Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China
Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China
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我国大口径地震台阵记录的微震中远震P、SV、SH波震源位置
DOI：
10.1016/j.epsl.2016.05.035
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发表时间：
2016-09-01
影响因子：
5.3
通讯作者：
Reading, Anya M.
中科院分区：
文献类型：
--
作者：
Liu, Qiaoxia;Koper, Keith D.;Reading, Anya M.
在广泛的周期内，人们经常在环境地震能量中观察到横向偏振地震波，但人们对它们的起源知之甚少，因为相应的震源区域要么未定义，要么约束较弱，而且几乎所有微震生成模型都采用垂直方向的单一力作为激励机制。为了更好地了解周围地震波场中横向极化能量的起源，我们首次系统地尝试定位在微震（2.5-20 s）噪声中观察到的远震 SH 波的源区域。我们关注体波而不是表面波，因为使用传统阵列技术可以限制源区域的方位角和距离。为了定位 SH 波（以及 SV 和 P 波）的微震源，我们连续反投影了 2013-2014 年中国部署的大孔径阵列记录的环境地震波场的垂直、径向和横向分量。正如预期的那样，在北大西洋、北太平洋和印度洋观测到持续性 P 波源，主要是在 2.5-10 秒的周期内，这些区域具有产生次生微震所需的强烈海浪相互作用。通常观察到 SV 波的起源位置与 P 波源无法区分，但信噪比较小。我们还观察到 SH 波的信噪比约为 SV 波的一半或更低。 SH源区明确位于太平洋的深水部分，远离被认为对微震洛夫波的产生很重要的倾斜大陆架，但靠近经常产生远震P波的区域。因此，观测到的 SH 波的激发机制可能与 P 波通过某种散射过程与小波长测深特征（例如海山和盆地）的相互作用有关。 (C) 2016 Elsevier B.V. 保留所有权利。
Transversely polarized seismic waves are routinely observed in ambient seismic energy across a wide range of periods, however their origin is poorly understood because the corresponding source regions are either undefined or weakly constrained, and nearly all models of microseism generation incorporate a vertically oriented single force as the excitation mechanism. To better understand the origin of transversely polarized energy in the ambient seismic wavefield we make the first systematic attempt to locate the source regions of teleseismic SH waves observed in microseismic (2.5-20 s) noise. We focus on body waves instead of surface waves because the source regions can be constrained in both azimuth and distance using conventional array techniques. To locate microseismic sources of SH waves (as well as SV and P waves) we continuously backproject the vertical, radial, and transverse components of the ambient seismic wavefield recorded by a large-aperture array deployed in China during 2013-2014. As expected, persistent P wave sources are observed in the North Atlantic, North Pacific, and Indian Oceans, mainly at periods of 2.5-10 s, in regions with the strong ocean wave interactions needed to produce secondary microseisms. SV waves are commonly observed to originate from locations indistinguishable from the P wave sources, but with smaller signal-to-noise ratios. We also observe SH waves with about half or less the signal-to-noise ratio of SV waves. SH source regions are definitively located in deep water portions of the Pacific, away from the sloping continental shelves that are thought to be important for the generation of microseismic Love waves, but nearby regions that routinely generate teleseismic P waves. The excitation mechanism for the observed SH waves may therefore be related to the interaction of P waves with small-wavelength bathymetric features, such as seamounts and basins, through some sort of scattering process. (C) 2016 Elsevier B.V. All rights reserved.