High-resolution crustal structure in the Songliao basin

High-resolution shallow crustal structure beneath the Songliao basin of Northeast （NE） China has obvious economic and scientific significance. To constrain the sediment and crustal structure of the Songliao basin, H-β grid search method based on wavefield downward continuation and decomposition is used with teleseismic data recorded from portable broadband seismic arrays in the NE China. The results show that the estimated sediment thickness is 0.2−2.5 km, and becomes thinner from the central depression toward the margin of the basin, with the thinnest sediment in the southwestern region. The crustal thickness varies from 24 km to 34 km, and its lateral variation correlates with the distribution of sedimentary thicknesses to a certain extent. The crustal stretching factor is calculated from the sedimentary and crustal thicknesses, with an average close to the lithospheric stretching estimation from previous receiver function studies. Thus, we infer that the thinning of the crust and lithosphere is dominated by pure shear mode during the extensional process of the Songliao basin. Moreover, the Songliao basin has a high crustal v_P/v_S ratio, indicating possible magmatic underplating during the lithospheric extension beneath the Songliao basin.