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New Approaches to Multifrequency Sp Stacking Tested in the Anatolian Region
Journal of Geophysical Research: Solid Earth ( IF 3.9 ) Pub Date : 2020-10-20 , DOI: 10.1029/2020jb020313
J. Hua 1 , K. M. Fischer 1 , M. Wu 1 , N. A. Blom 2
Affiliation  

This study presents an improved approach to common‐conversion point stacking of converted body waves that incorporates scattering kernels, accurate and efficient measurement of stack uncertainties, and an alternative method for estimating free surface seismic velocities. To better separate waveforms into the P and SV components to calculate receiver functions, we developed an alternative method to measure near‐surface compressional and shear wave velocities from particle motions. To more accurately reflect converted phase scattering kernels in the common‐conversion point stack, we defined new weighting functions to project receiver function amplitudes only to locations where sensitivities to horizontal discontinuities are high. To better quantify stack uncertainties, we derived an expression for the standard deviation of the stack amplitude that is more efficient than bootstrapping and can be used for any problem requiring the standard deviation of a weighted average. We tested these improved methods on Sp phase data from the Anatolian region, using multiple band‐pass filters to image velocity gradients of varying depth extents. Common conversion point stacks of 23,787 Sp receiver functions demonstrate that the new weighting functions produce clearer and more continuous mantle phases, compared to previous approaches. The stacks reveal a positive velocity gradient at 80–150 km depth that is consistent with the base of an asthenospheric low‐velocity layer. This feature is particularly strong in stacks of longer period data, indicating it represents a gradual velocity gradient. At shorter periods, a lithosphere‐asthenosphere boundary phase is observed at 60–90 km depth, marking the top of the low‐velocity layer.

中文翻译:

在安那托利亚地区测试多频Sp叠加的新方法

这项研究为转换后的体波的共转换点叠加提供了一种改进的方法,该方法结合了散射核,精确有效地测量叠加不确定性以及估算自由表面地震速度的另一种方法。为了更好地将波形分为PSV组件来计算接收器函数,我们开发了一种替代方法来测量粒子运动产生的近表面压缩波和切变波速度。为了更准确地反映共转换点堆栈中转换后的相位散射核,我们定义了新的加权函数,仅将接收器函数的幅度投影到对水平不连续性敏感的位置。为了更好地量化堆栈不确定性,我们推导了堆栈幅度标准偏差的表达式,该表达式比自举更有效,并且可用于需要加权平均标准偏差的任何问题。我们在Sp上测试了这些改进的方法来自安纳托利亚地区的相位数据,使用多个带通滤波器来成像不同深度范围的速度梯度。共有23,787 Sp Sp接收器功能的通用转换点堆栈证明,与以前的方法相比,新的加权功能可产生更清晰,更连续的地幔阶段。烟囱在80-150 km深度处显示出正速度梯度,这与软流圈低速层的基底一致。此功能在较长时期数据的堆栈中特别强大,表明它代表了逐渐的速度梯度。在较短的时期内,在60-90 km深度观察到岩石圈-软流圈边界相,标志着低速层的顶部。
更新日期:2020-11-22
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