Publication Date:
2024-04-03
Description:
The main sources of the ambient seismic wavefield in the microseismic frequency band (peaking in the ∼0.04–0.5 Hz range) are earth's oceans, namely the wind‐driven surface gravity waves (SGW) that couple 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 that in turn generate distinct microseismic signatures. In this study, we perform a polarization (i.e., three‐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 Eastern Canada. 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. Both seismic surface wave types show clear cyclone‐related microseismic signatures that are consistent with a colocated generation at near‐coastal or shallow regions, however the Love wavefield is comparatively less coherent. We identify two different kinds of intermittent signals: (a) azimuthally progressive signals that originate with a nearly constant spatial lag pointing toward the trail of the hurricanes and (b) azimuthally steady signals remaining nearly constant in direction of arrival even days after the hurricane significantly changed its azimuth. This high complexity highlights the need for further studies to unravel the interplay between site‐dependent geophysical parameters, SGW forcing at depth and microseismic wavefield radiation and propagation, as well as the potential use of cyclone microseisms as passive natural sources.
Description:
Plain Language Summary:
Ocean waves are responsible for the generation of microseisms, faint ground vibrations with complex characteristics and which comprise a major portion of the background seismic noise of the earth. In this study, we implement an onshore seismic detection method to study microseisms generated by cyclones in the North Atlantic ocean (hurricanes), as these are known to be major generators of large ocean waves. We observed that cyclones only seem to generate detectable microseisms as they move over certain regions in the ocean, namely near coastal or shallow water regions. The direction of arrival of these microseisms is sometimes constant, at other times it shifts azimuth along with the hurricanes. Understanding the relationship between ocean waves and cyclone‐related microseisms is an important step for the potential use of these vibrations to study the earth, ocean and atmosphere.
Description:
Key Points:
Primary and secondary microseismic Love and Rayleigh waves excited by Atlantic cyclones were detected via onshore polarization beamforming.
We observed microseisms related to cyclones as they pass over the northwestern Atlantic margin off Newfoundland.
Some microseisms have constant direction of arrival, others are azimuthally progressive and reflect the advance of the cyclone.
Description:
German Research Foundation
Description:
https://doi.org/10.7289/V5NK3BZP
Description:
https://www.fdsn.org/networks/detail/CN/
Description:
http://ds.iris.edu/wilber3/
Description:
ftp://ftp.ifremer.fr/ifremer/ww3/HINDCAST
Keywords:
ddc:551.22
;
ambient seismic noise
;
ocean microseisms
;
hurricanes
;
ocean gravity waves
;
array seismology
;
marine geophysics
Language:
English
Type:
doc-type:article
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