Seismic Anisotropy in the Deep Mantle, Boundary Layers and the Geometry of Mantle Convection

1998 ◽  
Vol 151 (2-4) ◽  
pp. 565-587 ◽  
Author(s):  
S. Karato
Keyword(s):  
Boundary Layers ◽  
Mantle Convection ◽  
Seismic Anisotropy ◽  
Mantle Boundary ◽  
Deep Mantle

scholarly journals Synthetic seismic anisotropy models within a slab impinging on the core–mantle boundary

2014 ◽  
Vol 199 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Sanne Cottaar ◽  
Mingming Li ◽  
Allen K. McNamara ◽  
Barbara Romanowicz ◽  
Hans-Rudolf Wenk
Keyword(s):  
Seismic Anisotropy ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core

An investigation of seismic anisotropy in the lowermost mantle beneath Iceland

2019 ◽  
Vol 219 (Supplement_1) ◽  
pp. S152-S166 ◽  
Author(s):  
Jonathan Wolf ◽  
Neala Creasy ◽  
Angelo Pisconti ◽  
Maureen D Long ◽  
Christine Thomas
Keyword(s):  
Seismic Anisotropy ◽  
Horizontal Flow ◽  
Mantle Flow ◽  
Small Data ◽  
Vertical Flow ◽  
Low Velocity ◽  
Data Set ◽  
Study Region ◽  
Deep Mantle ◽  
Lowermost Mantle

SUMMARY Iceland represents one of the most well-known examples of hotspot volcanism, but the details of how surface volcanism connects to geodynamic processes in the deep mantle remain poorly understood. Recent work has identified evidence for an ultra-low velocity zone in the lowermost mantle beneath Iceland and argued for a cylindrically symmetric upwelling at the base of a deep mantle plume. This scenario makes a specific prediction about flow and deformation in the lowermost mantle, which can potentially be tested with observations of seismic anisotropy. Here we present an investigation of seismic anisotropy in the lowermost mantle beneath Iceland, using differential shear wave splitting measurements of S–ScS and SKS–SKKS phases. We apply our techniques to waves propagating at multiple azimuths, with the goal of gaining good geographical and azimuthal coverage of the region. Practical limitations imposed by the suboptimal distribution of global seismicity at the relevant distance ranges resulted in a relatively small data set, particularly for S–ScS. Despite this, however, our measurements of ScS splitting due to lowermost mantle anisotropy clearly show a rotation of the fast splitting direction from nearly horizontal for two sets of paths that sample away from the low velocity region (implying VSH > VSV) to nearly vertical for a set of paths that sample directly beneath Iceland (implying VSV > VSH). We also find evidence for sporadic SKS–SKKS discrepancies beneath our study region; while the geographic distribution of discrepant pairs is scattered, those pairs that sample closest to the base of the Iceland plume tend to be discrepant. Our measurements do not uniquely constrain the pattern of mantle flow. However, we carried out simple ray-theoretical forward modelling for a suite of plausible anisotropy mechanisms, including those based on single-crystal elastic tensors, those obtained via effective medium modelling for partial melt scenarios, and those derived from global or regional models of flow and texture development in the deep mantle. These simplified models do not take into account details such as possible transitions in anisotropy mechanism or deformation regime, and test a simplified flow field (vertical flow beneath the plume and horizontal flow outside it) rather than more detailed flow scenarios. Nevertheless, our modelling results demonstrate that our ScS splitting observations are generally consistent with a flow scenario that invokes nearly vertical flow directly beneath the Iceland hotspot, with horizontal flow just outside this region.

scholarly journals Radial 1‐D seismic structures in the deep mantle in mantle convection simulations with self‐consistently calculated mineralogy

2012 ◽  
Vol 13 (11) ◽  
Author(s):  
Takashi Nakagawa ◽  
Paul J. Tackley ◽  
Frédéric Deschamps ◽  
James A. D. Connolly
Keyword(s):  
Mantle Convection ◽  
Deep Mantle
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