利用接收函数方法研究喜马拉雅东构造结地区地壳结构

Crustal structure of Eastern Himalayan Syntaxis revealed by receiver function method

本文使用位于喜马拉雅东构造结地区布置的24个宽频带地震台站记录的远震波形数据,利用P波接收函数的方法研究了台站下方的Moho面深度、泊松比和地壳速度结构.结果表明,东构造结内Moho面深度呈现出自南西向北东方向逐渐变深的趋势,地壳厚度在54~60 km范围内,其中东久一米林走滑断裂带附近Moho面最浅,东构造结周围拉萨地块的Moho面深度在60 km以上.东构造结西部东久一米林走滑断裂带附近地壳泊松比较高.嘉黎断裂带南北两侧的泊松比差别较大,说明该断裂带两侧地壳结构存在显著差异.东构造结周边拉萨地块地壳内普遍存在低速层,分布在20~40 km深度范围内,厚度约为5~15 km.

In this study, we make use of the P-wave receiver function method and waveform data recorded by 24 broadband seismic stations to probe the depth of Moho discontinuity, Poisson＇s ratio and velocity structure of the crust beneath the Eastern Himalayan Syntaxis （EHS）. The results show that the depth of Moho discontinuity within the EHS deepens from the southwest to the northeast, ranging 54~60 km. The shallowest part is located on the west side of EHS near the Dongjiu-Milin strike-slip fault. The Moho discontinuity beneath the Lhasa block surrounding the EHS is deeper than 60 km. The Poisson＇s ratio near the Dongjiu-Milin strike-slip fault at the western EHS is relatively high. There is an obvious difference in Poisson＇s ratio between the northern and southern sides of Jiali fault, indicating the difference in the crustal structure. There are low velocity layers in the crust of the Lhasa block surrounding the EHS at depth of 20~40 km with thickness of 5~15 km.