Mariano you should read "Fischer, K. M., H.A. Ford, D.L. Abt, and C.A. Rychert (2010), The Lithosphere-Asthenosphere Boundary, Annu. Rev. Earth Planet. Sci., 38(1), 551–575, doi:10.1146/annurev-earth-040809-152438.". She explains how to pick the LAB using different methods. 

However estimating the LAB using receiver functions alone is complicated due to the nature of the LAB. It is better to combine your receiver function analysis with other methods, for example shear wave tomography. I did that in my research and is published in EPSL called " Lithospheric Expression of Cenozoic Subduction, Mesozoic Rifting and the Precambrian Shield in Venezuela". 

Also in the past during AGU fall meetings I heard several talks indicating how the LAB estimation from receiver functions and other methods can lead to different results unless there is a joint interpretation and they gave some examples. If I remember correctly one of the talks was given by Meghan Miller. 

I hope this helps

Best Regards, 

Jeniffer 

Thanks Jeni. But I am mostly interested in estimating the velocity structure, more than the LAB depth. Can that be estimated?

Yes, you may do it by making a joint inversion of Ps and Sp receiver functions. 

PRFs are sensitive to Vs and SRFs are sensitive to both Vp and Vs

You may read the papers from our group on the Azores, cape Verde and Iberia. They are available in my page.

Thank you Graça! I will download your papers.