Sequencing seismograms: A panoptic view of scattering in the core-mantle boundary region

TL;DR

This paper introduces a manifold learning approach called 'the Sequencer' to analyze thousands of seismograms simultaneously, revealing widespread heterogeneity and new deep Earth features near the core-mantle boundary.

Contribution

The study applies a novel manifold learning algorithm to seismic data, providing a comprehensive view of scattering and heterogeneity at the core-mantle boundary region.

Findings

Detection of pervasive lateral heterogeneity near the core-mantle boundary.

Identification of a plume root beneath Hawaii.

Discovery of an ultralow-velocity zone beneath the Marquesas Islands.

Abstract

Scattering of seismic waves can reveal subsurface structures but usually in a piecemeal way focused on specific target areas. We used a manifold learning algorithm called "the Sequencer" to simultaneously analyze thousands of seismograms of waves diffracting along the core-mantle boundary and obtain a panoptic view of scattering across the Pacific region. In nearly half of the diffracting waveforms, we detected seismic waves scattered by three-dimensional structures near the core-mantle boundary. The prevalence of these scattered arrivals shows that the region hosts pervasive lateral heterogeneity. Our analysis revealed loud signals due to a plume root beneath Hawaii and a previously unrecognized ultralow-velocity zone beneath the Marquesas Islands. These observations illustrate how approaches flexible enough to detect robust patterns with little to no user supervision can reveal distinctive insights into the deep Earth.