Characteristics of Love and Rayleigh waves in ambient noise: wavetype ratio, source location and seasonal behavior

Abstract:

Ambient seismic noise has become an important source of signal for
tomography and monitoring purposes. Better understanding of the noise
field characteristics is crucial to further improve noise applications.
Our knowledge about the common and different origins of Love and
Rayleigh waves in the microseism bands is still limited. This applies in
particular to constraints on source locations and source mechanisms of
Love waves.

Here, 3-component beamforming is used to distinguish between the
differently polarized wave types present in the noise field recorded at
several arrays across Europe. The focus lies on frequencies around the
primary and secondary microseismic bands. We compare characteristics of
Love and Rayleigh wave noise, such as source directions and frequency
content. Further, Love to Rayleigh wave ratios are measured at each
array, and a dependence on direction is observed. We constrain the
corresponding source regions of both wave types by backprojection. By
using a full year of data in 2013, we are able to track the seasonal
changes in our observations of Love-to-Rayleigh ratio and source locations.