DOI: 10.1016/j.epsl.2020.116724
论文题名: Subcretionary tectonics: Linking variability in the expression of subduction along the Cascadia forearc
作者: Delph J.R. ; Thomas A.M. ; Levander A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 556 语种: 英语
中文关键词: forearc structure
; orogenesis
; seismic imaging
; subduction
; underplating
英文关键词: Acoustic wave velocity
; Percolation (fluids)
; Plates (structural components)
; Seismology
; Shear waves
; Topography
; Wave propagation
; Discontinuity model
; Geophysical phenomena
; Internal reflectivity
; Lateral heterogeneity
; Non-volcanic tremors
; Recurrence intervals
; Shear wave velocity models
; Spatial correlations
; Shear flow
; discontinuity
; forearc basin
; orogeny
; plate tectonics
; S-wave
; seismic velocity
; subduction
; underplating
; Cascadia
英文摘要: A number of seismic and other geophysical phenomena exhibit significant lateral heterogeneity along the strike of the Cascadia forearc. Both the overriding and downgoing plate have been invoked to play the dominant role in controlling along-strike correlations between seismogenic behavior, potential field measurements, morphological/tectonic characteristics, and seismic structure; however, significant feedbacks likely exist between the two. In this study, we apply a 3D velocity correction to receiver function data and interpret the resulting discontinuity model alongside a recently published shear-wave velocity model to understand the possible causative relationships between correlative along-strike variations. Our discontinuity model indicates that the forearc crust thickens as it approaches the mantle wedge corner before progressively thinning toward the magmatic arc, likely due to the basal accretion of material from the downgoing plate to the overriding plate. In the northern and southern portions of the forearc, this “subcreted” material is characterized by thick (∼10 km) anomalously low shear-wave velocity zones. The thickness, high internal reflectivity, and low Bouguer gravity signatures associated with the low velocity zones likely indicate that this subcreted material is composed of dominantly (meta)sedimentary material that has been emplaced through successive subcretion events over geologic timescales. Furthermore, the anomalously low velocities and spatial correlation with high non-volcanic tremor (NVT) density and short slow slip recurrence intervals indicate that these regions are fluid-rich. While first-order variations in the fluids that control NVT and slow slip likely result from differences in the permeability of the downgoing slab as inferred from its stress state and the distribution of intraslab seismicity, these subcreted packages likely represent thick, vertically-impermeable regions in the lower crust that further accentuate this correlation. Variability in the amount of subcretion explains patterns of exhumation and uplift along the Cascadia margin and the resulting forearc topography over geologic timescales, and is likely controlled by some combination plate interface geometry/rheology and overriding plate architecture. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165445
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907, United States; Department of Earth Sciences, University of Oregon, 100 Cascade Hall, Eugene, OR 97403, United States; Department of Earth, Environmental and Planetary Sciences, Rice University, 6100 Main St., Houston, TX 77005, United States
Recommended Citation:
Delph J.R.,Thomas A.M.,Levander A.. Subcretionary tectonics: Linking variability in the expression of subduction along the Cascadia forearc[J]. Earth and Planetary Science Letters,2021-01-01,556