HR: 0800h
AN: U41B-0403    [Abstracts]
TI: Mantle Plumes: Seismic and Dynamic Models
AU: * Boschi, L
EM: larryboschi@gmail.com
AF: Institut fuer Geophysik ETH, Hoenggerberg HPP, Zuerich, 8093, Switzerland
AU: Becker, T
EM: twb@usc.edu
AF: Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy., Los Angeles, CA 90089, United States
AU: Steinberger, B
EM: bernhard.steinberger@ngu.no
AF: Center for Geodynamics, Geological Survey of Norway, Leiv Eirikssons vei 39, Trondheim, 7491, Norway
AB: Global-scale seismic tomography is a good tool to test the plume hypothesis and mantle models. We attempt to objectively characterize coherent, plume-likeslow/hot anomalies in recent maps of P and S velocity throughout the mantle, combining the following methodological improvements: (i) A "plume-detection" algorithm, inspired by geodynamic studies. This method identifies a variety of vertically coherent features, with similar properties, in all considered tomographic models. (ii) Quantification of the similarity (e.g. correlation) between tomographic and geodynamic plume-conduit models. Our results favor the idea that only a subset of known hotspots have a lower-mantle origin. Most of those that do can be associated with the large low-velocity zones in the lowermost mantle. From tests of different geodynamic forward models, we find that plume conduits that are distorted in mantle flow yield much better correlations with slow tomographic anomalies than vertical conduits. We complement a formal statistical analysis with Monte- Carlo tests and show that the plume-match is highly significant for several tomographic models. This finding provides further evidence that our geodynamic models adequately describe the nature of hot upwellings rising in mantle flow. We also find that models that allow for moving plume sources in the lower mantle match tomography better than those that have the plumes origin fixed. This is consistent with a thermal boundary layer source, and implies that anchoring by thermo-chemical piles is not required. Our flow-based results are complicated by a circularity issue: Plume conduits depend on mantle flow, which is driven by density anomalies, and density anomalies are in turn inferred from seismic tomography. We address this issue by modeling plume conduits from different tomography models, and show that the match between predicted plumes and tomography is a robust feature of all models.
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8121 Dynamics: convection currents, and mantle plumes
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8180 Tomography (6982, 7270)
SC: Union [U]
MN: 2007 Fall Meeting