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We extend three-component plane wave beamforming to a more general form and devise a framework, which incorporates velocity heterogeneities of the seismic propagation medium and allows us to estimate accurately sources that do not follow the simple plane wave assumption. This is achieved by utilizing fast marching to track seismic wave fronts for given surface wave phase velocity maps. The resulting matched field processing approach is used to study the surface wave locations of Rayleigh and Love waves at 8 and 16 s based on data from four seismic arrays in the western United States. By accurately accounting for the path propagation effects, we are able to map microseism surface wave source locations more accurately than conventional plane wave beamforming. In the primary microseisms frequency range, Love waves are dominant over Rayleigh waves and display a directional radiation pattern. In the secondary microseisms range, we find the general source regions for both wave types to be similar, but on smaller scales differences are observed. Love waves are found to originate from a larger area than Rayleigh waves and their energy is equal or slightly weaker than Rayleigh waves. The energy ratios are additionally found to be source location dependent. Potential excitation mechanisms are discussed which favor scattering from Rayleigh-to-Love waves.

Item Type:	Refereed Article
Research Division:	Earth Sciences
Research Group:	Geophysics
Research Field:	Seismology and seismic exploration
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the earth sciences
UTAS Author:	Gal, M (Mr Martin Gal)
UTAS Author:	Reading, AM (Professor Anya Reading)
ID Code:	130344
Year Published:	2018
Funding Support:	Australian Research Council (DP150101005)
Web of Science® Times Cited:	18
Deposited By:	Mathematics and Physics
Deposited On:	2019-01-21
Last Modified:	2019-03-12
Downloads:	96 View Download Statistics