M. Sylvander et A. Souriau, P-VELOCITY STRUCTURE OF THE CORE-MANTLE BOUNDARY REGION INFERRED FROMPKP(AB)-PKP(BC) DIFFERENTIAL TRAVEL-TIMES, Geophysical research letters, 23(8), 1996, pp. 853-856
PKP(AB)-PKP(BC) differential travel time residuals from the bulletins
of the International Seismological Centre are inverted to retrieve the
P-velocity anomalies in the lowermost 300 km of the mantle. We show t
hat a realistic core-mantle boundary (CMB) topography may have only a
marginal contribution to the residuals. The block parametrization used
allows us to discard poorly sampled areas prior to a least-squares in
version. The main features are negative anomalies beneath Eurasia and
North America and a positive anomaly beneath the Southwest Pacific. Th
e inferred map is not consistent with other maps resulting from previo
us P- and S-velocity studies, which are correlated at long wavelengths
with each other. The preferred explanation for this challenging incon
sistency is the presence of a thin heterogeneous layer just above the
CMB.