加拿大阿尔伯塔大学Cheng Zhang课题组提出了利用接收函数非线性反演恢复加拿大阿尔伯塔盆地的沉积构造。相关论文于2023年2月21日发表于国际顶尖学术期刊《JGR地球》杂志上。

在这项研究中，研究人员介绍了一种非线性波形反演算法，该算法与加拿大西部沉积盆地(WCSB)阿尔伯塔盆地记录的前5秒接收函数相匹配。他们的算法搜索沉积盖层的最佳厚度，以及在沉积盖层内部和下面可选择的合适的剪切速度。结合反演和正演模拟，课题组人员确定了加拿大西部沉积盆地80个区域宽频地震台站的地壳上地层。反演模型显示，东部逐渐变细的沉积层，其厚度从加拿大落基山脉山麓下约6公里到阿尔伯塔盆地下3-4公里不等。

这一发现与区域测井资料确定的沉积层相一致。沉积层包含不同厚度和振幅的低速带，根据位置的不同，这些低速带可能受到沉积、成分或变形历史等机制的影响。基底顶部附近的剪切速度模型补充了现有的声波测井或单分量地震数据，并为加拿大西部沉积盆地的沉降历史提供了新的约束条件。可分辨的深度范围(0-14 km)有效地弥补了测井垂直尺度(0-6 km)和涉及接收函数和面波与传统宽带分析(>10公里)之间的差距。

据介绍，来自接收器的接收函数的二次转换波对地球表面以下的物理性质高度敏感。当建模正确时，转换波的波形对沉积、地壳和地幔界面的阻抗对比度、深度和P-S速度比提供了直接约束。

附：英文原文

Title: Recovery of the Alberta Basin sedimentary structures in southern-central Alberta using Nonlinear Inversions of Receiver Functions

Author: Cheng Zhang, Yu Jeffrey Gu, Ramin M.H. Dokht, Yunfeng Chen

Issue&Volume: 2023-02-21

Abstract: Secondary converted waves from receiver functions are highly sensitive to physical properties below the Earth’s surface. When modeled properly, the waveforms of converted waves offer direct constraints on the impedance contrast, depth, and P-to-S velocity ratio pertaining to sedimentary, crustal and mantle interfaces. In this study we introduce a nonlinear waveform inversion algorithm that matches the first 5 seconds of receiver functions recorded in the Alberta Basin within the Western Canada Sedimentary Basin (WCSB). Our algorithm searches for the optimal thickness of the sedimentary cover and shear velocities of appropriately selected layers within and below it. Combining inversions with forward simulations, we determine the supracrustal stratigraphy from 80 regional broadband seismic stations in the WCSB. The inverted models show east tapering sedimentary layers with their thicknesses ranging from ～6 km beneath the foothills of the Canadian Rocky Mountains to 3-4 km beneath the Alberta basin. This finding is consistent with the sedimentary strata determined from regional well-logging data. The sedimentary layer contains low velocity zones of variable thicknesses and amplitudes that, depending on the locations, may be caused by mechanisms involving deposition, composition or deformation history. Our shear velocity models near the top of the basement complement the existing sonic-logs or single component seismic data and offer new constraints on the subsidence history of the WCSB. The resolved range of depths (0-14 km) effectively bridges the gap between the vertical scales of well logging (0-6 km) and those of traditional broadband analysis (> 10 km) involving receiver functions and surface waves.

DOI: 10.1029/2022JB024813

Source: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JB024813