Lithospheric structure beneath northeastern boundary region of the North China Craton from Rayleigh wave dispersion inversion

We have inverted Rayleigh wave dispersion data to produce a high resolution image of the S-wave velocity structure of the lithosphere beneath northeast boundary region of the North China Craton and adjacent areas. Based on waveform data recorded from 60 stations and 11 events, Rayleigh wave phase velocities were measured at periods from 25 to 150 s. The phase velocities were utilized in subsequent inversion to solve for the S-wave velocity structure from 40 km down to 300 km depth. The result shows strong lateral seismic heterogeneity. The lithospheric thickness increases sharply across the Solonker suture from the Yanshan-Liaoning region to the Xing'an-Mongolian orogen. In addition, the S-wave velocity contrast between the lithosphere and asthenosphere beneath the Solonker suture is smoothed, compared to other areas. Based on our S-wave velocity image, we speculate that (1) Pacific plate subduction may play an important role in lithospheric thinning in northeastern boundary region of the North China Craton, while the far field effect of this subduction is not evident to the northwest of Solonker suture; (2) the lithospheric thickness change beneath the Solonker suture may induce regional upwelling mantle flow and decompression melting, decreasing the S-wave velocity of the lithosphere.