Zhouchuan Huang

2022

1. GRL

   Seismotectonics of Mongolia and Baikal Rift Zone Controlled by Lithospheric Structures

   Zhouchuan Huang, and Dapeng Zhao

   Geophysical Research Letters, Aug 2022

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   Active tectonics are developing in Mongolia and the Baikal rift zone, where large crustal earthquakes (Mw ≥ 6.0) occur frequently. To clarify the mechanism of these earthquakes, we determine a high-resolution 3-D P-wave velocity model of the crust and upper mantle beneath Mongolia and the Baikal rift zone. We find an annular high-velocity zone in the lithosphere; whereas low-velocity anomalies exist both inside and around the high-velocity ring as well as beneath the rift zone. Strong interactions between the high-velocity ring and the surrounding terranes may have induced many moderate-to-large earthquakes (Mw 5–7). By contrast, mega-earthquakes (Mw ≥ 8.0) occurred right above the high-velocity ring. We propose that the high-velocity ring is strong as a whole; it sustains the stress arising from the India-Asia collision and causes the mega-earthquakes. Meanwhile, the ring could protect the Hangay Dome from the regional compression, leading to weak seismicity under the dome.

2. EPSL

   Restricted lithospheric extrusion in the SE Tibetan Plateau: Evidence from anisotropic Rayleigh-wave tomography

   Cunrui Han, Zhouchuan Huang, Shijie Hao, and 3 more authors

   Earth and Planetary Science Letters, Nov 2022

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2021

1. EPSL

   Layered crustal azimuthal anisotropy beneath the northeastern Tibetan Plateau revealed by Rayleigh-wave Eikonal tomography

   Shijie Hao, Zhouchuan Huang, Cunrui Han, and 4 more authors

   Earth and Planetary Science Letters, Jun 2021

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2020

1. JGR

   Sharp Lateral Moho Variations Across the SE Tibetan Margin and Their Implications for Plateau Growth

   Mijian Xu, Zhouchuan Huang, Liangshu Wang, and 5 more authors

   Journal of Geophysical Research: Solid Earth, May 2020

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   The tectonic uplift of the Tibetan Plateau is a focus in the geosciences. Middle‐lower crustal flow is a popular model to interpret the geodynamic mechanism on the margin of the Tibetan Plateau. The model predicts different surface and Moho topographies across the plateau boundary due to the different strengths of the surrounding blocks, that is, sharp boundaries on the eastern plateau boundary and gentle variations in the southeastern plateau boundary. Here, we employ receiver function and common conversion point stacking analysis with the seismic waveforms recorded by the dense ChinArray and other local seismic stations to accurately define the Moho topography in southeastern (SE) Tibet. We find that the Moho under the Tibetan Plateau is much deeper than that under the surrounding Yangtze Craton and Indochina block; abrupt Moho changes are found across the southeastern plateau margin, similar to that under the eastern plateau margin. We interpret these sharp Moho variations across the plateau margin to have developed when the Tibetan Plateau was extruded southeastward in the late Miocene. Subsequent gravity collapse resulted in crustal extension and gentle topographic variation, while the sharp Moho slope was preserved.

2019

1. JGR

   \textitP and \textitS Wave Tomography Beneath the SE Tibetan Plateau: Evidence for Lithospheric Delamination

   Zhouchuan Huang, Liangshu Wang, Mingjie Xu, and 3 more authors

   Journal of Geophysical Research: Solid Earth, Oct 2019

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   The SE Tibetan Plateau is located between the eastern Himalayan syntaxis and the stable Yangtze craton; its tectonic evolution is important for understanding the plateau expansion. However, interactions between the plateau and its adjacent subduction zone and craton are still unclear. In this study, we determine updated high‐resolution P and S wave tomographic models of the crust and upper mantle beneath the SE Tibetan Plateau. We confirmed the existence of a high‐velocity layer in the upper mantle down to 200‐km depth beneath the Sichuan basin, the core of the Yangtze craton, representing the stable cratonic root. Another high‐velocity body is located beneath Burma, reflecting the subducting Indian slab in the upper mantle and possibly the remnant Burman slab in the mantle transition zone. A strong low‐velocity column exists above the high‐velocity body in the transition zone and reaches the Moho under the Tengchong volcano. In addition, we find high‐velocity fragments in the upper mantle beneath the Yangtze craton and northern Indochina, which may reflect delaminated lithosphere beneath the SE Tibetan Plateau. The lithospheric delamination may be closely related to mantle flow extruded from the high plateau and possible thermal upwelling from the lower mantle. Our results provide new insight into the deep interactions between the Tibetan plateau and its surrounding blocks near the SE plateau margin.

