Anisotropic Rayleigh wave tomography of Northeast China using ambient seismic noise

• Significant NNE fast direction exists in the shallow crust of Sonliao basin.
• The lithospheric mantle of Songliao block shows high-velocity and weak anisotropy.
• The fast directions in the mantle reflect the strikes the Paleozoic tectonic.
• The lithospheric deformation in North China Craton is more complicated.

The ambient noise data recorded by 249 seismic stations in the permanent and temporary networks in Northeast China are used to invert for the isotropic phase velocity and azimuthal anisotropy of Rayleigh waves in the period band 5–50 s. The inversion results reflect the structure from the shallow crust to upper mantle up to approximately 120 km depth. Beneath the Songliao basin, both the fast direction in shallow crust and strike of a low-velocity anomaly in the middle crust are NNE–SSW, which is coincident with the main tectonic trend of the (Paleo) Pacific tectonic domain. This indicates that the rifting of the Songliao basin is influenced by the subduction of (Paleo) Pacific plate. The upper mantle of Songliao block (except the central area of Songliao basin) to the west of Mudanjiang fault, and the east of the North–South Gravity Lineament, is characterized by high-velocity and weak anisotropy up to approximately ​120 km depth. We infer that there is delamination of lithospheric mantle beneath the Songliao block. Obvious N–S, NE–SW, and E–W trending fast directions are found in the lithospheric mantles of the east, west, and south sides of Songliao block, respectively, which coincide with the strikes of the Paleozoic tectonic in these areas. This suggests that the frozen-in anisotropic fabric in the lithospheric mantle can be used to indicate the historical deformation of the lithosphere. In the northern margin of the North China Craton, the spatial variations of phase velocity and azimuthal anisotropy are more dramatic than those in Northeast China blocks, which indicates that the lithosphere of the North China Craton has experienced more complicated tectonic evolution than that of the Northeast China blocks.