Chunyu Liu, Khurram Aslam, Charles A. Langston

Cross-correlations of ambient seismic noise from 277 broadband 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 analyzing the azimuthal distribution of the signal-to- noise ratio (SNR) and positive/negative amplitude differences. We use 84 stations with continuous 1-year recordings to explore seasonal variations of SNRs and amplitude differences. We also investigate the seasonal ambient noise ground motions using 2D frequency-wavenumber analysis of a 50-station array composed of the Northern Embayment Lithosphere Experiment. We observe that (1) two major azimuths can be identified in the azimuthal distribution of SNRs and amplitude difference. We also observe two minor azimuths in the seasonal variation of SNRs, amplitude difference, and 2D FK power spectra. Monthly 2D FK power spectra reveal that two energy sources are active in northern hemisphere winter and two relatively weak sources are active in summer. (2) Back-projection 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) The azimuthal distribution of amplitude difference of sedimentary Love waves in the period band of 1-5s indicates a local source related to the basin-edge of the ME.