  The concept of seismic interferometry embraces the construction of waves
traveling between receivers or sources with cross-correlation techniques. In
the present study cross-correlations of coda waves are used to measure travel
times of shear waves between earthquake locations for five event clusters of
the 2018 West Bohemia earthquake swarm. With the help of a high quality
earthquake catalog, I was able to determine the shear wave velocity in the
region of the five clusters separately. The shear wave velocities range between
3.5 km/s and 4.2 km/s. The resolution of this novel method is given by the
extent of the clusters and better than for a comparable classical tomography.
It is suggested to use the method in a tomographic inversion and map the shear
wave velocity in the source region with unprecedented resolution. Furthermore,
the influence of focal mechanisms and the attenuation properties on the
polarity and location of the maxima in the cross-correlation functions is
discussed. The intra-cluster ratio of P wave to S wave velocity is
approximately fixed at 1.68.
