Extraction of triplicated PKP phases from noise correlations
Extraction of triplicated PKP phases from noise correlations
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从噪声相关性中提取三重 PKP 相位
DOI：
10.1093/gji/ggw015
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发表时间：
2015-12
影响因子：
2.8
通讯作者：
Wang Tao
中科院分区：
文献类型：
--
作者：
Xia Han H.;Song Xiaodong;Wang Tao
背景噪声相关法在面波提取和层析成像中得到了广泛的应用。体波的提取一直非常有限，但最近的报告表明，深入射波的承诺。在这里，我们报告我们的第一次观察三重PKP阶段（研究地球核心的重要阶段），并确认其他体波核心阶段的观测噪声相关性。我们在南美洲和中国区域地震台网中使用了距对极145°的密集地震台阵。我们可以清楚地观察到不同的PKP分支（df，bc和ab）在站站相关性的堆栈。环境噪声和地震尾波都对PKP相位有贡献。然而，贡献随频率和体波相位而变化。在较短的周期（5-20 s）内，可以从环境噪声中提取PKP的三个分支（df、bc和ab），并从地震尾波中提取ab相。在较长的周期（15-50秒），地震尾波是有效的，在产生的DF分支，但不是AB分支。从地震尾波中产生PKIKP震相（df分支）与震源机制和震源深度无关。然而，远离台站的地震比靠近台站的地震贡献更大。最佳尾波窗口为10000 - 40000 s，最佳震级阈值为MW大于6.8或6.9。从噪声相关性中观测三重PKP分支为研究地球深部内部，特别是内核各向异性提供了一种新型数据，克服了传统地震研究的一些局限性（如有限的震源分布和震源位置误差）。
Ambient noise correlation method has been widely used to extract surface waves and tomography. The extraction of body waves has been very limited, but recent reports have suggested promises for deep incident waves. Here we report our first observations of triplicated PKP phases (important phases for studying the Earth's core) and confirm observations of other body-wave core phases from noise correlations. We use dense seismic arrays in South America and China Regional Seismic Networks at distances from 145° to the antipode. We can clearly observe different PKP branches (df, bc and ab) in stacks of the station–station correlations. Both ambient noise and earthquake coda contribute to PKP phases. However, the contributions vary with frequency and with body-wave phases. At shorter periods (5–20 s), three branches of PKP (df, bc and ab) can be extracted from ambient noise and the ab phase from earthquake coda. At longer periods (15–50 s), earthquake coda are effective in generating the df branch, but not the ab branch. The generation of the PKIKP phase (df branch) from earthquake coda does not depend on earthquake focal mechanisms or focal depths. However, earthquakes far from the stations contribute more than events closer by. The best coda window is around 10 000–40 000 s and the best magnitude threshold isMwgreater than 6.8 or 6.9. The observation of triplicated PKP branches from noise correlations provides a new type of data for studying the Earth's deep interior, in particularly the inner core anisotropy, which overcomes some of the limitations of traditional earthquake-based studies (such as limited source distributions and source location errors).
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