S-Wave Tomography in the Eifel Volcanic Area

The Eifel is an intraplate volcanic region, located in central Europe. Volcanism started 45 Ma BP and the last eruption occurred 11-12 ka BP. Previous analysis of P-wave data revealed a low velocity structure, the Eifel Plume, which could be resolved down to at least 410 km depth. We now present the results of a S-wave tomography for the same area. The data set consists of 62 earthquakes recorded at 145 permanent and mobile seismic stations. Since the long period S-waves (15s) were poorly recorded by the short period stations (natural period 1s) the respective seismograms were successfully restituted to 15s by inverse filtering. The resulting data show relative travel time residuals of +3s in the Eifel region corresponding to a low velocity anomaly. The tomographic inversion of 3773 relative S-wave travel time residuals reveals a zone of reduced S-wave speed in the mantle below the Eifel volcanic fields, reaching down to at least 500 km depth. The inversion results are strongly supported by several resolution tests.