利用接收函数研究滇西北地区地壳厚度及泊松比特征

The Characteristics of Crustal Thickness and Poisson Ratio in Northwest Yunnan Revealed by Receiver Function

摘要:

计算了滇西北地区的16个固定地震台和喜马拉雅台阵项目的103个流动台站（共119个地震台站）记录的238个5.8级以上的远震事件，从中挑选了5558个信噪比高、震相清晰的接收函数，采用人工读取震相到时的方法，获得了各个台站下方的地壳厚度和泊松比。结果显示：滇西北地区地壳厚度等值线呈ES向舌状突出，地壳厚度和泊松比横向变化明显。经拟合，研究区域内地壳厚度和海拔呈正相关线性特征，深大断裂对区域构造特征和深部动力环境起控制作用。澜沧江断裂和怒江断裂北部可能是青藏高原物质向川滇侧向挤出的通道，丽江-小金河断裂深部存在流变物质。

Abstract:

We choose 238 events recorded in the seismic stations of Ximalaya array(103 stations) and fixed stations(16 stations) with magnitudes from 5.8 to 8.0,and selected 5558 receiver functions with high signali-to-noise ratio and clear waveform,to calculate the depth of Moho and the crust poisson's ratio through the method of manually reading the time of seismic phase. The results show that the thickness of the crust presents a tongue-shaped protrusion to the southeast. The crustal thickness and poisson's ratio in the northwest Yunnan region varied significantly. After fitting,the crustal thickness under the mostly seismic station is positively correlated with the local altitude. The faults play a controlling role in regional structural characteristics and the change of deep dynamic environment. The north of Lancangjiang Fault and Nujiang Fault may be the passing channel for the material from Qinghai-Tibet plateau to extrude laterally to Sichuan and Yunnan. Rheological material exists in the deep of Lijiang-Xiaojinhe fault.