Directional and seasonal variations of seismic ambient noise in southeastern Canada and the NE USA
Directional and seasonal variations of seismic ambient noise in southeastern Canada and the NE USA
复制标题
加拿大东南部和美国东北部地震环境噪声的方向性和季节性变化
DOI：
10.1093/gji/ggac342
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发表时间：
2023
影响因子：
2.8
通讯作者：
Bagherpur Mojaver O
中科院分区：
文献类型：
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作者：
Bagherpur Mojaver O
环境地震噪声主要是在海洋中通过大气、海浪和固体地球之间的相互作用产生的。因此，位于大陆边缘附近的研究区域容易受到不均匀噪声场的影响，这可能导致环境噪声波衰减测量和层析成像研究出现偏差。加拿大东南部和美国东北部的环境地震噪声特征首次在区域范围内进行了详细研究，这是由于69个宽带地震仪记录的2年多（2013-2015）的数据可用性。这个大的，密集的数据集，使我们能够使用反投影技术来调查环境噪声的方位角和时间变化。这种方法是基于统计分析的信号-噪声比（SNR）的波形中计算的经验绿色的功能对站。我们提出了一种新的分析方法，通过修改现有的概念，风扇图，包括因果和非因果成分的噪声交叉相关图的分析的SNR。我们调查的方向和季节性变化的记录噪声数据在整个研究区域的地震噪声谱的三个主要通带，包括二次微震（SM; 3-10秒），主要微震（PM; 10-30秒），和地震嗡嗡声（PM; 30-300秒）。我们观察到，最强和最弱的信号分别在SM和UWB波段接收。考虑到这项研究的结果沿着从以前的研究，我们得出的结论是，最强的地震噪声到达在本研究中所研究的三个通带（即SM，PM和PM）产生在大西洋，太平洋和北冰洋的不同位置。
Ambient seismic noise is mainly generated in oceans through the interactions between the atmosphere, ocean waves and the solid Earth. Study areas located near the edges of continents are thus subject to receiving an inhomogeneous noise field that could cause bias in ambient noise wave attenuation measurements and tomography studies. Ambient seismic noise characteristics across SE Canada and the NE USA are studied in detail at a regional scale for the first time, due to the availability of over 2 yr of data (2013–2015) recorded at 69 broad-band seismographs. This large, dense data set allowed us to use a back-projection technique to investigate both the azimuthal and temporal variations of the ambient noise. This method is based on a statistical analysis of signal-to-noise ratios (SNRs) of the waveforms in the calculated empirical Green’s functions for pairs of stations. We propose a new method of analysing the SNR by modifying the already existing concept of fan diagrams to include both causal and acausal components of the noise cross-correlograms in the analysis. We investigate directional and seasonal variations of the recorded noise data across the study area at the three main passbands of the seismic noise spectrum including the secondary microseisms (SM; 3–10 s), the primary microseisms (PM; 10–30 s), and the seismic hum (Hum; 30–300 s). We observe that the strongest and weakest signals are received at the SM and Hum bands, respectively. Considering the results of this study along with those from previous studies, we conclude that the strongest seismic noise arrivals at the three passbands investigated in this study (i.e. SM, PM and Hum) are generated at different locations in the Atlantic, Pacific and Arctic oceans.