Secondary Microseism Propagation Across the Mid-Atlantic Ridge: Insights from 3D Seismo-Acoustic Modelling and OBS Observations

The North Atlantic Ocean has a significant role in the Earth’s climate and local weather conditions. Ocean wave-wave interactions generate seismo-acoustic noise known as secondary microseisms, which provide valuable information on storm activity, long-term climate variability, and ocean-land-atmosphere coupling. While terrestrial seismic stations have been shown to successfully detect and localize deep-ocean secondary microseism sources, the recorded wavefields are inevitably influenced by propagation effects along the source-receiver path, including attenuation, scattering, and interactions with complex Earth structures. The extent to which major tectonic features modify these signals remains an active area of research. 

This study investigates secondary microseism propagation effects in the North Atlantic with a focus on the Mid-Atlantic Ridge, a major tectonic structure located along the path of microseisms generated south of Greenland as they propagate towards Europe. A combined approach is adopted using numerical simulations and ocean-bottom seismometer (OBS) observations from the SEA-SEIS project in order to provide new constraints on microseism wave propagation in structurally complex oceanic environments that define mid-ocean ridges. A 3D seismo-acoustic model of the northern Mid-Atlantic Ridge region is generated, incorporating realistic bathymetry and crustal structure. Synthetic seismograms reveal that the ridge strongly modifies seismic wave amplitudes and frequency content, with pronounced scattering and mode conversions observed near the ridge axis.  

The simulations further suggest a partial screening effect across the ridge, whereby signals from synthetic microseism sources located on one side of the ridge show reduced amplitudes at stations on the opposite side. This effect is likely associated with scattering from shallow bathymetric structure linked to the ridge’s complex morphology, while deeper structural heterogeneity and velocity variations also contribute. In addition, the analysis of the OBS stations in the Eastern Atlantic region reveal interesting patterns in ambient noise cross-correlations when combined with the expected microseisms source regions derived from ocean wave models. Preliminary results show that there seems to be no clear dominant propagation direction towards the East when sources are located south of Greenland, west of the ridge. These observations are consistent with the simulation results and indicate the significant influence of bathymetry on microseism propagation.