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 (κ) as well as the Poisson's ratios beneath 34 stations were estimated using the H-κ 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°E, however, thinner in the east of longitude 122°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.