[S03-3] Imaging of heterogeneities in the Earth with seismic scattered waves and ambient noise III

[S03-3-05] Comparison of microseismic Rayleigh and Love waves sources around Scandinavia

Hamzeh Sadeghisorkhani, ^○Olafur Gudmundsson, Roland Roberts, Ari Tryggvason (Uppsala University, Uppsala, Sweden)

Use of the ambient noise wave field to image Earth structure has extensively increased during the past decade. Information about noise-source locations and their excitation process can be useful for the application of the ambient-noise method and interpretation of its results. The source locations and mechanism of microseismic Rayleigh waves have been studied in many areas. However, few studies have been published about the source distributions and processes of microseismic Love waves. The lack of information about Love wave source locations and their excitation mechanism applies in particular to the secondary microseisms.
An inversion of cross-correlation envelopes over one year (2012) in five sub-arrays of the Swedish National Seismic Network (SNSN) is used to map and compare the azimuthal source distributions of Rayleigh and Love waves within the primary and secondary microseisms around Scandinavia. The results from all sub arrays can be combined to map the potential source locations of the Rayleigh and Love waves. Comparison of the source locations of the two waves types indicates that Rayleigh and Love waves within the primary microseismic band arrive from similar directions, whereas in the secondary microseismic band the source locations are not always co-located. Our results suggest that most of the energy of the secondary microseisms originates in near-coastal areas (mainly along the western coast of Norway), and could be related to channel-shaped features in the ocean bottom bathymetry. Also, the dominant source locations of different period ranges of the secondary microseisms varies, especially for the Love wave.