Crust and upper mantle structure beneath Bohai Sea inferred from receiver function study

We analyzed teleseismic waveforms recorded by 36 stations near Bohai Sea region and obtained 2 248 high quality receiver functions. The crustal thickness (H) and average crustal v(P)/v(S) ratio (kappa) as well as the Poisson's ratios beneath 34 stations were estimated using the H-kappa stacking method. The results indicate that crustal thicknesses near the Liaoning province range from 30.0 to 35.5 km, and the corresponding v(P)/v(S) ratios vary from 1.72 to 1.89 which corresponds to Poisson's ratio with a range from 0.243 to 0.305. We also apply a common conversion point (CCP) stacking method of receiver function (RF) to image the upper mantle discontinuity structure beneath Bohai Sea region. Both the 410-km and the 660-km discontinuities (hereafter called the 410 and the 660) show clearly in the study region. The transition zone (TZ) thickness shows a different picture from the west to the east of the study region, which is a little bit thicker than that of the global average in the west of longitude 122(circle) E, however, thinner in the east of longitude 122(circle) E. We suggested that the dehydration of sinking slab into the lower mantle or a small-scale mantle plume from the lower mantle generated hot upwelling beneath this region.