2018

1. JGR

   \textitP Wave Anisotropic Tomography of the SE Tibetan Plateau: Evidence for the Crustal and Upper‐Mantle Deformations

   Zhouchuan Huang, Liangshu Wang, Mingjie Xu, and 1 more author

   Journal of Geophysical Research: Solid Earth, Oct 2018

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   The upper crust in the SE Tibetan Plateau is rotating around the eastern Himalayan syntax clockwise, and the western margin of the Yangtze Craton has been involved in the active tectonics. However, it is still unclear whether and how the deep crust and upper mantle respond to the plateau expansion. In this study we present a high-resolution three-dimensional model of P wave velocity tomography and azimuthal anisotropy in the crust and uppermost mantle beneath the SE Tibetan Plateau determined using traveltime data recorded by a dense seismic network. Widespread low-velocity zones are revealed around a high-velocity body in the deep crust and uppermost mantle beneath the southwest Yangtze Craton, where fast-velocity directions of the azimuthal anisotropy are mostly parallel to the contour lines of the surface topography and the Moho depth along the plateau margin. These results indicate that gravitational potential plays an important role in the crustal and uppermost-mantle deformations in the SE Tibetan Plateau. Meanwhile, the shallow crust may drop down to the deep crust and drive the ductile deep-crustal material to intrude into the adjacent regions. The extruded crust is trapped in a deep-crustal corner and obstructed by the surrounding strong blocks. The trapped crustal material may rise up, causing significant uplift and high heat flow at the surface.

2017

1. EPSL

   Insight into NE Tibetan Plateau expansion from crustal and upper mantle anisotropy revealed by shear-wave splitting

   Zhouchuan Huang, Frederik Tilmann, Mingjie Xu, and 5 more authors

   Earth and Planetary Science Letters, Nov 2017

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2015

1. JGR

   \textitP wave tomography and anisotropy beneath Southeast Asia: Insight into mantle dynamics

   Zhouchuan Huang, Dapeng Zhao, and Liangshu Wang

   Journal of Geophysical Research: Solid Earth, Jul 2015

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   Southeast Asia is surrounded by subduction zones resulting from the interactions of several lithospheric plates. Its evolution has been also influenced by active tectonics due to the Indo-Asian collision in the Cenozoic. In this study, we use a large number of arrival-time data of local and regional earthquakes to determine 3-D P wave tomography and azimuthal anisotropy in the mantle beneath SE Asia. High-velocity (high-V) anomalies representing the subducting slabs are clearly visible in the upper mantle and the mantle transition zone (MTZ). Low-velocity (low-V) zones with trench-normal anisotropy are revealed in the uppermost mantle, which indicate back-arc spreading or secondary mantle-wedge flow induced by the slab subduction. In contrast, trench-parallel anisotropy dominates in the deep upper mantle and reflects structures either in the subducting slab or in the upper mantle surrounding the slab. The trench-parallel anisotropy is also significant in the lower MTZ, which may contribute to shear wave splitting observations. A low-V body extending down to the lower mantle is visible under the Hainan volcano far away from the plate boundaries, suggesting that Hainan is a hot spot fed by a lower-mantle plume. The low-V body under Hainan is connected with low-V zones in the upper mantle under SE Tibet and Vietnam. Our P wave anisotropy results reflect significant mantle flow existing in the asthenosphere from SE Tibet to Hainan and further southwestward to Vietnam. The present study, especially the 3-D P wave anisotropy results, provides important new insight into mantle dynamics in SE Asia.

