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Beamforming of Rayleigh and Love waves in the course of Atlantic cyclones
  • Julián David Pelaez Quiñones,
  • Dirk Becker,
  • Celine Hadziioannou
Julián David Pelaez Quiñones
University of hamburg

Corresponding Author:[email protected]

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Dirk Becker
Institute of Geophysics, Centre for Earth System Research and Sustainability (CEN), Universität Hamburg
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Celine Hadziioannou
University of Hamburg
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Abstract

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.