Topography Of The 410-and 660-km Discontinuities Beneath The Central And Eastern China Using Receiver Function

It is important to understand the correlation between Earth interior and evolution of the Earth.Numerous studies indicate that seismic analysis technique can help us to understand the structure of the Earth interior.Therefore,in this study,I mainly focus on the 410-and 660-km discontinuities in the upper mantle.The topographic maps of the 410-and 660-km discontinuities beneath the central and eastern continental China are obtained by using P-to-s converted phase from teleseismic events recorded by relatively dense seismic stations through systematic receiver function analysis.I find that there are some abnormal relief of 410-and 660-km discontinuities beneath northeast China,southwest China,Hainan and Taiwan regions.For instance,I find big regional depressions of 660 km discontinuities beneath northeast and southeast China and I also find a thinner mantle transition zone(MTZ)beneath Hainan region.I also observed double 660-km discontinuities beneath Taiwan region.It is also found that both the 410-and 660-km discontinuities are consistently depressed beneath the east side of the North-South Gravity lineament(NSGL)in contrast with the west side.Considering the low water solubility in wadsleyite and ringwoodite that mainly constitute the MTZ,the depressions in the 660-km discontinuities are more likely caused by temperature effects on phase transition interfaces,however,the depressed 410-km discontinuity is the result of a low velocity zone above the 410-km discontinuity.Besides,tomographic image also suggests that the NSGL is roughly consistent with front of the stagnant Pacific slab.Therefore,lower temperatures around the 660-km discontinuity due to the stagnant Pacific slab in the MTZ lead to depressions of the 660-km discontinuity.In addition,the double discontinuities beneath Taiwan region may be the result of that South China Sea plate has been arrival at base of MTZ beneath Taiwan.I mainly summarized previous studies about other regional abnormal for interpret the observations.