Microcracks in geomaterials cause variations in the elastic moduli under
applied strain, thereby creating seismic wave velocity variations. These
are crucial for understanding the dynamic processes of the crust, such
as fault-zone damage, healing, and volcanic activities. Solid earth
tides have been used to detect seismic velocity changes responding to
crustal-scale deformations. However, no prior research has explored the
characteristics of the seismic velocity variations caused by large-scale
tidal deformation. To systematically evaluate the tidal response to
velocity variations, we developed a new method that utilized the
flexibility of a state-space model. The tidal response was derived from
hourly stacked noise autocorrelations using a seismic interferometry
method throughout Japan. In particular, large tide-induced seismic
velocities were observed in the low S-wave velocity region of the
shallow crust. Overall, the tidal responses to velocity variations can
provide new insights into the response mechanisms of the shallow crust
to applied strain.