2. JGR

   On the trade-off between seismic anisotropy and heterogeneity: Numerical simulations and application to Northeast Japan

   Zhouchuan Huang, Dapeng Zhao, and Xin Liu

   Journal of Geophysical Research: Solid Earth, May 2015

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   P wave tomography has been recently used to study 3-D azimuthal and radial anisotropy of subduction zones and continental regions. However, the fundamental issue about the trade-off between the isotropic and anisotropic structures is still unclear. In this study, we investigate this issue systematically with comprehensive synthetic tests. Our results indicate that good ray coverage in the azimuth (for azimuthal anisotropy) and incidence (for radial anisotropy) is required for determining reliable anisotropic models. The isotropic and anisotropic structures are strongly coupled, and smearing effects are significant when the rays used in the inversion are limited in a small range of azimuth or incidence. We therefore plot ray azimuth and ray incidence ellipses at every grid nodes and propose to use the normalized length of the short axis (i.e., the ratio of the short-axis and long-axis lengths) for estimating the ray coverage quantitatively. Applying our novel approach to a large number of high-quality arrival time data of local shallow- and intermediate-depth earthquakes, we obtained new tomographic images of 3-D P wave azimuthal and radial anisotropy in Northeast Japan. Both the azimuthal and radial anisotropy results are determined reliably for the shallow parts of the study region, whereas the smearing effects are significant in the deeper part of the mantle wedge and the subducting slab. Our results show dominant trench-normal and vertical-fast anisotropy in the mantle wedge while trench-parallel and horizontal-fast anisotropy in the subducting slab, which indicates different dynamics in different domains of the subduction zone.

3. EPSL

   Mantle structure and dynamics beneath SE Tibet revealed by new seismic images

   Zhouchuan Huang, Pan Wang, Mingjie Xu, and 7 more authors

   Earth and Planetary Science Letters, Feb 2015

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2014

1. JGR

   Three-dimensional \textitP wave azimuthal anisotropy in the lithosphere beneath China: 3D P-wave anisotropy beneath China

   Zhouchuan Huang, Pan Wang, Dapeng Zhao, and 2 more authors

   Journal of Geophysical Research: Solid Earth, Jul 2014

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   Seismic anisotropy in the upper mantle beneath East Asia has been studied extensively using shear wave (SKS) splitting measurements, which have provided important information on mantle dynamics in this region. However, SKS measurements have poor vertical resolution, and so their interpretations are usually not unique. In this work we use a large number of traveltime data from 34,036 local earthquakes recorded by 1563 seismic stations to determine the first model of 3-D P wave azimuthal anisotropy in the lithosphere beneath China. Our results show that the fast velocity directions (FVDs) are generally correlated with the surface geologic features, such as the strikes of the orogens, active faults, and tectonic boundaries. The FVDs in the upper crust are normal to the maximal horizontal stress (σH) in regions with extensive compression such as the Tibetan Plateau, whereas they are subparallel to σH in strike-slip shear zones such as the western and eastern Himalayan syntax. The comparison of the FVDs of P wave anisotropy with SKS splitting measurements indicates that beneath the Tibetan Plateau the seismic anisotropy in the lithosphere contributes significantly to the SKS splitting observations. In contrast, in east China the P wave FVDs in the lithosphere are different from the SKS splitting measurements, suggesting that the SKS splitting is mainly caused by the anisotropy in the deeper mantle such as the asthenosphere and the mantle transition zone under east China. These novel results provide important new information on the lithospheric deformation and mantle dynamics in East Asia.

2013

1. JAES

   Mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0) and tsunami: Insight from seismic tomography

   Zhouchuan Huang, and Dapeng Zhao

   Journal of Asian Earth Sciences, Jul 2013

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   To clarify the generating mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0) and the induced tsunami, we determined high-resolution tomographic images of the Northeast Japan forearc. Significant lateral variations of seismic velocity are visible in the megathrust zone, and most large interplate thrust earthquakes are found to occur in high-velocity (high-V) areas. These high-V zones may represent high-strength asperities at the plate interface where the subducting Pacific plate and the overriding Okhotsk plate are coupled strongly. A shallow high-V zone with large coseismic slip near the Japan Trench may account for the mainshock asperity of the 2011 Tohoku-oki earthquake. Because it is an isolated asperity surrounded by low-velocity patches, most stress on it was released in a short time and the plate interface became decoupled after the Mw 9.0 earthquake. Thus the overriding Okhotsk plate there was shot out toward the Japan Trench and caused the huge tsunami.

