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