Three-dimensional P-wave velocity image under the Carpathian arc

Abstract

An inversion of P-wave travel time residuals from selected earthquakes in the distance range 30°–98° to two seismic station networks was used to model P-wave velocity anomalies down to 250 km depth. In the first inversion experiment a region between 43.5°–47.5°N and 21°–29°E was modelled, using 35 seismic stations, while in the second one a region between 44°–47°N and 25°–29°E was modelled, using 19 seismic stations. The 4-layer block model of the first inversion offers 19% reduction in residual variance, while the 5-layer block model of the second one offers 26% reduction, the rest being explained by noise and smaller scale heterogeneities. The obtained velocity anomalies correlate remarkably well with the gravity anomalies and with the tectonic model for the Vrancea region of Fuchs et al. (1979).