Mantle model SP12RTS
To constrain the origin of seismic velocity anomalies, information on both the shear-wave velocity and compressional-wave or bulk-sound velocity variations are required. Improved constraints of the ratios and correlations of these different velocities allow us to estimate the relative importance of thermal and chemical variations within the Earth's mantle.
Model SP12RTS (Koelemeijer et al., GJI (2016)) is our most recently developed tomographic model of both shear-wave and compressional-wave velocity variations in the mantle. SP12RTS is derived using the same methods and data types as employed in the construction of shear-wave velocity models S20RTS and S40RTS (see Jeroen Ritsema's website). SP12RTS is based on four million Rayleigh wave dispersion, 300,000 shear-wave traveltime, 400,000 P-wave traveltime and 7000 normal mode splitting function coefficients. Large-low-velocity provinces (LLVPs) are observed for both the shear- and compressional-wave velocity part of SP12RTS. SP12RTS also features an increase of their ratio up to 2500 km depth, followed by a decrease towards the core–mantle boundary. A negative correlation between the shear-wave and bulk-sound velocity variations is observed for both the LLVPs and the surrounding mantle in the lowermost mantle.
| Download model SP12RTS here: | |
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| We provide a gzipped TAR file with the model in spline and spherical harmonics format, codes to read the model coefficients and GMT scripts for plotting cross-sections and maps (with a choice for GMT4 or GMT5). Alternatively, ZIP files with model slices at different depths can be downloaded. Note that generally the degree 0 component (radial average) is removed. | |
| SP12RTS_plotting.tar.gz: Model coefficients at 21 depth splines up to spherical harmonic degree 12 for GMT4. Alternatively, download SP12RTS_plotting_GMT5.tar.gz for use with GMT5. | |
| SP12RTS.1x1.zip: Model values at 1x1 degrees spanning (-180,180) longitude and (-90,90) latitude. Files either contain 65341 points (uniform grid) or 44792 points (equidistant grid). | |
| SP12RTS.2x2.zip: Model values at 2x2 degrees spanning (-180,180) longitude and (-90,90) latitude. Files either contain 16472 points (uniform grid) or 11242 points (equidistant grid). | |
| SP12RTS.5x5.zip: Model values at 5x5 degrees spanning (-180,180) longitude and (-90,90) latitude. Files either contain 2702 points (uniform grid) or 1780 points (equidistant grid). | |
| If you are interested in using models based on different damping parameters, please contact me. For tomographic filtering using the resolution operator of SP12RTS, please see here. | |
| If you are using model SP12RTS, please reference: | |
| Koelemeijer, P., J. Ritsema, A. Deuss & H.-J. Van Heijst (2016). SP12RTS: a degree-12 model of shear- and compressional-wave velocity for Earth's mantle. Geophy. J. Int, Vol. 204(2), 1024-1039, doi:10.1093/gji/ggv481. |
Maps of (left) shear-wave and (centre) compressional-wave velocity structure (in %) in model SP12RTS and (right) histograms of the corresponding ratios at different depths in the lowermost mantle.