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Artefacts & Optical Illusions in Tomography
With emphasis on the roles of slabs, backarc basins, volatiles & cratonic roots
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FACE
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What is the ambient color?
The optical illusion of inversion. Is yellow hot or just not cold?
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HOT COLORS ARE COLD MANTLE
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One cause of vertical streaking artefacts(there are many)
No plumes
Multiple plumes
Shallow anisotropy & heterogeneity can bleed into the lower mantle
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Relative vs. absolute wavespeeds
Add the reference model back in
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Absolute wavespeeds
Absolute wavespeeds
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Relative wavespeeds
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Plumes under California, slab under Yellowstone?
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The pale yellow areas become slightly positive when a background reference model with slabs at 650 km is added back in and the blue regions above 650 become bluer.
In contrast to global reference models, the actual Earth has a global LVZ between 600 and 650 km. Correcting to this new reference turns the red patches above 650 into pale blue or neutral patches & blue regions into flat slab like anomalies.
1000 km
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Actual anomalies are ~2.5 times larger
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