Small‐Scale Intraslab Heterogeneity Weakens Into the Mantle Transition Zone

Abstract

Multiscale seismic structures of subducting slabs provide fundamental constraints on the slab thermal and petrological properties. Extensive investigations have been conducted on the large-(>100 km) and intermediate-scale (10-100 km) slab structures. For example, subducting plates imaged from tomographic models are characterized as large-scale high-velocity anomalies descending into the mantle with complicated destinies (e.g.

On the Origin of Small‐Scale Seismic Scatters at 660‐km Depth

“…While models with basalts distributed inside the harzburgite layer, they do not exhibit as strong scatter signals as Case D1 (Figure S16b in Supporting Information S1). Considering that seismic velocity contrast between basalt and harzburgite at 300-600 km depth in cold slab is significantly smaller than those at ∼660 km (Figure S15 in Supporting Information S1), a thicker layer of harzburgite with basalt heterogeneities inside the slab might explain the decrease in the strength of scattering signals in the slab observed by Shen et al (2021).…”

“…Sun et al (2014) argued that heterogeneities in the top 40 km of the slab are required to fit the high frequency coda wave at the Calabria subduction zone above 300 km depth. Shen et al (2021) argued that the strength of scatters, especially those within the top of the slab, weakens below 410 km in the Japan subduction zone. We also perform calculations with heterogeneities only in the bottom 50 km (Kennett & Furumura, 2015) to test the influence of distribution of heterogeneities in the slab.…”

“…Shen et al. (2021) argued that the strength of scatters, especially those within the top of the slab, weakens below 410 km in the Japan subduction zone. We also perform calculations with heterogeneities only in the bottom 50 km (Kennett & Furumura, 2015) to test the influence of distribution of heterogeneities in the slab.…”

“…The origin of such intrinsic heterogeneities remains uncertain. The origin of the elongated heterogeneity inside the oceanic lithosphere is interpreted as frozen melts as the oceanic plate moves away from the mid‐ocean ridge (Furumura & Kennett, 2005) or intraslab hydrous minerals (Shen et al., 2021). The origin of the observed seismic scatters at 660 km depth might not just come from the subducted oceanic lithosphere, but also from the delaminated continental lithosphere which might also be stagnant in the mantle transition zone (Peng et al., 2022), as the averaged auto‐correlation wavelength A is 4 km and the perturbation $$\sigma $$ is 4% from surface to 200 km depth (Shearer & Earle, 2004), which is similar to those at 660 km depth.…”

On the Formation of Global Inter‐Source Correlations and Applications to Constrain the Interiors of the Earth and Other Terrestrial Planets

“…Inter‐source correlations can turn seismic events into virtual receivers in areas remote from seismic networks or at specific depths underground (Curtis & Halliday, 2010; Curtis et al., 2009; Liu et al., 2016; Poliannikov et al., 2012; Saengduean et al., 2021; Shen & Zhan, 2020; Tonegawa & Nishida, 2010). This allows for forming deep virtual seismometers to detect seismic signals sensitive to deep‐earth structures with minimal signal disturbance due to shallow‐depth structure heterogeneities (Shen & Zhan, 2020; Shen et al., 2021). Also, the inter‐source correlations are used for imaging crustal structures (Shirzad et al., 2019), shear‐wave velocities in areas around different source clusters (Eulenfeld, 2020), and monitoring of micro‐earthquakes (Morency & Matzel, 2017).…”