particular interest because the data sample across the boundary of the Pacific Large Low Shear Velocity Province (LLSVP). The Weddell Sea region near Antarctica is also well sampled, providing new information on a region that has not been previously studied. A correlative scheme between a large database of 1-D synthetic seismograms and the observed ScP data demonstrates that ULVZs are required in both study regions. Modeling uncertainties limit our ability to definitively define ULVZ characteristics but also likely indicate more complex 3-D structure. Given that ULVZs are detected within, along the edge of, and far from the Pacific LLSVP, our results support the hypothesis that ULVZs are compositionally distinct from the surrounding mantle and are not solely related to partial melt. ULVZs may be ubiquitous along the CMB; however, they may be thinner in many regions than can be resolved by current methods. Mantle convection currents may sweep the ULVZs into thicker piles in some areas, pushing these anomalies toward the boundaries of LLSVPs.
KW - ScP
KW - southern hemisphere
KW - ultra-low velocity zones
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U2 - 10.1016/j.epsl.2020.116142
DO - 10.1016/j.epsl.2020.116142
M3 - Article
AN - SCOPUS:85079354320
SN - 0012-821X
VL - 536
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 116142
ER -