Journal Article

Structure and Dynamics of Lithosphere and Asthenosphere in Asia: A Seismological Perspective

Ma, Jincheng, Bunge, Hans‐Peter, Chang, Sung‐Joon, Tian, You, Fichtner, Andreas

2023

Overview

Knowledge of lithospheric structure is essential for understanding the impact of continental collision and oceanic subduction on surface tectonic configurations. Full‐waveform tomographic images reveal lateral heterogeneities and anisotropy of the lithosphere and asthenosphere in Asia. Estimating lithospheric thickness from seismic velocity reductions at depth exhibits large variations underneath different tectonic units. The thickest cratonic roots are present beneath the Sichuan, Ordos, and Tarim basins and central India. Radial anisotropy signatures of 11 representative tectonic provinces uncover the different nature and geodynamic processes of their respective past and present deformation. The large‐scale continental lithospheric deformation is characterized by low‐velocity anomalies from the Himalayan Orogen to the Baikal rift zone in central Asia, coupled with the post‐collision thickening of the crust. The horizontal low‐velocity layer of ∼100–300 km depth extent below the lithosphere points toward the existence of the asthenosphere beneath East and Southeast Asia, with heterogeneous anisotropy indicative of channel flows. Plain Language Summary The lithospheric plates, like mosaics of the Earth’s surface, are moving coherently over the weaker, convecting asthenosphere. The lithospheric structure and thickness dictated by mantle dynamics play a first‐order role in understanding the active tectonics and morphological evolution of the Asian region. Here, the latest high‐resolution full‐waveform tomographic model, SinoScope 1.0, is employed to investigate the seismic structure and dynamics of the lithosphere and asthenosphere from a seismological perspective. The lithospheric thickness of known various geological units and cratonic blocks is retrieved with large variability. The observed anisotropic signatures within the lithosphere and asthenosphere provide important constraints on the deformation state and history of different tectonic provinces. The India‐Eurasia collision primarily induced large‐scale lithospheric deformation and thickening of the crust in the west of the North‐South Gravity Lineament. The narrow low‐velocity layer below the lithosphere lies beneath East and Southeast Asia and is bounded by subduction trenches and cratonic blocks, which provides seismic evidence for the low‐viscosity asthenosphere that partially decouples plates from mantle flow beneath and allows plate tectonics to work above. The lithospheric thinning and extension, intensive magmatism, and mineralization are potentially associated with the strong interaction between the lithosphere and asthenospheric flow in the eastern Asian margin. Key Points Full‐waveform tomographic images reveal lateral heterogeneities and anisotropy in the lithosphere and asthenosphere beneath the Asian region India‐Eurasia collision induced large‐scale low‐velocity anomaly and crustal thickening spanning from the Himalayas to the Baikal rift zone Asthenosphere in East and SE Asia exhibits strong vsh, > vsv, and partially decouples lithosphere, bounded by subduction trench and cratonic keels

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Anisotropy / Anomalies / Asthenosphere / Channel flow / Deformation / Dynamics / Earth mantle / Earth surface / Gravity / Lithosphere / Magma / Mineralization / Mosaics / Orogeny / Plate tectonics / Plates / Plates (tectonics) / Rift zones / Seismic velocities / Seismology / Signatures / Strong interactions (field theory) / Subduction / Subduction (geology) / Tectonics / Thickening / Thickness / Velocity / Viscosity / Waveforms