The main sources of the ambient seismic wavefield in the microseismic
frequency band (peaking in the ~0.04-0.5 Hz range) are
the earth’s oceans, namely wind-driven surface gravity waves (SGW)
coupling oscillations into the seafloor and the upper crust underneath.
Cyclones (e.g. hurricanes, typhoons) and other atmospheric storms are
efficient generators of high ocean waves with complex but distinct
microseismic signatures. In this study, we perform a polarization (i.e.
3-component) beamforming analysis of microseismic (0.05-0.16 Hz)
retrograde Rayleigh and Love waves during major Atlantic hurricanes
using a virtual array of seismometers in North America. Oceanic
hindcasts and meteorological data are used for comparison. No continuous
generation of microseism along the hurricane track is observed but
rather an intermittent signal generation at specific oceanic locations
along the track. Both seismic surface wave types show clear
cyclone-related microseismic signatures and are consistent with a
colocated generation at near-coastal or shallow regions, however the
Love wavefield is comparatively less coherent. We identify two different
kind of signals: a) intermittent signals that originate with a constant
spatial lag at the trail of the hurricanes and b) signals remaining
highly stationary in direction of arrival even days after the hurricane
passed the presumable source region. This high complexity highlights the
need for further studies to unravel the interplay between site-dependent
geophysical parameters and SGW forcing at depth, as well as the
potential use of cyclone microseisms as passive natural sources.