Reply to comment by R. Montelli, G. Nolet and F. A. Dahlen on 'Banana-doughnut kernels and mantle tomography'

Montelli et al. comment on a paper that we wrote in response to an earlier 'comment' and in which we argue that the Princeton models with or without banana-doughnut theory are effectively the same and that, thus, the beneficial effects of the use of banana-doughnut kernels (BDKs) on global tomography have been overstated. The models are highly correlated. There are (of course) differences, and some anomalies in the banana-doughnut models have higher amplitudes (perhaps by as much as 50 per cent or more) than in the ray theoretical models. However, this occurs mainly for small, weak anomalies, whose resolution by long period data has not been demonstrated. Because of differences in data and inversion strategy, and in absence of a 'ground truth', comparisons of MIT and PRI models do not provide insight into the efficacy and validity of BDKs or the accuracy of the models. With regard to plumes: if they indeed exist and have the appearance as suggested by Montelli et al. then our models are-in that respect-inaccurate. However, this is unrelated to the main point of our paper.