Post on 01-Aug-2020
Week 8: Deep Interior
Interior 1-‐D structure • Adams-‐Williamson Equa0on
• What (and deriva0on) • How good are the predic0ons?
• 1D: VP, VS, elas0c moduli (µ, K), ρ, P, g, aDenua0on Q
Interior 3D structure • Seismic tomography – what is it? • Overall amplitude of 3D vs 1D structure • Key spa0al structure at various depths
The SB4L18S model is parameterized by 18 layers of roughly 100km thickness in the upper mantle and transi0on zone and 200km thickness in the lower mantle. Each layer is divided into equal-‐area blocks of dimension 4 degrees at the equator. The dataset to make the models includes surface wave phase velocity maps, free oscilla0on structure coefficients (i.e. normal modes) and long-‐period body wave absolute and differen0al travel 0mes.
Amplitude shown as % of mean Vs at that depth
Seismic tomography
No0ce that the velocity models made from tomography have very small perturba0ons rela0ve to the 1D models. Although small they are important…..
SB4L18: see text book S-‐wave tomography model
Masters et al., 2000
S16B30
This is an older (by just 4 years) model that is basically a lower resolution version of SB4L18.
Masters et al., 1996
P16B30
Models built from P waves not S waves.
Bolton and Masters, 1996
Cross sec0on similar to the one shown in the text.
Another example of P-wave model versus an S-wave model. We discussed in class.
Plate 13 from the text book.