Combined shear wave velocity model SL2013sv/SMEAN2

In order to combine global upper and lower mantle velocity models, two tomographic velocity models are each cut and interconnected at a discontinuity (e.g. 410- or 660 km discontinuity). SMEAN is a composite shear wave velocity model by Becker and Boschi (2002). Included in its development are the 3D tomographic models s20rts (Ritsema et al., 1999), SB4L18 (Masters et al., 1999) and Grand (Grand et al., 1997).  It is a regularly gridded model with 0.5°x0.5°x25 km grid cell spacing from 25 km depth to the core-mantle boundary.  The input models are retrieved from body-wave tomography (all), surface-wave tomography (all) and normal modes inversion (s20rts and SB4L18). The models are combined by calculating the weighted average velocities in depth intervals, thus smoothing small wavelength heterogeneities.

Since 2016 an updated version of SMEAN is available, SMEAN2. It is determined using the same procedure as for SMEAN but includes newer models: S40RTS (Ritsema et al. 2011), GyPSUM-S (Simmons et al. 2010) and SAVANI (Auer et al., 2014).

The perturbation extensions and amplitudes are expected to decrease with depth. Since the long wavelength anomalies in the SMEAN/SMEAN2 model smooth the velocity perturbation amplitudes, the upper mantle must be approached by an extra model.  For the shallow mantle up to 410 km, the SL2013sv model (Schaeffer and Lebedev, 2013) is considered. The vertical shear wave velocities are derived from automated multimode inversion of surface and S-wave forms and has the same horizontal resolution as the SMEAN models ranging from 20 km to 660 km depth. The depth intervals are irregular between 16 and 100 km.


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