Novel anisotropic teleseismic body-wave tomography code AniTomo to illuminate heterogeneous anisotropic upper mantle: Part I — Theory and inversion tuning with realistic synthetic data

Munzarová, Helena; Plomerová, Jaroslava; Kissling, Eduard

doi:10.1093/gji/ggy296

Cited by 20 publications

(26 citation statements)

References 82 publications

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“…Slowness ( S 0 ) at the isotropic grid nodes and anisotropic parameters (i.e., A , B , and C ) at the anisotropic grid nodes are determined by tomographic inversion. Previous studies of anisotropic tomography linearize theoretical travel times by the first-order Taylor expansion referencing to a starting model and then iterate the calculation and generate a model sequence to approach the optimal model ( 11 – 13 , 17 , 33 ). These linearization methods are effective when (i) the starting model is close enough to the optimal model or (ii) the nonlinearity of the tomographic problem is weak, so that a linearization using the first-order Taylor series is accurate enough to approximate the theoretical model.…”

Section: Methodsmentioning

confidence: 99%

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3D anisotropic structure of the Japan subduction zone

Wang

Zhao

2021

Sci. Adv.

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How mantle materials flow and how intraslab fabrics align in subduction zones are two essential issues for clarifying material recycling between Earth’s interior and surface. Investigating seismic anisotropy is one of a few viable technologies that can directly answer these questions. However, the detailed anisotropic structure of subduction zones is still unclear. Under a general hexagonal symmetry anisotropy assumption, we develop a tomographic method to determine a high-resolution three-dimensional (3D) P wave anisotropic model of the Japan subduction zone by inverting 1,184,018 travel time data of local and teleseismic events. As a result, the 3D anisotropic structure in and around the dipping Pacific slab is firstly revealed. Our results show that slab deformation plays an important role in both mantle flow and intraslab fabric, and the widely observed trench-parallel anisotropy in the forearc is related to the intraslab deformation during the outer-rise yielding of the subducting plate.

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Section: Methodsmentioning

confidence: 99%

“…3 ). In this case, the conventional linear methods may easily fail to converge to the optimal solution, unless initial models and parameters are chosen very carefully for the inversion ( 17 ).…”

Section: Methodsmentioning

confidence: 99%

3D anisotropic structure of the Japan subduction zone

Wang

Zhao

2021

Sci. Adv.

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“…Given a relation of 100 km thickness for every second of delay time, one obtains a thickness of 100-200 km for the anisotropic layer, which matches the observed thickness of the −V p layer. A well-known effect of azimuthal anisotropy is to retard nearvertically incident body waves (Hammond, 2014;Munzerová et al, 2018), thus providing a possible explanation for the anomalous −V p layer. Taken together, this suggests that the −V p layer in the lower European lithosphere is structurally anisotropic and may have accommodated viscous flow.…”

Section: Nature Of Low-velocity Domains In the Greatermentioning

confidence: 99%

Orogenic lithosphere and slabs in the greater Alpine area – interpretations based on teleseismic P-wave tomography

et al. 2021

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Abstract. Based on recent results of AlpArray, we propose a new model of Alpine collision that involves subduction and detachment of thick (∼ 180 km) European lithosphere. Our approach combines teleseismic P-wave tomography and existing local earthquake tomography (LET), allowing us to image the Alpine slabs and their connections with the overlying orogenic lithosphere at an unprecedented resolution. The images call into question the conventional notion that downward-moving lithosphere and slabs comprise only seismically fast lithosphere. We propose that the European lithosphere is heterogeneous, locally containing layered positive and negative Vp anomalies of up to 5 %–6 %. We attribute this layered heterogeneity to seismic anisotropy and/or compositional differences inherited from the Variscan and pre-Variscan orogenic cycles rather than to thermal anomalies. The lithosphere–asthenosphere boundary (LAB) of the European Plate therefore lies below the conventionally defined seismological LAB. In contrast, the lithosphere of the Adriatic Plate is thinner and has a lower boundary approximately at the base of strong positive Vp anomalies at 100–120 km. Horizontal and vertical tomographic slices reveal that beneath the central and western Alps, the European slab dips steeply to the south and southeast and is only locally still attached to the Alpine lithosphere. However, in the eastern Alps and Carpathians, this slab is completely detached from the orogenic crust and dips steeply to the north to northeast. This along-strike change in attachment coincides with an abrupt decrease in Moho depth below the Tauern Window, the Moho being underlain by a pronounced negative Vp anomaly that reaches eastward into the Pannonian Basin area. This negative Vp anomaly is interpreted as representing hot upwelling asthenosphere that heated the overlying crust, allowing it to accommodate Neogene orogen-parallel lateral extrusion and thinning of the ALCAPA tectonic unit (upper plate crustal edifice of Alps and Carpathians) to the east. A European origin of the northward-dipping, detached slab segment beneath the eastern Alps is likely since its down-dip length matches estimated Tertiary shortening in the eastern Alps accommodated by originally south-dipping subduction of European lithosphere. A slab anomaly beneath the Dinarides is of Adriatic origin and dips to the northeast. There is no evidence that this slab dips beneath the Alps. The slab anomaly beneath the Northern Apennines, also of Adriatic origin, hangs subvertically and is detached from the Apenninic orogenic crust and foreland. Except for its northernmost segment where it locally overlies the southern end of the European slab of the Alps, this slab is clearly separated from the latter by a broad zone of low Vp velocities located south of the Alpine slab beneath the Po Basin. Considered as a whole, the slabs of the Alpine chain are interpreted as highly attenuated, largely detached sheets of continental margin and Alpine Tethyan oceanic lithosphere that locally reach down to a slab graveyard in the mantle transition zone (MTZ).

