Ambient noise tomography in northeast China

Northeast China is the only one of the deep earthquake zone in China. In order to study the subduction of the west Pacific plate, the deep earthquakes and volcanic activity, it has very important scientific significance to obtain the crustal and upper mantle structure of this region. By using the vertical component of continuous data, recorded by 159 permanent stations from January 2011. to June 2012 and 27 portable stations from January 2011 to June 2011 in northeast China, we calculated the inter-station Green functions, and measured the group velocity and phase velocity dispersion curves of Rayleigh wave by using the frequency-time analysis method based on continuous wavelet transform. According to quality control and screening, we finally obtained 2204 group/phase velocity dispersion curves at periods ranging from 5 s to 40 s. Checkerboard tests show that the inversion results have a good resolution of 2 degrees x 2 degrees. By utilizing Ditmar & Yanovskaya method, we got the Rayleigh wave group velocity and phase velocity maps at periods between 8 similar to 30 s in the study area (105 degrees E-135 degrees E, 39 degrees N-52 degrees N), which revealed the lateral changes of S-wave velocity at different depths. The results showed that the crust and upper mantle S-wave velocity structures have lateral heterogeneity. Group/phase velocity maps at short period (e. g. 8 s) are well related with the geology units on the surface, with high-speed anomalies corresponding to the main mountain ranges and low-speed anomalies coinciding with the major sedimentary basins. But the effect controlled by the topography becomes weaker at the intermediate periods (e. g. 15 s, 22 s). For group/phase velocity maps at longer periods (e. g. 30 s), they are closely related with crustal thickness.