One-dimensional physical reference models for the upper mantle and transition zone: combining seismic and mineral physics constraints

One-dimensional seismic reference models are known to be a nonunique solution to global seismic data, hampering an interpretation in terms of physical structure. Here we test the compatibility of the simplest hypothesis of a mantle convecting as a whole, with a constant pyrolitic composition with phase transitions, directly against the kind of seismic data that went into global seismic reference models, focusing on upper mantle structure down to 800 km depth. By randomly varying the elastic and anelastic parameters of the main mantle minerals within their uncertainty bounds, we generate a set of 100,000 adiabatic, pyrolitic models. A small number of these models (