Receiver function study on the crustal and upper mantle structure beneath southeastern China

Recently, receiver function analysis has been widely used for obtaining the crustal and mantle structure. Since December 2008 to April 2010, 11 broadband portable seismic stations were deployed in Zhejiang province. A total of 246 high quality receiver functions were calculated from teleseismic records. H-k stacking, common conversion point-phase weighted stacking and cross correlation methods were used for studying the crustal and upper mantle structure beneath southeastern China. The results suggest that the crustal thickness ranges from 31.4 to 35.4 km with an average of 33.6 km. From continent to offshore of the Zhejiang Province, the crustal thickness decreases. The corresponding Vp/Vs ratio ranges from 1.676 to 1.782 with an average of 1.723. There's no obvious change in the Poisson's ratio, which may be due to the fact that the widely distributed Mesozoic granite in this region are mainly Late Yanshanian granite with identical chemical and mineral compositions. Generally, there exist three fast shear wave oscillation directions (FSODs), NW and NEE mainly, and then NNE direction. The delay time ranges from 0 to 0.425 s, with an average of 0.17±0.12 s. The depths of 410 and 660 km discontinuities are the same as that in IASP91 model. The 520 km discontinuity is also observed. The stagnant slab imaged by the seismic tomography in the mantle transition zone little affects the above-mentioned upper mantle discontinuities. It suggests that the temperature fields around the discontinuities are normal.