Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources
Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources
复制标题
DOI：
10.1002/jgrb.50233
复制
发表时间：
2013-08
期刊：
影响因子：
--
通讯作者：
M. Obrebski;F. Ardhuin;É. Stutzmann;M. Schimmel
中科院分区：
文献类型：
--
作者：
M. Obrebski;F. Ardhuin;É. Stutzmann;M. Schimmel
在地震噪声中嵌入的不同类型的波中，体波具有吸引人的特性，但提取仍然具有挑战性。在这里，我们首先验证了微地震压缩(P)体波数值模拟的最新改进，然后展示了该工具如何实现快速检测和定位震源。我们在南加州地震台网的典型P远震距离（30-90°）内计算了~0.2 Hz的震源，并分析了最重要的离散震源。计算得到的源的位置和相对强度与波束形成分析结果一致。这54个噪声源表现出高度不均匀的分布，并沿着太平洋和大西洋通常的风暴路径聚集。它们大多发生在公海，在2800至5600公里的水深或附近，最可能发生在风暴中，或者作为涌浪传播的海浪遇到另一个涌浪或风海的地方。然后，我们强调两个特别强的风暴来描述他们如何产生噪声源在他们的尾迹。我们还使用这两个特定的噪声爆发来说明微震体和表面波在震源分布和由此产生的可记录的地面运动方面的差异。体波和面波的不同模式是由海浪引起的压力扰动的不同放大和不同的地震衰减造成的。我们的研究证明了数值模拟的潜力，可以提供快速准确的约束，以确定何时何地会出现微震体波，这对地震成像和气候研究具有重要意义。
Among the different types of waves embedded in seismic noise, body waves present appealing properties but are still challenging to extract. Here we first validate recent improvements in numerical modeling of microseismic compressional (P) body waves and then show how this tool allows fast detection and location of their sources. We compute sources at ~0.2 Hz within typical P teleseismic distances (30–90°) from the Southern California Seismic Network and analyze the most significant discrete sources. The locations and relative strengths of the computed sources are validated by the good agreement with beam‐forming analysis. These 54 noise sources exhibit a highly heterogeneous distribution, and cluster along the usual storm tracks in the Pacific and Atlantic oceans. They are mostly induced in the open ocean, at or near water depths of 2800 and 5600 km, most likely within storms or where ocean waves propagating as swell meet another swell or wind sea. We then emphasize two particularly strong storms to describe how they generate noise sources in their wake. We also use these two specific noise bursts to illustrate the differences between microseismic body and surface waves in terms of source distribution and resulting recordable ground motion. The different patterns between body and surface waves result from distinctive amplification of ocean wave‐induced pressure perturbation and different seismic attenuation. Our study demonstrates the potential of numerical modeling to provide fast and accurate constraints on where and when to expect microseismic body waves, with implications for seismic imaging and climate studies.