TY - JOUR
T1 - Mega ultra low velocity zone and mantle flow
AU - Thorne, Michael S.
AU - Garnero, Edward
AU - Jahnke, Gunnar
AU - Igel, Heiner
AU - McNamara, Allen K.
N1 - Funding Information:
We thank the Arctic Region Supercomputing Center at the University of Alaska, Fairbanks and the Center for High Performance Computing at the University of Utah for use of their supercomputing facilities. MT was partially supported by NSF grant EAR-1014749 . EJG was partially supported by EAR-0453944 . AKM was partially supported by NSF grants EAR-0456356 and EAR-0510383 . We also thank the Incorporated Research Institution for Seismology and EarthScope for the freely available data used in this study. We thank two anonymous reviewers whose comments strengthened this manuscript. We gratefully acknowledge support through the EU project SPICE.
PY - 2013/2/5
Y1 - 2013/2/5
N2 - Mantle flow in Earth's interior has been inferred from a variety of geo-disciplines. Two continental-scale, nearly antipodal, large low shear velocity provinces (LLSVPs) at the base of the mantle, thought to be dense and chemically distinct likely play a significant role in mantle dynamics and plume generation, and hence are targeted in a high-resolution seismic study. We analyze broadband SPdKS waveforms using a 2.5D axi-symmetric finite difference wave propagation algorithm PSVaxi. Here we find patches of greatly reduced seismic wave speeds at the core-mantle boundary, i.e., ultra-low velocity zones (ULVZs), within the Pacific LLSVP, including the largest ULVZ detected to date, roughly 250×800. km in lateral dimension and 10-15. km thick, in an apparent hole in the LLSVP. The presence of this ULVZ in the LLSVP hole is well explained by dynamically merging, chemically-distinct piles containing ULVZs at their margins. The consequence of these merging piles may be to initiate anomalously large, infrequent plumes, as well as to provide a means to transfer isotopes to the surface.
AB - Mantle flow in Earth's interior has been inferred from a variety of geo-disciplines. Two continental-scale, nearly antipodal, large low shear velocity provinces (LLSVPs) at the base of the mantle, thought to be dense and chemically distinct likely play a significant role in mantle dynamics and plume generation, and hence are targeted in a high-resolution seismic study. We analyze broadband SPdKS waveforms using a 2.5D axi-symmetric finite difference wave propagation algorithm PSVaxi. Here we find patches of greatly reduced seismic wave speeds at the core-mantle boundary, i.e., ultra-low velocity zones (ULVZs), within the Pacific LLSVP, including the largest ULVZ detected to date, roughly 250×800. km in lateral dimension and 10-15. km thick, in an apparent hole in the LLSVP. The presence of this ULVZ in the LLSVP hole is well explained by dynamically merging, chemically-distinct piles containing ULVZs at their margins. The consequence of these merging piles may be to initiate anomalously large, infrequent plumes, as well as to provide a means to transfer isotopes to the surface.
KW - Core-mantle boundary
KW - LLSVPS
KW - Mantle convection
KW - Seismic wave propagation
KW - ULVZ
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U2 - 10.1016/j.epsl.2012.12.034
DO - 10.1016/j.epsl.2012.12.034
M3 - Article
AN - SCOPUS:84873704814
SN - 0012-821X
VL - 364
SP - 59
EP - 67
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -