Clear PKIKP precursors were observed from the Lanzhou CTBTO seismic array.We measured their incident angles,arriving azimuths and differential travel times with respect to the PKIKP arrivals using array analysis techniques.These measurements allowed us to locate the scatterers that generated the observed precursors.We found that the scatterers are located in the lowermost mantle beneath eastern Tibet,which is featured by a high-velocity anomaly based on previous tomographic studies.The high velocity anomaly was interpreted as the slab remnants of the ancient Tethys subduction.We thus speculate that the observed scatterers are either related or induced by the subducted slab.
SHEN XuZhang 1,2,3 & ZHOU HuiLan 1 1 Laboratory of Computational Geodynamics,Graduate University of the Chinese Academy of Sciences,Beijing 100049,China
中国东北西太平洋俯冲带位于欧亚板块与西太平洋板块的交界部位，西太平洋板块的俯冲运动从日本海沟开始一直延伸到了中国东北地区。层析成像（Gudmundsson＆Sambridge，1998；Huang＆Zhao，2006）结果表明，西太平洋板块和该区域‘660’的相互作用，导致了该区域上地幔结构的复杂性。接收函数和其它地震学方法（Niu＆Kawakatsu，1996;Li＆Yuan，2003；Lebedev et al，2002；
It is shown in this note that the three methods,the orthonormalization method,the minor matrix method and the recursive reflection-transmission matrix method are closely related and solve the numerical instability in the original Thomson-Haskell propagator matrix method equally well.Another stable and efficient method based on the orthonormalization and the Langer block-diagonal decomposition is presented to calculate the response of a horizontal stratified model to a plane,spectral wave.It is a numerically robust Thomson-Haskell matrix method for high frequencies,large layer thicknesses and horizontal slownesses.The technique is applied to calculate reflection-transmission coefficients,body wave receiver functions and Rayleigh wave dispersion.
