An upper-mantle S-wave velocity model for East Asia from Rayleigh wave tomography

SUMMARY This research provides new constraints on the intermediate depth upper-mantle structure of the Hellenic lithosphere using a three-step Rayleigh-wave tomography. Broadband waveforms of about 1000 teleseismic events, recorded by ∼200 permanent broad-band stations between 2010 and 2018 were acquired and processed. Through a multichannel cross-correlation technique, the fundamental mode Rayleigh-wave phase-velocity dispersion curves in the period range 30–90 s were derived. The phase-velocities were inverted and a 3-D shear velocity model was obtained down to the depth of 140 km. The applied method has provided 3-D constraints on large-scale characteristics of the lithosphere and the upper mantle of the Hellenic region. Highlighted resolved features include the continental and oceanic subducting slabs in the region, the result of convergence between Adria and Africa plates with the Aegean. The boundary between the oceanic and continental subduction is suggested to exist along a trench-perpendicular line that connects NW Peloponnese with N. Euboea, bridging the Hellenic Trench with the North Aegean Trough. No clear evidence for trench-perpendicular vertical slab tearing was resolved along the western part of Hellenic Subduction Zone; however, subcrustal seismicity observed along the inferred continental–oceanic subduction boundary indicates that such an implication should not be excluded. The 3-D shear velocity model supports an N–S vertical slab tear beneath SW Anatolia that justifies deepening, increase of dip and change of dip direction of the Wadati-Benioff Zone. Low velocities found at depths <50 km beneath the island and the backarc, interrelated with recent/remnant volcanism in the Aegean and W. Anatolia, are explained by convection from a shallow asthenosphere.

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Lithospheric structure of Hubei Province, central China, from Rayleigh wave tomography: insight into the spatial contact relationship between the Yangtze Plate and the eastern Qinling-Dabie orogenic belt

Geophysical Journal International ◽

10.1093/gji/ggaa102 ◽

2020 ◽

Vol 221 (3) ◽

pp. 1669-1683

Author(s):

Tengfei Wu ◽

Shuangxi Zhang ◽

Zijun Cao ◽

Mengkui Li ◽

Yujin Hua ◽

...

Keyword(s):

Rayleigh Wave ◽

Wave Velocity ◽

Hubei Province ◽

Orogenic Belt ◽

Central China ◽

S Wave ◽

Dabie Orogenic Belt ◽

Wave Tomography ◽

Yangtze Plate ◽

Rayleigh Wave Tomography

SUMMARY Knowledge about the spatial contact relationship between the Yangtze Plate and the eastern Qinling-Dabie orogenic belt can not only provide a scientific basis for the exploration of mineral resources, disaster prevention and earthquake prediction in the region, but also play an important role in reconstructing the geological process of the central orogenic belt. Hence, high-resolution lithospheric velocity model is essential to address these geological problems. In this study, using waveform data from 48 stations in Hubei Province and adjacent regions, central China, we invert for a 3-D S-wave velocity structure model of the crust and upper mantle from Rayleigh wave tomography. Our model reveals the complex subduction pattern of the Yangtze Plate to the north and the thrust-nappe tectonics of the Qinling-Dabie orogenic belt along the Mianlue suture with different scales and different deformation strengths. In addition, in the central part of Hubei Province, the local Yangtze slab has been broken into several pieces, among which the upwelling low-velocity anomalies appear. Moreover, the southern margin of the Dabie orogenic belt has undergone thrusting-nappe movement, and a series of associated structures are formed in the northern margin of the middle Yangtze platform. The contact zone between the two blocks in this area is composed of a series of thrust faults with dextrorotation slip component. Finally, based on the 3-D S-wave velocity image of Hubei Province and its vertical cross-section profiles along three different directions, three dynamic models are proposed to explain the spatial contact relationship between the Yangtze Plate and the eastern Qinling-Dabie orogenic belt in different regions.

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Crustal and upper-mantle structure of the Eastern Caribbean and Northern Venezuela from passive Rayleigh wave tomography

Tectonophysics ◽

10.1016/j.tecto.2020.228711 ◽

2020 ◽

pp. 228711

Author(s):

Mariano S. Arnaiz-Rodríguez ◽

Yang Zhao ◽

Ana K. Sánchez-Gamboa ◽

Franck Audemard

Keyword(s):

Rayleigh Wave ◽

Upper Mantle ◽

Mantle Structure ◽

Upper Mantle Structure ◽

Wave Tomography ◽

Eastern Caribbean ◽

Rayleigh Wave Tomography

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Antarctic Upper Mantle Rheology

Geological Society London Memoirs ◽

10.1144/m56-2020-19 ◽

2021 ◽

pp. M56-2020-19

Author(s):

E. R. Ivins ◽

W. van der Wal ◽

D. A. Wiens ◽

A. J. Lloyd ◽

L. Caron

Keyword(s):

Wave Velocity ◽

Upper Mantle ◽

Effective Viscosity ◽

Seismic Velocity ◽

Imaging Techniques ◽

Three Dimensional ◽

Velocity Model ◽

Mantle Flow ◽

S Wave ◽

Velocity Changes

AbstractThe Antarctic mantle and lithosphere are known to have large lateral contrasts in seismic velocity and tectonic history. These contrasts suggest differences in the response time scale of mantle flow across the continent, similar to those documented between the northeastern and southwestern upper mantle of North America. Glacial isostatic adjustment and geodynamical modeling rely on independent estimates of lateral variability in effective viscosity. Recent improvements in imaging techniques and the distribution of seismic stations now allow resolution of both lateral and vertical variability of seismic velocity, making detailed inferences about lateral viscosity variations possible. Geodetic and paleo sea-level investigations of Antarctica provide quantitative ways of independently assessing the three-dimensional mantle viscosity structure. While observational and causal connections between inferred lateral viscosity variability and seismic velocity changes are qualitatively reconciled, significant improvements in the quantitative relations between effective viscosity anomalies and those imaged by P- and S-wave tomography have remained elusive. Here we describe several methods for estimating effective viscosity from S-wave velocity. We then present and compare maps of the viscosity variability beneath Antarctica based on the recent S-wave velocity model ANT-20 using three different approaches.

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