The missing craton edge: Crustal structure of the East European Craton beneath the Carpathian Orogen revealed by double-difference tomography

The Trans-European Suture Zone (TESZ) is the most important and extensive continental suture in Europe, marking edge of East European Craton (EEC), from North Sea to Black Sea. It corresponds significant changes surface geology deep crustal structure, evident seismic, gravitational magnetic studies. However, TESZ disappears beneath Eastern Carpathians accretionary nappes Neotethys ophiolites, thrusted over subducted EEC passive margin Romania that may have experienced progressive southward break-off generating post-collisional volcanism anomalous seismicity Vrancea region South-East Carpathians. To illuminate missing section investigate change properties Precambrian across collisional orogen impact related volcanism, we determined a 3D seismic model P S wave velocities Romania. With advent new permanent broadband short-period stations Romanian Seismic Network, were able lower earthquake magnitude detection threshold 0.5 ML, largely expanding database create images crust Using double-difference tomography waveform cross-correlation differential times, relocated local earthquakes between 2010 2017 jointly inverted for -wave velocity structure down Moho discontinuity. Our study provides highest resolution this area date emphasizes manifestation tectonic boundaries at depths. highlighted mid-to lower-crustal depths Carpathian nappes, east volcanic belt, as gently-dipping transition high Vp eastern footwall, dipping basement, low Orogen west downward decrease Vp/Vs. In parts region, Vp/Vs ratios increase suggesting presence fluids, mafic material partial melts altered TESZ. Relocated hypocenters are vertically distributed zone especially youngest volcanoes south, consistent with hypothetically active magmatic plumbing system. northern segment, where older, relatively estimated tends cluster top 10 km, likely connected recently reactivated fault Seismicity foreland aligns along NW-SE trending major faults continues thrust basement extends far belt.