Cross-correlations of ambient seismic noise from 277 broad-band stations within the Mississippi embayment (ME) with at least 1 month of recording time between 1990 and 2018 are used to estimate source locations of primary and secondary microseisms. We investigate source locations by analysing the azimuthal distribution of the signal-to-noise ratios (SNRs) and positive/negative amplitude differences. We use 84 stations with 1 yr of continuous recordings to explore seasonal variations of SNRs and amplitude differences. We also investigate the seasonal ambient noise ground motions using 2-D frequency–wavenumber (FK) analysis of a 50-station array. We observe that: (1) two major azimuths can be identified in the azimuthal distribution of SNRs and amplitude differences. We also observe two minor azimuths in the seasonal variation of SNRs, amplitude differences and 2-D FK power spectra. Monthly 2-D FK power spectra reveal that two energy sources are active in the Northern Hemisphere winter and two relatively weak sources are active in summer. (2) Backprojection suggests that primary microseisms originate along the coasts of Australia or New Zealand, Canada and Alaska, Newfoundland or Greenland and South America. (3) Secondary microseisms are generated in the deep water of the northern and southern Pacific Ocean, along the coasts of Canada and Alaska associated with near-shore reflections and in the deep water of south of Greenland. (4) Weak energy is observed in the third quadrant of the azimuthal distribution of amplitude differences of sedimentary Rayleigh and Love waves in the period band of 1–5 s and correlates with the direction of widening of the basin.

中文翻译：

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密西西比河隔间环境噪声的方向性

在1990年至2018年之间，密西西比河（ME）内277个宽带站的环境地震噪声与记录时间至少为1个月的互相关用于估计主要和次要微震的震源位置。我们通过分析信噪比（SNR）和正/负振幅差的方位角分布来调查源位置。我们使用84个电台进行1年的连续记录，以探究SNR和振幅差异的季节性变化。我们还使用50站阵列的二维频率-波数（FK）分析来调查季节性环境噪声地面运动。我们观察到：（1）在SNR和振幅差的方位角分布中可以识别出两个主要方位角。我们还在SNR的季节变化中观察到两个较小的方位角，振幅差和2-D FK功率谱。每月的二维FK功率谱显示，北半球冬季有两个能源活跃，夏季有两个相对较弱的能源活跃。（2）反投影表明，主要的微地震起源于澳大利亚或新西兰，加拿大和阿拉斯加，纽芬兰或格陵兰和南美的海岸。（3）次生微地震在北太平洋和南太平洋的深水，加拿大和阿拉斯加沿岸的近海反射以及格陵兰南部的深水中产生。（4）在1–5 s的周期带内，在沉积瑞利波和洛夫波振幅差的方位角分布的第三象限中观察到弱能量，并且与盆地的扩展方向相关。