Abstract
Differential PKP AB -DF travel-time measurements are compared directly with predicted residuals for mantle tomographic models to investigate the heterogeneity of the lowermost mantle. Much of the AB -DF time is accumulated in the lowermost portions of the mantle, resulting in heavy weighting of 3-D lowermost mantle structure on the differential travel-time perturbations. Comparisons of the observations with tomographic models show strong model dependence. The best variance reductions are achieved using the recent P-wave model of van der Hilst et al. [1997] (up to 20%), but the heterogeneity in the lowermost mantle may be 8 times larger than what shown by the tomographic model. The predictions for present S-wave tomographic models correlate poorly with the observations if we assume P-velocity anomalies are proportional to S-velocity anomalies. We argue that S-velocity anomalies in the lowermost mantle do not always track P-velocity anomalies. Our study shows no obvious evidence of slab effect on the observed AB - DF anomalies and, thus, the use of PKP phases is likely to provide a powerful tool in mapping the P-velocity structure in the lowermost mantle.
Original language | English (US) |
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Article number | 97GL01761 |
Pages (from-to) | 1863-1866 |
Number of pages | 4 |
Journal | Geophysical Research Letters |
Volume | 24 |
Issue number | 15 |
DOIs | |
State | Published - 1997 |
Externally published | Yes |
ASJC Scopus subject areas
- Geophysics
- General Earth and Planetary Sciences