基于多频段Pds波振幅的地幔过渡带间断面横波速度结构反演方法及应用  

Inversion and Application of Shear Velocity Structure Near Transition Zone Discontinuities Based on Multiband Pds Amplitude

作　　者：薛静 于欣鑫 李君 XUE Jing;YU Xinxin;LI Jun(College of Geophysics,Chengdu University of Technology,Chengdu 610059,China;Second Monitoring and Application Center,China Earthquake Administration,Xi’an 710054,China)

机构地区：[1]成都理工大学地球物理学院,成都610059 [2]中国地震局第二监测中心,西安710054

出　　处：《太原理工大学学报》2022年第4期640-648,共9页Journal of Taiyuan University of Technology

基　　金：国家自然科学青年基金资助项目(41904086)。

摘　　要：地幔过渡带间断面的厚度和其上下的地震波速差异可提供对过渡带附近的水含量和矿物组分的重要约束。通过构建不同的地幔过渡带间断面速度模型,计算了理论接收函数,提取了不同频段的间断面Pds转换波的振幅信息。正演结果显示,跨越间断面的横波速度变化主要影响Pds/P振幅比的大小,而间断面的厚度同时影响幅值大小和其随频率的变化规律。提出利用多频段Pds/P振幅比,基于马尔科夫链蒙特卡洛方法同时反演间断面的厚度和跨越间断面的横波速度变化。理论测试表明,该方法可有效给出间断面厚度和横波速度变化及其不确定性。将该方法应用于中国东部地区的实际数据,结果表明,该地区660间断面较为尖锐,在小于2 km的深度范围内横波速度增加了6.1%.Sharpness of the transition zone seismic discontinuities and seismic velocity jump across the discontinuities provide important constraint on water content and mineral composition near the transition zone.The velocity models were constructed with different discontinuity sharpness and velocity jump to calculate corresponding receiver functions and analyze the Pds/P amplitude ratio in multiple frequency bands.The forward modeling results show that the shear velocity contrast across the discontinuity mainly affects the amplitude of Pds/P ratio while the thickness affects both the amplitude and decaying trend versus frequency.Simultaneous inversion were proposed for the discontinuity thickness and velocity jump by using a Markov Chain Monte Carlo method.Synthetic test indicates the method can effectively constrain the thickness and velocity jump.The method was applied to collected receiver function in eastern China.Results show a relatively sharp 660 km discontinuity with a 6.1%shear velocity increase over less than 2 km depth range.

关 键 词：地幔过渡带 接收函数 660间断面 间断面厚度 蒙特卡洛法 

分 类 号：P631.4[天文地球—地质矿产勘探]