Global P wave tomography of Earth's lowermost mantle from partition modeling

Determining the scale‐length, magnitude, and distribution of heterogeneity in the lowermost mantle is crucial to understanding whole mantle dynamics, and yet it remains a much debated and ongoing challenge in geophysics. Common shortcomings of current seismically derived lowermost mantle models are...

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Bibliographic Details
Published in:Journal of geophysical research. Solid earth 2013-10, Vol.118 (10), p.5467-5486
Main Authors: Young, M. K., Tkalc̆ić, H., Bodin, T., Sambridge, M.
Format: Article
Language:English
Subjects:
Anisotropy
Bayesian analysis
Bayesian inversion
Earth
Earth sciences
Earth, ocean, space
Earthquakes, seismology
Estimates
Exact sciences and technology
Geophysics
Heterogeneity
hierarchical
Internal geophysics
Iron
lowermost mantle structure
Mantle
Mathematical models
P waves
P-wave velocity
Parametrization
Seismic Tomography
Tomography
transdimensional
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Summary:Determining the scale‐length, magnitude, and distribution of heterogeneity in the lowermost mantle is crucial to understanding whole mantle dynamics, and yet it remains a much debated and ongoing challenge in geophysics. Common shortcomings of current seismically derived lowermost mantle models are incomplete raypath coverage, arbitrary model parameterization, inaccurate uncertainty estimates, and an ad hoc definition of the misfit function in the optimization framework. In response, we present a new approach to global tomography. Apart from improving the existing raypath coverage using only high‐quality cross‐correlated waveforms, the problem is addressed within a Bayesian framework where explicit regularization of model parameters is not required. We obtain high‐resolution images, complete with uncertainty estimates, of the lowermost mantle P wave velocity structure using a hand‐picked data set of PKPab‐df, PKPbc‐df, and PcP‐P differential travel times. Most importantly, our results demonstrate that the root mean square of the P wave velocity variations in the lowermost mantle is approximately 0.87%, which is 3 times larger than previous global‐scale estimates. Key Points Mantle heterogeneity is three times stronger than previous results P‐wave velocity perturbations are mapped in lowermost mantle Transdimensional, hierarchical Bayesian inversion of differential travel times
ISSN:2169-9313
2169-9356
DOI:10.1002/jgrb.50391