Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California

Jiang, Chengxin; Schmandt, Brandon; Hansen, S. M.; Dougherty, S. L.; Clayton, Robert W.; Farrell, Jamie; Lin, F. C.

doi:10.1016/j.epsl.2018.02.009

Cited by 41 publications

(67 citation statements)

References 90 publications

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“…Nevada (Jiang et al, 2018). Thus, we favor the interpretation that the Isabella anomaly is instead a fossil slab fragment of the Farallon plate (Cox et al, 2016;Jiang et al, 2018;Nicholson et al, 1994;.…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 57%

“…In addition, the position of the Isabella anomaly in the mantle fails to support the connection between the Isabella anomaly and the Sierra Nevada (Jiang et al, ). Thus, we favor the interpretation that the Isabella anomaly is instead a fossil slab fragment of the Farallon plate (Cox et al, ; Jiang et al, ; Nicholson et al, ; Wang et al, ). The resulting N‐S fast orientations in the lithosphere of the GV possibly represent fossil anisotropy inherited from the subducted Farallon plate where trench‐parallel fast orientations are expected to develop, which has been extensively observed in the subducting slabs surrounding the Pacific (e.g., Liu & Zhao, ; Long & Silver, ; Wei et al, ; Zhao et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…The Isabella anomaly is revealed to be possibly attached to the Monterey microplate (Cox et al, ; Jiang et al, ; Nicholson et al, ; Wang et al, ). Modeling results (Pikser et al, ) indicate that it is feasible to transport the Isabella anomaly hundreds of kilometers along‐strike to its current place while remaining intact and attached.…”

Section: Resultsmentioning

confidence: 99%

“…A conspicuous high‐V anomaly resting around the Moho has been revealed beneath the Salton Trough (e.g., Han et al, ; Hauksson, ; Jiang et al, ; Lee et al, ; Tape et al, ), whereas its asthenosphere is depicted as a comparatively low‐V anomaly (e.g., Humphreys et al, ; Raikes, ; Schmandt & Humphreys, ). The crustal high‐V anomaly possibly reflects a shallow Moho depth or the ongoing upward basaltic intrusion where negative radial anisotropy (Figure ) and high heat flow are revealed (Lachenbruch et al, ; Lachenbruch & Sass, ).…”

Section: Resultsmentioning

confidence: 99%

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Lithospheric Deformation and Asthenospheric Flow Associated With the Isabella Anomaly in Southern California

Zhao

2018

JGR Solid Earth

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Both laboratory experiments and seismic observations indicate that the solid Earth is composed of strongly anisotropic materials and its dynamics can be better constrained by exploring seismic anisotropy. Due to the limited number and poor depth resolution of currently available seismic anisotropy measurements, tectonic regimes of upper mantle deformations beneath Southern California still remain enigmatic and controversial. Here we present high‐resolution three‐dimensional models of P wave azimuthal and radial anisotropy in the crust and upper mantle beneath Southern California obtained by a joint inversion of local‐seismic and teleseismic P wave data. Our results reveal significant depth‐dependent anisotropy in which fast orientations in the lithospheric mantle closely follow the strike of the San Andreas fault and those in the asthenosphere are characterized as a predominantly circular pattern centered in the robust high‐velocity Isabella anomaly beneath the Great Valley. The Isabella anomaly is possibly a remnant of the fossil Farallon slab and is currently experiencing a tectonic regime of lithospheric downwelling, contributing to the development of a circular asthenospheric flow. High‐velocity anomalies are revealed below 300‐km depth beneath areas surrounding the Great Valley, which may reflect the delaminated lithospheric segments. Different rifting processes may take place beneath the Inner Borderland and the Salton Trough whose developments are possibly related to regional mantle upwelling and lithospheric stretching, respectively.

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Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Lithospheric Deformation and Asthenospheric Flow Associated With the Isabella Anomaly in Southern California

Zhao

2018

JGR Solid Earth

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“…The green lines offshore show the latest magnetic strips (19–20 Ma) of the Monterey microplate (MM). The dashed cyan circles denote the 4% velocity contour of Isabella anomaly at 60 km depth from Jiang et al (). The blue arrows indicate the Pacific plate (PAC) and North American plate (NAM) motions (Gripp & Gordon, ).…”

Section: Introductionmentioning

confidence: 99%

An Anisotropic Contrast in the Lithosphere Across the Central San Andreas Fault

Jiang

Schmandt

Clayton

2018

Geophysical Research Letters

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Seismic anisotropy of the lithosphere and asthenosphere was investigated with a dense broadband seismic transect nearly orthogonal to the central San Andreas fault (SAF). A contrast in SK(K)S splitting was found across the SAF, with a clockwise rotation of the fast orientation~26°closer to the strike of the SAF and greater delay times for stations located within 35 km to the east. Dense seismograph spacing requires heterogeneous anisotropy east of the SAF in the uppermost mantle or crust. Based on existing station coverage, such a contrast in splitting orientations across the SAF may be unusual along strike and its location coincides with the high-velocity Isabella anomaly in the upper mantle. If the Isabella anomaly is a fossil slab fragment translating with the Pacific plate, the anomalous splitting east of the SAF could indicate a zone of margin-parallel shear beneath the western edge of North America. Plain Language SummaryDirectional dependence of seismic wave speeds, referred to as anisotropy, can illuminate preferred orientations or fabrics in the Earth organized by deformation. Seismic anisotropy near the sharply defined central segment of the San Andreas fault was investigated with a new dense temporary seismic transect. A contrast in uppermost mantle anisotropy across the fault was identified, with nearly fault parallel orientations only on the east side of the fault. We suggest that development of asymmetric anisotropy about the central San Andreas may arise due to fault-parallel movement of a fossil slab beneath the western edge of North America.

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Synthesis of the Seismic Structure of the Greater Alaska Region: Subducting Slab Geometry

Pavlis,

Jadamec,

Everett Mann

et al. 2024

Geophysical Monograph Series

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Rayleigh and S wave tomography constraints on subduction termination and lithospheric foundering in central California

Cited by 41 publications

References 90 publications

Lithospheric Deformation and Asthenospheric Flow Associated With the Isabella Anomaly in Southern California

Lithospheric Deformation and Asthenospheric Flow Associated With the Isabella Anomaly in Southern California

An Anisotropic Contrast in the Lithosphere Across the Central San Andreas Fault

Synthesis of the Seismic Structure of the Greater Alaska Region: Subducting Slab Geometry

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