Forearc seismogenesis in a weakly coupled subduction zone influenced by slab mantle fluids

Cordell, Darcy; Naif, Samer; Evans, Rob; Key, Kerry; Constable, Steven; Shillington, Donna; Bécel, Anne

doi:10.1038/s41561-023-01260-w

Cited by 4 publications

(8 citation statements)

References 57 publications

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“…The combination of preferentially oriented pre‐existing structures and an increase in slab dip outboard of the Shumagin Gap (west of ∼157°W) promote more bending faulting and are thus expected to produce increasing hydration of the incoming lithosphere, in comparison to the region outboard of the Semidi segment (east of ∼157°W) where the number and size of bending faulting is lower, A westward increase in hydration can be inferred from the westward increase in number of faults and larger fault throws and is consistent with observations of a double‐seismic zone in the downgoing plate in the Shumagin Gap (Wei et al., 2021), prominent conductors at depth in magnetotelluric data (Cordell et al., 2023), and geochemical signatures consistent with fluids in arc volcanism in the western Shumagin Gap (Wei et al., 2021).…”

Section: Discussionsupporting

confidence: 78%

“…) where the number and size of bending faulting is lower, A westward increase in hydration can be inferred from the westward increase in number of faults and larger fault throws and is consistent with observations of a doubleseismic zone in the downgoing plate in the Shumagin Gap (Wei et al, 2021), prominent conductors at depth in magnetotelluric data (Cordell et al, 2023), and geochemical signatures consistent with fluids in arc volcanism in the western Shumagin Gap (Wei et al, 2021).…”

Section: Implications For Hydrationsupporting

confidence: 85%

“…Higher degrees of bending faulting to the west are also expected to result in greater hydration of the crust and upper mantle, stored in hydrous minerals or as free water. Dehydration and migration of fluids at depth could also influence megathrust properties and behavior (e.g., Cordell et al., 2023; Saffer & Tobin, 2011; Saffer & Wallace, 2015). Thus, increased bending faulting and thinner sediment cover on the incoming plate in the western part of the study area may lead to a heterogeneous and fluid‐rich megathrust interface and promote creep.…”

Section: Discussionmentioning

confidence: 99%

“…However, the eastern part of the deep Shumagin Gap recently ruptured in a M7.8 earthquake in July 2020 (Liu et al., 2022; Xiao et al., 2021) and hosted an intraplate M7.6 earthquake in October 2020 (Zhou et al., 2022). Greater roughness at the top of the subducting plate due to increased bending faulting (e.g., Li et al., 2018; Wang & Bilek, 2014) and fluids from the hydrated lithosphere (Cordell et al., 2023; Li & Freymueller, 2018) have been proposed to contribute to changes in locking and earthquake history.…”

Section: Tectonic Backgroundmentioning

confidence: 99%

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Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Regalla

et al. 2024

Geochem Geophys Geosyst

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Oceanic plates experience extensive normal faulting as they bend and subduct, enabling fracturing of the incoming lithosphere. Debate remains about the relative importance of pre‐existing faults, plate curvature and other factors controlling the extent and style of bending‐related faulting. The subduction zone off the Alaska Peninsula is an ideal place to investigate controls on bending faulting as the orientation of the abyssal‐hill fabric with respect to the trench and plate curvature vary along the margin. Here, we characterize faulting between longitudes 161°W and 155°W using newly collected multibeam bathymetry data. We also use a compilation of seismic reflection data to constrain patterns of sediment thickness on the incoming plate. Although sediment thickness increases over 1 km from 156°W to 160°W, most sediments were deposited prior to the onset of bending faulting and thus should have limited impact on the expression of bend‐related fault strikes and throws in bathymetry data. Where magnetic anomalies trend subparallel to the trench (<30°) west of ∼156°W, bending faults parallel magnetic anomalies, implying that bending faults reactivate pre‐existing structures. Where magnetic anomalies are highly oblique (>30°) to the trench east of 156°W, no bending faults are observed. Summed fault throws increase to the west, including where pre‐existing structure orientations are constant (between 157 and 161°W), suggesting that another factor such as the increase in slab curvature must influence bending faulting. However, the westward increase in summed fault throws is more abrupt than expected for gradual changes in slab bending alone, suggesting potential feedbacks between pre‐existing structures, slab dip, and faulting.

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Section: Discussionsupporting

confidence: 78%

Section: Implications For Hydrationsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Tectonic Backgroundmentioning

confidence: 99%

See 2 more Smart Citations

Controls on Bending‐Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Regalla

et al. 2024

Geochem Geophys Geosyst

Self Cite

View full text Add to dashboard Cite

show abstract

“…The combination of preferentially oriented pre-existing structures and an increase in slab dip outboard of the Shumagin Gap promote more bending faulting and are thus expected to produce increasing hydration of the incoming lithosphere. A westward increase in hydration can be inferred from the westward increase in number of faults and larger fault throws and is consistent with observations of a double-seismic zone in the downgoing plate in the 35 Shumagin Gap, prominent conductors at depth in magnetotelluric data (Cordell et al, 2023), and geochemical signatures consistent with fluids in arc volcanism in the western Shumagin Gap (Wei et al, 2021).…”

Section: Implications For Hydrationsupporting

confidence: 86%

Controls on Bending-Related Faulting Offshore of the Alaska Peninsula

Clarke,

Shillington,

Christine

et al. 2023

Preprint

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Oceanic plates experience extensive normal faulting as they bend and subduct, enabling fracturing of the crust and upper mantle. Debate remains about the relative importance of pre-existing faults, plate curvature and other factors in controlling the extent and style of bending-related faulting. The subduction zone off the Alaska Peninsula is an ideal place to investigate controls on bending-related faulting as the orientation of abyssal-hill fabric with respect to the trench and plate curvature vary along the margin. Here we characterize bending faulting between longitudes 161°W and 155ºW using newly collected multibeam bathymetry data. We also use a compilation of seismic reflection data to constrain patterns of sediment thickness on the incoming plate. Although sediment thickness increases by over 1 km from 156°W to 160°W, most sediments were deposited prior to the onset of bending faulting and thus have limited impact on the expression of bend-related fault strikes and throws in bathymetry data. Where magnetic anomalies trend subparallel to the trench (<30°) west of ~156ºW, bending faulting parallels magnetic anomalies, implying bending faulting reactivates pre-existing structures. Where magnetic anomalies are highly oblique (>30°) to the trench east of 156ºW, no bending faulting is observed. Summed fault throws increase to the west, including where pre-existing structure orientations do not vary between 157-161ºW, suggesting that the increase in slab curvature directly influences fault throws. However, the westward increase in summed fault throws is more abrupt than expected for changes in slab bending alone, suggesting potential feedbacks between pre-existing structures, slab dip, and faulting.

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