加入多次波的长时窗接收函数主成分分析及其在张八岭构造带地壳分析中的应用

接收函数主成分分析方法可以有效地提取单台接收函数中蕴含的台站下方地壳结构和速度各向异性信息, 本文在原有理论基础上将该方法应用于加入了多次波的长时窗接收函数.通过位于郯庐断裂带张八岭构造带的滁州台和嘉山台的数据进行分析验证, 并估计了该地区地下结构和速度各向异性信息.测试结果表明: 相较于仅对Ps转换波的接收函数主成分分析研究, 扩大时窗范围、加入多次波后, 利用第二主成分重构的径向接收函数中信息更加丰富, 且更有利于对构造特征和速度各向异性进行约束.研究同时发现, 重构的接收函数在多次波的时窗内的稳定性更强.实际数据结果显示: 张八岭构造带东缘滁州台下方地壳底部具有倾向指北、向下倾斜不超过20°的构造特征, 壳内具有快轴方向近似平行于郯庐断裂带走向且不大于7%的速度各向异性.而嘉山台下的地壳横向结构变化幅度不大, 具有较弱的速度各向异性特征, 但沉积层底界面表现为近北东走向, 向东南下倾的构造特征.这种差异的地壳结构特征也指示出该构造带在演化过程中具有较高的非均一性.

Principal component analysis of long time window receiver function considering the multiples and its application to crustal characteristics analysis of Zhangbaling tectonic belt

The principal component analysis of receiver function is an effective method in elucidating and retrieving crustal structure and velocity anisotropy from the receiver functions of a single station. Based on existing theories, we applied this method to long time window receiver functions considering the multiples. In addition, the feasibility of the method was validated by processing field data from two permanent stations named CHZ and JAS, located in the Zhangbaling uplift segment on the east region of the Tanlu Fault Zone. We then estimated the deep structural features and velocity anisotropy within this domain. The test results revealed that, under the circumstance of utilizing a longer time window and considering the multiples, the reconstructed radial receiver functions via second component not only carried more information but were more conducive to constraining the crustal structure and velocity anisotropy than the previous method simply based on the conversions (Ps). Furthermore, the study verified also that more robust results of the reconstructive receiver function can be achieved in the time window containing the multiples. The recuperated parameters from the involved real case disclosed that the crustal bottom of the eastern marginal of Zhangbaling uplift segment beneath CHZ dips down to the north nearly 20°. Moreover, the crust yields less than 7% velocity anisotropy with a fast symmetry axis nearly parallel to strike off the Tanlu fault zone. The transverse crustal structure beneath JAS is relatively flat, and the crust cultivates weak velocity anisotropy. Nevertheless, the bottom of the sedimentary layer exhibits a near-northeast strike and southeast-dipping structure. These crustal structural features constrained the high heterogeneity in the geological evolution process within the study area.