Data Services Products: EMC-ak135-f A velocity reference Earth model

A Note on the Upper Mantle Density Model

A Note from Philip Crotwell on Q_kappa vs. Q_alpha

The paper that is the reference for this model, Montagner and Kennett, says:

“We did not attempt to invert for Q_kappa ,which is
known to be poorly resolved. To a first approximation, 1/Q_kappa
is very close to zero except in the core.”

and then says in eqn 2.6 that:

1/Q_alpha = (4/3)(beta/alpha)^2 (1/Q_beta)
where Q_beta = Q_mu..

Checking the given values versus values calculated by this formula shows that the Q_kappa column to actually be Q_alpha (within +-0.03) for all values except fluid layers, where Q_alpha is set to a generic large value of 57822.0, which is about the same default value used in PREM. So I think this column should be labeled Q_alpha and not Q_kappa. Likely this is not a big deal and would not cause problems unless someone thought they needed to calculate Q_alpha from this value and effectively applied the conversion twice. Hopefully everyone just assumes this is Qp.

For comparison, the PREM model here does in fact have Q_kappa as the last column in PREM_1s.csv and all of the values are 57823
except in the inner core where it is 1327.7, which jives with the 1/Q_kappa being approx. zero except in the inner core.

My understanding is that Q_beta = Q_mu, and so it could be labeled either.