Mountain building at northeastern boundary of Tibetan Plateau and craton reworking at Ordos block from joint inversion of ambient noise tomography and receiver functions

The Semail Ophiolite is the world&#8216;s largest and best exposed oceanic lithosphere on land and a primary reference site for studies of creation of oceanic lithosphere, initiation of subduction, geodynamic models of obduction, subduction and exhumation of continental rocks during obduction. Five decades of geological mapping, structural, petrological and geochronological research provide a robust understanding of the geodynamic evolution of the shallow continental crust in northern Oman and how the late Cretaceous obduction process largely shaped the present-day landscape. Yet, prior to obduction, other first-order tectonic processes have left their imprint in the lithosphere, in particular the Neoproterozoic accretion of Arabia and Permian breakup of Pangea. Due to the scarcity of deep structure imaging below the ophiolite, the presence and significance of inherited structures for the obduction process remain unclear.We discuss a new 3-D anisotropic shear wave velocity model of the crust below northern Oman derived from ambient noise tomography and Receiver Function analysis which allows to resolve some key unknowns in geodynamics of eastern Arabia: (1) Several NE-trending structural boundaries in the middle and lower crust are attributed to the Pan-African orogeny and align with first-order lateral changes in surface geology and topography. (2) The well-known Semail Gap Fault Zone is an upper crustal feature whereas two other deep crustal faults are newly identified. (3) Permian rifting occurred on both eastern and northern margins but large-scale mafic intrusions and/or underplating occurred only in the east. (4) While obduction is inherently lithospheric by nature, its effects are mostly observed at shallow crustal depths, and lateral variations in its geometry and dynamics can be explained by effects on pre-existing Pan-African and Permian structures. (5) Continental subduction and exhumation during late Cretaceous obduction may be the cause for crustal thickening below today&#8216;s topography. (6) Thinning of the continental lithosphere below northern Oman in late Eocene times &#8211; possibly related to thermal effects of the incipient Afar mantle plume - provides a plausible mechanism for the broad emergence of the Oman Mountains and in particular the Jabal Akhdar Dome. Uplift might thus be unrelated to compressional tectonics during Arabia-Eurasia convergence as previously believed.

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First step towards an integrated geophysical-geological model of the W-Alps: A new Vs model from transdimensional ambient-noise tomography

10.5194/egusphere-egu21-3197 ◽

2021 ◽

Author(s):

Ahmed Nouibat ◽

Laurent Stehly ◽

Anne Paul ◽

Romain Brossier ◽

Thomas Bodin ◽

...

Keyword(s):

Group Velocity ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Ambient Noise ◽

Receiver Functions ◽

Time Inversion ◽

Geological Model ◽

Ambient Noise Tomography ◽

Low Velocity

We have successfully derived a new 3-D high resolution shear wave velocity model of the crust and uppermost mantle of a large part of W-Europe from transdimensional ambient-noise tomography. This model is intended to contribute to the development of the first 3-D crustal-scale integrated geophysical-geological model of the W-Alps to deepen understanding of orogenesis and its relationship to mantle dynamics. We used an exceptional dataset of 4 years of vertical-component, daily seismic noise records (2015 - 2019) of more than 950 permanent broadband seismic stations located in and around the Greater Alpine region, complemented by 490 temporary stations from the AlpArray sea-land seismic network and 110 stations from Cifalps dense deployments.We firstly performed a 2-D data-driven transdimensional travel time inversion for group velocity maps from 4 to 150 s (Bodin & Sambridge, 2009). The data noise level was treated as a parameter of the inversion problem, and determined within a Hierarchical Bayes method. We used Fast Marching Eikonal solver (Rawlinson & Sambridge, 2005) jointly with the reversible jump algorithm to update raypath geometry during inversion. In the inversion of group velocity maps for shear-wave velocity, we set up a new formulation of the approach proposed by Lu et al (2018) by including group velocity uncertainties. Posterior probability distributions on Vs and interfaces were estimated by exploring a set of 130 millions synthetic 4-layer 1-D Vs models that allow for low-velocity zones. The obtained probabilistic model was refined using a linearized inversion. For the ocean-bottom seismometers of the Ligurian-Provencal basin, we applied a specific processing to clean daily noise signals from instrumental and oceanic noises (Crawford & Webb, 2000) and adapted the inversion for Vs to include the water column.Our Vs model evidences strong variations of the crustal structure along strike, particulary in the subduction complex. The European crust includes lower crustal low-velocity zones and a Moho jump of ~8-12 km beneath the W-boundary of the external crystalline massifs. We observe a deep LVZ structure (50 - 80 km) in the prolongation of the European continental subduction beneath the Ivrea body. The striking fit between the receiver functions ccp migrated section across the Cifalps profile and this new Vs model validate its reliability.

