The Scripps 3D Mantle Models
This is the web site for the "Scripps mantle tomographic models". This page includes
short summaries of the models, links to basic figures,
and a list of references where to find more extensive descriptions.
The link to SB4L18 includes a brief tutorial which
summarizes the general features that are found in
most current seismic tomographic models.
This site also provides links to
our anonymous ftp area. The models are provided with README files, postscript
plots of the models and
Fortran 77 computer code to read the models. If you need assistance with the
handling of our models, please don't hesitate to contact us.
Note that our models are strictly mantle models and stop at the Moho (the
global average of the Moho depth is 22 km).
Our data have been corrected for crustal effects
(CRUST 5.1) prior to the
inversions. Hence, the signal in the data resulting from variations in crustal
structure has to be added to the
predictions of the mantle models when comparing them to measured data.
SB4L18
This model is the latest Scripps "high-resolution" model. Our
combined dataset
to make the mantle models includes
our surface wave phase velocity maps , free
oscillation structure coefficients and long-period body wave absolute and
differential travel times.
The model is parameterized by 18 layers of roughly 100km thickness in
the upper mantle and transition zone and 200km thickness in the lower
mantle. Each layer is devided into equal-area blocks of dimension 4 degrees
at the equator.
Our inversions employ the LSQR algorithm and we include first-difference
smoothing both radially and laterally.
SB4L18 shows the typical features commonly found in mantle tomographic models:
- large amplitude anomalies in the upper mantle
- moderately large amplitude anomalies in the lowermost mantle
- small-amplitude but significant anomalies in the mid-mantle
picture
- strong anomalies in the upper mantle that correlate with surface
tectonics (picture)
- slab-like features in the mid-mantle (picture)
- large harmonic degree 2 structure near the base of the mantle
picture)
Go to ftp section for downloading this model.
This figure shows a slice through SB4L18
that goes through the center of the Earth. The cut of the slice is along the
great circle that is marked by the blue circle in the center of the plot.
One of the most prominent features is a seismically fast slab-like
anomaly that extends from the surface beneath the Continental US well
throughout the whole mantle. This is thought to be the image of the
subducted Farallon plate.
Other marked features include two large slow
anomalies under Africa and the central Pacific Ocean that
originate at the CMB (core-mantle boundary) and extend well
up into the lower mantle.
Also prominent are the seismically fast continental
shields in the upper mantle: the South and West African Cratons, the southern
extension of the Canadian Shield and the Australian Shield.
Mid-ocean ridges are associated with slow
anomalies in the upper mantle.
The black circle marks the 670km discontinuity
between upper and lower mantle.
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SB10L18
This model is our joint Vs/Vp model. Our
combined dataset
to make this model includes
our surface wave phase velocity maps , free
oscillation structure coefficients and long-period body wave absolute and
differential travel times.
The model is parameterized by 18 layers of roughly 100km thickness in
the upper mantle and transition zone and 200km thickness in the lower
mantle. Each layer is devided into equal-area blocks of dimension 10 degrees
at the equator. SB10L18 was obtained in a joint inversion for shear velocity,
Vs, and bulk sound speed, Vc. See notes for retrieving Vp.
Our inversions employ the LSQR algorithm and we include first-difference
smoothing both radially and laterally.
SB10L18 shows some interesting features that can be found in other joint models as
well:
- large amplitude anomalies in the upper mantle
- moderately large amplitude anomalies in the lowermost mantle
- small-amplitude but significant anomalies in the mid-mantle
- the perturbations in Vs and Vp correlate throughout the mantle
- perturbations in Vs are typically 3 times as large as those in Vc or Vp
- the correlation of Vs and Vc decreases with depth
- Vs and Vc are strongly negatively correlated in the lowermost mantle
picture
Point 7 implies that the anomalies in the lowermost mantle are most likely
not caused by thermal effects (thermal effects make Vs and Vc correlate)
but that chemical effects (composition) play a role. The strongest anti-correlation
is found in the central Pacific.
Go to ftp section for downloading this model.
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S16B30
This model is the 1996 Scripps model. Our
combined dataset
included
our surface wave phase velocity maps , free
oscillation structure coefficients and long-period body wave absolute and
differential travel times.
The model is parameterized by 30 natural cubic B-splines radially and
by spherical harmonics up to degree 16 laterally.
Our inversion was a direct matrix inversion using second-derivative
smoothing both radially and laterally.
S16B30 is basically a smoothed version of SB4L18 as these models correlate very well,
except in the transition zone (picture).
Go to ftp section for downloading this model.
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P16B30
This model is the 1996 P velocity model of Bolton and Masters. The
combined dataset included
our Rayleigh wave phase velocity maps , free
oscillation structure coefficients and long-period P wave absolute and
differential travel times.
The model is parameterized by 30 natural cubic B-splines radially and
by spherical harmonics up to degree 16 laterally.
Our inversion was a direct matrix inversion using second-derivative
smoothing both radially and laterally.
The rms amplitudes in P16B30 vary very much like those of Vp in SB10L18 with depth
though the correlation of these models is not quite as good as between
S16B30 and SB4L18.
(picture).
Go to ftp section for downloading this model.
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Related Sites
Try out other workers' models:
==> Harvard Web Page
==> Berkeley Page
==> Steve Grand's home page
(email: steveg-at-maestro.geo.utexas.edu)
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Publications
Models SB4L18 and SB10L18 are described in:
Masters G., Laske, G., Bolton, H. and Dziewonski, A., 2000.
"The Relative Behavior of Shear Velocity, Bulk Sound Speed, and Compressional
Velocity in the Mantle: Implications for Chemical and Thermal Structure"
in: S. Karato, A.M. Forte, R.C. Liebermann, G. Masters and L. Stixrude (eds.)
"Earth's Deep Interior", AGU Monograph 117, AGU, Washington D.C.
Model S16B30 is described in:
Masters, G., Johnson, S., Laske, G. and Bolton H., A shear-velocity model
of the mantle. Phil. Trans. R. Soc. Lond. A, 354, 1385-1411, 1996.
Model P16B30 is described in:
Bolton H., Long Period Travel Times and the Structure of the Mantle.
PhD Thesis, La Jolla, 204 pages, 1996.
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FTP section
All models are available on anonymous ftp.
Download SB4L18
here
Download SB10L18
here
Download S16B30
here
Download P16B30
here
Please check the README files for instructions.
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THIS RESEARCH IS FUNDED BY NSF.
Guy Masters (
gmasters-at-ucsd.edu)
Gabi Laske (
glaske-at-ucsd.edu)
Goto Gabi's Home page
To IGPP Home
SB4L18 shows the typical features commonly found in mantle tomographic models:
This figure shows a slice through SB4L18
that goes through the center of the Earth. The cut of the slice is along the
great circle that is marked by the blue circle in the center of the plot.
One of the most prominent features is a seismically fast slab-like
anomaly that extends from the surface beneath the Continental US well
throughout the whole mantle. This is thought to be the image of the
subducted Farallon plate. 
SB10L18 shows some interesting features that can be found in other joint models as
well:
S16B30 is basically a smoothed version of SB4L18 as these models correlate very well,
except in the transition zone (picture).
The rms amplitudes in P16B30 vary very much like those of Vp in SB10L18 with depth
though the correlation of these models is not quite as good as between
S16B30 and SB4L18.
(picture).
