Focusing Effects of Teleseismic Wavefields by the Subducting Plate Beneath Cascadia

Pang, Guanning; Abers, G. A.; Keken, Peter E. van

doi:10.1029/2022jb025486

Cited by 3 publications

(2 citation statements)

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“…4b). The models are more fully described in Pang et al (2023) and are available in the Supplementary Information (see data availability statement). These models show that heat flow and position of the volcanic arc are not satisfied by a very shallow (40 km) or deep (100 km) decoupling point, but that a depth of around 70-80 km gives satisfactory model results.…”

Section: The Cold Corner Requires Mechanical Decoupling Between the S...mentioning

confidence: 99%

An introductory review of the thermal structure of subduction zones: I—motivation and selected examples

Keken

Wilson

2023

Prog Earth Planet Sci

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The thermal structure of subduction zones is fundamental to our understanding of physical and chemical processes that occur at active convergent plate margins. These include magma generation and related arc volcanism, shallow and deep seismicity, and metamorphic reactions that can release fluids. Computational models can predict the thermal structure to great numerical precision when models are fully described but this does not guarantee accuracy or applicability. In a trio of companion papers, the construction of thermal subduction zone models, their use in subduction zone studies, and their link to geophysical and geochemical observations are explored. In part I, the motivation to understand the thermal structure is presented based on experimental and observational studies. This is followed by a description of a selection of thermal models for the Japanese subduction zones.

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Section: The Cold Corner Requires Mechanical Decoupling Between the S...mentioning

confidence: 99%

An introductory review of the thermal structure of subduction zones: I—motivation and selected examples

Keken

Wilson

2023

Prog Earth Planet Sci

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“…Another potential reason is multipathing or focusing effects. Pang et al (2023) use full wave propagation simulations to show that these effects can mimic attenuation. The simulated S waves in that study had dominant periods of 20 s, which corresponds to wavelengths in the uppermost mantle on the order of 80 km.…”

Section: Synthetic Recovery Testmentioning

confidence: 99%

Lateral Variations in Teleseismic Attenuation of the Conterminous U.S. and New Insights Derived From Its Relationship to Mantle Seismic Velocity

Bezada,

Byrnes,

Zhu

et al. 2023

JGR Solid Earth

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Much of our knowledge of the North American lithosphere comes from imaging seismic velocities. Additional constraints on the subsurface can be gained by studying seismic attenuation, which has different sensitivity to physical properties. We produce a model of lateral variations in attenuation across the conterminous U.S. by analyzing data recorded by the EarthScope Transportable Array. We divide the study area into 12 overlapping tiles and differential attenuation is measured in each tile independently; and twice for four of the tiles. Measurements are combined into a smooth map using a set of linear inversions. Comparing results for adjacent tiles and for repeated tiles shows that the imaged features are robust. The final map shows generally higher attenuation west of the Rocky Mountain Front than east of it, with significant small length scale variations superimposed on that broad pattern. In general, there is a strong anticorrelation between differential attenuation and shear wave velocities at depths of 80–250 km. However, a given change in velocity may correspond to a large or small change in attenuation, depending on the area; suggesting that different physical mechanisms are operating. In the western and south‐central U.S., as well as the Appalachians, velocity variations are large compared to attenuation changes, while the opposite is true in the north‐central and southeastern U.S. Calculations with the Very Broadband Rheology calculator show that these results are consistent with the main source of heterogeneity being temperature and melt fraction in the former regions and grain size variability in the latter ones.

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Disentangling the Roles of Subducted Volatile Contributions and Mantle Source Heterogeneity in the Production of Magmas Beneath the Washington Cascades

Walowski,

Wallace,

DeBari

et al. 2024

Geochem Geophys Geosyst

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The compositional diversity of primitive arc basalts has long inspired questions regarding the drivers of magmatism in subduction zones, including the roles of decompression melting, mantle heterogeneity, and the amount and composition of slab‐derived materials. This contribution presents the volatile (H2O, Cl, and S), major, and trace element compositions of melt inclusions from basaltic magmas erupted at three volcanic centers in the Washington Cascades: Mount St. Helens (two basaltic tephras, 2.0–1.7 ka), Indian Heaven Volcanic Field (two <600 ka basaltic hyaloclastite tuffs), and Glacier Peak (late Pleistocene to Holocene basaltic tephra from Whitechuck and Indian Pass cones). Compositions corrected to be in equilibrium with mantle olivine display variability in Nb and trace element ratios indicative of mantle source variability that impressively spans nearly the entire range of arc magmas globally. All volcanic centers have magmas with H2O and Cl contributions from the downgoing plate that overlap with other Cascade Arc segments. Volatile abundances and trace element ratios support a model of melting of a highly variably mantle wedge driven by a subduction component of variably saline fluid and/or slab partial melt. Magmas from Glacier Peak in northern Washington have unusually high Th/Yb ratios that are similar to Lassen region basalts, indicating possible contributions of “subcreted” metasediments that geophysical data suggest are not present beneath central Oregon and southern Washington. This data set adds to the growing inventory of primitive magma volatile concentrations and provides insight into spatial distributions of mantle heterogeneity and the role of slab components in the petrogenesis of arc magmas.

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Focusing Effects of Teleseismic Wavefields by the Subducting Plate Beneath Cascadia

Cited by 3 publications

References 61 publications

An introductory review of the thermal structure of subduction zones: I—motivation and selected examples

An introductory review of the thermal structure of subduction zones: I—motivation and selected examples

Lateral Variations in Teleseismic Attenuation of the Conterminous U.S. and New Insights Derived From Its Relationship to Mantle Seismic Velocity

Disentangling the Roles of Subducted Volatile Contributions and Mantle Source Heterogeneity in the Production of Magmas Beneath the Washington Cascades

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