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Crustal seismogenic structures and deformation styles along the Longmen Shan Fault belt in the eastern Tibetan Plateau inferred from ambient noise tomography

Tectonophysics ◽

10.1016/j.tecto.2020.228689 ◽

2021 ◽

Vol 798 ◽

pp. 228689

Author(s):

Mei Feng ◽

Hui Qian ◽

James Mechie ◽

Meijian An ◽

Haibing Li ◽

...

Keyword(s):

Tibetan Plateau ◽

Ambient Noise ◽

Eastern Tibetan Plateau ◽

Ambient Noise Tomography ◽

Longmen Shan Fault ◽

Seismogenic Structures ◽

Fault Belt

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Penetration of mid-crustal low velocity zone across the Kunlun Fault in the NE Tibetan Plateau revealed by ambient noise tomography

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2014.08.040 ◽

2014 ◽

Vol 406 ◽

pp. 81-92 ◽

Cited By ~ 46

Author(s):

Chengxin Jiang ◽

Yingjie Yang ◽

Yong Zheng

Keyword(s):

Tibetan Plateau ◽

Ambient Noise ◽

Ambient Noise Tomography ◽

Low Velocity ◽

Low Velocity Zone ◽

Velocity Zone ◽

Ne Tibetan Plateau

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Seismic Structure of the Changbai Intraplate Volcano in NE China From Joint Inversion of Ambient Noise and Receiver Functions

Journal of Geophysical Research Solid Earth ◽

10.1029/2018jb016600 ◽

2019 ◽

Vol 124 (5) ◽

pp. 4984-5002 ◽

Cited By ~ 5

Author(s):

Hongxiang Zhu ◽

You Tian ◽

Dapeng Zhao ◽

Honghao Li ◽

Cai Liu

Keyword(s):

Ambient Noise ◽

Joint Inversion ◽

Receiver Functions ◽

Seismic Structure ◽

Ne China

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High resolution 3-D crustal structure beneath NE China from joint inversion of ambient noise and receiver functions using NECESSArray data

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2015.01.044 ◽

2015 ◽

Vol 416 ◽

pp. 1-11 ◽

Cited By ~ 35

Author(s):

Zhen Guo ◽

Y. John Chen ◽

Jieyuan Ning ◽

Yongge Feng ◽

Stephen P. Grand ◽

...

Keyword(s):

High Resolution ◽

Crustal Structure ◽

Ambient Noise ◽

Joint Inversion ◽

Receiver Functions ◽

Ne China

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Structure of the Ecuadorian forearc from the joint inversion of receiver functions and ambient noise surface waves

Geophysical Journal International ◽

10.1093/gji/ggaa237 ◽

2020 ◽

Vol 222 (3) ◽

pp. 1671-1685 ◽

Cited By ~ 1

Author(s):

Clinton D Koch ◽

Colton Lynner ◽

Jonathan Delph ◽

Susan L Beck ◽

Anne Meltzer ◽

...

Keyword(s):

Oceanic Crust ◽

Crustal Structure ◽

Ambient Noise ◽

Joint Inversion ◽

Receiver Functions ◽

Surface Wave Dispersion ◽

Data Set ◽

Megathrust Earthquakes ◽

High Magnitude ◽

Accreted Terranes

SUMMARY The Ecuadorian forearc is a complex region of accreted terranes with a history of large megathrust earthquakes. Most recently, a Mw 7.8 megathrust earthquake ruptured the plate boundary offshore of Pedernales, Ecuador on 16 April 2016. Following this event, an international collaboration arranged by the Instituto Geofisico at the Escuela Politécnica Nacional mobilized a rapid deployment of 65 seismic instruments along the Ecuadorian forearc. We combine this new seismic data set with 14 permanent stations from the Ecuadorian national network to better understand how variations in crustal structure relate to regional seismic hazards along the margin. Here, we present receiver function adaptive common conversion point stacks and a shear velocity model derived from the joint inversion of receiver functions and surface wave dispersion data obtained through ambient noise cross-correlations for the upper 50 km of the forearc. Beneath the forearc crust, we observe an eastward dipping slow velocity anomaly we interpret as subducting oceanic crust, which shallows near the projected centre of the subducting Carnegie Ridge. We also observe a strong shallow positive conversion in the Ecuadorian forearc near the Borbon Basin indicating a major discontinuity at a depth of ∼7 km. This conversion is not ubiquitous and may be the top of the accreted terranes. We also observe significant north–south changes in shear wave velocity. The velocity changes indicate variations in the accreted terranes and may indicate an increased amount of hydration beneath the Manabí Basin. This change in structure also correlates geographically with the southern rupture limit of multiple high magnitude megathrust earthquakes. The earthquake record along the Ecuadorian trench shows that no event with a Mw >7.4 has ruptured south of ∼0.5°S in southern Ecuador or northern Peru. Our observations, along with previous studies, suggest that variations in the forearc crustal structure and subducting oceanic crust may influance the occurrence and spatial distribution of high magnitude seismicity in the region.

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