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PKP differential travel times: Implications for 3-D lower mantle structure

Song, Xiaodong and Helmberger, Don V. (1997) PKP differential travel times: Implications for 3-D lower mantle structure. Geophysical Research Letters, 24 (15). pp. 1863-1866. ISSN 0094-8276. doi:10.1029/97GL01761.

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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.

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Additional Information:© 1997 American Geophysical Union. Received 28 April 1997; accepted 1 June 1997. We are grateful for the antipodal measurements of Poupinet et al. [1993] provided by Annie Souriau. We thank Steve Grand and Rob van der Hilst for providing the updated versions of their models. The work benefited from discussion with Steve Grand and comments from Michael Wysession, Ed Garnero, and an anonymous reviewer. It was supported by the NSF grants EAR-9316441 (Caltech) and EAR-9506708 (LDEO). Division of Geological and Planetary Sciences, Caltech, contribution 5506 and Lamont-Doherty Earth Observatory of Columbia University, contribution 5677.
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Caltech Division of Geological and Planetary Sciences5506
Columbia University Lamont-Doherty Earth Observatory5677
Issue or Number:15
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Official Citation: Song, X. and D. V. Helmberger (1997), PKP differential travel times: Implications for 3‐D lower mantle structure, Geophys. Res. Lett., 24(15), 1863–1866, doi:10.1029/97GL01761.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35724
Deposited By: Ruth Sustaita
Deposited On:29 Nov 2012 18:35
Last Modified:09 Nov 2021 23:17

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