Rayleigh phase velocity maps for central Europe including the Eifel volcanic province

High-resolution Rayleigh phase velocity maps can help to improve our understanding of the 3-D vs anisotropic structure of the lithosphere of central Europe and its relationship to surface tectonics and volcanism.
Using seismic broad-band recordings for the time period from 1990 to 2020, 600,000 inter-station fundamental mode Rayleigh wave phase velocities have been automatically determined by performing strict quality checks. Only smooth and reliable phase velocity curves with path-wise averaging and a standard error of 0.5% were chosen. For periods between 8 s and 350 s azimuthally anisotropic phase velocity maps were calculated for Central Europe. The phase velocity maps at short periods of up to 30 seconds show an NW-SE fast propagation direction along the East European Craton. At periods longer than 60 s, the anisotropic fast propagation direction shows slight variations from NE-SW to ∼N-S. At 150 s map, a NE-SW fast direction is observed. This might indicate a layering of anisotropy. Along the Tornquist-Teisseyre Zone, the fast propagation direction at all periods is NW-SE, except along its northern part as it shows slight variations. This might be due to the sharp change from the Precambrian continental mantle lithosphere to the younger Phanerozoic Europe. At short periods, central Europe anisotropy is following the Variscan front which changes abruptly to SE-NW near the Elbe line, whereas at longer periods the fast direction follows the Rheic suture and Saxothuringian suture.
For the inversion of local azimuthally anisotropic phase velocity curves, we apply a newly elaborated stochastic inversion algorithm, the Particle Swarm Optimization algorithm (PSO). The result for extensive inversion and parameter tests of Rayleigh dispersion curves tests are shown. The lateral, as well as the vertical resolution of the resulting azimuthally anisotropic S-wave velocities and indications for layered anisotropy, are discussed.