Dynamical links between small- and large-scale mantle heterogeneity: Seismological evidence

Daniel A. Frost, Edward J. Garnero, Sebastian Rost

Research output: Research - peer-reviewArticle

Abstract

We identify PKP•PKP scattered waves (also known as P•P) from earthquakes recorded at small-aperture seismic arrays at distances less than 65°. P•P energy travels as a PKP wave through the core, up into the mantle, then scatters back down through the core to the receiver as a second PKP. P•P waves are unique in that they allow scattering heterogeneities throughout the mantle to be imaged. We use array-processing methods to amplify low amplitude, coherent scattered energy signals and resolve their incoming direction. We deterministically map scattering heterogeneity locations from the core–mantle boundary to the surface. We use an extensive dataset with sensitivity to a large volume of the mantle and a location method allowing us to resolve and map more heterogeneities than have previously been possible, representing a significant increase in our understanding of small-scale structure within the mantle. Our results demonstrate that the distribution of scattering heterogeneities varies both radially and laterally. Scattering is most abundant in the uppermost and lowermost mantle, and a minimum in the mid-mantle, resembling the radial distribution of tomographically derived whole-mantle velocity heterogeneity. We investigate the spatial correlation of scattering heterogeneities with large-scale tomographic velocities, lateral velocity gradients, the locations of deep-seated hotspots and subducted slabs. In the lowermost 1500 km of the mantle, small-scale heterogeneities correlate with regions of low seismic velocity, high lateral seismic gradient, and proximity to hotspots. In the upper 1000 km of the mantle there is no significant correlation between scattering heterogeneity location and subducted slabs. Between 600 and 900 km depth, scattering heterogeneities are more common in the regions most remote from slabs, and close to hotspots. Scattering heterogeneities show an affinity for regions close to slabs within the upper 200 km of the mantle. The similarity between the distribution of large-scale and small-scale mantle structures suggests a dynamic connection across scales, whereby mantle heterogeneities of all sizes may be directed in similar ways by large-scale convective currents.

LanguageEnglish (US)
Pages135-146
Number of pages12
JournalEarth and Planetary Science Letters
Volume482
DOIs
StatePublished - Jan 15 2018

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mantle
Earth mantle
Scattering
scattering
slab
slabs
hot spot
distribution
energy
method
gradients
Array processing
Earthquakes
Direction compound
mantle structure
core-mantle boundary
seismic velocity
earthquake
travel
remote regions

Keywords

  • deep Earth
  • mantle dynamics
  • mantle structure
  • scattering
  • seismic arrays
  • seismology

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Dynamical links between small- and large-scale mantle heterogeneity : Seismological evidence. / Frost, Daniel A.; Garnero, Edward J.; Rost, Sebastian.

In: Earth and Planetary Science Letters, Vol. 482, 15.01.2018, p. 135-146.

Research output: Research - peer-reviewArticle

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