Crustal structure of the Tethyan Himalaya,southern Tibet:new constraints from old wide-angle seismic data
作者单位：Department of Geophysics Stanford University Stanford CA94305-2215 USA
会议名称：《中国科学院地质与地球物理研究所第十届(2010年度)学术年会》
会议日期：2011年
学科分类：070801[理学-固体地球物理学] 07[理学] 0708[理学-地球物理学]
基 金：funded by the Ministry of Science and Technology of China(Grant number 2002CB412604) the Chinese National Nature Sciences Foundation(Grant numbers 40721003 and 40830315) the Chinese Academy of Sciences(CAS)(Grant number KZCX2- YW-132)
关 键 词：Controlled source seismology Continental tectonics:compressional Crustal structure Asia
摘 要：A wide-angle seismic profile between Peigu Tso(85.5°E) and Pumoyong Tso(90.5°E) in southern Tibet,acquired under a joint Sino-French program in 1981,passes through the South Tibetan Detachment System(STDS,the eastern segment of the profile) and the central part of the Tethyan Himalaya(the western segment).We herein reinterpret this wide-angle seismic profile,which has a total length of～480 km,in order to improve our understanding of the crustal structure of the Tethyan *** identify multiple P- and S-wave wide-angle reflections within the crystalline crust and from the Moho,but cannot identify any refracting waves beneath the *** model the structure of P- and S-wave velocity throughout the whole crust,while acknowledging the significant uncertainties that are inherent in many places. A low-wave speed cover sequence may be identified with the Tethyan sedimentary cover(Vp5.8 km s),from the surface to a depth of(typically) 5-10 km,which is only absent where the profile crosses the Kangmar *** may be presumed that these sedimentary rocks overlay a felsic upper-crustal basement(5.8Vp6.3 km s),which in places extends as far down as 35 km,and which itself overlays a 5-10-km-thick mid-crustal low-velocity *** a depth of 30 and 45 km at the base of the low-velocity zone and the Moho at a depth of～73 km,the observed velocities gradually increase from 6.2 to 6.8 km *** low-velocity layer(LVL) may consist of a partial melt due to the high geothermal gradients found in the felsic rocks,or of a fluid-rich shear zone as in the ductile channel of a channel flow *** difference in depth of the LVL between the western(central Tethyan Himalaya) and eastern segments(nearly along the STDS) at the boundary of the Dingye-Mabjia fault,leads to a north-south dip estimate of the LVL of 8.5°,which is consistent with the estimated dip of the MHT obtained from the INDEPTH-I project,and can support the channel flow *** north-south low dip angle of subduct