Upload
vanessa-walker
View
223
Download
0
Embed Size (px)
Citation preview
Artefacts & Optical Illusions in Tomography
With emphasis on the roles of slabs, backarc basins, volatiles & cratonic roots
FACE
What is the ambient color?
The optical illusion of inversion. Is yellow hot or just not cold?
HOT COLORS ARE COLD MANTLE
One cause of vertical streaking artefacts(there are many)
No plumes
Multiple plumes
Shallow anisotropy & heterogeneity can bleed into the lower mantle
Relative vs. absolute wavespeeds
Add the reference model back in
Absolute wavespeeds
Absolute wavespeeds
Relative wavespeeds
Plumes under California, slab under Yellowstone?
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
Actual anomalies are ~2.5 times larger