2011

1. EPSL

   Seismic anisotropy and mantle dynamics beneath China

   Zhouchuan Huang, Liangshu Wang, Dapeng Zhao, and 2 more authors

   Earth and Planetary Science Letters, Jun 2011

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   We analyzed the shear-wave splitting at 138 permanent seismograph stations to study seismic anisotropy and mantle dynamics under Mainland China. To obtain reliable results we used three different methods to measure the shear-wave splitting parameters using core phases (SKS, SKKS, SKiKS and PKS) as well as the direct S waves from regional and distant earthquakes. Our results show that the fast orientations of the anisotropy (WNW–ESE) in eastern China are generally consistent with the absolute plate motion (APM) direction of the Eurasian plate, suggesting that the anisotropy is mainly located in the asthenosphere resulting from the lattice-preferred orientation of olivine due to the shear deformation there. The fast axes in western China generally agree with the strikes of the orogens and active faults, while they are perpendicular to the direction of the maximum horizontal stress, suggesting that the anisotropy in the lithosphere contributes significantly to the observed shear-wave splitting. The fast axes in western China are also consistent with the APM direction, suggesting that the APM-driven anisotropy in the asthenosphere is another source of the shear-wave splitting there. These results suggest that APM-driven anisotropy commonly exists under continents, similar to that under oceanic regions, even though the continental lithosphere has suffered extensive deformation.

2. GJI

   Seismic heterogeneity and anisotropy of the Honshu arc from the Japan Trench to the Japan Sea: Heterogeneity and anisotropy of Honshu arc

   Zhouchuan Huang, Dapeng Zhao, and Liangshu Wang

   Geophysical Journal International, Mar 2011

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   Most Popular Paper

   We determined P- and S-wave tomography and P-wave anisotropic structure under the Honshu arc from the Japan Trench to the backarc area under the Japan Sea using 310 749 P- and 150 563 S-wave arrivals from 4655 local earthquakes recorded by 982 seismograph stations. Arrival times from 1451 suboceanic earthquakes relocated with sP depth phases enable us to determine the structures under the Pacific Ocean and Japan Sea, which expand the study region from the land area to the whole arc from the Japan Trench to the Japan Sea with a width of more than 500 km. The results show strong heterogeneities above the subducting Pacific slab under the Pacific Ocean and most large thrust-type earthquakes occurred in the high-velocity areas where the Pacific slab and the overriding continental plate may be strongly coupled. Low-velocity (low-V ) zones are imaged in the mantle wedge with significant along-arc variations under the volcanic front. The mantle-wedge low-V zone extends westwards under the Japan Sea and it is connected with the subducting Pacific slab at depths of 150–200 km under the backarc. The results indicate that the H2O and fluids brought downwards by the subducting Pacific slab are released into the mantle wedge by dehydration and are subsequently transported to the surface by the upwelling flow in the mantle wedge. Significant P-wave anisotropic anomalies are revealed under the Honshu arc. The predominant fast velocity direction (FVD) is E–W in the mantle wedge while it is N–S in the subducting Pacific slab. The anisotropy in the mantle wedge is the result of deformation caused by the subduction of the Pacific plate and the induced mantle-wedge convection, while the FVD pattern in the middle of the mantle wedge argues for the 3-D mantle flow or the specific alignment of the olivine in the partial-melting mantle. The N–S (trench-parallel) FVD in the subducting Pacific slab represents either the original fossil anisotropy when the Pacific plate formed or the trench-parallel crystallographic and shaped preferred orientation in the subducting slab due to the slab bending. The present results shed new light on the structural heterogeneities and seismic anisotropy under the Honshu arc, which may improve our understanding of the dynamic processes of subduction zones.

3. G-cubed

   Shear wave anisotropy in the crust, mantle wedge, and subducting Pacific slab under northeast Japan

   Zhouchuan Huang, Dapeng Zhao, and Liangshu Wang

   Geochemistry, Geophysics, Geosystems, Jan 2011

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2008

1. GRL

   Shear wave splitting in the southern margin of the Ordos Block, north China

   Zhouchuan Huang, Mingjie Xu, Liangshu Wang, and 3 more authors

   Geophysical Research Letters, Oct 2008

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