简介：At06:34(CST)onNov.18,2017,anM6.9earthquakeoccurredintheMainlingCounty,NyingchiRegionofXizangAutonomousRegion,China.Theepicenterislocatedat95.02°E,29.75°Nandthefocaldepthisabout10km(Figure1).Theepicenterisabout100kmfromtheMainlingCounty.Theaverageelevationwithin5kmisabout3100m.Thisearthquakehascausedwidespreadconcernamongmembersofgovernment,researchinstitutions,andpublicmedia.

简介：TheTibetanPlateau,knownas“theroofoftheworld”and“thethirdpoleoftheearth”,isaproductofthecollisionbetweenIndiaandAsiaduringthelast~50Ma.Theregionaltectonics–inparticular,growthandexpansionoftheplateau–hasbeenattributedprimarilytodeformationwithinthelithosphere.Theroleandpatternoftheunderlyingasthenosphericflow,however,remainmostlyunaddressed.Inlightofrecentseismictomographicimagesandpublishedseismicanisotropicdescriptionsoftheuppermantle,hereweproposethatanentrainedmantleflowislikelytoexistunderTibet,inducedbythenorthwardadvancingIndianplate.ThedirectionofmantleflowischaracterizedbyagradualrotationfromnorthwardinthesouthtoeastwardinthenorthasaresultofdeflectionbythedeeprootoftheTarimblock.Thepresenceofanunderlyingmantleflowisnotonlyabletoaccountforthewest-eastorientedfast-axisofseismicanisotropyinnorthernTibet,butcanalsoadequatelyexplainthesporadicnullsplittinginsouthernTibet.Specifically,thenullsplittingresults,atleastinpart,fromupwellingsofasthenosphericflowthroughtearsoftheunderthrustingIndianplatethathavebeenrevealedbyvariousseismicobservations.ThemantleflowmayinturnpromotetheblockextrusionunderTibetthathasbeenobservedinGPSmeasurements;hotasthenosphericupwellingsmayalsoleadtowidespreadpost-collisionalmagmatisminsouthernTibet.