Crustal Structure Of SE Tibet By Receiver Function

As the front region of plate collision,the southern Tibet has always been the hotspot in geoscience research.In order to improve the resolution of the crust structure in the southeast of the Tibet Plateau and reveal its characteristics,we used the teleseismic data recorded by 14 broadband mobile stations deployed by Nanjing University and the teleseismic data recorded by 24 broadband mobile stations provided by IRIS,the events whose magnitude greater than or equal to 5.5 and epicentral distance within the range of 30° to 90° were selected,then we calculate the receiver function.Finally,we used 2487 tele-seismic records recorded by 38 broadband stations in the southeast Tibet.Then we calculated the crustal thickness and Poisson's ratio of this area by CCP stacking and H-? stacking.The results show that the crustal thickness obtained by the two methods are in good agreement,and the crustal thickness in the southeastern Tibet has obvious difference in east-west and north-south.The depth of Moho varies greatly in the Himalaya tectonic zone,ranging from 65 to 80 km.The depth of Moho in Lhasa block ranges from 72 km to 80 km.In accordance with the characteristics that the thickness of the crust of the Tibet Plateau is twice of the normal crust.The depth of the Moho near the Yarlung Zangbo suture zone reached the maximum value in the study area.The crustal thickness on both sides of the Yarlung Zangbo suture has been abruptly changed.The diff-erence in thickness between the north side and the south side of the suture is about 8 km.The ratio of wave speeds in the study area was obtained by H-? stacking.Based on this result,the Poisson's ratio of the crust in the study area was calculated.The results show that the Poisson's ratio values under different stations vary widely,and the average Poisson's ratio of the study area is 0.24,which is consistent with the feather that the Poisson ratio in most orogenic belts is low.Analysed the the CCP stacking results we found that the stratification in the crust of the study area is obvious,indicating that deep melting or partial melting occurred in the crust and leaded gravitational differentiation,then a high-speed thin layer was formed in the middle-lower crust.A strong transition interface exists widely in the middle and lower crust of the study area,combined the result of the velocity structure,we analyzed the interface may be the upper interface of the high-speed layer in the middle-lower crust,with a depth of 40?70 km.