High-Resolution Moho Depth and Vp/Vs Mapping Beneath the Carpatho–Pannonian Region Using P-Wave Coda Autocorrelation

Abstract

The Carpathian–Pannonian Region (CPR), including Austria, Slovakia, Hungary, Croatia, Serbia, Romania, and Ukraine, exhibits significant seismic activity, necessitating detailed crustal studies. Despite recent improvements in understanding CPR's crustal structure, it remains poorly known. Here, we applied improved autocorrelation of the P-wave coda for the first time in CPR to image the Moho and Vp/Vs ratio. We present Moho depth estimates beneath 231 broadband seismic stations using autocorrelation of teleseismic P-wave coda. Our results indicate a shallow Moho beneath the Pannonian, Vienna, and Danube basins, with depths between 20 and 30 km, while the deepest Moho is observed beneath the Southern Carpathians, Apuseni Mountains, and Southeast Carpathians, where it reaches depths of 45–55 km, deeper than previously reported. The shallower Moho beneath the basins indicates crustal thinning, while thicker Moho in neighboring mountain belts indicates orogenic thickening. Additionally, we estimated the crustal Vp/Vs ratio beneath 212 stations. The whole crust Vp/Vs ratio varies from 1.6 to 2.0, with notably high ratios (1.9 to 2.0) beneath the Pannonian, Vienna, and Danube basins. We also observed a Vp/Vs ratio greater than 1.80 beneath a few stations where mid-crustal low-velocity zones were detected. The average Vp/Vs ratio across the region is 1.76, slightly lower than the global average for continental crust. The lateral variations of Vp/Vs ratio indicate variation in crustal composition across CPR. These findings contribute valuable insights into the tectonics and crustal architecture of CPR.