On the robustness of attenuation measurements on teleseismic P waves: insights from micro-array analysis of the 2017 North Korean nuclear test
On the robustness of attenuation measurements on teleseismic P waves: insights from micro-array analysis of the 2017 North Korean nuclear test
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DOI：
10.1093/gji/ggz169
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发表时间：
2019-04
影响因子：
2.8
通讯作者：
M. Bezada;J. Byrnes;Z. Eilon
中科院分区：
文献类型：
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作者：
M. Bezada;J. Byrnes;Z. Eilon
尽管它们的重要性作为一个基本的约束地球属性，区域尺度的测量体波地震衰减是稀缺的。部分原因是难以对衰减作出可靠的估计。本文着重研究了在地震记录上测量微分衰减的方法。我们研究了2017年朝鲜核试验的五个记录的独特数据集，这些记录是在五个宽带地震站测量的，这些地震站部署在几米之内，但使用不同的安装程序。鉴于它们的极端接近，我们期望不同记录之间的零差异固有衰减。然而，我们发现不同的衰减测量方法和实施参数实际上会产生显著的表观差分衰减（Δt*）。频域方法可根据测量带宽和信号处理的细微差别，在台站之间产生各种Δt* 估计值。这种测量不稳定性随着时间窗口的延长而增加。时域方法在很大程度上对所考虑的频带不敏感，但对所选择的时间窗口敏感。我们确定，信号产生的噪声可以影响测量在频域和时域。在某些情况下，结果的范围相当于最近一项研究确定的美国全境差分衰减范围的一个重要部分。我们提出了一些方法来管理这些测量中固有的不稳定性，并推荐了自信地估计体波衰减的最佳实践。
Despite their importance as a fundamental constraint on Earth properties, regional-scale measurements of body-wave seismic attenuation are scarce. This is partially a result of the difficulty in producing robust estimates of attenuation. In this paper, we focus on measuring differential attenuation on records of teleseismic P waves. We examine a unique data set of five records of the North Korean nuclear test of 2017 measured at five broad-band seismic stations deployed within a few metres of each other but using different installation procedures. Given their extreme proximity, we expect zero differential intrinsic attenuation between the different records. However, we find that different attenuation measurement methods and implementation parameters in fact produce significant apparent differential attenuation (Δt*). Frequency-domain methods yield a wide range of Δt* estimates between stations, depending on measurement bandwidth and nuances of signal processing. This measurement instability increases for longer time windows. Time domain methods are largely insensitive to the frequency band being considered but are sensitive to the time window that is chosen. We determine that signal-generated noise can affect measurements in both the frequency and time domain. In some cases, the range of results amounts to a significant fraction of the range of differential attenuation across the conterminous United States as determined by a recent study. We suggest some approaches to manage the inherent instability in these measurements and recommend best practices to confidently estimate body wave attenuation.