Seismic Full‐Waveform Inversion of the Crust‐Mantle Structure Beneath China and Adjacent Regions

Abstract

We present the first‐generation full‐waveform tomographic model (SinoScope 1.0) for the crust‐mantle structure beneath China and adjacent regions. The three‐component seismograms from 410 earthquakes recorded at 2,427 stations are employed in iterative gradient‐based inversions for three successively broadened period bands of 70–120 s, 50–120 s, and 30–120 s. Synthetic seismograms were computed using GPU‐accelerated spectral‐element simulations of seismic wave propagation in 3‐D anelastic models, and Fréchet derivatives were calculated based on an adjoint‐state method facilitated by a checkpointing algorithm. The inversion involved 352 iterations, which required 18,600 wavefield simulations. SinoScope 1.0 is described in terms of isotropic P‐wave (VP), horizontally and vertically polarized S‐wave velocities (VSH and VSV), and mass density (ρ), which are independently constrained with the same data set coupled with a stochastic L‐BFGS quasi‐Newton optimization scheme. It systematically reduced differences between observed and synthetic full‐length seismograms. We performed a detailed resolution analysis by repairing input random parametric perturbations, indicating that resolution lengths can approach the half propagated wavelength within the well‐covered areas. SinoScope 1.0 reveals strong lateral heterogeneities in the lithosphere, and features correlate well with geological observations, such as sedimentary basins, Holocene volcanoes, Tibetan Plateau, Philippine Sea Plate, and various tectonic units. The asthenosphere lies below the lithosphere beneath East and Southeast Asia, bounded by subduction trenches and cratonic blocks. Furthermore, we observe an enhanced image of well‐known slabs along strongly curved subduction zones, which do not exist in the initial model.

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

“… Topographic map shows the geographic locations of the samples and the cross‐section (black line with white dots) for which the vertical profile is shown in Figures 3a–3d. Lateral averages for vertically/horizontally polarized shear‐wave velocity ( v sv and v sh ) and radial shear‐wave anisotropy ( ξ ) of 11 tectonically distinct provinces, corresponding to the color‐matched shaded areas as shown in the map, which are extracted from SinoScope 1.0 (Ma et al., 2022) and illustrated by red ( v sh ), green ( v sv ), and blue ( ξ ) lines. Bold white ( v sh ), yellow ( v sv ), and magenta ( ξ ) lines are overall 1‐D radial profiles of SinoScope 1.0 (Ma et al., 2022) and are plotted for comparison with specific tectonic units.…”

“…The model parameters involved in the inversion include the wave velocities of vertically and horizontally propagating/polarized P‐ and S‐waves ( v pv , v ph , v sv , and v sh ) and mass density ( ρ ). The data that enter the inversion process is mostly sensitive to variations in v sv and v sh ; sensitivity kernels with respect to v pv , v ph , and ρ are small or negligible (Ma et al., 2022), which are not used to facilitate the interpretation of tomographic images in the following sections. Radial anisotropy is a type of transverse isotropy with a radial symmetry axis, which produces differences in propagation speed between horizontally and vertically polarized shear waves, irrespective of their propagation azimuth (e.g., Hess, 1964; Montagner & Tanimoto, 1991).…”

“…AV, Arxan Volcano; CDDB, Chuan‐Dian Diamond Block; CV, Changbai Volcano; DV, Datong Volcano; HB, Himalaya Block; HV, Hainan Volcano; JB, Junggar Basin; JV, Jeju Volcano; KV, Kunlun Volcano; OB, Ordos Basin; QDB, Qaidam Basin; QFB, Qilian Fold Belt; SCB, Sichuan Basin; SGFB, Songpan Ganzi Fold Belt; SLB, Songliao Basin; TV, Tengchong Volcano; UV, Ulleung Volcano; WV, Wudalianchi Volcano. (b)–(d) Map views of the absolute isotropic shear‐wave velocity at depths of 15 km, 50 km, and 100 km (Ma et al., 2022).…”

“…The Asian region is characterized by diverse and complex patterns of extensive magmatism and intracontinental deformation, which are recorded in its geological and tectonic history and revealed by seismic imaging (Figure 1; Ma et al., 2022; Ren et al., 2013; Yin, 2010). Cenozoic (66 ‐ 0 Ma) deformation dominates the tectonic configuration of the Asian continent along the Eastern Tethyan orogen, expressed by developments of the Tibetan Plateau and Iranian Plateau resulting from collisions of Indian and Arabian plates toward the Eurasian Plate (Chang & Zheng, 1973; DeCelles et al., 2002; Dewey, 1989; Reilinger et al., 2006).…”

“…Lateral averages for vertically/horizontally polarized shear-wave velocity (v sv and v sh ) and radial shear-wave anisotropy (ξ) of 11 tectonically distinct provinces, corresponding to the color-matched shaded areas as shown in the map, which are extracted from SinoScope 1.0(Ma et al, 2022) and illustrated by red (v sh ), green (v sv ), and blue (ξ) lines. Bold white (v sh ), yellow (v sv ), and magenta (ξ) lines are overall 1-D radial profiles of SinoScope 1.0(Ma et al, 2022) and are plotted for comparison with specific tectonic units. Dashed lines represent depth profiles for isotropic models with ξ = 0.…”