Abstract
We propose a new approach capable of measuring local seismic anisotropy
from 6C (three-component translation and three-component rotation)
amplitude observations of ambient seismic noise data. Our recent theory
demonstrates that the amplitude ratio of 6C cross-correlation functions
(CCFs) enables retrieving the local phase velocity. This differs from
conventional velocity extraction methods based on travel time. Its local
sensitivity kernel beneath the 6C seismometer allows us to study
anisotropy from azimuth-dependent CCFs, avoiding path effects. Such
point measurements have great potential in planetary exploration, ocean
bottom observations, or volcanology. We apply this approach to a small
seismic array at Pinon Flat Observatory (PFO) in southern California,
array-deriving retrieves rotational ground motions from microseismic
noise data. The stress and structure-induced anisotropy is well resolved
and compatible with other tomography results, providing constraints on
the origin of depth-dependent seismic anisotropy.