Seismic receiver functions revealing crust and upper mantle structure beneath the continental margin of southeastern China

1446 teleseismic P-wave receiver functions were selected from the seismographs of two NE-oriented profiles deployed along the coast and in the midland of Fujian Province, respectively. H-kappa auto-searching stacking and CCP stacking methods were used to study the crust and upper mantle structure characteristics beneath the continental margin of southeastern China (SE China). With the data from 25 permanent stations of Fujian Seismic Network joined, we obtained an image of crustal thicknesses characterized by gradually thinning from inland to coast in the region of SE China margin (Fujian region). It is shown that the crust beneath Fujian region thins from about 33 km in the mountain area of northwestern Fujian to <29 km along the coast of southeastern Fujian around Xiamen, with an average of 31. 3 km, which embodies the transition from continental crust to oceanic crust. Meanwhile, the Poisson's ratios of the coastal crust (>0. 26) are higher than that of the inland crust (<0. 26). The CCP migrated receiver function stacking images of crust and uppermost mantle (0 similar to 200 km) for the two profiles show that the NW trending faults like Minjiang Fault cut through the Moho, causing severe drop or uplift and different attitudes of the Moho across the faults, but such characteristics seem unobvious toward inland. NW trending faults like Minjiang affect the distributions of factors like crustal thicknesses and earthquakes in this region. There are no breaks and surge of 410 and 660 km discontinuities appearing on the image of CCP stacking results for the depths of upper mantle (300 similar to 700 km). The depths of 410 and 660 km discontinuities are slightly larger than that of IASP91 while the thicknesses of the mantle transition zone are normal (250 +/- 5 km), which indicates that the mantle transition zone beneath this area is less affected by the collisions between Eurasian and Philippine Sea plates. It is inferred that there are no any subducting plates existing beneath SE China margin and Taiwan Strait or the frontier of the subducting plates has not reached the depth of 410 km.