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“…Recent advancements in both computational seismology and seismic observations have led to the development of 3‐D high‐resolution tomographic images including depth‐dependent azimuthal and radial anisotropies in different tectonic regimes (e.g., Zhao, 2015), such as in subduction zones (e.g., Eberhart‐Phillips & Henderson, 2004; Ishise & Oda, 2005; Liu & Zhao, 2016, 2017; Wang & Zhao, 2008, 2012), continental regions (e.g., Huang & Zhao, 2013; Tian & Zhao, 2013; Wei et al, 2016), and a tectonically stable region (Munzarova et al, 2018). These extensive studies demonstrate that P wave anisotropic tomography is an effective and powerful technique to reveal 3‐D variations of seismic anisotropy in the crust and mantle, since it provides improved vertical resolution compared with SWS measurements (e.g., Zhao et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Isotropic and Anisotropic P Wave Velocity Structures of the Crust and Uppermost Mantle Beneath Turkey

et al. 2020

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Compressional and extensional tectonics following northward plate convergences since the Miocene have formed the major surface features in Turkey, such as faulting and orogeny. Despite increasing efforts in last few decades aiming to elucidate the current architecture of the crust and mantle beneath Turkey, several issues regarding the depth extent of the deformation zones, crust-mantle interaction (e.g., coupling and decoupling) in relation to the deformation, and stress transmission in the lithosphere remain elusive. Here we present high-resolution 3-D P wave isotropic and azimuthal anisotropic velocity models of the crust and uppermost mantle beneath Turkey by inverting 204,531 P wave arrival times of 8,103 local crustal earthquakes. Our results reveal low-velocity anomalies or velocity contrasts down to the uppermost mantle along the North and East Anatolian Fault Zones. The fast velocity directions (FVDs) of azimuthal anisotropy in the lower crust and uppermost mantle are parallel to the regional maximum extensional directions in western Turkey, and the FVDs in the crust and uppermost mantle are parallel to the surface structures in southeastern Turkey. These results indicate that vertically coherent deformation between the crust and uppermost mantle occurs in western and southeastern Turkey. However, in central northern Turkey, the FVDs in the uppermost mantle are oblique to both the FVDs in the lower crust and the maximum shear directions derived from GPS measurements, suggesting that the crust and lithospheric mantle are decoupled there. Owing to increasing efforts in passive seismic monitoring in Turkey, the number of temporary and permanent seismic stations has increased dramatically in the past decade, which has greatly improved the station coverage and so the spatial resolution of various seismic imaging results (e.g.,

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Novel anisotropic teleseismic body-wave tomography code AniTomo to illuminate heterogeneous anisotropic upper mantle: Part I — Theory and inversion tuning with realistic synthetic data

Cited by 20 publications

References 82 publications

3D anisotropic structure of the Japan subduction zone

3D anisotropic structure of the Japan subduction zone

Orogenic lithosphere and slabs in the greater Alpine area – interpretations based on teleseismic P-wave tomography

Isotropic and Anisotropic P Wave Velocity Structures of the Crust and Uppermost Mantle Beneath Turkey

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