Crustal structure beneath the Xisha Islands of the South China Sea simulated by the teleseismic receiver function method
Crustal structure beneath the Xisha Islands of the South China Sea simulated by the teleseismic receiver function method
复制标题
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
H. Hai;Qiu Xue
中科院分区：
文献类型：
--
作者：
H. Hai;Qiu Xue
利用陈行岛临时地震台站（CHH）和永兴岛永久地震台站（YXN）的数据，建立了南海西沙群岛地壳结构的一维横波速度模型。利用P波形清晰的远震记录获取各台站的接收函数，利用反演和正演相结合的方法推断各台站下地壳结构。模拟结果表明，地壳顶部存在一个厚2 km、横波速度为2.0 km/s的低速层。其成因为本区碳酸盐沉积。上地壳为速度梯度带，横波速度从2 km处的3.4 km/s逐渐增大到12 km处的3.8 km/s。下地壳厚度为12 km，具有显著的低横波速度，为3.5 km/s。莫霍线位于26~28 km深度，横波速度在3.8 ~ 4.6 km/s范围内变化，存在速度梯度带。泊松比大于0.3。我们认为下地壳低速层和泊松比异常是由于深部韧性流变带和热地幔活动引起的岩石和矿物各向异性的存在。
1-D shear wave velocity models for the crust structure beneath the Xisha Islands of the South China Sea are constructed using the data from a temporary seismic station at Chenhang island(CHH) and a permanent seismic station at Yongxing island(YXN).Receiver functions for each station were obtained from teleseismic records with clear P waveforms and a combination of inversion and forward modeling was used to infer the crustal structure below each station. Modeling results show that a 2 km thick low-velocity layer with shear wave velocity of 2.0 km/s exists on the top of crust.It is attributed to carbonate sediments in this area.Upper crust is a velocity gradient zone in which the shear wave velocity gradually increases from 3.4 km/s at the depth of 2 km to 3.8 km/s at the depth of 12 km.Lower crust is 12 km thick and has a prominent low shear wave velocity of 3.5 km/s.The Moho lies at the depth of 26～28 km and also has a velocity gradient zone with shear wave velocity changing from 3.8 km/s to 4.6 km/s.The Poisson s ratio shows a higher value greater than 0.3.We suggest that the low-velocity layer in lower crust and the anomalous Poisson s ratio result from the presence of anisotropy of rocks and minerals which arises from the ductile rheological zone and hot mantle activity in the depth.