Data from: Seismic low-velocity equatorial torus in the Earth's outer core: Evidence from the late-coda correlation wavefield
Data files
May 24, 2024 version files 83.64 GB
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data_2000.tar
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data_2001.tar
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README.md
Abstract
Thermochemical inhomogeneities in the Earth's outer core that enhance our understanding of the geodynamo have been elusive. Seismic constraints on such inhomogeneities would provide clues on the amount and distribution of light elements in the core apart from iron and nickel. Here, we present evidence for a low-velocity volume within the outer core via the global coda-correlation wavefield. The dataset in this study include about 9-hour long waveform in SAC format between the year 2000 and 2021. Firstly we selected the waveforms in the time window 3-9 hours after the event origin time. We applied the temporal normalization and spectral whitening methods to seismograms of all receivers and calculated cross-correlations by multiplying the whitened spectrum of one receiver with the complex conjugate spectrum of another. Then the spectral cross-correlations were inversely Fourier transformed and folded at the time zero to yield cross-correlation functions in the time domain. Subsequently, the cross-correlation functions for receiver pairs were linearly stacked in inter-receiver distance bins with an interval of 1° and band-pass filtered in the period band of 15–50 s for a single-event correlogram. Based on the processed data, we find several key correlogram features with a unique sensitivity to the liquid core show variations with wave paths significantly slower in the equatorial than polar planes. We constrain a torus at low latitudes with ~2% lower velocity than the surrounding liquid outer core via waveform modeling. We propose a thermochemical origin for such a low-velocity torus, providing new constraints on the dynamical processes of the Earth’s outer core.