Lowvelocity zone atop the 410km seismic discontinuity in the northwestern United States T'R'A' Song,

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Low-velocity zone atop the 410-km seismic
discontinuity in the northwestern United
States T.-R.A. Song, D.V. Helmberger, S.P.
GrandNature 427, 2004

• Pei-Ying Patty Lin
• Earthscope Seminar,
  Feb.12, 2007

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DATA
XL
XK
XM
TriNet
Song et al., Nature 427, 530 (2004).
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Method
Song et al., Nature 427, 530 (2004).
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Profile A(d1417o)
Thickness of LVZ(km) 0
40 20 Topography
depression(km) 60 0
20
TriNet
Song et al., Nature 427, 530 (2004).
Song et al., Nature 427, 530 (2004).
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Triplication curves
record section B
record section A
Song et al., Nature 427, 530 (2004).
Song et al., Nature 427, 530 (2004).
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Profile C,F,D,E(d2124o)
H of LVZ(km) 20 70
90 90 Topo
(km) 20 20
60 60
Song et al., Nature 427, 530 (2004).
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Results
119o115oW 41.5o 40.2o
Patches White no detected LVZ Red with dashed
outline a possible LVZ Red with solid outline
clear LVZ
dots (receiver functions) White no negative
pulse above 410 and relative strong simple 410
peaks Red strong negative pulse above 410
116o114oW 38.9o 37.5o
Preferred model 2090 km thick with 5 S-wave
velocity reduction
Song et al., Nature 427, 530 (2004).
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Interpretation
low Water solubility
high Water solubility
low Water solubility
Bercovici and Karato, Nature 425, 39 (2003).
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Additional Thoughts

• Which one is the best-fit velocity model?
• A?LVZ atop the 410 exists in some regions but may
  be too thin to be detected.
• Is there a possibility of detecting the LVZ with
  short-period data?